Indoor Plants PDF

HO-103 Indoor Plants By George Pinyuh, Extension agent emeritus, King and Pierce counties; E. Blair Adams, Extension horticulturist (deceased); Arthur L. Antonelli, Extension entomologist; and S.J. Collman, Extension agent emeritus, all of Washington State University. Adapted for use in Kentucky by...

HO-103 Indoor Plants By George Pinyuh, Extension agent emeritus, King and Pierce counties; E. Blair Adams, Extension horticulturist (deceased); Arthur L. Antonelli, Extension entomologist; and S.J. Collman, Extension agent emeritus, all of Washington State University. Adapted for use in Kentucky by Sharon Bale, Extension horticulture specialist and Richard Durham, consumer horticulture Extension special- ist and state Master Gardener coordinator, University of Kentucky. plant or with local county Extension agents. Houseplant books In this chapter: (there are hundreds, many available at libraries) and garden encyclopedias (also available at libraries) are also a source Management 01 of information. In general, a plant needs an environment as similar as pos- Potting and Repotting 04 sible to that in which it grows naturally. Understory plants Houseplant Problems 06 (those that live on the forest floor) can grow in diffuse light. Plants from deserts or other open environments require strong light. Tropical and subtropical species generally do best in C ultivating plants inside the home is both a popular humid conditions, and desert species require arid conditions. hobby and an interior decorating technique. More than Cool-climate species prefer cool nights and warm days, while 75 percent of all American families use living plants as tropical species prefer warm temperatures at all times. Learn part of their home decor or cultural expression. about the specific plants you are growing (or plan to acquire) To keep plants healthy and attractive, you must control a and place them in a location that provides the best combination number of environmental factors such as light, temperature, of environmental factors for their needs. humidity, water, and plant nutrients. The right combination Cultivating houseplants is enjoyable and rewarding. The results in healthy plants. Too much or too little of any factor basic culture is not difficult, and most plants require only a few results in poor plant health or death. minutes of attention each week once their basic environmental A houseplant is simply an outdoor plant that is grown requirements are satisfied. They do, however, require this mini- indoors. Not all plants are suitable for indoor culture. Some mal care on a regular basis. Plants are living things and must be require environmental conditions that are impossible to dupli- managed so that their life-support systems function properly cate indoors. Others adapt to indoor culture if their minimum at all times. The following sections discuss several important growth requirements are provided. The key to successful indoor aspects of plant care. plant culture is to select plants that are adaptable to the condi- tions in your home. Light The normal home provides a number of different environ- Perhaps the major environmental factor limiting plant ments. Light varies from sunny windows to dim corners. Plants growth indoors is lack of adequate light. As natural light enters in living areas receive long hours of light (either natural or arti- homes, it decreases very quickly. For example, a plant one foot ficial) year-round, but those in bedrooms normally receive only away from a window may receive 100 foot-candles of light. If minimal supplemental light. Humidity usually is much higher it is moved two feet away from the window, it will receive only in kitchens and bathrooms than in living rooms. Temperatures 25 foot-candles of light. At three feet it receives only 11 foot- vary widely. The overall climate may range from humid sub- candles, and very few, if any, houseplants do well at such low tropical to arid desert in various locations. light intensities. The most expedient method of adjusting light intensity is Management to move the plant closer to or farther from a light source such as a window. Unfortunately, this may place the plant in an The environmental factors of light, temperature, and humid- inconvenient spot. ity are to a large extent determined by how you manage your home environment for family comfort. Other environmental To increase light intensity, you can try these measures: factors, such as water and nutrient availability, can be man- Move the plant to a lighter room (southern versus northern aged solely for your plants’ sake. By selecting the best site for exposure). each plant and managing the supply of water and nutrients, it Place the plant near an electric light. is possible to grow most common houseplants in any home. Provide separate artificial light for the plant. Each plant has its own set of desired environmental con- Provide reflected light with a light-colored wall or mirror. ditions. There are many sources of information for specific Keep leaves free of dust and grime. cultural requirements. Check with the store that supplied the CHAPTER 19 Indoor Plants To reduce light intensity, you can take these steps: Water Place a lace curtain between the plant and window. Use venetian blinds to intercept and divert direct sunlight. Watering is the most important (and most often abused) Reduce reflected light with a dark backdrop. cultural practice. Plants must have a continuous and adequate Shade the plant with another plant. supply of water, but they can absorb water from the soil only Move the plant back from a strong light source (for example, under certain conditions. a south-facing window). First, there must be available water in the soil. Soil particles hold some water too firmly for plants to take up. The water available to plants is water in excess of that required to satisfy Temperature the soil itself. The quantity and type of soil mix will determine Home temperatures are adjusted for the comfort of people, how much water the pot retains for plant use. but temperatures vary considerably in most homes. Bedrooms Second, some air must be in the soil for plant roots to func- usually are cooler than bathrooms or living areas. Southern- tion and absorb water. Therefore, the soil must not contain so exposure rooms usually are warmer during the day than much water that no room is left for air. A good potting soil will northern-exposure rooms. Fortunately, most plants tolerate a not hold too much water if a hole in the bottom of the container fairly broad range of temperatures and thrive at normal home allows excess water to drain away. temperatures if other environmental factors are satisfactory. The difference between these two extremes (no available water versus saturated soil) is called the available water supply. Humidity Proper water management avoids both extremes and maintains a supply of available water at all times. Many plants require a more humid climate than the average The following guidelines may help you establish a satisfac- home. Ferns, ivies, and other humid-climate plants may grow tory watering schedule: best in bathrooms or kitchens, where the air usually is more Use a well-prepared potting soil to assure good water-reten- humid. You can increase relative humidity around a plant by tion capacity as well as space for air. placing its pot on a shallow tray of moist gravel (Figure 19.1a). Make sure containers have at least one drainage hole so excess The gravel will evaporate water into the air around the plants. water can drain away. Damp sphagnum moss packed between pots in planters When watering, apply enough water to run out the drainage also evaporates water into the air (Figure 19.1b). Moss has the hole. This usually assures that you have replenished the avail- added advantage of acting like a wick to draw up and dispose able water supply and also reduces salt buildup. of excess water in the bottom of the planter box. Do not let pots sit in excess water. Pour it away or raise pots Grouping plants together in the same room raises the so they always are above the level of drained-out water in relative humidity for all. Plants transpire (emit moisture) water the saucer. continuously. The more plants you grow, the more water they Do not water on a time schedule. Allow the soil to become dry transpire into the air. on the surface before you water again. This method maintains A humidifier is another way to raise humidity. The higher a good balance of air and water in the soil. relative humidity that plants prefer also is healthier for people. If some plants require frequent watering, move them into Misting plants does not significantly increase humidity. It slightly larger pots (with greater water-holding capacity). may, however, help keep leaves clean, which also is desirable. Some plants, such as desert cacti and succulents, should be watered only a little, if at all, during the short days of winter. With the exception of seedlings and very young plants, these plants need no water from about mid-November to mid-March. Most cacti and many succulents are best kept bone-dry and quite cool during the winter. Highly organic soils are difficult to rewet once they dry out. They also tend to shrink away from container sides. This can allow water to run between the soil and the inside of the pot without ever moistening the soil. If this happens, submerge the entire pot in water until the medium is fully moistened. Flush soluble salts from pots on a regular basis, about every six months. Water three times at 30-minute intervals to wash salts out the drainage hole. a)a)Gravel Gravel b)b)Sphagnum Sphagnummoss moss Keep these additional factors in mind when watering: Figure 19.1. Two ways to increase humidity around a plant: (a) A layer Chlorine in tap water will not harm plants. of moist gravel or pebbles in a tray beneath the pot and (b) a pot inside a large planter filled with moistened sphagnum peat moss. 19-2  Indoor Plants CHAPTER 19 Table 19.1.—Houseplant problem symptoms, possible causes, and treatments. Symptoms (What You See) Possible Causes Treatment (Corrective Action) Plants are spindly, and stems grow abnormally Too little light Move plant closer to a window or other light source. Don’t fertilize long. Leaves lack color, are undersized, and when plants are dormant (winter). may fall off. Old leaves curl under. New leaves are smaller Too much light Move plant farther from window or light source, or filter light than old leaves. Leaves may brown around through a curtain. margins. Yellow, brown, or white (bleached) spots on Sun scorch caused by Shade plant. Move plants from shade to sun gradually so they can leaves (particularly on upper leaves). sudden increase in light adapt. Some always require shade. intensity Leaves turn yellow, curl downward, or wilt. Too much heat Move plant to a cooler spot. Avoid placing plants near heat registers or hot-air outlets. Plants wilt even if soil is moist. Margins and Salt buildup in soil Water three times at 30-minute intervals to wash the salts out the tips of leaves burn. White crust may appear on drainage hole. Do not use soft water. leaf edges and on the soil surface when dry. White crust on rim and sides of porous pots. Salt accumulation on pot Leach soil as above. Wash excess salts off pot with clear water. Wax Leaves touching rim wilt and die. the rim of the pot to prevent future salt deposits that might touch leaves. White or yellow spots on leaves of African vio- Cold water on leaves or Use room-temperature to lukewarm water for watering plants. lets, gloxinias, and other hairy-leafed plants. in soil Dark brown spots around leaf margins of tropi- Raw natural gas or Check gas lines and fittings for gas leaks. Adjust gas burners for blue cal foliage plants (especially philodendrons). incompletely burned gas flame. Have furnace checked for leaks or adjustments. in home Plants wilt between waterings. Roots fill pot Plant is too big for its pot Repot in a larger container with a good potting soil mixture. and may grow out drainage hole. Growth slow. Sudden wilting or shedding of foliage during Chilling Move plant away from chilling drafts. cold weather. Wilting and loss of foliage after repotting or Transplant shock Give optimum care until plant adjusts to its new situation. initial potting. Tips of leaves turn brown, and leaves wilt. Not enough water Water until some water runs out the drainage hole, or submerge the Lower leaves turn yellow and fall off. pot in a pail of water for five minutes. Drain off excess water. Repeat when soil is dry to touch. Lower leaves curl and wilt. Stems become Too much water Water less frequently. Use pots with drainage holes in the bottom. mushy and rot. Soil in pot usually is wet. Do not allow pot to stand in water more than 30 minutes. Leaf edges are crinkly and brown. Tips of new Lack of humidity Increase humidity around plants by standing pots on a bed of moist leaves often dry up. gravel or placing them in planters with moist sphagnum moss packed around the pots. Use a humidifier or move plants to a more humid area (such as a bathroom or over the kitchen sink). Plants grow rapidly with lots of foliage but few, Too much fertilizer Fertilize less often or at half the suggested rate. Use low-nitrogen if any, flowers. fertilizer during blooming season. Do not fertilize when plants are dormant. Lower leaves lose color and may drop off. New Too little fertilizer Fertilize regularly when plants are growing. Use a soluble fertilizer leaves are progressively smaller than previous and apply per package directions. leaves. Stems are stunted. Brown or black spots on leaves. Tip and mar- Fluoride in water supply Use rain or distilled water. Keep pH up to 6.5. ginal burning. Spider plants (Chlorophytum), corn plants (Dracaena), and palms are espe- cially sensitive. 19-3 CHAPTER 19 Indoor Plants Fluoride in tap water can damage sensitive plants. (See Table 19.1.) Room-temperature water is best. Plants such as African violets and their relatives may require even warmer water. Nutrients Plants growing in containers have a limited volume of soil from which to extract mineral nutrients (fertilizer). The sup- ply of nutrients rapidly becomes exhausted when the plant is actively growing. Replenish nutrients regularly. The easiest way is to water them with a solution of soluble fertilizer. Many soluble fertilizers are available in garden stores. Since they vary in strength (percent of fertilizer nutrients), dilute or dissolve them in your watering can according to the label directions. Mix only enough solution to water your plants once Figure 19.2. If roots are growing out of the drainage hole, it’s time to each time you fertilize. repot. During the long days of the year (Easter to Thanksgiving), when plants are actively growing, fertilize about every other you do not have to remove many roots to fit the plant into the week. During the short days of the year (Thanksgiving to container. Pot rooted cuttings when the roots are about one- Easter), fertilize only every four to six weeks. If plants are totally half inch long. Seedling plants transplant most readily as soon dormant, do not fertilize until new growth starts. as the first true leaves have formed. Here are some fertilizing hints: Slow or time-release fertilizers are a good way to fertilize Plant Condition houseplants. Follow label directions. Most plants transplant best when they are actively growing. Plants grow best with small amounts of nutrients constantly Dormant plants or those in flower may not produce root growth available. and establish themselves in the new pot as readily. Plants should Do not apply fertilizers to dry soil. not be wilted when transplanted. Be sure your plants are well Do not overfertilize. More is not better. Plants can die from watered and free of insects before repotting. too much fertilizer. It’s better to underdo than overdo. Both organic and synthetic fertilizers are acceptable sources Container Type of plant nutrients. Plants can be grown in almost any container, but it is best to use containers with drainage holes. To establish plants in decora- Potting and Repotting tive containers without drainage holes, pot the plants in draining Cultivating plants in containers requires occasional replant- pots that fit inside the other containers. You can combine several ing from one container to another. Small, rapidly growing plants small pots in a larger planter by packing sphagnum moss around may require repotting into larger containers every three to the sides of the pots for support and to help evaporate excess four months. You can repot mature houseplants on an annual water. Clay pots are no better than plastic ones, but porous and basis or allow them to remain in containers until they have nonporous pots require different management. For one thing, outgrown them or become pot-bound (Figure 19.2). If a plant soil in clay pots dries more rapidly and requires more frequent is not doing well, and no obvious reason can be found, it may watering than that in plastic pots. benefit from repotting. Handle plants carefully when potting or repotting to avoid Container Size injury and to provide optimum growth in the new container. Normally it is best to keep a plant in the smallest container When transplanting, consider such factors as size and condition needed for its current stage of development. This practice of the plant, size and type of container, type and amount of soil conserves growing space, reduces the likelihood of overwater- mixture, and prevention of damage to the plant. ing, allows for gradual increases in pot size (and new soil) as the plant develops, generally looks better (small plants in large Plant Size pots look lost), and allows more versatility in moving plants or Small plants transplant more easily than larger ones; how- arranging them in groups. ever, any plant that already is established in a container can be Adjust container size to manage irrigation schedules. Move repotted. When first planting into pots, select small plants so plants that need more frequent watering to larger pots with more water-storage capacity. 19-4  Indoor Plants CHAPTER 19 Potting Soil Mixtures Many houseplants, such as African violets, gloxinias, philo- dendrons, rubber plants, and most other tropical foliage plants, Plants growing in containers require specially prepared soils may do better in a mix containing a higher proportion of organic or growth media. A container-grown plant cannot extend its matter. Adding extra peat moss to the general potting mixture root system to gather water and nutrients; it is limited to the adjusts the mixture to their needs. small volume of soil in the container. Potted plants use the soil in their pots much more intensively than they would if growing Desert Plant Mix unrestrained outdoors. Even the most fertile garden soil will not one part general potting mixture sustain this intensive use for more than a short time. one part sand or coarse perlite Ready-to-use potting soil mixes are available in garden stores. Cacti and other succulents grow best in a soil mixture with Some of these commercially prepared potting soils are excellent a lower proportion of organic matter that dries rapidly and, but expensive. If you have only a few houseplants, prepared therefore, does not retain large quantities of water. Mix the mixes are convenient and probably the most practical. However, general soil mix with an equal volume of sand or perlite to create if you grow numerous houseplants, it may be more economical an appropriate potting mixture for these plants. to prepare your own potting soil. Good potting soil differs from garden soil. It should contain a Orchid Plant Mix much higher proportion of coarse mineral particles to maintain two to three parts fir bark (medium to course grade) sufficient pore spaces in the soil for air, water, and root growth. one part perlite It must have enough organic matter to hold water and condition one part sphagnum moss, with large fibers chopped into the soil (keep it from compacting). It also must contain sufficient quarter- to half-inch pieces mineral nutrients to supply a large part of the plants’ needs. (All Most orchids grown as houseplants are epiphytes, mean- houseplants need supplemental fertilizer on a regular basis.) ing that they typically grow attached to the trunks and limbs Good potting soils can be prepared by mixing garden soil, of tropical plants. Therefore, orchid planting mix should be coarse sand, pumice or perlite, and peat moss. Most potted composed of relatively large particles to allow for air movement plants grow quite well in a mix containing equal parts of these into and through the medium. A few orchids are terrestrial, ingredients if you adjust management techniques (watering meaning they grow in soil. Terrestrial orchids will usually do and fertilizing) to suit their different needs. You can modify well in a general mixture or a high-organic mix. this general potting mixture with additional coarse mineral material or peat moss to satisfy specific plant requirements. The instructions in this section can be used to create some Sterilizing Soil common potting mixtures. It normally is unnecessary or even undesirable to sterilize potting soils. Garden soils contain millions of beneficial living General Mixture organisms. Only rarely do they contain disease organisms that one part garden soil (not clay) might damage houseplants. Seedlings are most susceptible to one part washed builder’s sand, perlite, or pumice attack by soilborne disease organisms during their first two one part horticultural peat moss to four weeks of growth. To prevent damping-off disease on one quart steamed bonemeal per bushel (eight gallons) of seedlings, it may help to heat-treat the soil used for seedling mixture production. one pint dolomitic lime per bushel of mixture Baking soil in an oven is the easiest method of heat-treating. Mix all ingredients thoroughly by shoveling them from one Place slightly moist soil in a heat-resistant container, cover it, pile to another at least three times. Pulverize any large lumps and bake it in an oven at 250°F. Use a candy or meat thermom- or clods as you mix. When the mix is thoroughly blended, add eter to ensure that the mix reaches 140°F for at least 30 minutes. sufficient water to moisten it. Then store it in a sheltered spot until you are ready to use it. A garbage can, wastebasket, or large Using Potting Mixes bucket makes a handy storage container. By making a supply of general potting soil mixture and retain- This general potting mixture provides a suitable growth ing a small quantity of additional peat moss and sand, you can medium for most container plants, including vegetables, bed- adjust your mixture for any type of plant. This arrangement ding plants, geraniums, begonias, fuchsias, and ivy. requires only a minimal amount of storage space, and your pot- ting soil is ready to use at any time. Before using it, be sure it is High-Organic Mix damp. Dry soil mixture is difficult to handle and may damage one part general potting mixture tender roots before the plant is watered. one part horticultural peat moss 19-5 CHAPTER 19 Indoor Plants The Potting Process and get varieties that grow successfully in the conditions you are able to provide. It is not necessary to cover drainage holes. Any item that Other problems are caused by insects. Some of the more might inhibit free drainage of surplus water from the pot is best common ones are described in the “Major Pests” section of this avoided. Plants will not suffer if a bit of potting mix comes out chapter. Prevention is a key to managing houseplant pests. If with the first irrigation or two. Do not use a gravel layer or other your plants develop a pest problem, there are various chemical so-called drainage material at the bottom of the pot. It actually and nonchemical controls available. The key to success against slows down drainage by shortening the soil column. Different pests is to get control of all their life stages. Consistent appli- layers of material also are likely to lead to perched water tables cation of a pesticide every five to seven days for a period of a (restricted drainage) in the container. Always fill the entire pot month or more may be necessary. Nonchemical controls also with the growing medium—right to the bottom. must be consistent. If you are repotting from another pot, gently remove the Diseases normally are not a problem for plants grown in plant and crumble some of the old soil ball away (Figure 19.3). homes or other typical indoor environments. (An exception is If you are potting a new plant, trim the root system if neces- powdery mildew on a very few species of plants, such as grape sary to fit the pot (Figure 19.4). Do not bend or wind roots into ivy.) Plants grown in greenhouses, however, are susceptible to the pot. It is better to prune them to fit without bending. several disease problems. Place the resulting ball in the center of the new container and fill around it with potting soil while holding the plant in the desired position (Figure 19.5). To help settle the medium, slap the sides of the container as the soil filters around the plant roots. Thumping the bottom of the pot on the potting bench also aids in this process. Avoid pressing or tamping the soil down too hard. This often eliminates air space in the mix and causes drainage problems. Finish filling the pot to approximately one-half inch from the top. In standard flower pots, fill to one-half the depth of the rim. This leaves enough space for applying sufficient water to saturate the soil. As soon as you finish potting or repotting plants, fill the Figure 19.3. Removing plants from pots. pot to the brim with water. Keep adding water until it comes out the drainage hole to be sure you have completely filled the reservoir capacity of the potting soil. If extensive root pruning was necessary, keep the plant away from strong light or heat until new roots grow. Increasing the humidity around the plant will help in reestablishment. Propagation Many houseplants are easily propagated by cuttings. For further information on propagating houseplants, see Kentucky Cooperative Extension publication Propagating Figure 19.4. Trimming roots before repotting. Plants in and around the Home (HO-67) or refer to Chapter 3, Plant Propagation. Houseplant Problems Most houseplant problems are related to cultural or envi- ronmental stress. Table 19.1 shows symptoms, possible causes, and treatments to help you recognize and deal with some of the many houseplant problems. Unhealthy container plants usually return to normal, healthy growth once they receive acceptable growing conditions. This recovery may require a few weeks to several months. If you find you cannot achieve proper condi- tions for certain types of plants, it may be best to discard them Figure 19.5. Repotting a plant. 19-6  Indoor Plants CHAPTER 19 Major Pests Chemical control of adults often is impossible. The female usually lays eggs under a scale. When eggs hatch, tiny crawlers Aphids emerge and begin to move about in search of a place to feed. Aphids are small insects about one-sixteenth to one-eighth The crawler stage is the most easily killed with chemical sprays. of an inch long. They are six-legged and variously colored, and some look powdery or woolly. Both wingless and winged forms Mealybugs can be found on plants. Under the right conditions, aphids Several different mealybugs are among the most serious multiply rapidly and can spread quickly to other plants in the pests of houseplants. Most appear powdery. They are about house. Aphids have sucking mouthparts that pierce plant tis- three-sixteenths of an inch long, flat, and slender. Some have sue and suck out juices. Damaged leaves lose their green color waxy filaments extending from their bodies. Most species and look stunted, distorted, or curled. Heavy infestations may move freely but slowly on plants. Females are wingless, while damage or actually kill plants. males have a single pair of wings. Eggs are laid in clusters and The excreta (honeydew) given off by aphids is another prob- are covered by waxy or fuzzy material. lem associated with this pest. This material is sticky, gives leaf Mealybugs attack all plant parts. Damage is similar to that surfaces a shiny look, and provides food for the development caused by aphids. Honeydew and sooty mold frequently occur of sooty mold. on plants infested with mealybugs. Whiteflies Spider Mites Whiteflies are tiny insects about one-tenth to one-sixteenth Mites often are referred to as insects. However, they are not of an inch long that resemble tiny moths. Their bodies and insects, since they have eight legs, only two body regions, and no wings are covered with a white, powdery substance. When at wings. They are, in fact, closely related to spiders. Spider mites rest, they hold their wings rooflike over their bodies. Both the are extremely small. A hand lens of at least 10X magnification immature stages and adults have sucking mouthparts. There often is needed to see them. are five distinct stages in the whitefly’s development: Usually, mite damage appears long before the mites them- 1. The egg, which is laid on the underside of a leaf and often is selves are noticed. Plants damaged by mites lack vigor, lose covered with a powdery material color, and have speckled leaves. Webbing is characteristic of 2. The newly hatched or “crawler” nymph, which is flat, nearly spider mites. The web helps them spread to other plants, often transparent, and can move on air currents. 3. The intermediate nymph, which has no antennae or legs and There are three stages in a mite’s development: egg, a series therefore cannot move of nymphal stages, and adult. All stages except the egg stage 4. The dark nymphal stage, which is somewhat segmented damage plants. 5. The adult A single female can lay up to 400 eggs, and whiteflies continu- Cyclamen Mites ously breed in homes and greenhouses. Damage by whiteflies Although named for cyclamens, these mites also damage resembles aphid damage. In addition, the adults are active fliers many other plants. Adults are too small to see with the naked and become a household nuisance. eye. Under a magnifying glass, they are seen as oval, amber or tan-colored, semitransparent, and glistening. The young are Scales even smaller and milky white. Several different scales infest houseplants. The adults gener- These mites are found mostly in protected places on young, ally are quite small, ranging from one-sixteenth to one-eighth tender leaves, young stem ends, buds, and flowers. They crawl of an inch in diameter, and may be white, black, brown, gray, from plant to plant where leaves touch. They also can be trans- or tan. They attach rigidly to plants. Many scales are shaped ferred to other plants by hands or clothing. somewhat like a ball and have no distinctive features except for Damage consists of twisted, curled, and brittle leaves, being flat or slightly bulging. Some have distinctive shapes, such deformed buds, and flowers that often are streaked with darker as oyster shells (that is, oystershell scale), while others look like color. Blackening of leaves also is common. turtle shells. The scale actually is a hard or soft covering that protects the insect. The adult male is the only winged member Minor or Less Common Pests of the scale group. These pests are uncommon in the home but if houseplants Damage by scales is similar to that from aphids and white- are moved outdoors during the summer they may be exposed or flies. Honeydew and sooty mold often are present. Severe plant you may inadvertently bring these pests along when you move injury or death may be the final result of poor control. your houseplants back indoors come fall. Always inspect new plants for pests when you are introducing plants to your home environment. See below for more information on preventing pest problems. 19-7 CHAPTER 19 Indoor Plants Leafminers Leafhoppers Many different insects commonly are called leafminers. Leafhoppers are small to moderate-sized sucking pests Members of the fly, sawfly, and moth/butterfly groups are the (one-sixteenth to one-quarter inch long) related to aphids. Only most common. The larval stage is responsible for the leafmin- occasionally are they pests of houseplants. They vary in color ing damage, which appears as a winding, discolored trail or an and are wedge shaped. Damage usually appears as mottling irregular blotch within leaf tissue. Damage from these insects or speckling of leaves and may be confused with mite injury. rarely is serious; it usually is merely unsightly. Simply remove and destroy the infested leaves to solve the problem. Springtails Springtails are small (one-fifth of an inch or less) and vary Fungus Gnats in color. They are wingless, and as the name implies, many are These small, black flies are first noticed around windows. capable of jumping. Although they may chew on small seedlings The larvae feed on decaying matter and therefore most often or tender plant parts, they mostly prefer to feed on decaying are found in highly organic soils. Most species seldom damage organic matter. They can become a nuisance when numerous. plant roots unless a great many insects are present. Generally, they are merely annoying. Slugs and Snails These soft-bodied, fleshy, legless creatures are related to Caterpillars clams. They can be very destructive to a wide variety of plants. The larvae of many moths and some butterflies sometimes They usually require a moist environment. Houseplants may feed on houseplants. They range from very tiny (one-eighth of become infested when they are placed outdoors. Slugs and an inch or so) up to one and one-half inches long. Color of adults snails are voracious feeders and frequently devour whole plants and caterpillars varies, although gray, whitish, and brownish or plant parts. Their presence is marked by the slime trails they are most common. Caterpillars may have stripes, spines, or leave behind. bumps in any combination according to species. They have These animals lay small, round, milky white eggs in the three pairs of true legs and also may have a series of false legs soil. Some commercial slow-release fertilizer pellets closely along the tail end. resemble slug eggs and often are identified as such even by Their presence usually is the result of an uninvited, fertile professionals. female moth who slips past a screen door and lays eggs inside. Hand removal of slugs usually is all that is necessary. Look for Caterpillars, as well as other pests, also can develop on plants them under mulch, pots, and pot rims. Placing shallow dishes that have been placed outdoors during the summer. Remove of beer near plants is helpful, as slugs are attracted to beer and and destroy the eggs or caterpillars when you notice them. will crawl in and drown. Beetles Millipedes Flea beetles and other leaf-feeding beetles are potential Millipede populations can build up in potted plants. They houseplant pests. These beetles have chewing mouthparts. sometimes feed on plant parts, but more frequently on decay- Beetles have four life stages: egg, larva, pupa, and adult. In many ing organic material. They become a nuisance when present in species, both adults and larvae feed on plant tissue. large numbers. Many species can occur on plants. They vary in In most species, the adults can fly, which in some cases color and can be tiny or up to one and one-half inches or more may explain their presence in homes. Again, the likelihood of in length. They are easily identified by their many legs, round beetle infestation increases when plants are placed outdoors. shape, and slow movement. Removal of the insects probably is the most convenient and effective control. Centipedes These animals are not plant pests. They feed on many insects Thrips and insect relatives and thus are beneficial. While they resemble Thrips are small, slender insects about one-sixteenth of an millipedes because of their many legs, they are very flat and fast inch long. Many have two pairs of fringed wings, which are moving. They vary in size (one-quarter to two inches) as well folded flat over the back when at rest. Some are predators and as in color. Some of the larger ones often bite when disturbed. some are scavengers, but most are serious plant pests. Their If their presence is annoying, remove them carefully and place mouthparts are used for rasping leaf surfaces. Damage appears them outdoors where they can continue to be useful in nature’s as whitening or speckling of leaves. Small, black droplets also scheme of things. may be noticeable, and some plants may have a silvery appear- ance. Flowers also are damaged. 19-8  Indoor Plants CHAPTER 19 Preventing Pest Problems most effective if done at night using a flashlight. Where scales or mealybugs are few in number, a thumbnail or toothpick can Routine precautions will help you avoid unhappy encounters remove them. After removing pests, watch plants closely for a with houseplant pests. First, when you buy plants, inspect the few weeks in case you overlooked some smaller individuals. leaves and stems carefully. Even those that seem clean might harbor pests. Isolate new plants for a week or two in a separate Swabbing with Alcohol room or garage to prevent pests from flying from the new plants Cotton swabs dipped in rubbing alcohol are effective in to your existing ones. Keep close watch on the plants to see controlling aphids and mealybugs. This method is practical for whether a pest population is building up. light infestations but is extremely tedious for heavy infestations, Putting houseplants outdoors in the summer can invite particularly on large plants. a whole series of pest problems. If you put your plants out- side, treat them as newly purchased when you bring them Spraying with Soapy Water back indoors. Using soapy water gives good control if done correctly. The Sometimes pests come indoors on their own. Good authors have used soapy water with good results on several screen windows keep out most flying insects such as moths kinds of plants. and beetles. Some plants may be harmed by this technique, so try it on Using soil from outdoors is another source of infestation; a small area of a plant first. Use only insecticidal soap that is you might bring in uninvited members of the soil fauna such as registered for use on houseplants. Read the label carefully, not mites and slug eggs. Commercially prepared potting soil might only for use instructions but also for information concerning be a better choice. If you use outside soil, pasteurization at 140°F possible plant damage. is an option; it normally eliminates undesirable organisms but This treatment is not totally effective against winged adults does not harm desirable ones. (See “Sterilizing Soil,” earlier in (such as whiteflies), since they leave the plant during treatment this chapter.) and return later. Thus, it is necessary to spray the adults with Pests are transferred from plant to plant in a variety of ways. a registered insecticide to get complete control of all stages of Some of the more subtle ways are through human activity. the pest. Consider the times you handle garden store plants or admire a Chemical Control friend’s collection. In doing so, you can pick up scale crawlers or Few pesticides are registered for indoor use on houseplants. mites and bring them home to your own plants. It is wise to be Read labels carefully for where and how to use a pesticide. If on the lookout for plant pests before you handle strange plants. indoor use is not designated, take the plant to be treated out- Many pests survive because they have suitable hiding doors away from child and pet traffic areas. Do not bring it back places. Avoid buildup of dead leaf material that might provide indoors until the spray has dried. It may be well to leave the such sites. plant in the garage a day or two for extra safety. Another solu- tion is to use pesticides that are formulated to be added to the Controlling Pests soil as either a granule or drench. Again, be sure the pesticide Nonchemical Control is labeled for indoor, houseplant use. Several techniques can be alternatives to chemical controls. Avoid spraying houseplants indoors, even according to label Some require more work than using chemical sprays, but they directions, as many sprays have objectionable odors and can often give equally good control. cause allergic reactions in some people. Do not use pesticides where spray can drift onto cooking utensils or food. Removal of Infested Parts If only a few leaves are infested (for example, with leafmin- Plant Damage from Pesticides ers), it is quite effective to simply remove and destroy that Injury to plants from pesticide applications has several com- portion of the plant. If roots are being damaged by mealybugs mon symptoms: or grubs, it is advisable to take a cutting and start over. Discard Total burn, marginal burn, or spotting of leaves or flowers infested soil and thoroughly clean the pot or container. Cupped, curled, and yellow leaves Distorted leaf or flower buds Disposal As a rule, flowers and flower buds in advanced stages of Some plants may be so badly damaged that they are too far development are most susceptible to pesticide injury. gone to save. Getting rid of them is the simplest answer. Usually, these injuries do not kill a plant. Leaves may drop, Hand Removal but new leaves form and the plant usually recovers. This method is fairly effective for a number of pests and usu- Soil-applied pesticides also may produce these symptoms ally needs no supplemental chemical control. Slugs, caterpillars, or stunted growth because of injury to the root system. Severe many beetles, and other large insects can be eliminated in this root injury causes sudden wilting and death of aboveground manner. Many of these pests feed at night. Thus, this method is plant parts. 19-9 CHAPTER 19 Indoor Plants Reduce the possibility of damage by applying pesticides during the cooler hours of the day and by letting plants dry in a well-ventilated place. Powders and dusts generally are less injurious to plants than are spray concentrates, although they may leave an unsightly residue. Carefully read the pesticide label. In many cases, it will indi- cate specifically which plants are sensitive to the pesticide and those for which it is recommended. Revised 01-2024