PlantAmerica's Plant Care Sheet
Rhizactonia Root and Stem Rot
Rhizactonia, a fungus found in most soils, enters the plant through the roots or the stem at soil level. The infection moves up the plant, lower leaves affected first. It thrives in warm, fertile, well-drained soils that tend to be moist.
Prevention and Control: If you suspect Rhizactonia, first decrease watering. If a plant is too far gone (all the leaves from the bottom up are wilted), remove it. Treat soil with triophanate-methyl. For a container plant, discard the soil and wash the pot with a bleach and water solution.
Fungi:
Powdery Mildew
Powdery mildew is a widespread fungal disease that often attacks plants lacking sufficient air circulation or light. The problem is worse where nights are cool and days are warm and humid. The powdery white or gray fungus is usually found on the upper surface of leaves or fruit. Leaves often turn yellow or brown, curl up, and drop off. New foliage emerges crinkled and distorted. Fruit is dwarfed and often drops early.
Prevention and Control: Plant resistant varieties and space plants properly so they receive adequate light and air. Always water from below, keeping water off of foliage. This is paramount for roses. Go easy on the nitrogen fertilizer. Apply fungicides according to label directions before problem becomes severe and follow directions exactly, not missing any required treatments. Clean up, remove, and destroy all leaves, flowers, and debris in the fall.
Leaf Spots
These brown or black spots and patches (ragged or circular, with water soaked or yellow-edged appearance) can be caused by a variety of bacteria and fungi. Insects, rain, dirty garden tools, or people can spread bacteria.
Prevention and Control: Remove infected leaves, water plants at the base, and avoid spraying foliage when watering. Use sulfur spray on woody plants in winter.
Sooty Mold
A fungus found on the surface of leaves, sooty mold feeds on honeydew excreted from aphids, mealybugs, scale, or ants. Though it is not serious, it is unattractive and can spread by splashing water. The best way to eliminate sooty mold is to control the insects that make the honeydew. Wash away sooty mold by wiping from leaves with a damp cloth or with a hose-end sprayer.
How-tos:
Rejuvenate Freeze-Damaged Plants
Freeze damaged plants often recover if pruned. Cutting back the dead tissue and surviving buds (even from below the surface) may rejuvenate the plant. Frost damaged foliage, especially new growth, turns black a few days after being “”burnt.”” You can tell if a stem is alive by scraping the bark off a bit. If the tissue is alive the green cambium layer will show. If the tissue is brown, test the branch a little further down. Cut when you hit green.
About Pruning
Pruning is one of the most commonly misunderstood aspects of plant care maintenance. Pruning does not hurt plants; rather it is often necessary to prune in order to maintain plant health. On the other side of the coin, not all plants must be pruned. Prune to remove weak, diseased or dead branches; to correct damage from wind and ice storms; to thin dense growth; to reduce the size of a plant that has gotten too big for a landscape; to cut down on water loss after transplanting; to give a plant a special shape such as a hedge or topiary; to remove dead flowers and seed pods; to encourage flowers and fruit; and to rejuvenate a tired old shrub.When pruning first think, then cut. Look at the plant from all angles. Visualize the outcome before you cut. Start with obvious problems like diseased and dead wood, or crossing and crowded limbs. Avoid damaging bark and leaving too much exposed cut surface. Cut close buds without injuring them. Cut at a 45 degree angle unless buds are opposite, in which case cuts may be perpendicular to the branch. Prior to pruning, make sure that blades are sharp so wood does not tear and split. This prevents dieback and wounds where disease and insects may enter. Recent studies show that wound sealant does not enhance healing.
Preparing Garden Beds
Use a soil testing kit to determine the acidity or alkalinity of soil prior to beginning. This helps determine which plants are best suited for your site. Check soil drainage and correct drainage where water remains standing. Clear weeds and debris from planting areas and continue to remove weeds as soon as they come up.
At 7-10 days before planting, add 2-4 in. of manure or compost and work into the planting site to improve fertility. If soil composition is weak, add a layer of topsoil as well. Whether sand or clay, soil can be improved by adding ample organic matter. Work deep into the soil. Prepare beds 18 in. deep for perennials. This considerable effort will pay off later. It’s a bigger job once plants have become established.
Fertilizing Young Plants
Young plants need extra phosphorus to encourage root development. A starter fertilizer such as 6-18-6 or sterilized bonemeal helps satisfy this need. Apply recommended amount for plant per lable directions at time of planting or at least during the first growing season. Phosphorus does not ”move” in the soil like nitrogen or potassium, therefore most fertilizers have lower middle numbers. The second growing season, switch to a 16-4-8 or other comparable fertilizer with a 4:1:2 ratio.
Fertilizing Established Plants
Established plants benefit from a yearly fertilization. If you have a sandy soil, fertilizing twice per year may be in order. Apply a 16-4-8 or 4:1:2 fertilizer according to label directions, but do not forego the soil test. Organic mulches greatly benefit all plants, keeping roots cool, weed down, moisture in, and enriching the soil. Never fertilize just before frost; this encourages new growth that will be burned by cold weather. The safest time to fertilize is early spring or when you know that new growth will not suffer damage from late frost.
Fertilizing Houseplants
Houseplants may be fertilized with either water-soluble, quick release fertilizers, temperature controlled slow-release fertilizers, or organic fertilizers such as fish emulsion. Water soluble fertilizers are used every two weeks or per lable instructions. Controlled, slow-release fertilizers are worked into the soil usually only once during the growing season or per label directions. For organic fertilizers, such as fish emulsion, follow label directions.
Pinching and Thinning Perennials
Merely planting a perennial does not assure years of maintenance-free gardening. Perennials need care, just like any other plant. One thing that distinguishes perennials is that they tend to be active growers that have to be thinned out occasionally or they loose vigor.
As perennials establish, they require occasional pruning back and thining out. This prevents them from completely taking over an area to the exclusion of other plants, and increases air circulation thereby reducing the incidence of diseases like botrytis and powdery mildew.
Many species also flower abundantly and produce ample seed. As blooms fade it is advisable to deadhead plants; that is, remove spent flowers before they form seed. This prevents plants from seeding all over the garden and conserves the considerable energy it takes the plant to produce seed.
As perennials mature, they may form dense root masses that eventually sap vigor. Occasionally thin out a stand of such perennials. Divide the root system, making new plants to plant in another area of the garden or to give away. This root pruning will also stimulate new growth and rejuvenate the plant. Most perennials may be successfully divided in either spring or fall, with fall being the favorite because roots are allowed to develop without producing food for growing tops during the winter dormancy period.
Preparing Containers
Containers are excellent when used for their ornamental value, as a planting option when there is little or no soil, or for plants that require a soil type not found in the garden. When growing more than one plant in a container, make sure that all have similar cultural requirements. Choose a container that is deep and large enough to allow root development and growth as well as proportional balance between the fully developed plant and the container. Plant large containers in the place you intend them to stay. All containers should have drainage holes. A mesh screen or paper coffee filter placed over the hole will keep soil from washing out. It is not necessary to add pebbles or broken crockery to the bottom of the pot, especially if you are using a high quality potting soil. The potting soil you select should be an appropriate mix for the plants you have chosen. Quality soils (or soil-less media) absorb moisture readily and evenly when wet. Water running off of soil upon initial wetting indicates a need for amendment.
Prior to filling a container with soil, wet the potting soil in a tub or wheelbarrow until evenly moist. Fill container about halfway full or to a level that allows plants to be just below the rim of the pot. Rootballs should be level with soil line when the project is complete. You may add a layer of decorative moss, mulch, or pebbles to top of pot to hold soil in place. Water well.
Planting Perennials
Determine appropriate perennials for your garden by considering sun and shade through the day, exposure, water requirements, climate, soil makeup, seasonal color desired, and position of other garden plants and trees.The best times to plant are spring and fall, when soil is workable and out of danger of frost. Fall plantings have the advantage that roots can develop without competing with developing top growth as in spring. Spring is more desirable for perennials that dislike wet conditions or for colder areas, allowing full establishment before first winter. Planting in summer or winter is not advisable for most plants, unless planting a more established one gallon sized container.
To plant container-grown plants: Prepare planting holes with appropriate depth and space between. Water plants thoroughly and let excess water drain before carefully removing from containers. Carefully loosen the root balls and place the plants in holes, working soil around the roots as you fill. For extremely root bound plants, gently separate roots with fingers. A few slits made with a pocket knife are OK, but keep to a minimum. Continue filling in soil, then water thoroughly, protecting from direct sun until stable.
To plant bare-root plants: Plant as soon as possible after purchase. Prepare suitable planting holes, spread and work soil among roots as you fill in. Water well and protect from direct sun until stable.
To plant seedlings: A number of perennials produce self-sown seedlings that can be transplanted. You may also start your own seedling bed for transplanting. Prepare suitable planting holes, spacing appropriately for plant development. Gently lift each seedling and as much surrounding soil as possible with your garden trowel, and replant it immediately, firming soil with fingertips and water well. Shade from direct sun and water regularly until stable.
Preparing Raised Peat Beds
Prepare raised peat beads for plants that require acid soil in a garden that is alkaline or when heavy clay does not permit planting into the soil. Mound beds on top of existing grade, as when planting azaleas and rhododendron, or construct sides with any appropriate building materials (brick, logs, rocks, etc.). Layer the bottom with stones or other coarse material appropriate for drainage, at least 2-3 in., add a layer of 3-6 in. of peat and fill in with topsoil appropriate for your planting selection.
Pests:
Mealybugs
Small, wingless, dull-white, soft-bodied insects that produce a waxy powdery covering. They have piercing mouth parts that suck the sap out of plant tissue. Mealybugs often look like small pieces of cotton and they tend to congregate where leaves and stems branch. They attack a wide range of plants. The young tend to move around until they find a suitable feeding spot, then they hang out in colonies and feed. Mealybugs can weaken a plant leading to yellow foliage and leaf drop. They also produce a sweet substance called honeydew (coveted by ants) which can lead to an unattractive black surface fungal growth called sooty mold.
Prevention and Control: Control ants, which want mealybugs around for the honeydew they produce. Isolate infested plants from those that are not infested. For small plants you might treat with a cotton swab soaked in a 50% rubbing alcohol solution. Encourage natural enemies such as lady beetles in the garden. On citrus and large ornamentals, spray with a horticultural oil on overcast day as not to burn leaves. Severe infestations may be treated with pyrethrum, neem, malathion, or acephate (ornamentals only).
Whiteflies
Whiteflies are small, winged insects that look like tiny moths, which attack many types of plants. The flying adult stage prefers the underside of leaves to feed and breed. Whiteflies can multiply quickly as a female can lay up to 500 eggs in a life span of 2 months. If a plant is infested with whiteflies, you will see a cloud of fleeing insects when the plant is disturbed. Whiteflies can weaken a plant eventually leading to plant death if they are not checked and they can transmit many harmful plant viruses. They also produce a sweet substance called honeydew (coveted by ants) which can lead to an unattractive black surface fungal growth called sooty mold.
Possible controls: keep weeds down, use screening in windows to keep them out, remove infested plants away from non-infested plants, use a reflective mulch (aluminum foil) under plants (this repels whiteflies), trap with yellow sticky cards, apply labeled pesticides such as soaps and oils, take advantage of natural enemies such as parasitic wasps in the garden, and sometimes a good steady shower of water will wash them off the plant.
Slugs and Snails
Slugs and snails favor moist climates and are mollusks, not insects. They can be voracious feeders, eating just about anything that is not woody or highly scented. They may eat holes in leaves, strip entire stems, or completely devour seedlings and tender transplants, leaving behind tell-tale silvery, slimy trails.
Prevention and control: Keep your garden as clean as possible, eliminating hiding places such as leaf debris, over-turned pots, and tarps. Ground cover in shady places and heavy mulches provide protection from the elements and can be favorite hiding places. In the spring, patrol for and destroy eggs (clusters of small translucent spheres) and adults during dusk and dawn. Drop them in a container of kerosene or sprinkle them with salt (not for the squeamish). Set out beer traps from late spring through fall – slugs are suckers for fresh brew and will drown as they greedily drink. Spray adults with a 30% solution of household ammonia.
Some gardeners believe that copper stripping, stood upright like a short fence, will help to protect young vegetables. It is believed that the copper reacts with the slug’s or snail’s slime, causing a shock. Stripping works best if stood upright. Many chemical controls are available on the market, but can be poisonous and deadly for pets; take care when using them as directed by the lable. Slugo is one chemical that works well on slugs and snails and seems to be safe to use around pets.
Thrips
Thrips are small, winged insects that attack many types of plants and thrive in hot, dry conditions (like heated houses). They multiply quickly as a female lays up to 300 eggs in a lifespan of 45 days without mating. Most of the damage to plants is caused by the young larvae which feed on tender leaf and flower tissue. This leads to distorted growth, injured flower petals and premature flower drop. Thrips also transmit many harmful plant viruses.
Prevention and Control: Keep weeds down and use screening on windows to keep them out. Remove or discard infested plants, keeping them away from non-infested plants. Trap with yellow sticky cards or take advantage of natural enemies such as predatory mites. Sometimes a good steady shower of water will wash them off the plant. If thrips are found on annuals, forego the color and get rid of all plants rather than treating. If the infestation is on established ornamentals, prune and discard infected areas. You may spray, after bloom, with an insecticide containing pyrethrum, rotenone, neem, diazanon, malathion or acephate. Do not use systemics on edibles, especially roses, rose petals, or rose hips that may be eaten or used in baths or perfumes.
Spider Mites
Spider mites are small, 8 legged, spider-like creatures which thrive in hot, dry conditions (like heated houses). Spider mites feed with piercing mouth parts, causing plants to appear yellow and stippled. Leaf drop and plant death can occur with heavy infestations. Spider mites can multiply quickly, as a female lays up to 200 eggs in a life span of 30 days. They also produce a web which can cover infested leaves and flowers.
Prevention and Control: Keep weeds down and remove infested plants. Dry air seems to worsen the problem, so make sure plants are regularly watered, especially those preferring high humidity such as tropicals, citrus, and tomatoes. Always check new plants prior to bringing them home from the nursery. Take advantage of natural enemies such as ladybug larvae. Sometimes a good steady shower of water will wash them off the plant. Dusting edibles with sulfur kills mites too. Insecticidal soaps can be used, but confirm that it is OK for vegetables prior to spraying. On citrus or ornamentals, spray with horticultural oil such as Sunspray. Insecticides don’t kill mites because mites are not insects. Mitacides must be used, but always verify safety for your ornamental. Never use on food.
Scale Insects
Scales are troublesome pests related to mealybugs that infest an enormous variety of plants. They can appear as stationary teardrop-sized lumps of brown, cream, or black on stems and leaves, or as cottony masses, but there are many variations. These visible signs are actually the adult females, which lose their legs, lay eggs, and die … leaving the shells of their bodies to protect the eggs. When the young hatch, they crawl along the stems and leaves until they find a good feeding site, then settle down and repeat the process. Scales weaken plants by sucking sap from its tissues with their piercing mouthparts, leading to yellow foliage and leaf drop. They also produce a sweet substance called honeydew (coveted by ants) that can lead to an unattractive black surface fungal growth called sooty mold.
Prevention and Control: Once established, they are hard to control—contact sprays are minimally effective since young are well protected by their shell covering for most of their lives. Isolate infested plants. Where practical, remove scale by hand and apply rubbing alcohol to the area to eliminate the eggs and young beneath. Alternatively, prune all infested branches and destroy—don’t compost. Dormant oil sprays in winter are usually effective at keeping populations under control. Insecticidal sprays labeled for use against scale will only yield good results if used when the young are in the ‘crawler’ stage, the timing of which can be tricky at best. Finally, encourage natural enemies such as parasitic wasps in the garden.
Tools:
Tools for Pruning
Proper tools for pruning may include hand pruning shears for twigs and small branches, lopping shears for thicker branches, hedge clippers, pruning saws for large branches, and power tools. Keep cutting edges sharpened to make clean cuts. Clean tools between uses to avoid spreading plant diseases and lightly oil tools to avoid rusting.