Tidewater Gardening - August 2008

Summer At Its Peak


K. Marc Teffeau

    August is the time for vacations, heat and dryness in the garden and landscape. It is also time to start preparing for the fall. Insect and disease problems are now at their peak. Take our tiny friend the spider mite. There are different kinds of spider mites but they all thrive in hot, dry weather and they leave webs on the underside of the leaves of shrubs in which they lay their eggs. The grayish, stippled appearance of leaves infested with spider mites is a result of their feeding on the plant juices. For mild infestations, hose the foliage to wash off the mites. You could also try some of the soap sprays that are on the market. Be sure to spray the undersides of the plant’s leaves or needles for best control.
     When spraying for insect and mite control on plants, be sure to water your plants several hours before applying pesticides, especially during dry weather. Drought-stressed plants have less water in their tissues so the chemicals that enter the leaves will be more concentrated and may burn the leaves. Whenever you apply pesticides, adhere strictly to the directions on the package. Do not spray when temperatures are over 85° or when it is windy.
     A general cleanup of the flower bed is in order at this time, even though its hot outside and you might not feel like it. I suggest you do it a little bit before dusk when the air temperature is starting to cool down. Pulling out plants that have gone past their prime is an important method of preventing a build-up of disease and insect problems.
     Plants suspected of viral and fungal diseases should be removed and disposed of. Do not put diseased plant material in the compost pile. The longer these plants are left laying in the garden, the greater the chance for carrying over problems to next year. Clean up fallen rose and peony leaves as they can harbor disease and insect pests over the winter if allowed to remain on the ground.
     Deadhead (remove) the spent flowers on your annuals and perennials to make sure that your hybrid, annual flowers do not go to seed. This weakens the plants and reduces bloom. In addition, the seed of annual flowers is not desirable to save because the resulting seedlings usually will be very different from the parent and often of poorer quality. Do not allow phlox to go to seed. Seedlings do not come true to parent color and may overtake your planting, giving the impression that the parent plants have reverted.
     Keep tall flowers staked and remove dead stalks. Also, don’t forget to weed. Letting existing weeds go to seed will just increase your weed problem next year. Do not add weeds with ripened seed heads to the compost pile. Many weed seeds can remain viable and germinate next year when the compost is used.
     August is the time to carefully water the garden and landscape, especially if we have been short on thunderstorms coming through the area and dropping some moisture. It is important that you water correctly during this period.
     First, realize that lack of water, especially when coupled with intense heat, slows down many biological processes in plants. This is called heat dormancy, although lack of moisture is as responsible for it as the heat.
     Plants compensate for the stress by relative inactivity. Ordinary cultural practices, instead of being beneficial, can induce further stress. Fertilizers will burn dry root hairs; pruning can force the plant to use reserves to make new growth and pesticides may be toxic to dry foliage.
     Plants look wilted on hot afternoons even when there is moisture in the soil. Their roots can’t take up water fast enough to compensate for the water being lost through the leaves. If there is enough soil moisture, plants will recover by late afternoon. If they don’t perk up, water deeply.
     It is especially important to keep newly planted trees and shrubs well watered. Many plants, including camellias and rhododendrons, are starting buds for next season’s bloom. Immature berries of hollies and pyracantha may drop if the plants are water stressed. Since newly planted container-grown plants have a limited area from which to absorb water, plants in a sunny location may require watering several times a day. Check plants often to avoid water stress.
     Mulched shrubs may not develop mature stem tissue where they touch the mulch. To harden stems so they can withstand early frost damage, remove about 2 to 3 inches of the mulch from the base of the stems in mid-August. Also, avoid deep cultivation around evergreens that have roots near the ground surface so that roots are not damaged.
     Avoid deep cultivation in your flower beds during hot, dry August days. Loosening the soil under these conditions reduces water uptake by increasing loss of soil moisture and damaging surface roots. Plants often look much worse after cultivation than before.
     Take cuttings of your favorite annuals or sow seeds in pots for winter flowering indoors. Bedding plants that root easily are coleus, geraniums, impatiens, wax begonias and fuchsia. Many plants in the flower border will make excellent house plants this winter. Those that are easy to maintain indoors are begonia, coleus, geranium and ivy. If they are already being grown in containers, it is a simple matter to bring them indoors.
     Start moving them in at night when the temperature drops below 60° to maintain their vigor and flower production. For optimum bloom, locate the plants where they receive sunlight equivalent to what they received outdoors.
     If you are planning to take some garden plants indoors for early fall bloom, use a sharp knife to root prune them now to a size a little smaller than the pot. Remove all buds and flowers and cut back the top growth severely. Water well until you are ready to pot them.
     Be sure to order peony roots or buy now for planting in September. Plant the roots about a month before the average first frost date in our area, which is toward the end of October. The planting should be completed before the first killing frost occurs.
     Plant bulbs of the hardy amaryllis or magic lily in August. They will produce foliage in the spring that dies down by late summer. Clusters of six to nine lily-like pink flowers borne on 3-foot stalks appear in August. The bulbs will live almost indefinitely and grow better if not disturbed.
     With a little watering and mulching, most fibrous-rooted perennials can be moved during any season. Move them in some of their own soil, and don’t let them wilt. Fleshy-rooted and tap-rooted perennials are best moved when dormant.
     Oriental poppies can be safely planted, transplanted or divided this month. Plant these hardy long-lived perennials in well-drained soil in full sun. However, do not mulch oriental poppies. They prefer hot sun-baked ground while resting.
     Keep roots of lilies cool for best growth. Unless the foliage of surrounding plants shades the roots, mulch the ground with grass clippings or similar weed-free material.
     The best time to buy chrysanthemums is in late summer, as soon as they become available. For a longer blooming period, choose plants that are just coming into bud instead of those already in full bloom. For mums already in the landscape, do some disbudding to produce larger blooms. Most mums, except spray types, respond well to disbudding.
     A favorite fall flowering plant is the Stonecrop sedum, Sedum spectabile. This is a succulent, pest-resistant perennial which grows about 18 inches high. Flat clusters of magenta-pink flowers open in late summer, attracting both honeybees and butterflies. Since its flower heads turn reddish-bronze and persist into winter, this easy-to-grow plant can be the backbone of the fall garden. The flower clusters are also attractive in dried arrangements. The cultivar ‘Autumn Joy’ is outstanding.
     Start selecting your favorite spring flowering bulb varieties now by searching out bulb catalogs. It is time to order so bulbs can be planted this fall. A good guideline to use is ‘biggest is best’ in regard to bulb size. Be careful about so-called “bargain” bulbs as they may be small or of inferior quality.
    In the vegetable garden, temperatures over 90° can cause blossoms to drop off tomatoes, pepper and squash. Blossom end rot – patches on the bottom/blossom end of tomatoes and peppers can occur now. This condition is prompted by uneven watering and calcium transport in the plant. Cut off the discolored part of the tomato or pepper and eat the rest. Even watering and mulching should eliminate the problem.
     Plant your fall vegetable crops now – snow peas, green peas, spinach and lettuce. They all need to go in by mid-August. Start lettuce seed in containers and keep them cool until the seeds germinate, then transplant.
     Harvest onions and garlic when the foliage starts to die back. You can try braiding these alliums by pulling the bulbs and letting the foliage wilt. Use a piece of string to help you braid them together.
     Happy gardening!!!