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  MG Manual Reference
Ch. 14, pp. 6 - 12

[ Annuals: culture and maintenance | controlling insects and diseases | special uses | special uses cont. | environments ]

Annual flowers live only one growing season, during which they grow, flower, and produce seed, thereby completing their life cycle. Annuals must be set out or seeded every year since they don't persist. Some varieties will self-sow, or naturally reseed themselves. This may be undesirable in most flowers because the parents of this seed are unknown and hybrid characteristics will be lost. Plants will scatter everywhere instead of their designated spot. Examples are alyssum, petunia, and impatiens. Some perennials, plants that live from year to year, are classed with annuals because they are not winter-hardy and must be set out every year; begonias and snapdragons are examples. Annuals have many positive features. They are versatile, sturdy, and relatively cheap. Plant breeders have produced many new and improved varieties. Annuals are easy to grow, produce instant color, and most important, they bloom for most of the growing season.
There are a few disadvantages to annuals. They must be set out as plants or sowed from seed every year, which involves some effort and expense. Old flower heads should be removed on a weekly basis to ensure continuous bloom. If they are not removed, the plants will produce seed, complete their life cycle, and die. Many annuals begin to look disreputable by late summer and need to be cut back for regrowth or replaced.
Annuals offer the gardener a chance to experiment with color, height, texture, and form. If a mistake is made, it's only for one growing season. Annuals are useful for filling in spaces until permanent plants are installed, to extend perennial beds and fill in holes where an earlier perennial is gone or the next one has yet to bloom; to cover areas where spring bulbs have bloomed and died back; and to fill planters, window boxes, and hanging baskets.
Culture and maintenance of annuals Top

Site Selection. Consider aspects of the site that affect plant growth such as light, soil characteristics, and topography. Different annuals perform well in full sun, light shade, or heavy shade. The slope of the site will affect temperature and drainage. Soil texture, drainage, fertility, and pH influence plant performance.
Site Preparation. Preparation is best done in the fall. Proper preparation of soil will enhance success in growing annuals. First, have the soil tested and adjust the pH if needed. Check and adjust drainage. To do this, dig a hole about 10 inches deep and fill with water. The next day, fill with water again and see how long it remains (should not exceed 8 hours). If drainage is poor, plan to plant in raised beds. The next step is to dig the bed. Add 4 to 6 inches organic matter to heavy clay to improve soil texture. Dig to a depth of 12 or 18 inches and leave "rough" in fall or early spring. Finally, in spring, add fertilizer, spade again, and rake the surface smooth.
Seed Selection. To get a good start toward raising vigorous plants, buy good seed packaged for the current year. Seed saved from previous years usually loses its vigor. It tends to germinate slowly and erratically and produce poor seedlings. Keep seed dry and cool until planted. If seed must be stored, place in an air-tight container with powdered milk to absorb excess moisture, and refrigerate. When buying seed, look for new varieties listed as hybrids. Plants from hybrid seed are more uniform in size and more vigorous than plants of open-pollinated varieties. They usually produce more flowers with better substance.

Make shallow depressions in the medium to facilitate uniform seeding.

Sow the seeds thinly and evenly, then label each variety
Starting Plants Indoors. The best media for starting seeds is loose, well-drained, fine-textured, low in nutrients, and free of disease-causing fungi, bacteria, and unwanted seeds. Many commercial products meet these requirements. Fill clean containers about 2/3 full with potting medium. Level the medium and moisten it evenly throughout. It should be damp but not soggy. Make a furrow an inch deep. Sow large seed directly in the bottom of the furrow. Before sowing small seed, fill the furrow with vermiculite; sow small seed on the surface of the vermiculite. Seed may be sown in flats following seed package directions or directly in individual peat pots or pellets, two seeds to the pot. After seed is sown, cover all furrows with a thin layer of vermiculite, then water with a fine mist. Place a sheet of plastic over seeded containers and set them in an area away from sunlight where the temperature is between 60 and 75º F. Bottom heat is helpful. As soon as seeds have germinated, remove plastic sheeting and place seedlings in the light. If natural light is poor, fluorescent tubes can be used. Place seedlings close to the tubes. After germination remove the plastic from the container, the new plants need watering and fertilizing, since most planting material contains little or no plant food. Use a mild fertilizer solution after plants have been watered. When seedlings develop two true leaves, thin plants in individual pots to one seedling per pot. Transplant those in flats to other flats, spacing 1 or more inches apart, or to individual pots.

Cover seeds with dry vermiculite, then water carefully
Planting Times. Do not be in a rush to start seeds outdoors or to set out started plants. As a general rule, delay sowing seed of warm-weather annuals outdoors or setting out started plants until after the last frost date. Most such seeds will not germinate well in soils below 60º F. If soil is too cold when seed is sown seeds will remain dormant until soil warms, and may rot instead of germinating. Some cold-loving annuals, like larkspur or Shirley poppies, should be sown in late fall or very early spring.
Sowing Seed Outdoors. Annuals seeded in the garden frequently fail to germinate properly because the surface of the soil cakes and prevents entry of water. To avoid this, sow seed in vermiculite-filled furrows. Make furrows in soil about one inch deep. If soil is dry, water the furrow, then fill it with fine vermiculite and sprinkle with water. Then make another shallow furrow in the vermiculite and sow the seed in this furrow. Sow at the rate recommended on the package. Cover the seed with a layer of vermiculite, and using a nozzle adjusted for a fine mist, water the seeded area thoroughly. Keep the seed bed well-watered or cover with a mulch, such as newspaper, to prevent excess evaporation of water. Remove mulch promptly after germination starts, so that young seedlings will receive adequate sunlight.
Setting Out Transplants. By setting started plants in the garden you can have a display of flowers several weeks earlier than if you sow seeds of the plants. This is especially useful for annuals (such as verbena and scarlet sage) which germinate slowly or need several months to bloom. You can buy plants of these or other annuals or you can start your own. Buy only healthy plants, free of pests and diseases. Before setting out transplants, harden them off by exposing them to outside conditions during the day which will provide more light and cooler temperatures than they received inside. After the last frost date, annual plants may be set out. Dig a hole for each plant large enough to accept its root system comfortably. Lift out each plant from its flat with a block of soil surrounding its roots. Set the soil block in a planting hole and backfill it so the plant sets at the same level. Irrigate each hole with a starter solution of high phosphate fertilizer which is water-soluble. Follow package directions.
If plants are in fiber pots, remove the paper from the outside of the root mass and set the plant in a prepared planting hole. When setting out plants in peat pots, set the entire pot in the planting hole, but remove the upper edges of the pot so that all of the peat pot is covered when soil is firmed around the transplant. If a lip of the peat pot is exposed above the soil level, it may produce a wick effect, pulling water away from the plant and into the air. After setting the plants, water them with a starter solution as described above. Provide protection against excessive sun, wind, or cold while the plants are getting settled in their new locations. Inverted pots, newspaper tunnels, or cloches can be used.
Thinning. When most outdoor-grown annuals develop the first pair of true leaves, they should be thinned to the recommended spacing. This spacing allows plants enough light, water, nutrients, and space for them to develop fully above and below the ground. If they have been seeded in vermiculite-filled furrows, excess seedlings can be transplanted to another spot without injury. Zinnias are an exception to this rule of thinning. In many varieties of zinnias, flowers will appear with a large, nearly naked corolla and few colorful petals. This phenomenon is sometimes referred to as Mexican hats. To avoid such plants in your garden, sow two or three seeds at each planned location. Wait until the plants bloom for the first time, then remove the plants with this undesirable characteristic. Thin the remaining plants to the recommended 8 to 12 inch spacing. Another exception to the rule for thinning is sweet alyssum. This annual is particularly susceptible to damping-off. To insure a good stand of plants, sow the seed in hills and do not bother to thin the seedlings.
Watering. Do not rely on summer rainfall to keep flower beds watered. Plan to irrigate them from the beginning. When watering, moisten the entire bed thoroughly, but do not water so heavily that the soil becomes soggy. After watering, allow the soil to dry moderately before watering again. A soaker hose or drip tape are excellent for watering beds. Water from the soaker hose or drip tape seeps directly into the soil without waste and without splashing leaves and flowers. The slow-moving water does not disturb the soil or reduce its capacity to absorb water. Water wands are also good. Sprinklers are not as effective as soaker hoses. Water from sprinklers wets the flowers and foliage, making them susceptible to diseases. Structure of the soil may be destroyed by impact of water drops falling on its surface; the soil may puddle or crust, preventing free entry of water and air. The least effective method for watering is with a hand-held nozzle. Watering with a nozzle has all the objections of watering with a sprinkler. In addition, gardeners seldom are patient enough to do a thorough job of watering with a nozzle; not enough water is applied, and the water that is applied is usually poorly distributed over the bed.
Mulching. Mulches help keep the soil surface from crusting and aid in preventing growth of weeds; organic mulches can add humus to the soil. Grass clippings make a good mulch for annuals, if they do not mat. Sheet plastics also may be spread over the soil surface to retard evaporation of water and to prevent growth of weeds. However, these materials are unsightly for use in the flower garden.
Weeding (cultivating). After plants are set out or thinned, cultivate only to break crusts on the surface of the soil. When the plants begin to grow, stop cultivating and pull weeds by hand. As annual plants grow, feeder roots spread between the plants; cultivation is likely to injure these roots. In addition, cultivation stirs the soil and uncovers weed seeds that then germinate.
Deadheading (removing old flowers). To maintain vigorous growth of plants and assure neatness, remove spent flowers and seed pods. This step is particularly desirable if you are growing ageratum, calendula, cosmos, marigold, pansy, scabiosa, or zinnia.
Staking. Tall-growing annuals like larkspur, or tall varieties of marigold or cosmos, need support to protect them from strong winds and rain. Tall plants are supported by stakes of wood, bamboo, or reed large enough to hold the plants upright but not large enough to be conspicuous. Stakes should be about 6 inches shorter than the mature plant so their presence will not interfere with the beauty of the bloom. Begin staking when plants are about 1/3 their mature size. Place stakes close to the plant, but take care not to damage the root system. Secure the stems of the plants to stakes in several places with paper-covered wire or other materials that will not cut into the stem. Plants with delicate stems (like cosmos) can be supported by a framework of stakes and strings in crisscrossing patterns.
Fertilizing. When preparing beds for annuals, fertilizer should be added according to recommendations given by soil sample analysis, or derived from observation of plants that have grown on the site. Fertilizer should be added in the spring so it will not leach out before plants can benefit from it.
Once annuals have germinated and begin to grow, additional fertilizers may be needed. This is especially true if organic mulches are added, because microorganisms decomposing the mulch take up available nitrogen. Thus a fertilizer high in nitrogen should be used in these situations. A teaspoon of 10-6-4 per plant every 2 to 3 weeks is sufficient. Be sure to work the fertilizer in around the plants in such a way as to avoid direct contact between the stems and the fertilizer. Apply fertilizers to damp soil.

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