Annual plants complete their life cycle in a single season; seeds germinate and the plant grows, blooms, sets seeds and dies in one year or less. Even the smallest garden has room for annuals. This can be no more than a few pots or hanging baskets of petunias or marigolds. Today’s trend toward low maintenance landscapes (with paving and gravel ground covers) does not preclude the use of annuals. In fact, these areas often need more color for interest.
Annuals can provide a succession of bloom throughout the year. In southern Nevada annuals are planted several times during the year. Plant September-November for winter and spring color. Plant March-June for summer color.
Annuals grow best in a well-drained soil rich in plant nutrients. If the soil is very poor and rocky or consists mostly of caliche, remove it to a depth of 6 to 12 inches and replace with soil containing organic material.
Organic matter should be added to an existing flowerbed every year. For a new flowerbed, spread a 2- to 4-inch layer of organic matter over the garden area. For a 100 square-foot area, spread 1 to 2 pounds of commercial or organic fertilizer and 5 to 7 pounds of soil sulfur over the compost or organic matter. Spade these amendments into the top foot of soil. Level and moisten the area before planting. If in doubt of pH of soil, a soil test by a nursery or lab is recommended. If annuals are planted year after year in the same bed as is done in commercial plantings, soil should be sterilized or replaced once every year or so. Soil pathogens can build up and kill newly planted annuals.
Before planting seeds, check the package directions for recommended planting depth. Make sure the beds have been prepared properly. Seeds most often fail to germinate or survive as seedlings due to lack of consistent and frequent irrigation. On the back of the seed packet you will find specific directions. You can sow in rows or broadcast the seed at the depth recommended on the package. After planting from seed, sprinkle a light layer of mulch over the area and firm the soil with the back of a rake. Soak the seeded bed with a fine misting sprayer. If you have to water by hand, adjust the nozzle to a fine spray and go back and forth over the bed until the soil is well soaked. Do not use a strong jet of water or it will displace the seed and create puddles of water. Always keep the soil moist until the seeds germinate. This usually takes seven to ten days after which watering can be less frequent.
If you want to get a head start, start the seeds indoors. This method also protects the seedlings from possible attack by other living organisms until they become established. This method is more successful than direct seeding for most annuals. It will take a month or two for the seedlings to mature enough to be set outside If you sow seeds too early, the seedlings will be leggy and root bound when planting time arrives. Use commercial potting mix for best results. Soil from the garden is a poor choice because it could contain weed seeds, insects and fungus. It will drain poorly and become waterlogged. Then fill the flat or container with the soilless mix until it is ½ inch from the top. Before planting the seed, check the package directions for recommended planting depth. Scatter the seeds on the surface and cover with the media to the recommended depth and firm with a flat board. Then cover the soil with a dampened piece of newspaper or paper towel and place it in a warm spot, but not in direct sun. Moisten when needed. After three or four days, begin checking daily for signs of sprouting. When the first sprouts appear, remove the paper and place the container in more light (filtered sun), but not direct sunlight. Then when the seeds have developed two sets of true leaves, transplant them into 2-inch pots, Styrofoam cups with drain holes or peat pots filled with moist soilless media or sand. To do this, loosen the soil around each plant, gently grasp one of the leaves and carefully pull out the seedling. Use a pencil to poke a hole in the new planting mix, drop the seedling in and firm the soil around it. Keep the plants in the shade a day or two; then move them into filtered light until they are ready to be set out permanently.
Bedding plants purchased in plastic flats, six packs or small containers usually have pot-bound root systems. As with all plants, buy only those that are disease, insect and weed free. If planted intact, the root system will be slow to establish in the surrounding soil and the plants will suffer moisture stress. A preferred method is to loosen and untangle the root system without breaking the soil ball. Plants will usually recover rapidly and become established quickly. Spacing of plants in a bed should be based on the directions included on the nursery identification tag. Bedding plants must be watered immediately after planting and then daily until they have become established. After establishment, they should be watered on an “as-needed” basis. Wilting will reduce flowering on many bedding plants and should not be allowed to happen. Frequency of watering depends on the soil type, exposure to sunlight and wind, variety of the bedding plants and season of the year.
Weeds should be controlled either by mulching and/or hand weeding. Herbicides can be used, but only as a last resort. Compost and many wood and bark mulches are composed of fine particles and should not be applied any deeper than 2 to 3 inches. Never place compost or organic mulch next to the stems of plants because this can encourage stem rot. If a good time-release fertilizer has been used at planting, little, if any additional fertilizer, will be needed. The compost incorporated at planting will also add nutrients. Both liquid and granular fertilizer can be added, as needed, during the growing season. Remember—a lower nitrogen fertilizer will help encourage minimal growth and good flowering. After flowers have completed their blooming cycle, cut or pinch off faded blossoms to promote more flowering. The object of pinching off these faded blooms is to prevent the development of unsightly seed heads that drain energy from the plant that would otherwise be used in flowering. Insects and disease can also be problems to annuals. Plants should be checked on a regular basis. At the first sign of a problem, the less toxic method of control should be used. Never spray any chemical control until the problem is correctly identified and no other method is available. Winter annuals are cold hardy, but the blooms are not. During severe cold temperature, they should be covered with blankets or commercial row covers. Never use plastic next to plant material.
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Roberts, A., and Robinson, M. L., 1998, Plant Annuals for Color, Extension, University of Nevada Reno, FS-98-94
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