If you want plants that come to flower quickly and provide a long season of blooms, choose annuals. They are among the most adaptable of garden plants, demanding little more than good light, sufficient water, and reasonably fertile soil. Even if your conditions fall short of this ideal, you will likely find annuals that will work for you. In fact, some of the most striking annual gardens are found in what would appear to be the most inhospitable places.
Here are some general guidelines for planting and maintaining annuals.
Soil
The majority of annuals prefer full sun and well-drained soil with a moderate humus content. If your soil is clay, you can amend it with compost or well-rotted manure; after the first year, you should need only a light reapplication in spring.
Some annuals, including cosmos, gazania and nasturtium, require little in the way of fertilizer and, in fact, do better in relatively infertile soil. Portulaca is at its best where the soil is poorest, which is why its multicoloured roselike blossoms brighten so many seaside gardens. You will reap only frustration trying to grow the plant in fertile soil. The same holds true for poppies, whose gorgeous blooms are at their best in the dry, fast-draining soil of stony banks and alpine rock gardens.
PH
If your soil PH falls within the 6.0-7.4 range, you should be able to grow most annuals. If test reveal that your soil is too acid or alkaline, it can be altered with amendments, such as lime for acid soil and aluminium sulphate for alkaline soil. Some soils, specifically those found in the desert Southwest, are extremely alkaline and can’t be modified sufficiently to suit the vast majority of annuals. This doesn’t mean that Southwesterners are consigned to cultivating cactus. There are annuals, such as sweet pea, dianthus and strawflower, that do well in alkaline soils.
Choosing Stock
Many annuals are easy to grow from seed, and some can even be started outdoors right in the garden, but if you plan to buy stock from a nursery, choose your plants carefully. Look for deep green, healthy plants that are neither too compact nor too spindly. They will do better if they are not yet in bloom when planted. If you can’t plant them right away, keep them in a lightly shaded spot and water carefully.
When to Plant
Tender annuals cannot be planted until after all danger of frost has passed and the soil is warm. Half-hardy annuals can be safely planted if nights are still cool as long as there will be no more frost. Hardy annuals can be planted in early spring as soon as the ground can be worked.
How to Plant
The best time to plant is late in the afternoon. Before planting, water your plants and the soil in your bed well. Remove the plants from their pots gently to disturb the roots as little as possible. If they are in peat pots, tear the pots slightly to make it easy for the roots to grow through. If the roots are compacted, loosen them gently before planting.
Dig a hole slightly larger than the root ball, and set the plant in at the same level at which it was growing. Carefully firm the soil around the roots. Water well after planting and keep moist until the plants are established and new growth has started. Once they are established, addition of a soluble fertilizer will encourage them to bloom.
Sun
Most annuals like at least 6 to 8 hours of sun a day. There are many annuals that will do well in part shade or filtered sun. These include ageratum, browallia, coleus, dianthus, fuschia, impatiens, lobelia, pansy, salvia, Inca, and wishbone flower. Few if any annuals will do well in complete shade.
Fertilizing
Most annuals don’t require a lot of fertilizer, but will do much better if adequate nutrients are available. In general, you can fertilize once or twice during the growing season. Overfertilizing will cause a build-up of soluble salts in the soil, especially if the soil is heavy, and result in damage to the plants. Soil that has been enriched with compost will not generally need additional fertilizer.
Watering
Annuals need about an inch of water a week. If Mother Nature doesn’t provide, you will have to help. When you must water, water deeply to encourage deep root growth. Try to keep the foliage dry during watering. If you must use an overhead sprinkler, use it early in the day so the foliage will be dry by nightfall, lessening the chance of disease.
If you live in a very dry climate, or if you are concerned about conserving water, choose annuals that are drought tolerant. Try cleome, dusty miller, globe amaranth, petunias and zinnia. If your soil stays wet or boggy, try one of these varieties: browallia, fuchsia, nicotiania, or pansy.
Mulching
The addition of a two to three inch layer of mulch will make the bed more attractive, reduce weeds, and conserve soil moisture. Organic mulches are best. Try bark chips, pine needles, shredded leaves or peat moss. The following year the mulch can be incorporated into the soil and new mulch added on top, resulting in an improved soil.
Weeding
Weeding not only keeps the bed more attractive, but also eliminates possible hosts for insects and disease and allows the flowers to receive the full benefit of the available moisture and nutrients. Weed carefully when the annuals are young so as not to disturb the young roots.
Pruning
The amount of care required by annuals varies. Most will need to have faded flowers removed (called deadheading) to encourage new blooms and keep the plant attractive. Many will become bushier if the top is pinched out. Remove the plants in the fall when the foliage begins to fade.