Perennials are the backbone of a flower garden. Annuals put on a beautiful show, flowering all season long in many cases, but it's the perennials that give a garden character, reliably returning year after year. Most perennial flowers die back to just a crown and root system each year; the crown and roots are dormant during the winter, then the top growth returns in spring. Most perennials bloom for only a few weeks during summer, so careful planning is necessary to ensure color in your garden all season long.
- Perennial plants fall into one of two classes. There are woody perennials, such as trees and bushes, which do not die back each year and there are herbaceous perennials, which do die back. Most perennial flowers are herbaceous.
- Perennials are much more expensive than annuals. You'll probably want to plan your garden on paper before setting any plants in the ground, so that you don't have to move them later. An alternative is to grow them from seeds, although perennials can be notoriously difficult to sprout. Some have to be exposed to cold temperatures, then warm; some need to be soaked in water; and for others, you'll need to scrape the seed coat, which is called scarification.
- Consider when each plant will bloom. Do you want a continuous show of color all summer or do you want a burst of riotous color all at once? Also consider which perennials will grow best in your location. To help determine this, it's helpful to consult a USDA Zone map. If you have your heart set on a particular species that is too tender for your area, it may be possible to grow it in a pot during the summer and bring it inside when temperatures start to drop.
- Once you've decided where to plant each perennial, prepare the ground. This step is very important, because the plants will quite likely stay in the same spot for several years. If the area to be planted has never been cultivated, you'll need to solarize the soil. To do this, lay down clear or black plastic mulch over the area where the garden will be and leave it in place for the summer. This will kill any grass in the area, along with most pests and weed seeds. Apply several inches of organic fertilizer, such as compost or well-rotted manure. Work it into the soil. This will also give structure to sandy soil and help break up clay soil. The soil should have a fine, crumbly texture when you are finished.
- If you have chosen spring-flowering perennials, they can be put into the garden in the autumn. Most autumn-flowering perennials prefer to be planted in spring, so if you've solarized your soil, you may need to wait until next year to plant these.
- To set your plants, dig a hole that is twice as large as the rootball of your plant. Remove the plant from the pot in which it came. If your plant is root-bound, gently loosen the roots. This may cause a bit of transplant shock, but it should recover quickly. Place it in the prepared hole, then fill in the soil all around it. Firm up the soil with the palm of your hand, and add more if necessary. The soil level should be approximately the same as it was in the pot.
- Read the labels on your plants carefully. Some plants may take several years to reach full size, so plant them according to how you want your garden to look in three years.
- If you garden site tends to be boggy or very dry, choose perennials that will tolerate these conditions. It's unlikely that you'll be successful in changing your soil, unless you want to spend a lot of time and effort in building raised beds.
- Know the water needs of your plants and water accordingly. Two moderate waterings per week is better than one heavy watering. Frequent, light sprinklings really do no good at all. The water will evaporate before it reaches the plant's roots and the constant splashing around among wet leaves is likely to spread disease.
- Apply a layer of organic mulch to conserve moisture and provide nutrients to plants. Mulches are preferable to liquid fertilizers because mulch breaks down slowly, providing a constant supply of nutrients over a long period of time.
- To keep your perennials blooming as long as possible, deadhead them regularly. This means to remove spent blooms before they go to seed. If they are allowed to produce seed, it signals the plant that the end of the growing season is near, and they will stop producing blooms.
- If, after several years, your perennials begin to look crowded and aren't growing as vigorously, they may need to be divided. Carefully dig up the plant and cut it apart into several individual plants. If the plant is very large, it may be easier to divide it by using two garden forks held back to back and pulling the roots apart.
- Cut back perennials in the fall. Remove all top growth up to three inches above the crown. Toss the clippings into your compost pile. If you leave them in the garden, they can attract disease and pests.
- After the ground is completely frozen, apply a thick layer of mulch to protect the roots. This helps to prevent the ground from heaving, which could uproot your plants.
You may prefer to intersperse your perennial bed with annuals for the first couple of years until it begins to fill in. After that, you should have a flower bed that is a joy to behold all season long, with very little maintenance!