Perennials are plants that live year after year. Trees and shrubs are perennial. Most garden flowers are herbaceous perennials. This means the tops of the plants — the leaves, stems, and flowers die back to the ground each fall with the first frost or freeze. The roots persist through the winter and every spring, new plant tops arise. Any plant that lives through the winter is said to be hardy. In the fall, after the foliage of perennials has died down, remove dead leaves, stems, and spent flowers. These materials often harbor insects and disease-causing organisms. Apply winter mulch after the soil temperature has dropped.
There are advantages to perennials, the most obvious being that they do not have to be set out, like annuals, every year. Some perennials, such as delphiniums, have to be replaced every few years. Another advantage is that with careful planning, a perennial flower bed will change colors, as one type of plant finishes and another variety begins to bloom. Also, since some varieties of perennials have a limited blooming period of about 2 to 3 weeks, deadheading, or removal of old blooms, is not as frequently necessary to keep them blooming. However, they do require pruning and maintenance to keep them attractive. Their relatively short bloom period is a disadvantage, but by combining them with annuals, a continuous colorful show can be provided. Most require dividing every 3 years.
It is best to select plants with a purpose in mind, such as edging plants, accents for evergreens, masses of color, rock garden specimens, etc. With specific purposes in mind, you can choose perennials by considering their characteristics and deciding which plants best meet your requirements. For a good display from a limited number of plants in a limited space, select well known varieties. Observe the flowering times of perennials in your neighborhood. That way you will be able to choose plants that will flower together and plants that will be showy when little else is in bloom. The flowering time may vary as much as 6 weeks from year to year, but plants of the same kind and their cultivars usually flower at the same time. To obtain details on particular plants or groups of plants, consult plant societies, specialty books, nurseries that specialize in herbaceous perennials, and local botanical gardens. Plants of many perennials can be bought at a local nursery. Some varieties of parennials are in bloom when they are offered for sale, which allows you to select the colors you want. Buy perennial plants that are compact and dark green. Plants held in warm shopping areas are seldom vigorous and generally have thin, pale, yellow stems and leaves. Avoid buying these plants. Buy plants that have known characteristics of disease resistance, heat and cold resistance, growth habits and colors.
Setting Out Plants.
When the time comes to set plants out in the garden, remove them from flats by slicing downward in the soil between the plants. Lift out each plant with a block of soil surrounding its roots and set the soil block in a planting hole. If the plants are in fiber pots, remove the fiber from the outside of the root mass and set the plant in a prepared planting hole. When setting out plants in peat pots, remove the top edge of the pot to prevent it from drying out and limiting the root development of the plant. Thoroughly moisten the pot and its contents to help the roots develop properly. Drench the soil around the planting hole with Blooming and Rooting to stimulate root growth. Set the moistened pot in the planting hole and press the soil up around the plant. Allow plenty of space between plants, because perennials need room to develop. Perennials usually show up best when planted in clumps or groups of plants of the same variety.
Regular fertilization is necessary. Perennial plantings can rob the soil of its natural fertility. However, do not fertilize perennials heavily. A light fertilization program gives a continuous supply of nutrients to produce healthy plants. Use Osmocote fertilizer. Place fertilizer in small rings around each plant in March. Repeat twice at 6 week intervals. This should be enough to carry plants through the summer. Apply another treatment of fertilizer to late-blooming plants in late summer. Always water the bed after applying fertilizer. This will wash the fertilizer off the foliage and prevent burn. It will also make fertilizer available to the plants immediately.
After perennials have bloomed, spent flowers should be removed. Cut flower stems down to a healthy leaf or to the ground, if there are no more buds. This will keep the beds looking neat and will prevent plants from wasting energy setting seed. Delphiniums can be forced to reblossom if cut back severely after the first bloom.
To gain large blooms from perennials, as opposed to more numerous but smaller blooms, disbud them. In disbudding, small sized buds are removed, which allows the plant to concentrate its energy to produce one or a few large blooms. Peonies and chrysanthemums are examples of plants which are often disbudded.