Perennials grow best in a loose well drained soil. Annual applications of manure in the fall can be dug in the spring to improve soil texture and retain moisture. Plants like to be watered on a regular basis and it is important to cultivate the soil frequently. The small fibrous roots systems grow best in a loose well ventilated soil. Fertilizers should be applied annually. In early spring applications of 6-8-6 encourages new top growth. As plants come into flower, fertilize with a flowering plant food (4-10-10). Taller varieties do require staking. Perennials benefit from winter protection for the first year. Place a mulch 2-3” deep over the plants to protect them from the cold.
Most perennials are best planted in the spring. Some grow best in the sun, others in shade. Plant perennials as soon as all danger of frost has passed, and the ground is dry enough to work. Make sure to give plants plenty of room so that none of the roots are crowded. The crowns of the plants should not buried, or the plants will suffocate and rot. Some perennials are best planted in the fall. Bearded Iris, Oriental Poppies and Bleeding hearts can be planted in late August. Peonies and Lilies are best planted in September. Shallow rooted perennials such as Chrysanthemums and perennial Asters require a light dressing of soil in the spring. Soil should be applied only around the base of the plants.
If you’re planning a perennial border, a sunny location is best away from encroaching roots of trees or hedges. The border should be at least 6 feet wide to arrange plants properly. Before planting make a plan showing where each variety is to go. Know the height, colour and season of bloom to arrange plants to the best advantage. Plant the tallest plants at the back, then medium tall ones, shorter ones toward the front and ground and prostrate plants at the front edge. A few taller plants can be brought forward to break up the line of the border. Taller plants are best grouped in threes and intermediate and dwarf varieties in groups of five. Plant strong coloured perennials first, leaving adequate space in between for softer coloured perennials.
Watering thoroughly once or twice a week is preferable to several light watering. Most perennials do not like to have wet roots and excessive wetting of plant foliage encourages disease problems.
It is time to divide perennials as soon as plants begin to lose vigour. As a general rule, perennials that bloom in late summer and autumn are divided and replanted in spring, (Chrysanthemums, Asters). Dig up old plants when new growth is 1-2” high. Pull the roots apart to make pieces with three or four shoots. Plant only the most vigorous shoots. Replant and water with a good starter fertilizer such as 10-52-17 or Up Start. Spring flowering perennials (Aubretia, Alyssum, Carpet Phlox) may be divided immediately after flowering in the spring or in August.