Chrysanthemum is a genus which has contributed several species to the flower garden. Hardy chrysanthemums are among the popular and important garden flowers oust of the long, colorful show they put on in summer and fall. By choosing carefully the hundreds of varieties, the gardeners have chrysanthemum blooming nearly all year round. They can be grown in containers and watered carefully. The dwarfs can be dug with a generous earth when in bud or flower and moved to a dull corner of the garden. Few have such a variety of color and form, are excellent for cutting.
Hardy chrysanthemums require a great maintenance to keep them in top form. If you are a person who has little time to work with, you should avoid having large plants. While they can be propagated, cuttings and seed, most gardeners will divide. Indeed, (or at most, biennial) division in spring may help keep them flowering well. When looking at the clump, you will notice many pale usually with a tuft of small leaves spreading out among the darker roots base of the plant. Each one of these can grow into a large flowering plant by cut off as many as you will need and the rest of the old clump. If you started with larger divisions, use a sharp knife and cut pieces with several new crowns. Small divisions or stolons make the best and they should be set out in full sun in compost or rotted manure, which supplemented with bone meal or sludge are heavy feeders and will benefit from dressings of compost during the growing season. They must be watered carefully at all stages of growth: Drying of the soil in the heat of summer will stunt growth and diminish flowering.
When the young plants have grown six or eight inches tall, pinch out the tip of each stem to induce side-branching. Pinch again after each six inches of growth until mid-July, after which the plants should be left alone so they form flower buds. This early pinching induces heavier flowering and helps to keep tall varieties more compact. The cushion mums, which mature at 12 inches or less, are self-branching and should not be pinched. Some varieties, such as the football and spider mums which develop very large flowers, should be disbudded to make them look really spectacular. All secondary flower buds are removed, allowing each stem only one bud at the top which opens into a flower that can be five to eight inches across. Such varieties usually bloom too late to mature before frost and the flowers can’t take heavy rains, so they are best left to florists and greenhouses. While some-times advertised as being suitable for the open garden, they are really not.
Almost everyone knows of or owns chrysanthemum plants which seem to survive and bloom year after year with little or no winter protection. Even so, the term “hardy chrysanthemum” can be misleading because too often a newly bought variety which was planted in spring and bloomed in fall dies in the winter. This is often caused by poor drainage; while mums require abundant moisture during the growing season; their soil must never be soggy in winter. Try not to plant them in heavy clays if you wish to winter them in the garden. To prevent alternate freezing and thawing, cover the plants with airy mulch such as straw, evergreen boughs or an inverted basket in winter. To be sure that choice variety survives, dig them with earth balls after frost has killed the tops and store them under light mulch in a cold frame for the winter. In spring, plant several of the stolons and compost the old plants. Treated this way, any hardy mum will grow and bloom well each season.
There are several recognized flower types of hardy chrysanthemums of which the button, pompon, decorative, and single-flowered types are most suitable for the open border. There are many named varieties to choose from in each class, so check the catalogs for those which appeal to you most. The cushion or dwarf types might be the best for busy gardeners because they do not need pinching.