CHOOSING PERENNIAL PLANTS FOR EFFECT
Because hardy perennials as a whole are so adaptable and of such infinite variety, they offer enormous possibilities. But the right selection of plants is important, as it is through lack of attention to this point that failures occur or troublesome maintenance chores ensue. Lack of knowledge need not be a deterrent, as knowledge is something that grows with interest and experience, and foreknowledge of height, spread, colour and time of flowering can be gained from the list of suggested plants which follows.
Do not buy cheap plants, as these may well consist of divisions of older, less vigorous stock, or be immature and nondescript, all of which will certainly prove disappointing. Visit a good nurseryman to make a selection of quality plants, or study a hardy plant catalogue.
Although it may prove to be a little more expensive, it is well worth buying from a reliable nurseryman, as his plants will have been grown with skill and care and will give a good display in the first season. He has, or can obtain, the best varieties in the widest range.
Most specialists make up collections for border planting; but be sure that a collection made to fit a stereotyped plan is quite suitable to particular needs,and situation.
When a selection has been made, make a rough plan to scale on graph paper, then attach the names or reference numbers of each group to canes or sticks, or better still make permanent labels. Arrange these in position on the site in keeping with the plan. If no plan has been attempted, juggle the tags or labels about until satisfied that when the plants are ready to go in they will occupy the correct space, with all their growing factors accounted for.
Avoid flatness or too regular grading from dwarf to tall, as the best effect is gained from having adjoining groups of somewhat irregular heights. With plants that differ widely in form or shape when in flower, intersperse the bushy or flat-topped varieties with spiky plants, such as, lythrums or sidalceas.
SEASON FOR EFFECT
The flowering season for perennials for effect extends from April to November, so it is possible to make a selection for any given period. Though this would provide a blaze of colour at the chosen time, most people prefer to aim for maximum continuity and particularly like plants with a long flowering period. Some kinds flower for three months while others, such as irises or paeonies, are past their best after three weeks.
Planning for continuity calls for careful placing. Do not plant kinds that flower about the same time in adjacent groups. Place those that make a brief show and then have to be cut back or remain untidy behind or beside such plants as Michaelmas daisies, which become bushes and flower later.
Some people plan to have adjoining groups which give effective colour contrast or blend, while others prefer an overall effect of colour blending. Very few colours clash amongst perennials, and discordant effects are even less likely if plants of similar habit and time of flowering are well interspersed with others of different form flowering later or earlier.
Some kinds grow and spread faster than others, and here, too, discretion in selection and planning contributes greatly to success. The more robust kinds such as monardas and many Michaelmas daisies may well have treble the annual surface spread of others, and if planted in adjacent groups will give trouble later on. They are better avoided if space is limited, particularly if variety and continuity are desired. In the second season after planting, a fast spreader may encroach beyond its allotted space into that occupied by something less robust, and such harmful aggression may call for annual curbing. The slowest spreading kinds are often the choicest. Vigorous spread is not confined to the taller kinds.