The best time for planting most hardy perennials is early autumn, up to about mid-October, when theis warm and quick establishment is easy. This will allow a full display the following year.
There are some plants, such as scabious, pyrethrums and Aster amellus, which are better put in, in spring. However, a good nurseryman will deliver plants at the correct time for planting.
Avoid too much treading on damp soil, otherwise forking over will be necessary. If planting is not possible till spring some danger from over-dry soil may occur, though this seldom applies in autumn. If a fine sprinkler is available use-it after planting, but if the soil is very dry and clotty or dusty, give the site a reasonable soaking a day or so before planting. If no sprinkler is available, puddle in the plants, even in dry soil. Make holes with a trowel, insert the plants and cover the roots, fill the holes with water and when it has soaked in, replace the soil, making sure the plants are firm. Do not splash water from a can after planting. The drier the soil the heavier the firming should be, but on no account should wet, sticky soil be tightly jammed.
SPACING AND GROUPING
The best method is to plant groups containing several of each kind. Allow a greater distance between groups than between the individual plants comprising each group. The smaller bed or border needs three of a kind as a group, but the larger the scheme the larger the groups need to be. In a scheme 9 ft. wide by 50 ft. long, each group should have four to seven plants. If, for example, the plants comprise a group occupying 1 sq. yd., the spacing between the plants should be about 14 in. But between the groups in any direction there should be at least 20 in. This practice not only assists the natural spread, it also makes for easier hoeing etc., and allows freer access of light and air, which give strength to the stems, the plants stand more strongly and boldly as a group, and in many cases the need for supports is obviated. Slow-growing or dwarf plants need less space than those that are taller or more robust so choose between two alternatives — either have larger group spaces for the robust kinds at the expense of the slow-growing ones, or, if equal group spacing is preferred, have fewer robust plants and more slower-growing kinds.
Some easy soils may need only pricking up with a fork in autumn and winter, but soils that are liable to pack tightly may need turning over in autumn or early winter. Avoid deep digging except in open spaces, and use a small flat-tined fork, or what is known as a border fork, rather than a spade.
Weed control is essential and is more likely to be necessary during the first season after planting than in successive seasons. Hoe annualwhen they are tiny. should not appear at all if the site has been thoroughly prepared, but sacrifice a plant or two rather than allow a really pernicious perennial weed, which may have been missed, to gain a hold. Couch, ground elder, creeping forms of sorrel, and buttercup are the most pernicious. Dig in annual grass, chickweed and other free-seeding weeds during winter, and never let them seed. Hoe any weeds that appear after planting. Annual weeds can thus be easily destroyed, and the less troublesome such as creeping thistle and bindweed will be weakened. Do not use chemical weedkiller when plants are in position.
Nothing detracts more from the beauty of the plants than sticks and stakes, and as no chore is more troublesome than staking, support only those plants that become floppy or top-heavy when in flower, putting in the stakes well before growth reaches that stage. Do not try to impose rigidity on plants that are naturally a little floppy. For tall plants, such as, use a cane for each spike, otherwise use pea-sticks of varying heights; these are much more effective and less obtrusive. Well before buds open, place the peasticks in position, in and around groups that are likely to sag.
Perennials vary in their response to nutriment. Give them a good start and they should not need manuring for at least two seasons. After that, depending on the quality of the natural soil, fork in old manure, rotted, or peat with added organic fertilizer any time between November and March. Apply a mulch when the soil has begun to warm up in April. Peat makes an excellent mulch, but if using it first scatter organic fertilizer at 2 oz. per sq. yd. Between the plants. The covering of peat helps to retain moisture and keep down weeds.
Mulching is also helpful to certain plants that tend to lift out of the ground. Livery three or four years it may be necessary to dig up, divide and replant them deeply, especially such plants as monarda and Michaelmas daisy, which make a rapid surface spread and exhaust their vigour in the process. Use only the outer, livelier portions for replanting and discard the rest.
The seemingly easy or cheap way into any garden venture often results in having to take the hard or expensive way out. Experience gained in this way is costly, yet if only foreknowledge with the discrimination it allows can be put into practice, so much more interest and satisfaction can be obtained. A few initial errors may be made, but these can so easily be remedied. A misplaced group, for example, will show itself in the first flowering season, and the remedy is simply to make a transfer in autumn or spring. No one yet knows everything about the behaviour, cultivation or arrangement of plants so do not be afraid to make cautious experiments to test the adaptability of perennials. Juggling with groups is part of the pleasure.