Planning and Planting a perennial garden.
No single word or term has yet been accepted to cover garden plants, as distinct from bulbs and shrubs, which flower year after year.
`Herbaceous plants', 'hardy perennials', `border plants' are all inadequate or inaccurate in some respect. Strictly speaking, the word 'herbaceous' denotes the decay of each season's growth, with the plant itself remaining alive, but dormant. Delphiniums, phlox and many others have this habit but several, including iris and kniphofia do not, because they retain winter foliage.
The time is happily past when hardy perennials were relegated in so many gardens because the rewards they gave were disproportionate to the trouble entailed. One reason was because post-war demands for labor saving forced a swing to shrubs. The conventional herbaceous border was largely at fault because of its long narrow shape with a backing wall, hedge or fence. The plants suffered from overcrowding, weak growth and excessive competition for light and air. Quite often such borders were too narrow in relation to the height of the plants. All this accentuated the main disabilities to which perennials are prone if not given a fair chance —difficulty of access to the plants and the need for supports. Harmful competition between the ranker and the less vigorous kinds, and indiscriminate selection and planting almost invariably lead to trouble. Adaptability This calls for a fair-minded approach when one considers that nature herself has set the limitations. The majority of garden plants have their origin somewhere in the wild. An original type may have been improved upon by breeding and hybridization, but the varieties or cultivars retain their main parental characteristics, including those of adaptability. A species which for millions of years has been accustomed to certain conditions of soil, moisture, sun or shade can scarcely be expected to flourish so well where its natural preferences are lacking.
Most perennials are adaptable to ordinary garden conditions, but it would be as much a mistake to plant something which naturally prefers shade or moist soil into a dry open situation as it would the other way round. It would also be a mistake to plant something rank or invasive near something that is by nature of slow or lowly growth.
Light and Air
The problem of overcrowding is linked to this. Plants need light and air and overcrowding and overhanging by trees or other taller growth, which reduce these inevitably leads to stem weakness. Plants in close competition for light and air become excessively tall and spindly. It is a vicious circle and is the major cause of untidiness and the need for staking in congested borders, or those backed by tall trees, shrubs, hedges, fences or walls. Usually where staking is necessary, it is not the fault of the plants but of the conditions under which they are grown.
Some years ago well-known nurseryman, who specializes in hardy perennials, experimented with 'island beds' and showed that not only were the plants shown to greater advantage, with all-round access, but very few needed staking, whereas the great majority had needed supports in the conventional one-sided borders. Although first-year growth was shorter, in succeeding years the growth was just as sturdy, with only such heavy spiked or headed plants as delphiniums and tall Michaelmas daisies needing support. Since then the nurseryman has constantly advocated island beds as the best means of growing perennials. In the process, nurseryman has grown thousands of species and varieties.
However, the small rectangular plot which most people have, with similar plots on either side, rules out the informality of island beds and such gardens admit of little choice but to go in for flanking borders. Even so in a small or otherwise inhospitable site, there are still ways and means of growing perennials successfully.
The main thing is to select plants best suited to the place in which they are to grow. The range of available plants is sufficiently wide for this to be achieved, no matter how small the garden, or unkind the soil, so long as it is not completely hemmed in by tall buildings or overhung by large trees to exclude both light and air, and to compete for the available food and water. Even the conventional one sided border with a high backing can be improved by growing kinds most suitable or adaptable to it. Such borders are usually far too narrow in relation to the height of the plants. Some plants are often invasive and attempts to grow shorter, choicer kinds as well have failed because of unfair competition. What is needed is a new approach, a new appreciation of garden worthiness and adaptability.
The range should include certain hardy bulbs or corms, such as crocosmia, which contribute greatly to the summer display, also certain dwarf perennials. If they are adaptable for growing in front of taller kinds, in ordinary soil conditions, then there are very good reasons for including them. Plants of, say, 6 to 12 in. tall are by no means out of place as frontal groups and in small gardens where beds have to be small, then dwarf plants are both desirable and necessary.
Sites and Soils
Those moving into a newly built house must consider how to make the best use of the available garden space. It may be completely bare, a segment of farm or meadow land, and such factors as slope, exposure, drainage, and type of soil should be considered carefully.
Prepare the Site
Bearing in mind the need to select plants best adapted to the site, the preparation of a bed or border for hardy plants should include drainage if the soil appears excessively wet or sticky in winter or hard baked in summer. Thorough cultivation will usually suffice.
The fall is the best time for deep cultivation on heavy land as this will enable winter frosts to break down hard lumps and sods into a fine tilth for spring planting.
There is a tendency nowadays to avoid manual labor, but there is nothing like hand digging. A spade is still the best tool for lighter soils, but for heavy or sticky soils a strong digging fork is best. Trenching, or double digging is necessary where there is a pan below the top spit. This will improve drainage and will enable surface-rooting weeds to be buried, but if the second spit is of subsoil then it should merely be broken up or turned over, not brought up to the surface. Perennial weeds, such as couch grass, must be eliminated, either by forking and raking during dry weather, or by weed killers. However, weed killers may be persistent, and they should never be used unless you know the longterm as well as the short term effect they will have upon plant growth. Annual weeds are much easier to cope with. Contact sprays will kill them off quickly and leave the soil clear for plants within a few days. Normally perennial weeds that are deep rooted or spread by underground stems require drastic measures to kill them. If you are reluctant to use the lethal poisons which will ensure a complete kill, then it is best to fallow the ground rather than risk a permanent bed of hardy plants being ruined by perennial weeds.
On both light, poor soils and heavy clays, humus in the form of peatmoss, compost or well rotted manure should be dug in. This will improve the texture, as well as the fertility of the soil, and give plants such a good start that nothing but occasional top dressings of fertilizer will be needed for years.
Grass covered Sites
This soil preparation applies to any site, new or old, but where the surface is grass covered, a cultivator can be useful. If the turf is not wanted elsewhere or is of poor quality it will improve the soil fertility if it is buried, provided it is chopped up first. If an open trench is dug across the narrow end of a bed or border, the loose, chopped up turf can be pushed in, using a spade or digging fork to cover it well as the plot is dug, trench by trench. Large lumps of turf dug in often result in lack of consolidation as they slowly shrink during the much slower process of rotting.
Conventional styles in gardening are hard to change, but those who wish to give hardy plants a fair chance will see that there are quite a few variations open to them. There is no doubt that island beds give the best reward, just as narrow, hemmed in borders give the least return, in terms of value for money and effort in maintenance. An island bed can be sited anywhere provided all round access is possible, even if it is only a narrow path on one side or end. A backed border can be converted into an island bed provided there is sufficient width. No matter what the backing is, rear access can be provided either by a narrow grass path or paving used as stepping stones. If the backing is a wall, it can be used for vines and a strip allowed along the foot for bulbs or any of the wide variety of dwarf plants or climbers that like such a spot. The rear part of the bed itself should have as edging groups of dwarf early-flowering perennials such as bergenias, pulmonarias and epimediums, for even if the aspect is sunny, the taller perennials facing the adjoining groups will provide summer shading. This rear strip will prove a source of delight in spring and, even if color has gone by summer, you still have easy access to the rest of the bed for maintenance work, and there will be far less staking required, because the weakening effect of the backing is greatly lessened.
Width is, however, an important factor. So many conventional one sided borders are too narrow and should either be widened, or, if this is impracticable, then the tallest plants should be avoided. Some old borders have a graveled path along the front and perhaps a low hedge as edging. In most instances the graveled path is not necessary and could be dug up and incorporated as extra border width. The hedging could be removed, as it has little ornamental value and harbors slugs and snails.
Sometimes a border is flanked by a grass path or lawn and this presents no physical problem, if you wish to increase the width of a conventional border, whether or not it is to be converted into a semi-island bed. A curved edge could enhance the layout if the general lines of the garden lend themselves to this treatment. But irregular curves or a scalloped edge would be out of place if straight lines prevail elsewhere in the garden.
In island beds plants grow more sturdily, are less marred by supporting sticks, and can be viewed from all angles at a more convenient eye level. One-sided beds have become anachronisms; only those on a small scale, where heights of plants are in keeping with the width of the border are worth considering. If the site is unsuitable for an island bed and you have to have a one-sided border, it will inevitably be more troublesome to maintain, unless you select the plants carefully.
Planning and Planting
Width of Border Whatever type of border you decide to plan and plant its success and potential interest will depend not only on a well chosen site, well prepared soil and the right selection of plants, but on its width. The narrower the bed, the lower the plants should be. Nothing looks more incongruous than plants flowering at 4 or 5 ft. in a bed only 4 or 5 ft. wide. They inevitably harm dwarfer, choicer plants growing beside them, regardless of aspect. A safe guide in selecting plants is to measure the plantable width of the border in feet, and halve it to arrive at the maximum height of plants it should contain. This restricts a 4 ft. wide border to plants of no more than 2 ft. tall, but a little latitude can be allowed for the erect, spiked plants, such as kniphofias, to exceed the limit by a few inches. This is a rule that can be applied to any type of border island or one sided, bearing in mind that an island borders the tallest plants are placed in the center, and in one sided borders they are planted at the back.
Grouping should also be considered. Where space is very restricted and where variety is preferred, then there is a case for growing one plant only of each kind. But there is never any point in growing a single plant of the same kind in more than one position in the same bed or border. If the site is large enough, then plants should be grouped in threes, at least, in a bed of about 100 sq. ft. in area, and in groups of up to 10 to 15 in in the largest beds of a 1,000 sq. ft. or more.
The space between plants in a group should be less than that between the groups themselves. This is because the plants in a group will usually grow and mass together effectively when in flower. But they will probably differ in form and habit from neighboring groups, and will need extra space to allow for this as well as to allow for vital light and air to give sturdy growth and for access for maintenance. The average spacing should be about five plants to the square yard. If, for example, groups are of five plants of a kind, this gives a planting distance of about 16 in. from plant to plant within a group. But the space around the group, up to the outer plants in adjoining groups should be 20 in. Spacing depends on the vigor of the plant; a single plant may occupy a square yard or nine plants of a dwarf, slow growing plant may occupy the same area.
Do not allow the more robust or rapid spreading kinds to overshadow or encroach on those that expand slowly. Those plants with a similar habit and vigor should be placed near to each other to avoid harmful competition. If you are prepared to plan your own bed or border, it is better not to use a stereotyped plan unless you are quite sure that the plants offered are suitable for the site. Making your own plan is not difficult.
Planning on Paper
First obtain a sheet of squared paper each square inch subdivided into tenths. Using the most convenient scale that fits the paper, draw the outline of the bed or border. Within this outline, group spaces can be penciled in faintly to begin with, once you have decided roughly on the area each group should occupy— depending on whether variety or a more massed display is preferred. A large variety of plants will call for smaller groups but a square yard at least will be needed if groups are to be large enough for massed color, depending on the total space available.
It is better to space each group by means of numbers. If there are to be, say, 36 groups in a bed, get the numbers one to 36 down on paper, spaced over the area, and when you are satisfied draw in the outline of each group as indicated on the sample plan. Using the list of plants you have already chosen, the placing of each one becomes a stimulating task, as you take account of height, spread, color and flowering season. At this stage it is useful to know something about the habits of the plants and here the descriptions of the plants which appear later will prove helpful.
If in the process of making a new bed or border, an error in placing occurs it will show up during the first flowering season. Perhaps a dwarf kind should have been nearer the front or vice-versa, or two colors do not blend well. This matters little, for a switch can easily be made in the fall or spring, provided a note is made when the error is seen.
When to Plant
Generally speaking, fall planting is best — whether you are making adjustments or planting a complete new bed—provided the soil is in clean, friable condition. It may not be possible to obtain delivery of plants from a nursery in September or early October, the ideal time, but the whole of October is usually safe for planting except on heavy, sticky soils and in the coldest parts of the country. In warmer or drier districts and on well drained soils, it is safe to plant in November too, except for a few kinds, notably Aster amellus, erigerons, pyrethrums, Scabiosa caucasica, nepetas and some of the grasses, which it is safer to plant in spring. In the fall the soil is still warm and new roots form quickly, so that in spring plants soon make up growth and do not lack for moisture. Watering in is seldom needed in the fall, but in spring it is often necessary.
Planting a new bed poses few problems if you have a plan. When the consignment arrives, unpack and stand each plant or bundle upright, and sprinkle with water if dry. If the bed or border is all ready with its marker sticks or labels for each group in position, placing will be easy, but do not, if you can avoid it, lay out the plants too early lest sun or wind dry out the roots before they are safely covered with soil. If the soil is wet and sticky, move about the bed on one or two short planks, and do not tread in each plant too firmly. Lighter soils may be too dry, and if when you try to make a suitable hole with a trowel, you find that the soil tends to run back, then puddling is the answer. This is simply a matter of pouring water from the spout of a can, till the hole is almost full. The water will quickly soak away and then you can enlarge the hole sufficiently to take the plant and having inserted it with its roots well spread out, draw round some of the dry top soil and make a loose tilth round the plant.
In spring, the soil is usually moist enough for planting until about mid-April, although even in March the soil can be so dry that puddling is necessary. If, after planting, plants show signs of distress, whether or not they were watered in initially, do no splash water over them. It is the roots that need moisture and a mere surface watering can be harmfully deceptive as it may erode the soil, expose the roots or cake the surface without soaking in. What the plants need is a fine spray; this takes longer, but will penetrate more readily to the roots, with far less waste of water. The same method, preferably using a sprinkler with a fine nozzle, should be used during a summer drought on established plants which are showing signs of distress; it is best done in the morning, and after each overhead watering, especially on a newly planted bed, it is worth hoeing or raking over the surface, as it dries out again, so as to retain a fine tilth, a top layer of loose fine soil i in. thick, which enables growth to keep fresh for much longer as water is drawn up from the soil below.
A new bed, with soil well prepared will not need feeding for the first year or two if it is reasonably rich in humus. Sand, gravel, soils containing lime, are often shallow and lack humus. Although leaf mold is hard to come by, peatmoss is easy to obtain and apply, and is an excellent form of humus for such soils. It is useful by itself, either dug in or applied as a mulch that will retain moisture and keep down weeds. But if it is used in conjunction with an organic fertilizer it is most effective in promoting good growth. The best method where plants need both a feed and a mulch, is to apply the fertilizer in spring, at about 2 oz. per square yard and immediately hoe it in to the top 2 in. of soil.
This is worth while on any bed or border after the second season, but if a mulch, too, is needed, this should be applied during April or May, depending on weather, type of soil and locality. The soil at this time is warming up, and to mulch too early in late districts may retard growth a little, though it will catch up later. The warmer the district the earlier you can begin feeding, hoeing and mulching. Before peatmoss is used as a mulch it should be thoroughly moistened (dry peatmoss can absorb up to eight times its weight in water); in this condition it is easy to spread over bare patches of earth between the plants to a thickness of 1/2 to 1 in. If you fork over a bed or border in the fall or winter, a peatmoss mulch applied in spring will largely disappear, though it will continue to do good, as a soil improver.
This also improves the soil structure, although there is always a danger of damaging the roots of plants. This can be avoided by using a flat-tined fork, rather than a spade; the flat tines will keep each forkful more or less intact so that annual weeds can be turned in. At the same time any pieces of perennial weed which may appear can be picked out. Couch grass, sorrel, thistle and the like are such nuisances that no effort should be spared to get rid of even the tiniest piece, even if it means taking up a border plant to do so.
Before winter digging begins remove last year's stalks. If you are not going to dig between the plants the dead stems may be cut back to ground level at any convenient time in the fall or early winter. This applies only to the truly herbaceous kinds, which lose each season's growth above ground and start growing again in spring. However, any foliage, for example that of kniphofias, that remains green over winter in mild areas should be left until new spring growth is about to begin and then it is a matter merely of tidying up the decaying or sere outer leaves.
Other Methods of Growing
For most people, a bed or border appeals as a well-defined feature in a garden. But hardy perennials may be grown in other ways. Many kinds can be grown in company with shrubs so that both are enhanced. Such erect and trouble free plants as hemerocallis flower from midsummer onwards to add more than a touch of color to a background of shrubs. Apart from these, the wide range of ground cover plants form a pleasing carpeting effect over what would otherwise be bare earth between shrubs, and most of these, too, will contribute color.