You’ll need paper, pencil, and a little flexibility
ONCE YOU’VE DECIDED on your priorities in creating a border (see “Border Basics 1: Laying Plans,” January/February 2002), how do you go about designing it? We’ve found that it’s best to begin with a consideration of what structural features—both living and nonliving—you want to use, while keeping in mind the crucial elements of scale and plant compatibility. We also have some fairly unorthodox advice about the role of garden plans. The remarks that follow apply mainly to mixed borders, since they are more versatile and satisfying over a long period, whereas strictly herbaceous borders are much more limited—after all, viewing a stretch of bare ground through the bleak winter months isn’t exactly thrilling.
STRUCTURAL ELEMENTS: PLANTS
PERENNIALS It is almost impossible for a garden to be pleasing when it does not display some sort of visual continuity. Selected plants need to be repeated throughout the design to act as a bridge. If there is one of everything, the eye jumps around and cannot come to rest. This doesn’t necessarily mean, however, that you have to use the same plant over and over—it can be enough to repeat the general shape of the plant. For example, if you decide to use spiky plants to create a unifying effect, you can include yuccas, kniphofias, irises, and certain grasses. While the result will not be quite as structured as it would if you used a single kind of plant, the eye will still pick up on how the shapes echo one another. (See “Good Structural Perennials,” page 78.)
With formal borders, in particular, careful attention must be given to maintaining the desired shape and size of groups of repeated plants, since variations in soil, moisture, and the amount of light available, as well as competition from other plants, will alter the structural plants’ growth habit. Disease can also strike, resulting in what we call “gaposis” as key individuals disappear. If a soil-borne pathogen is introduced, it can be very difficult to eradicate, in which case it’s wise to think about altering your planting scheme.
WOODY PLANTS Obviously, woody plants can also play an important structural role in the border. Not only do they have the advantage of greater permanence, hut they also offer a range of useful shapes, from open and airy to dense and rounded to narrow and upright. You can choose shrubs that will accentuate the herbaceous performance or opt for an off-season display, which can be achieved by picking plants with interesting bark (Acer griseum, Betula nigra) berries (Ilex verticillata, Callicarpa spp.), seed heads, or winter tints (Cornsus sanguninea ‘Winter Fire’).
When incorporating woody material into a mixed planting, think about deciduous versus evergreen foliage. Some evergreen plants can coexist with their herbaceous neighbors, while others can’t. (See “Evergreens for the Mixed Border,” page 79.) The number of evergreens that will regenerate their foliage after being shaded out by their neighbors is small. Do some homework before you start planting so that you don’t make a frustrating and costly error. Deciduous shrubs can also be damaged by excessive shade from neighboring plants, which can cause lower branches to die, but since the shrubs lose their leaves in the winter, the damage isn’t as easy to detect or as harmful to the design.
USING PLANTS STRUCTURALLY In these borders, grasses play an important structural role, providing strong visual punctuation when used singly or a sense of continuity when used repeatedly. The key plants are Helictotrichon sempervirens (opposite); Stipa barbata and S. gigantea (above left); and Miscanthus sp., Helictotrichon, and Calamagrostis xacutiflora (above right).
2 Border Basics: Creating a Design
Finally, keep leaf coloration in mind, especially if you think you might want to alter the border’s overall color scheme sometime in the future, for while perennials may come and go, trees and shrubs usually stay put. If your “backbone” plantings consist of plants that are variegated or brightly colored in leaf, this will have a profound effect on your new color scheme. This is not to suggest that you should choose only larger plants with plain green foliage; only that you need to think carefully of what effects you will want to achieve over the lifetime of the plantings.
PLANT COMPATIBILITY In any border, the plants need to coexist. (That is why a strictly herbaceous border can, at times, be easier to maintain, since all the plants start each spring on an equal footing.) In a mixed border, the trees and shrubs should be given a head start, especially if they are small when they are planted. With young woody plants, it’s also a good idea to plant well-behaved annuals around them for the first few seasons, in order to preempt the impulse to plant larger-growing perennials, which may suffocate the woody plants. In two or three years, once the shrubby plants have grown a bit, you can think about editing and adding more permanent plantings. After the woody plants have taken hold and are growing well, they will need attention so that they remain gracefully in scale while accentuating the attributes they were planted for.
Also, make sure you know whether your woody plants have a tendency to form surface roots. Certain plants, such as many flowering cherries, form dense, invasive root systems, which can make it hard for herbaceous perennials to gain a foothold. Again, doing your homework will lead you to plants with deeper-questing roots, which will be far easier to garden underneath.
A final word of caution: As tempting as it may be to incorporate “thugs” into the garden, beware! You will rue the day if common sense abandons you in this matter, especially if your border is small. (See “Thugs to Avoid,” opposite.) A larger border can more readily accommodate vigorous plants, but even then it is better to group plants with approximately the same degree of vigor and let them battle it out.
STRUCTURAL ELEMENTS: HARDSCAPE
If you’re an insatiable collector and can’t bear the thought of giving up precious space to repeated groups of plants, then the use of nonliving structural elements, such as containers, trellises, or tuteurs, can achieve the desired effect. These elements lend themselves to both more formal, geometric designs and to more relaxed schemes (though success with the latter is much more difficult to achieve). While it may be expensive and time-consuming to come up with precisely the right objects or supports, a well-designed hardscape will both complement the plantings and look good throughout the year. In fact, in a setting like this, the plantings can often be less structured, since the plants don’t have to “carry” the entire garden. This is particularly evident in many formal herb gardens, where a beautiful pot or urn pulls a group of fairly scruffy plants into focus.
Good Structural Perennials
|Epimedium spp. (barrenwort)||4/5-9|
|Euphorbia polychroma ‘Major’||3-9|
|Hedychium spp. (ginger lily)||8-10|
|Helieborus foetidus (bear’s-foot hellebore)||6-9|
|Helleborus xhybridus (Lenten rose)||5-9|
|Hosta spp. (slug-resistant cultivars)||3-9|
|Iris sibirica (nonflopping cultivars)||4-10|
|Polystichum spp. (shield fern)||5-9|
|Sedum ‘Herbstfreude’, S. ‘Matrona’||4-10|
THE ROLE OF HARDSCAPE These borders would be less successful were it not for the structural contributions made by hardscape. In the border opposite, a well-crafted tuteur serves as a focal point; lattice panels painted black (above left) define the planting area and function almost as windows; and a handsome urn (above right) acts as counterpoint to dramatic foliage.
SCALE AND SHAPE We have found that too narrow a planting area can’t really function as what most of us think of as a border, with a rich variety of plants. While a space that is only two or three feet deep can certainly be planted, it’s a good idea to restrict yourself in these cases to a simple mixture with only one to three plant varieties used repeatedly. (Obviously, this does not apply if you are creating a rock garden or some other kind of miniature planting, but in these cases the setting will be crucial to the final effect.) In order to have a more varied mix, the bed needs to be deeper. How deep is up to the individual gardener, but we would recommend a minimum depth of six feet. Whatever the dimensions of the bed, the main point to keep in mind is access for weeding, staking, and grooming. If you’re going to incorporate an access path into the border, always make it wider than you’re initially inclined to. As plants continue to grow through the season, a three-foot-wide path in May can easily be reduced to a one-foot-wide path by July.
When determining the shape of your border, beware of tight, swoopy curves, which tend to look busy and are a nightmare to edge; long, gentle, simple curves tend to work better. Rectangular beds, of course, don’t run this risk. If you’re planning on making an island bed, remember that these are best suited to larger gardens. In a small garden, whatever the shape of your bed, bear in mind that an area of unified lawn is your best ally; without this space of neutral green, the border is apt to appear frenetic and choppy.
Evergreens for the Mixed Border
|PLANT||USDA ZONES||Aegopodium podagraria (bishop’s weed, goutweed)|
|Abelia ? grandiflora (glossy abelia)||6-10||Centaurea montana (perennial cornflower)|
|Buxus spp. (boxwood]||5-9||Euphorbia robbiae (in Pacific Northwest)|
|Cephalotaxus harringtonii (Japanese plum yew)||5-9||Geraniumpyrenaicum and other self-seeding species|
|Ilex spp. (holly)||variable||Lysimachiaclethroides (gooseneck loosestrife)|
|Lonicera nitida (boxleaf honeysuckle)||7-9||Lysimachia punctata fyellow loosestrife)|
|Lonicera pileata (privet honeysuckle)||6-8||Macleaya microcarpa (plume poppy)|
|Mahonia spp.||variable||Phalarisarundinacea ‘Picta’ (gardener’s garters)|
|Taxus spp. (yew)||4/5-9||Spartinapectinata (cord grass)|
PLANS ON PAPER Gardeners seem to love plans—they provide the comforting illusion that the border-to-be exists in some concrete, unchanging form. Still, they do help to organize your thinking. Graph paper works well for this purpose. Your first step should be to measure out the location and dimensions of the border and its surrounding environs. Determine a scale that will allow you to work comfortably. (With a scale of 1/2 inch = 1 foot, for example, you can accommodate a 20-foot border on an 8 1/2-by-11-inch sheet of graph paper.) Be sure to include any large structural elements, such as buildings, paths, fences, and walls, as well as large trees or shrubs.
Next, you will need to do some research to determine how large a space the plants you wish to use will occupy. As you add groups of plants to your plan, the general rule is to work out a gradation of plant heights from shorter in the front to taller in the back, especially if the border is backed by a fence or other structure. Nevertheless, it’s usually a good idea to break the short-to-tall rule at least once or twice in the border. Nature doesn’t proceed in such a controlled fashion, and there’s no reason that you have to either. Plants with an airy, transparent structure, such as tall alliums, Molinia caerulea ‘Skyracer’, Nectaroscordum siculum, Rudbeckia maxima, and Verbena bonariensis work particularly well at the front of a border, providing a variation in height without obscuring the plants behind them.
For an island bed, the planting should be asymmetrical: if the bed is divided longitudinally, with the “spine” running down the middle, the tallest plants should undulate rather than line up rigidly along the midpoint, perhaps even creating bays where some of the “spine” plants extend out into “ribs.”
This may sound like heresy, coming from two professional designers, but when it comes time to actually lay out your border, use the plan as a rough guide, not as some sacred document that has to be adhered to in every detail. No matter how carefully you plot out the border on paper, the reality will always be different. A shuffle here, a tweak there, a slap to the forehead and total rethinking of another area may all be appropriate. Also, don’t become too enamored of the birds-eye view of your design—that’s not the way most borders are actually experienced, unless you’re going to be looking down on the border from the house or some other structure. In all the years that the two of us have designed gardens, we have never once stuck totally to the plan.
In several years, you may find that parts of the design need to be reworked. Be aware of this from the start and treat it like a challenge. Very few borders can remain static for long periods, since the majority of plants want to grow and expand. Enjoy your successes and learn from your failures.
PART 3, “Site Preparation and Planting,” will appear in the September/October issue.
For more on garden design visit www.hortmag.com/features.
COLOR AS A UNIFYING ELEMENT Although plant shape plays a part in each of the borders shown above and opposite, it is color, above all, that ties the schemes together. In the border above, bright gold Lysimachia nummularia ‘Aurea’ is the key player, with purple-leaved berberis and ajuga playing a secondary role. In the spring border shown above left, repeated clumps of Phlox divaricata provide coherence, while delphiniums and Salvia nemorosa perform the same function above right.
How a plan changes The plan below shows actual changes that were made at planting time. Because the Photinia glabra ‘Variegata’ were so small, Carex testacea (F1) and Rhododendron cv. were moved to fill the empty space. Abelia grandiflora grew so quickly that Hosta ‘Sum and Substance’ (G1) and some bergenias (SS) had to be removed. Euphorbia schillingii (E1) and Rhododendron cinnabarinum were moved to add evergreen mass and play off the color of Abies concolor (K). Rhododendron williamsianum (RR) proved impossible to find, so ericas, bergenias, and ajuga were substituted. Moral: Be flexible when faced with the actual conditions of your site.
Culp’s and Alderfer’s 1790 farmhouse helps give the garden its strong regional flavor.
Opposite: A corner of the rain garden, with a potted phormium and cascading campanuals.