26 Basic Perennial Garden PlantinG & Maintenance
If a plant requires cutting back more than once or twice a season to look its
best (above and beyond normal spring or winter cleanup), it moves into the
higher-maintenance category. Some plants do best if cut back before flowering
for height control. They may also require frequent deadheading. And then they
may need cutting back once or twice to maintain a decent habit (the general form
or shape of a plant) and to rebloom after flowering. This can involve a lot of work.
You need to decide whether growing the plant is worth the extra work.
Perennials that need heavy feeding and a supply of supplemental nutrients
through the season mean additional maintenance. A rich, high-organic soil and
possibly a light spring fertilization is all that most perennials require.
An invasive plant can take over the world (or at least the garden) before you
know it! Or at least it can seem that way when your monarda, a cute
single-stemmed 4-in. plant, spreads by underground stems to fill a space 4 ft. × 4
ft. in your garden, devouring everything in its path. Certain species become
invasive because of prolific reseeding. Timely deadheading can help prevent
reseeding, but if this has been missed just once, populations can quickly get out
of control. A great amount of time is often required to keep invasive species
managed either by lifting seedlings or by digging out pieces of the expanding
clump. Unless you enjoy that kind of thing, use invasive species with caution.MAKING PLANTS “FIT”
Having considered the site and the types of plants you want to incorporate in the
perennial garden, you now need to look at the arrangement and spacing of the
plants. Proper spacing of perennials can be hard to determine even for the
experienced designer. Even when you think you have it all just right, a plant
grows larger than anticipated and another stays small, so at one time or another
something is too close and something else a bit too far away. This is just the way
of nature. Knowing the ultimate width of any perennials you want to use in your
design is crucial to planning. One recommendation is to plant perennials in
drifts (long-shaped planting of perennials) using odd numbers, preferably with
at least three of a kind of a single species. (Planting in groups of odd numbers is
based on the concept of “unity of three,” as visually the eye will tend to draw a
line between or divide even-numbered groupings of plants.) For genera like
Monarda, however, using many plants together may mean you and your family
moving out of your home to give your beebalm the space it will need. Even the
lovely lady’s mantle (Alchemilla mollis) can alarm the new gardener when its tiny
2 leaves turn into a 2-ft.-wide clump within a few years—normally a single plant
repeated in several spots along a border is more pleasing than a single group of
plants that would cover a 6 ft. × 6 ft. area.
I always keep the ultimate size of a plant in mind when designing, but I
also space plants rather close to reduce weed competition and to produce
the lush, full style I prefer within a short period of time. Closer spacing can
require more maintenance in the long term in the form of pruning or transplant-
ing (which I find more appealing than weeding), because plants may need to
be trimmed to stay in their own space, or they may eventually need to be thinned
or moved to maintain proper proportions—but results usually make it worth
the effort.
It is hard to give specifics on spacing because of the many variables, such as
initial plant size, regional differences, soil conditions, and so on. As a general
guideline, small plants (under 1 ft. tall) or plants at the front of the border should
be spaced 8 to 12 in. apart. Intermediate-sized plants (1 to 2 1/2 ft. tall) are best
spaced 15 to 24 in. apart. Spacing of 15 in. seems to work best for the majority of
perennials, including plants in the genera Coreopsis, Salvia, and Veronica. I
usually start the plants off in 1-quart containers (4 1/4-in. pots). When starting