On my calendar I have "PLANT PERENNIALS" in big red letters, next to the month of March.
This is because I have such success planting them at this time of the year. True, they can be planted at just about any time in the fall, winter or spring, but in March they waste no time in becoming something. They grow fast and strong and seem to bloom almost instantly.
They do not do this all of their own; I do spend a great deal of time and effort preparing the soil, digging it up and mixing in organic amendments and handfuls of granular fertilizer, and I water quite often for the first month, but they quickly take hold and are soon established and ready to flower.
The peak of flowering comes in May--a glorious month--and continues into June, and I make sure to plant some perennials that will bloom in summer and even in early fall. Once established, they take little work; I fertilize every couple of months and water about once a week or less.
Plan Your Watering
If the watering has you worried because of the continued drought and the chance of rationing this summer, consider that perennials tend to need less water than most annuals and certainly less than a lawn, which is one reason I converted part of my lawn to an expanded perennial bed.
If this knowledge doesn't assuage your concerns, consider planting perennials in one compact area where they can be watered while the rest of the shrubs and trees in the garden learn to get by on less. Most can, and a bed of perennials is certainly worth pampering.
I would set aside this area for perennial flowers because they are such a delight to grow, though they seldom flower as long or as profusely as annuals. While most annual bedding plants are neat and tidy and very uniform, perennials tend to be more varied, undisciplined and wild in appearance but their variety and exuberance can be delightful and often surprising.
But planting perennials is not a sure thing. Some perennials are turkeys, blooming poorly or growing weakly, so let me suggest some to plant now that are not. While I am at it, let me also suggest some strategy.
The idea, as I see it, is to take advantage of the tremendous variety available and contrast one kind against another--to contrast heights, foliage color or form (big leaves against little)--while the flower colors bring the harmony.
For instance, Lychnis coronaria Alba is one extreme, a low-growing tidy clump of fuzzy gray-green leaves that will spread in time to about two or even three feet across, but never grows above six inches high, except when it flowers. The small, white flowers come on slender spikes two or more feet tall.
Obviously, a plant this low with such exceptional foliage belongs up front in the planting scheme. The fact that the flower spikes are so much taller adds a little unregimented spice to the scheme.
If you have trouble finding this perennial, try another that looks much like it--lamb's ears. Lamb's ears has even prettier foliage, though it is not as long lived, looking poorly all winter and lasting about two years before needing to be replaced.
In compensation, it grows very fast, spreading to three feet by the end of the season. It too has flower spikes, but they are only two feet tall, with nearly invisible pink flowers. I usually cut them off, preferring foliage alone.
Now for a little contrast. Try that common perennial columbine just behind and off to the side of either the lamb's ears or the lychnis.
Columbine has leaves that pick up the gray in the other two, but the effect is of contrast because the plant is tall and airy, instead of low and dense. Flowers bloom off and on all spring and summer, and are lovely pastel hues on three foot stems. Start with good-sized plants, as columbines grow slow.
Another plant that contrasts well is the blue bedding salvia, Salvia farinacea , a perennial often grown as if it were an annual. It grows a little over a foot tall and just as wide, with slender spikes of purple.
In my own garden, these four perennials grow in front of roses, but to either side I plant perennials that colonize. They spread to form good-sized thickets. One of these is the double-flowered Shasta daisy named "Esther Read" that grows to about two feet tall, and the other is Physostegia , which grows to about three feet tall.
The Shasta daisies become the mainstay of the garden in June, blooming along with dwarf agapanthus, which, while common, are exceptional perennials nonetheless. The physostegia carries the garden into early fall, blooming at that time.
The Shasta daisies add the leavening effect of white to the garden, while the physostegia adds pink or purple. Both are what I call colonizing perennials because they spread underground to make small forests of stems.
Space small plants about a foot apart and they will fill in by summer's end. Each year, in winter, some must be pulled out to keep everything in bounds, and to keep them out of the roses.