September is upon us, hoorah, and we can get back to the business of gardening after the heat-driven ennui of high summer.
At garden centers, plants tend to sell when they’re in bloom and not sell when they’re not, but here’s a secret: It’s perfectly fine to purchase something in a pot that isn’t flowering its head off or even absurdly lush.
If I’m browsing for perennials at this time of year, I’m much more interested in the vigor and health of the root system and the condition of the crown bearing next year’s buds than I am in the top growth. The roots should fill the pot but not be so congested as to be pot-bound.
September is a great month to lift and divide perennials already in the garden and to plant new ones, whatever their stage of ornament. Fussing with out-of-season perennials (or shrubs, trees and vines, for that matter) serves another purpose, teaching us that gardening is not a springtime endeavor but a year-round enterprise. You would be amazed at how many people have not grasped that.
Sign Up and Save
Get six months of free digital access to The Idaho Statesman
No plant exemplifies the garden’s constancy better than a May-flowering perennial named false indigo, or baptisia. No sunny garden should be without one, and now would be a great time to get and install a young plant. Baptisia generally grows well in zones 5-8. Much of southern Idaho is in zone 6-7.
If you buy, say, an aster blooming in a one-gallon pot, you have a pretty good idea of how it will look in the garden, as a mounded mass of purple daisies. But with the baptisia, you have little sense - even if you buy it “in season” in spring - that the meager number of shoots will develop into a clump four feet high and five feet across, plumed with dozens of flower spikes redolent of lupines. (Both are in the pea family.) After flowering, its leaves have a bluish cast and function as a textural foil with other plants.
The reason for the baptisia’s slow start is that this perennial - as with a clematis - devotes its first three growing seasons to building a large, deep root system before turning its attention to the top bit. The gardener has to be forward-thinking and not crowd it in with other plants at planting time. Baptisia is free of pests and disease and thrives in hot, dry sites once established. I can think of only two minor vices: The “ankles” are a bit bare and could stand to be hidden among lower-growing neighbors, and plants nudged into the shade may flop.
But it is a big perennial, and it may help to think of it as a small to medium shrub in figuring out where to plant one and with what. Because of its deep roots, it’s a plant best left where it is. It blooms in the back end of May after the main spring fling, and flowers at the same time as catmint, early salvias, bearded iris, yarrow and cranesbills, to name a few.
The contemporary fortunes of baptisia only get better. As a handsome and low-maintenance native perennial that benefits pollinators as well as gardeners, it is charmed, and it has drawn the attention of plant breeders who have sought to improve upon the species, actually several species. The result is a number of varieties blooming in shades of blue and violet, bold yellow and white. Novelty colors run to reddish maroon and a muddy orange.
Much of the hybridizing has been focused on producing garden plants with great flower show and a more compact habit. The baptisias proved an ideal subject for evaluation by horticulturists at the Mount Cuba Center near Wilmington, Del., who looked at a total of 46 selections over four years and have just rated their top 10. Here are the results:
Screamin’ Yellow: Compact but wide, it produces an abundance of golden-yellow blooms and dense bluish foliage.
Lemon Meringue: A slightly softer yellow with attractive gray stems, it produces a broad vase shape 38 inches by 56 inches.
Ivory Towers: Consistently exceptional and the best-rated white variety, it is valued for its dramatic seed pods, which are coveted for floral arrangements. It grows to 46 inches high and 54 inches wide, but its upright shape makes it appear more slender.
Blue Towers: Again, a tall but slender baptisia, it’s valued for the density of its violet-blue flower spikes.
Purple Smoke: The Mount Cuba gardeners considered this variety, one of the oldest, to be a stellar performer with pale lavender blooms and smaller-than-average leaves that give it a fine texture. It grows to 36 inches by 48 inches.
Cherries Jubilee: This is a red-maroon variety that appears a dull orange from a distance. It has a medium-size habit and unusually numerous flower spikes.
Sunny Morning: This yellow variety has “excellent vigor and a stunning floral display,” according to Mount Cuba’s horticulturists. It grows to 40 inches by 58 inches.
Blueberry Sundae: This is deemed the best compact blue-flowered variety, packed with flowers and growing to just 32 inches by 38 inches.
Dutch Chocolate: Another novelty color, this variety has purplish maroon flowers and a compact habit.
Crème de Menthe: It has pale yellow blooms that are dramatically contrasted with the gray blooms of its stems and flower “cups,” or calyxes.
Mail-order sources include Bluestone Perennials, Plant Delights Nursery, Klehm’s Song Sparrow and Forestfarm.