While their flowers bring beauty to our borders, their roots supply nitrogen to the soil.
Too few gardeners are acquainted with members of the pea or pulse family, many of which grow in my rock garden and border. All excite inquiries and enthusiasm from visitors.
All are hardy, long-lived, and easy to grow, needing little or no special care.
Blooming Dwarf Genistas “Brooms”
The first to bloom are the dwarf genistas or brooms, rock garden treasures that differ only slightly from the cytisus, also called brooms.
Early in May, in my Maine garden, a neat little Genista pilosa begins to show a color change in its clump of small, grayish-green leafy stems.
The buds appearing thickly at every branch tip are pale lavender and wooly, but the little close-packed spikes soon open into a mound of golden pea-blossoms. The plant fairly blazes for several weeks.
Genista Sagittalis
Next to bloom is Genista sagittalis, with dull green strap-shaped leaves 6” to 8” inches long, nearly prostrate along the ground.
The fat buds and new leaf growth are strikingly different from the mature plant, much lighter green and intensely wooly, with little apparent relation to the foliage beneath.
The buds soon produce similar but larger bright yellow blossoms—a glorious splash of spring color cascading over a flat gray rock.
Genista Sylvestris Pungens
The oddest of all is tiny Genista sylvestris pungens, formerly listed as G. dalmatica, a dense, prickly little mat of spiny bright green stems with brilliant golden flowers.
This buds soon after G. sagittalis. All three genistas seem to delight in a light, sandy, gritty soil in full sun, with rocks as natural companions.
Although a limey soil is sometimes recommended for G. sylvestris pungens, it seems happy in the same rather acid soil as the others near bearberry, bird’s-foot violets, and bristled asters.
Genista Tinctoria
The old-time dyer’s greenweed, or common woadwaxen, thrives in the same sandy soil but requires much more room than the others.
A mature, well-established plant will stand about 3’ feet high, with a great spread of its brown, woody branches, making a thick, leafy clump.
The new stems are light green; the leaves, a light gray-green, are larger than those of G. pilosa and thickly set on the whiplike stems.
Last spring, many branches on one side of my plant grew across the path while the other stood almost straight up, backed against a large boulder.
The early-formed buds open in late June, producing a long-lasting wave of solid gold color over the green foliage clump.
The plant usually sends out a lesser burst of bloom in late summer when cut back again after blooming.
A clump of darker-foliaged heather makes a natural companion for this pea family member, especially effective when cold weather has shaded it to reddish-purple and bronze.
The dark gray-green rosettes mats of pussytoes (Antennaria dioica) are an interesting contrast as a ground cover beyond the shrubs.
Genistas may be grown from seed but have not germinated well for me; the seedlings usually fail to survive their first winter in the open. Layered branches or cuttings may be more successful.
Close Cousins
Close cousins to the genistas are the baptisias and Thermopsis, neither as commonly used as they deserve to be.
Thermopsis
The tallest of the Thermopsis species is Thermopsis caroliniana, often called the yellow lupin.
The handsome dark green foliage is three-parted and shows a close kinship to the lupins, also belonging to the pea family. The tall spikes of soft yellow blossoms appear in late June, along with the Siberian iris and the first delphiniums.
This makes thermopsis especially useful for color pictures in the border and for cut flowers. Established clumps may reach 5’ feet in height, with many spikes in bloom.
Blooming stalks may be cut back for the best appearance after bloom (unless seeds are wanted), or a few stalks and seeds may be left for the fall birds.
Thermopsis is easily grown from seed, usually blooming the second summer and increasing in size and strength each year.
Self-sown plants are sometimes found, enough for gifts to interested visitors. The plants seem satisfied in any good soil with reasonable moisture and full sun.
Baptisias
Baptisias also need plenty of room for their best development since they make large, rounded clumps of foliage, with individual plants covering an area of 3’ or 4’ feet in height and width by mid summer.
The blue wild indigo, Baptisia australis, is handsomely used as a hedge, with foliage of waxy light grayish-green on strong branches and light green stems. Countless erect stalks of large medium blue pea-blossoms cover the clumps in early June.
As soon as the large, rounded seed pods appear, it is best to cut back most of the branches to lessen the load, leaving only a few for seeds or dried bouquets. As they ripen, the heavy pods turn dull black, shining when wet with rain.
Self-sown seedlings often appear around the garden and may be easily moved while small. Large plants may be moved if necessary, even though the long taproots may be broken, but there may be several seasons in which they return to normal size and bloom.
The blackish shoots appear quite late in the spring, so other low-growing plants should be interplanted to provide earlier bloom.
Baptisia Leucantha
One or two plants of white-flowered Baptisia leucantha add contrast when planted among the blue kinds.
Although listed as lower-growing, it grows somewhat taller in our Maine garden, perhaps because it is even later starting into spring growth and thus is forced into topping the others for its share of sunshine.
The foliage is similar, but instead of a rounded clump, it spreads into a flattened umbrella shape just above the other plants. In July, the tail-branching stems of large white pea blossoms appear; the flowers are more scattered on the stems than those of B. australis.
Baptisia Tinctoria
A third baptisia, Baptisia tinctoria, is less husky. It has delicate light gray-green leaflets, more widely separated on the stalks, giving it a daintier appearance. The small light yellow blossoms in slender racemes appear in late July and early August.
Its yellow tones clash with the red-orange milkweed, so the two plants must be well separated. A well-established plant makes a wide spread clump 2’ to 3’ feet wide and high.
Baptisia Bracteata
I hope someday to grow the early-blooming dwarf Baptisia bracteata, with drooping cream-white spikes, but its seedlings have failed to survive the winter.
Like the closely related lupins, the baptisias are noted for storing nitrogen from the air in small white nodules on their roots. By thus enriching the soil, they make themselves doubly worthwhile as plants for our gardens.
44659 by Grace F. Babb