Doesn’t it seem so very green everywhere you look in late May? Is it the well-charged soil in early spring, full of moisture from the winter snows that is responsible? Perhaps it’s the cooler weather of March and April that delayed leafing out and now trees and shrubs are bursting out with more exuberance than usual.
Whatever the reason, green is supreme in our valley this spring. This makes the startling colours of the members of the broom family even more outstanding. Gardeners like to group together Cytisus scoparius, Genista lydia and Genista pilosa under the moniker “broom” just as there are about six or eight plants called “japonica.”
Regardless of which plant genus it is, broom does extremely well in our soils, loves the sun and thrives in hot summers. Both the Cytisus and Genista tolerate sandy, dry soils, as they are native to Central Europe. Cytisus scoparius, the Scotch broom, is the most common species found in the nursery trade. It will also grow well in clay soils. It’s so well adapted to poor growing conditions that I find gardeners who are working hard to keep them well-watered and fertilized often kill the plants!
Cytisus scoparius grows somewhat upright to about four to six feet tall, with finely textured foliage that remains green year-round. It’s cold hardy to Zone 5, fine for most of the valley but perhaps at the edge of its hardiness range as you get higher and away from the moderating influence of the lake. The flowers look like smaller versions of the sweet pea and cover almost the entire plant in May when in bloom.
In Europe, where the plant is extremely popular, there is a long list of cultivars available. This is not the case in North America, where the choices are limited to about ten cultivars, including those of Cytisus x praecox, a hybrid between two other species known commonly as the Warminster Broom. Perhaps we will see more of these beautiful colours coming from Europe in the future as it seems there are as many colours in broom as there are in petunias over there.
Genista lydia is covered in deep yellow blooms right now, forming a mound of arching stems about two feet high in the landscape. They look great massed together in groups. Like the cytisus it thrives in poor soils and in full sun and has fine textured branches and stems that remain effective over the winter.
If you’re looking for a plant that stays very low to the ground look for Genista pilosa. The flowers are similar to those of Genista lydia, and the plant grows about a foot high and three feet wide. The cultivar ‘Vancouver Gold’ was introduced by the UBC Botanical Garden back in the 1980’s.
For a splash of colour in a landscape border or on a cultivated hillside broom, whether it’s Cytisus or Genista, is an excellent choice, particularly given it’s adaptability to our growing conditions. A closely related plant is gorse, or Ulex europaeus. You’ve likely seen lots of that if you’ve ever golfed in the United Kingdom, especially in Scotland, and failed to keep your ball within the confines of the fairways.