During the winter months, when so many garden plants are taking a rest or going dormant, it is wonderful to have something which bursts into bloom and provides a shot of color when we need it most. Aloes are excellent choices for filling this need, with their spires of flowers in fiery colors. Not all aloes flower in winter, but many of them do. These range from tall plants with trunks, such as Aloe barberae (syn. – Aloe bainesii) or Aloe ferox, to stemless rosettes such as Aloe vanbalenii or Aloe microstigma, to dwarf plants such as Aloe humilis.
Most of these winter-blooming aloes come from South Africa, which lies in the Southern Hemisphere and thus has its winter at the opposite time of the year. The story is sometimes told that they are blooming in the same month that they would back in their native habitat, which causes them to flower here in the winter, when this would happen in summer back home. This is not true at all; they flower in response to the changing day length regardless of which hemisphere they are in, so the plant flowering in January in our gardens would be flowering in July back in South Africa. People sometimes also say that the plants which flower in winter are native to the winter-rainfall region of South Africa, and they spring into action when the rains arrive. This is also not true, since there are many winter-bloomers from the summer-rainfall part of South Africa, as well as from the winter-rainfall part. So why do so many species bloom in the winter? Perhaps part of the reason lies with their primary pollinators, the nectar-loving sunbirds. During the summer months there is lots of competition for the birds’ attention, but by flowering in the winter, when the competition dies down, the aloes are assured of getting noticed by providing a crucial source of food when the birds have few other options. It is a win-win situation: the sunbirds get the fuel to make it through the winter, and the aloes get pollinated.
We do not have sunbirds in North America, but the same kinds of nectar-producing flowers which appeal to them are also irresistible to our hummingbirds. Thus a garden full of aloes will also be a great place to witness the aerial acrobatics of these little speedsters.
All aloes are native to Africa, the Arabian Peninsula, and islands in the Indian Ocean (principally Madagascar), and it is not a coincidence that many of the species in cultivation are specifically South African. This is the part of their range farthest from the equator, where the seasons are more pronounced like our own, with shorter days and cold spells in the winter months. An aloe from the tropics might turn to mush when the temperature drops to freezing, but many of the South African kinds will take it in stride. There are limits to this, and few aloes (even those from South Africa) will tolerate temperatures below 25°F, but many can take lows down to 29°. It follows that there are more choices for successful growing in areas nearer to the coast, where winter temperatures are less extreme, and fewer options as you go farther inland and freezes are a fact of life. When considering plant choices for your garden, learning a little bit about the cold tolerances of the various kinds will be an asset.
By Brian Kemble
Ruth Bancroft Garden