Around the Garden

For a gardener, there’s more to sports than throwing balls around. Superbowl Sunday is history, and before March Madness begins, let’s talk about the other kind. Even before the discovery of DNA, keen observers of nature knew about mutations. Horticulturists use the term “sport” to describe a mutation of a plant that produces a branch or shoot with interesting characteristics. Merriam-Webster describes a sport as a “sudden spontaneous deviation from type.”

One of the most commercially successful sports was the one that allowed the breeding of the Dwarf Alberta spruce, an evergreen tree widely used as a foundation shrub. Like many sports, the Dwarf Alberta spruce bears little resemblance to its parent tree, the common White spruce. In fact, it was originally just another “witch’s broom,” a common phenomenon of conifers.

Where the White spruce has large, widely separated branches that grow around the trunk in whorls, the Dwarf Alberta has dense branching and even more dense side shoots. The needles are short and prickly, and the outer edge of the plant can appear to be an almost solid sheet of green.

The Dwarf Alberta is much beloved of landscapers, for it has a remarkable growth habit – an extremely regular cone-shape. For homeowners who like their shrubs pruned into geometric novelties, the Dwarf Alberta is a nearly perfect solution. (Of course, being a mutation, Dwarf Alberta spruces can’t be counted on to reproduce from seed; the nursery approach is to grow new trees from cuttings or tissue culture, so each new tree is basically a clone of its parent.)

I say nearly perfect because, eventually, the tree grows into its destined size – much, much larger than a foundation shrub should be. Unfortunately, that is just nature expressing itself: trees tend to keep growing taller and taller, and they really dislike being cut back.

Like most trees, the Dwarf Alberta will, if topped, sulk for some time. It will then do what trees do – produce several new leaders where once a single leader grew. Now the “shrub” has a perfect cone-shape, except at the top, where something like a bunch of bananas has burst forth. A careful gardener will remove those shoots, but this will again cause the would-be tree to sulk further. It’s often at this time that a villain appears on the scene – and I don’t mean the landscaper who recommended this tree where a shrub should have been planted.

This villain is really nasty – and voracious! The Spruce spider mite is a tiny eating-and-reproducing machine that infests not just the Spruce family, but most other conifers that grow in our area. The Dwarf Alberta spruce is good eating for these mites, and also provides great shelter. For those inclined to spray, the density of these trees presents a challenge. If you could just pick up each tree and dunk it in a vat of pesticide, you might win, but spraying usually has to be repeated several times, not least because the mites may produce several generations per year.

And, finally, the other problem with this tree is its very structure: that dense green outer coat of needles makes it difficult for sunlight to penetrate. Conifers like a lot of sun, and react to lack of sun by not producing new needles. So, if you separate the outer twigs, you will often see bare branches within the plant. Once this die-back occurs, pruning becomes extremely difficult: as soon as you cut off the first inch of a branch, you come to a bleak, bare inner branch. This is in effect a dead branch – you have just cut off its living tip, and the bare stretch all the way back to the trunk will not produce new needles or twigs.

The ultimate solution for gardeners who want to have uniform-sized plantings is to remove the entire plant. Sad to say, this “sport” is somewhat stacked against the gardener – sort of like that match-up between the Giants and the Patriots, unfortunately.