It’s the middle of December, we had a little snow overnight, and that is definitely going to influence this article. It’s winter and the plants on my mind are evergreens. When most people think about evergreens, they’re thinking about pine trees, but there are plants that keep their leaves all winter that aren’t conifers. They are called broadleaf evergreens and very few are native to Colorado. We do have some, though, and they are worth including in your garden: kinnikinnick, curl-leaf mountain mahogany, and creeping grape holly come to mind. These plants provide a break to all the brown and gray of winter, and are drought resistant, too. Their texture is different from the needles of pine trees, but they combine well with them. When people talk about gardens with winter interest, evergreens, both broadleaf and coniferous, are the main thing they are talking about–that, and the ornamental grasses that are a graceful counterpoint to evergreens of all kinds.
We have three different types of mountain mahogany at the nursery, the native one that grows on the hills around us, Cercocarpus montanus, sometimes called “true” mountain mahogany, Cercocarpus ledifolius, curl-leaf mountain mahogany, native to the Four-Corners region, and Cercocarpus intricatus, narrow-leaf mountain mahogany, native to the western part of Colorado and most of the western half of the U.S. The only drawback to these wonderful shrubs is that deer also think they are wonderful. A friend gave me a very special dwarf form of Cercocarpus intricatus and I said, “Thanks, but they’re all dwarf around here, because of deer browsing.” If you can protect them until they get established, and get to a certain size and strength, say for the first three years after planting, you can have a very fine shrub. Like most trees and shrubs, at a certain size they are either unappealing to deer, or they are big enough and strong enough to withstand some browsing.
We overwinter most of our potted shrubs in an unheated cold frame. Here is a picture taken inside the cold frame, and below that a picture of Cercocarpus ledifolius under a layer of winter blanket, and then finally a picture of C. ledifolius outside, in an area where we don’t cover them at all. Inside or out, they will survive the winter without damage; this is a tough plant! The pallets are put up to stop the deer from munching on the trees and shrubs in this area.
There are quite a few Mahonias native to the western half of the country, including Mahonia repens, commonly called creeping grape holly. It’s a great evergreen groundcover for dry shade. There are very few plants that will grow in dry shade, and this is one of the best. It has pretty bright yellow flowers in spring, blue berries in fall–it’s interesting all year around. There is an upright species, Mahonia aquifolium, AKA Oregon grape holly, that we plan to grow this year in the nursery. It is a beautiful shrub and in winter the foliage develops a burgundy cast that overlays the deep forest green. Excellent for an eastern or northern exposure. I used to think, because it’s called “Oregon,” that it wouldn’t be hardy here, but it is (to around 7200′ elevation.) It crosses with M. repens, too, so you can find some interesting natural hybrids. Mahonia aquifolium can get winter burn if it is in all day sun. Some shade is appreciated.
In general, broadleaf evergreens are more fire resistant that pines and other conifers, so when you think about adding winter interest to your garden, these are good choices for that reason, too.
Mahonia haematocarpa, Red Berry Mahonia, or Desert Holly, is native to the very far southern section of Eastern Colorado, as well as New Mexico and Arizona. At maturity it is tall, four to six feet in height, and almost that wide. The leaves are small and tough with a spiny tip. This shrub would make a good barrier! In spring it has yellow flowers, in summer red berries, and it keeps it’s leaves all year round. Deer don’t seem to like it. It can survive on our natural precipitation, even in the driest years. Here’s a picture of it in flower and one from the wild area outside our garden.
Stay tuned, The Garden Year in Review: Perennials 2017 will be posted next week!