North America is a vast land, and the seasons are very different, depending on what climate zones you are. This seems obvious, but when it comes to gardening, that variation means making different choices from among the often-bewildering range of plants available. For new gardener’s this is especially troublesome, so to help you make the best choices, avoid wasting money, and end up with a great garden, we are going to look more closely over the coming weeks at some key plants for different climate zones. Since winter is already upon us in many areas, a great place to start would be in cold zones, meaning zones 2, 3, and 4, where winter cold is severe enough to seriously limit the plants that will do well in your region. A backbone plant in those zones, where the range of evergreens is very limited, is the Easter Arborvitae, a tough-as-nails evergreen that comes in a wide range of sizes and shapes, and that has some valuable foliage color variations too.
Thuja or Arborvitae?
This is a bit of a fake question, since the answer is that they are the same thing – but it still makes a difference. Thuja is the name botanists use (notice the italics) to describe a group of evergreen conifers found across the breadth of North America, and also in parts of east Asia. There are currently only five species recognized, and only two of them grow in North America. Despite looking very similar in many ways, those two American ones are different when it comes to climate, and the name ‘arborvitae’ would be best used just for one – the Eastern Arborvitae, Thuja occidentalis. Indeed, it was this tree that first earned the name, which means ‘Tree of Life’, because its high vitamin C content saved early explorers from dying of scurvy.
Eastern Arborvitae – the Cold Climate Choice
If you garden in cold areas, this is your ‘go to’ evergreen for hedges and specimens. Generally hardy right through zone 2, why battle to keep more difficult trees alive, when this one is easy? No, it isn’t as fast a grower as Thuja Green Giant, but that plant, popular as it is, only grows in zone 5. Colder climate gardeners should avoid being seduced by the wonders of Thuja Green Giant and stick to the tried and tested Eastern Arborvitae. Also called ‘white cedar’, or simply ‘cedar’, this plant will grow a respectable 12 inches a year when young, if well cared for, and given the shorter growing season, solid hedges can still take just a few years to create. This isn’t the place to go into why ‘cedar’ is a confusing (and wrong name), except to say that the true cedars look very different and they are only suitable for warmer climates.
Emerald Green Arborvitae – the Universal Evergreen
Eastern Arborvitae in the wild is a variable tree. Usually upright and growing as much as 30 feet tall, it is rather open in growth for gardens. A much better garden plant is the variety called ‘Smaragd’, but normally known as Emerald Green, a pretty accurate translation from the original Danish. Discovered in Denmark in the 1950s, this tree has one huge advantage over the wild tree. It doesn’t discolor in winter, staying rich green, and looking a whole lot better for it. It is more compact too, another big plus, growing a bit more than 12 feet tall, and only 3 or 4 feet wide. It’s perfect for a smaller garden as a single plant, and you can make a quick and easy barrier – trimmed or untrimmed – by planting them in a row, spacing the plants 2 feet apart (or 3 feet apart if you are more patient). If you don’t plan to trim them, then really there is nothing more to do but keep them watered, especially over the first few simmers. For a formal hedge it pays to start trimming almost right away, to get the densest growth and the flattest surface on your hedge.
Emerald Green Arborvitae really is ‘the universal evergreen’, because it is so versatile around the garden. Need a hedge? ‘Check’. Need some screening? ‘Check’. Need a clump of attractive trees to fill a corner? ‘Check’ once more. For an easy and attractive look, space plants in groups of 3, 5, or even 7, spacing them a little irregularly. This is so much more natural looking, and so more attractive. This tree grows well in most soils, tolerates full sun and partial shade, and rarely has serious pest or disease problems. It does like water, so if your soil is often damp, perhaps with a lot of clay in it, this is one tree that will be right at home. It will also grow in most garden soils, and tolerate some drought when established, but in very dry and sandy soil it won’t do so well.
Degroot’s Spire Arborvitae
While very nice, Emerald Green is trumped as a specimen by the gorgeous ‘Degroot’s Spire’. A variation of the same eastern arborvitae, this great plant grows taller – to 25 feet in time – but it stays slim, reaching only 4 or at most 5 feet wide at the base, and keeping a slender pyramidal tapered look. The foliage is more textured too, with coral-like clustering of the branches, and it is best not to clip it, but to let it develop its own natural beauty. Considering how hardy this tree is, it’s not surprising it was in Canada, at Sheridan Nurseries, Toronto, that Constant DeGroot found this plant in a batch of seedlings in 1970. Life moved more slowly then, and they waited until 1980 to release it, once they had seen its development better. Iseli Nurseries, Inc. of Boring, Oregon, were responsible for its introduction into the USA.
Hetz’s Midget and Little Giant Arborvitae
Upright evergreens are very nice, and useful too, but often we need smaller accents, in the form of rounded shrubs. The eastern arborvitae steps in there too, and for colder climates nothing beats two similar small, rounded forms of this great plant. ‘Hetz’s Midget’ is the smaller, reaching no more than 3 feet across and wide, and naturally forms a perfect sphere that is great for turning the corners of beds, or planting among more irregular shrubs. ‘Little Giant’ is similar, but can become a little bigger, reaching 4 feet if not trimmed. Of course, like ‘Emerald Green’, these little guys can be trimmed as needed, to keep them especially neat, or to control their size, but it’s an optional extra.
Golden evergreens are always popular, but in colder zones they are notorious for burning and browning in winter, so there are few choices. In fact, in zone 2 there aren’t any (sorry about that!), but for zones 3 and 4 you do have some great plants available, that in sunny locations will be rich gold in spring, summer and early fall. In zone 4 and sheltered spots in zone 3 you can choose the Sunkist Arborvitae, which has fabulous coloring, even keeping some through winter, on a plant reaching at least 10 feet tall, with a rounded form, almost as wide as it is tall. Spring trimming will really bring out the best gold growth and control its size too.
Reliable in zone 3, but turning green in winter, the Polar Gold® Arborvitae lives up to its name, and looks great through spring to fall, glowing golden yellow in your garden. Reaching 15 feet tall, but only 5 or 6 feet wide, it makes a stunning specimen, and its really hardy, so like all the forms of the eastern arborvitae, it is easy to grow, and adds another great plant to the garden palette of northern gardeners.