Shrubs and Small Trees in Cold Climates

– Posted in: Book reviews, Plant info

The standard (and good) advice is to plan your garden first, and then plant the woodies, the trees and shrubs, before anything else. This advice is rarely followed. Why? Because most gardeners don’t plan on being gardeners. It sneaks up on them. And what usually snookers them in is not a tree, but some ravishing blooming plant under ten bucks. Before you know it, they’ve planted lots of plants pretty much wherever it was most convenient. Two or three years down the road, they somehow come to the realization that their garden doesn’t form a cohesive whole, it needs structure–the whole song-and-dance. Or they visit someone else’s garden and actually do fall in love with a tree or shrub. And that’s when they start thinking about design, and what trees and shrubs they want in their garden.

In my humble opinion, it is even more important to consider cold hardiness with trees and shrubs than it is with herbaceous perennials. For one thing, they don’t die to the ground in winter. Whatever’s going on in the frigid months, they have to deal with it. Also, they take longer to mature. Who wants to wait five years for a tree’s first bloom, only to have it die the winter before it was to have been spectacular? And, these plants are more expensive, so if you gamble, there’s more at risk. Enter Growing Shrubs and Small Trees in Cold Climates by Nancy Rose, Don Selinger, and John Whitman. This book will save the cold climate gardener a lot of heartache, grief, and money, for the reasons I outlined above. It will also save you time, because your list is whittled down for you ahead of time. This is especially valuable with genera such as rhododendrons or magnolias, where considerably more of the plants available are not hardy enough for USDA Zones 5 and colder.

This book is from the same series as the perennial book I reviewed last week, with the same thorough treatment of each genus. After a brief introduction, the general growth habit of the shrub or tree is described. You’ll learn about the genus’s root structure, single or multi-stem, foliage texture and color, flower structure, color, and season, notable attributes of the bark and seeds, and whether or not it self-sows, which is as close as you’ll get to suspecting if it’s invasive or not. After the plant’s habit, sections on where to plant, landscape use, planting techniques, transplanting advisability, general care, problems, propagation, special uses, and sources follow. A list of cultivars and their particular hardiness and other quirks ends the entry for a given genus. In the planting techniques section for each genus, you’ll be told which forms (bareroot, container, or ball-and-burlap) the plant is usually available in, which form or forms is most likely to grow successfully, and how to vary your planting technique depending on what form you’ve got. In the transplanting section (and sooner or later, we all decide to move the furniture) you’ll learn not only when to transplant, but whether it’s even possible with that particular plant. Under problems, you’ll learn whether the genus in question is especially tasty to deer, or if it’s vulnerable to winter burn or snow damage. When discussing cultivars, they tell you which of them are more fragrant, or hardier, or more floriferous or whatever it is that makes you smack your head later, when you find out that x is better than y, and, you, of course, bought y.

After we’ve gone through all the plants, we come to the second part of the book, where various principles and techniques in growing woody plants are elaborated on, things like what to consider when choosing them, what to look for when you go shopping, the best time and way to plant, selecting and preparing a site, and best care practices, including staking, deadheading, and pruning. They go into greater depth as to how to prevent problems and how to deal with them if they happen anyway. (“Humans often do more damage than animals, diseases, and insects combined.” Can you believe it?) There is a thorough section on propagation and another on special uses for shrubs and small trees, which primarily covers using them decoratively in the home.

A couple of things worth noting: the title says small trees, so when discussing conifers, they only deal with the dwarf ones, and you won’t find sugar maples in the Acer section. When discussing fruit-bearing trees and shrubs, you’ll know if the fruit is good for eating as well as ornament, though the discussion of apples, pears, and plums for eating is necessarily superficial. One thing that made me uneasy is they include a few genera that are “iffy” in my book. They leave Cornus florida, the flowering dogwood, out of their Cornus section, as well they should, but they include a section on Cercis, redbud, which I don’t think is any hardier. And they come right out and say “Wisteria has a reputation for being very difficult to grow in cold climates. The keys to success are simple: choose one of the five plants in the varietal chart and grow it exactly as indicated.” I guess they figure if crazy cold climate gardeners are going to try, they might as well give them their best chance for success, but to me, we’re getting into gambling territory here . . . not for the faint of heart.

Whether you’re a gambler or a nervous Nellie, this book will enable you to make a well-informed choice for your garden. So before you reach for your credit card, reach for this book.

About the Author

Kathy Purdy is a colchicum evangelist, converting unsuspecting gardeners into colchicophiles. She would be delighted to speak to your group about colchicums or other gardening topics. Kathy’s been writing since 4th grade, gardening since high school, and blogging since 2002.

In the end, this may be the most important thing about frost: Frost slows us down. In spring, it tempers our eagerness. In fall, it brings closure and rest. In our gotta-go world–where every nanosecond seems to count–slowness can be a great gift. So rather than see Jack Frost as an adversary, you could choose to greet him as a friend.

~Philip Harnden in A Gardener’s Guide to Frost: Outwit the Weather and Extend the Spring and Fall Seasons

Comments on this entry are closed.

Kathy Purdy November 28, 2006, 6:32 pm

So, Annie, it seems like where the redbud was originally grown makes a big difference. Now I don’t feel so bad for being leery of it.

Annie in Austin November 28, 2006, 3:50 pm

If you don’t mind some remarks from an IL-to-TX transplant, I know people who grew Cercis canadensis in the suburbs of Chicago … make that “tried to grow”. Just as the trees would start to get some bulk, a bad winter would kill them to the ground and the process would start again. So they lived, but were large shrubs rather than trees. I don’t think Chicago has had one of those winters in awhile, but we used to dip under -15ºF every 3 or 4 years, which usually meant farewell to that spring’s Forsythia blossoms and dead trunks on winterkilled Redbuds.

From the late 1980’s on, the Victory Garden on public TV inflicted even more zone envy on us Northern gardeners by repeatedly showing and planting the Cercis ‘Forest Pansy’ cultivar, then blithely mentioning that it was hardy to zone 6.

Here in Austin, we plant Cercis canadensis texensis or Cercis canadensis mexicana, because it’s too hot and alkaline for the Eastern Redbud. I’ve planted Texas redbuds at both my houses, but had to have a ‘Forest Pansy’ – now planted as an understory tree with afternoon shade from a Live Oak.

Annie at the Transplantable Rose

Kathy Purdy November 26, 2006, 9:53 am

Craig–On the book jacket it says of Don Selinger, one of the three authors of this book, “since 1973 he has worked for Bailey Nurseries.” The book is copyright 2001, so it is possible he no longer works there, but obviously he had the right kind of experience to contribute to the book. I will definitely start looking for the “right kind” of redbud. Anyone who knows of a mailorder source, please pipe up.

I have been growing Cornus mas ‘Spring Glow’ since 2001. This was the first year it really blossomed for me, and I believe it was later than my ‘Meadowlark’ forsythia. I planted it up the hill, so it could be seen from the back of the house (2nd story), and it wasn’t glowing enough for that. I did take pictures, but looking through my archives I see I never posted them. Maybe this winter? Anyway, I don’t think we’ve actually had a Zone 4 winter since I planted it (at least, not in terms of minimum temp), but we have had drought that possibly slowed it down. I’d rate it as worth a gamble, but slow to come into its own.

Craig Levy November 26, 2006, 7:36 am

My Cercis originated from the University of Minnesota program and is zone 4 hardy. It was such a pretty thing when it flowered this year and I’m glad I bought it. It was grown by Bailey Nurseries, a wholesale grower based in Minnesota. Their specialty is woody plants and they often have the cold hardiest forms of many plants. You can browse their library here. It’s unfortunate their website doesn’t list local dealers.

I bought a Cercis ‘Forest Pansy’ based on the positive report of an acquaintance. It is definitely not hardy. The purple leaf section above the graft died after its first winter and the rootstock, regular not-hardy C. canadensis, acts as a herbaceous perennial and has come back from the roots the last two years. Its dichondra-shaped foliage is pretty and provides great contrast but it will never flower, gain size, or become woody. Having this book would have saved me from re-inventing the wheel.

I don’t grow any of the taller or tree-like Cornus but a friend in a zone 5 has C. mas. It’s brilliant yellow flowers were spectacular this year. Imagine the color of a Forsythia on a very upright small tree. I’m sorely tempted but will have to look it up in the book!

Kathy: My “good” Cercis is in a nasty area. Its location is fully exposed: no nearby trees or buildings, full sun, and a constant winter wind. Spring or early summer are the recommended planting times but I, once again, planted mine in mid-fall. That it has succeeded owes more to the plant’s toughness than my efforts. It really is a unique looking plant, looks boffo with other plants, and you should try it if you can find the hardy strain.

Kathy Purdy November 24, 2006, 1:25 pm

Tracy: I will be the first to admit that winter hardiness in plants is actually quite complicated. On my country road, there is one Cornus florida growing that I believe is growing wild, that is, not planted by humans. It does look like it’s struggling, but it’s there. When that tree blooms, I see scattered white-blooming trees along the interstate that I suspect are also the flowering dogwood growing wild. We seem to be at the northern limits of its range. And yet, a landscaping firm sold and planted a flowering dogwood for my neighbor and it didn’t make it through one winter. It probably wasn’t grown from local stock.

I confess I’ve never tried growing a redbud. I’ve heard of too many failures. Even in the book, they do say redbuds “require a sheltered location in colder climates to reach their full potential.” They list the straight species and ‘Northland’ as hardy to -30F, and the white form as hardy to -25F. I have seen Cornus florida rated that hardy in other sources as well. To me they are both marginally hardy, and I was trying to warn people that the authors were more willing to gamble than I was. I think if I found a source for either tree that were grown from northern stock, I’d be sorely tempted, especially if I could figure out what was a sheltered location on my property.

Tracy November 23, 2006, 8:49 pm

Kathy: FYI – You mention the flowering dogwood as being approximately as hardy as the redwood. At least in Minnesota (where co-author Nancy Rose is located), the redbud has been growing successfully at the University of Minnesota Landscape Arboretum for probably 15-20 years, whereas they have never been able to establish a flowering dogwood. I suppose it depends on how exposed the location is, but there are redbuds that will grow (and flower) in zone 4a. However, neither is native to this area.