How (Not) to Pick a Plant

Over the coming months I’ll be basing a number of blog posts, including this one, on material from my forthcoming book, The Shady Lady’s Guide to Northeast Shade Gardening. The official publication date is May 6, 2014. You can learn more about the book here, here and here.

When you pick perennial plants to put in your shade garden, how do you do it? Most people would start out by picking plants they like—and that’s where they’d make their first, and worst, mistake.

Huh? What? Surely I can’t be advising you to pick out plants you don’t like?! No, of course not. But think about this for a second. When you go shopping for a new car, do you just pick out the one you like the best? No—at least not if you’re like most of us. If that were all it took, we’d all be driving around in Ferraris and Lamborghinis. The problem with that approach is that most sports cars won’t do what most people need a car to do: get up a snowy hill on a winter day and deliver you to your job in one piece, or get enough miles to the gallon to not break the fuel budget.

Instead of just picking out a car we like, most of us have to consider questions like these: How much will the monthly payment be? How much will it cost to insure? Is it expensive to maintain? Can it accommodate everything and everyone I need to cart around?

In other words, we consider practical things. As weird an idea as this will seem to many people, you should do the same thing when you pick out plants—if you want your garden to look good with minimal effort and expense for the longest possible season.

Not all plants are equally good at doing that. In fact, for any given type of garden in any given region, only a small number of plants will give that kind of superior performance, in the same way that, in all likelihood, only a small number of cars will satisfy your criteria for budget and functionality.

So, what are the practical questions you have to ask when picking out plants? First, the more obvious ones:

• Is the plant cold hardy where I live?
• Does the plant prefer the conditions I can offer it?

It’s self-evident why these are questions you should ask first. It makes little sense to populate your perennial garden with plants that won’t be, well, perennial in your area. It also makes little sense to invest in plants that won’t be happy with the growing conditions you provide them. Matching plants to growing conditions is an essential part of the art of garden design. I’m not going to go into detail here about the fine points of that process; what matters is that you realize its importance.

What else do you need to ask yourself in order to pick the best perennials for shade? Here are a few more:

• Is the plant disease resistant?
• Is the plant prone to insect infestation?
• Is the plant unpalatable to deer and other potential browsers?
• Does the plant spread or seed aggressively?
• Does the plant typically go dormant before first frost?
• Does the plant have foliage that looks good all season long?

(Notice that we still haven’t even allowed ourselves to ask about flowers, the thing most gardeners consider first, sometimes to the exclusion of all other things!)

The benefits of disease and pest resistance are obvious. Lungworts (Pulmonaria, see photo at left), for example, have unique speckled foliage that can brighten shady nooks and crannies, but most of them are prone to a disfiguring fungal disease called powdery mildew that leaves them coated with an unattractive whitish film. Luckily, some lungworts are resistant. If you buy only the resistant ones, you’ll be able to enjoy the beauty of disease-free lungworts, and you won’t have to expend extra effort to keep them that way.

It’s the same story for all the other questions above. By carefully selecting plants that aren’t palatable to most insect pests and browsing animals, you eliminate the need to take action to stop various critters from nibbling. Likewise, you reduce the need for work (and increase the percentage of your time in the garden devoted to enjoying it) by avoiding overly aggressive spreading plants.

Finally, as a general rule plants that perform well over a long season should be given priority over those that go dormant early or whose foliage declines in quality after flowering. Obviously, we’d all prefer a garden that looks full and good for the longest possible stretch of time.

Okay, we’ve covered a lot of ground. Are there other questions that should be on our list? You bet there are!

• Does the plant have attractive, prominent flowers? (Finally!)
• Do the flowers have a scent that’s nice, objectionable or simply absent?
• Do the flowers last a long time?

And there you have it: questions about flowers are in last place. Now, I want to clarify something. I understand perfectly why so many home gardeners give in to the temptation to fill their properties with plants having beautiful flowers. Beautiful flowers are lovely to look at—it’s as simple as that. The problem is that we don’t live in an ideal world. Flowers fade, and most perennials only produce flowers for two to three weeks every year under the best of circumstances. That’s not very long, so if you pick plants based on how well you like their flowers, you won’t get much bang for your buck.

I’m not saying that you should ignore a plant’s flowers when making choices. For instance, it is true that a small number of perennials will flower for a longer-than-average time, and can be worthwhile making room for these plants in your garden for that simple reason. One example is the Japanese anemone pictured above. I’m just saying that most of the time you should only be considering the flowers of plants that have passed muster in a lot of other ways first. Flowers should be your last consideration, not your first.

When you do get around to considering flowers and fragrance, you don’t need my advice, because this is where personal taste takes over. As one example of how variable that can be, I’ve always found it strange that some people cut off the flowers of hostas. I think they’re very showy, and sometimes they have a wonderful perfume, but you know the saying: there’s no accounting for taste.

In my next blog post, I’ll elaborate a little more on what makes a superior shade perennial and share a few examples.