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Made for the Shade?

Larry Hurley Maryland Shade Garden
Hosta; Polygonatum; "Yellow Native Azalea"; Probably Rhododendron austrinum, Florida Flame Azalea; Fothergilla Blue Mist; Hurley Garden, Bethesda

Larry & Stephanie’s Podcast

I recently recorded my first Podcast ever, for Beyond Behnke’s Stephanie Fleming for April 7, 20222. That’s one more than I’ve listened to, being more a fan of digital novels, WTOP all-news radio, and NPR. Since my retirement and our recent move to Wisconsin, I no longer have much need for WTOP weather and traffic updates, but I do check the app once in a while for DC area local news for old-time’s sake. I’m a fan of NPR, but don’t actually listen very often. I doubt that I’ll ever become a Podcast fan. That said, you should download Stephanie’s collection: I bet they’re great!

My Podcast topic was shade and shade-adapted perennials. The main point of the talk was (or would have been were it not for the occasional tangent): There are many factors that affect how well a plant will grow for you. How much sunlight the plant receives in the location in which you plant it is just one of the factors. The effect of shade on growing a garden plant isn’t an “either-or” situation: it’s a variable, with different qualities dictated by location, season, time of day, and density, which interacts with other growth factors such as the availability of water. Taking the time to learn the requirements for growing a plant that appeals to you and matching them to the conditions that exist in your garden should result in success.

Buying Perennials

There is always a risk when trying to explain something that we make it seem too complicated. I think it’s like cars. Once you know how to drive, you can rent a car pretty much anywhere, get in, and drive off. It may be manual transmission/stick shift, or the steering wheel may be on the other side, but basically, it’s a car and you can drive. But if you are buying a car you probably consider many factors: the brand, the model, the reliability, gas mileage or access to charging stations, size, safety rating, cost, sound system and so on. You don’t just walk into the dealer and look around and say: “Oh, that red one is pretty, I’ll take that one.” But that’s how many people shop for perennials: it’s in bloom, it’s in the sun or shade section, it’s pretty, it’s coming home with me! But for your conditions, it may turn out to be a lemon. I mean, it could actually BE a lemon.

You are probably not going to put the same effort into buying a $20 perennial that you would into buying a $40,000 car, but understanding your yard and finding the basic requirements for the plant you are considering will help you succeed. I have to give some credit to Ed Lyon, director of Reiman Gardens at Iowa State University, for getting me thinking about this. I watched a Zoom lecture that he presented a couple of weeks ago on shade gardening, for a Perennial Plant Association and Morton Arboretum joint one day symposium. This prompted me to buy and read his book from Timber Press, Growing the Midwest Garden, one of a series of Timber Press regional gardening books.

Basic requirements:

Temperature Tolerance/Climate. The USDA has broken the country into various regions based on average low winter temperature, with 1 the coldest and 10 the warmest, further broken to “a” and “b,” with b warmer than a. Washington, DC is in Zone 7b while Germantown, MD or Frederick, MD are in 7a. On the other hand, the American Horticulture Society has come up with a second set of numbers to represent heat tolerance. (This is more useful for people the further south you go as more plants have trouble tolerating the southern heat.)

Most of the hardy plants (those that should survive the winter if all goes well) at your local garden center will tolerate the temperature extremes of your area. There will probably also be some challenging (or doomed) outliers; like Russell lupines or delphiniums in Baltimore. My rule of thumb is if they look GREAT in Vancouver or Maine or England, and you don’t see them growing in gardens around town, then there is a good chance that they are going to be poorly adapted to parts of the country with hot, humid days and nights.

Those cool nights in say, Vermont, favor brighter colors, and that perennial that “blooms all summer” might actually do it up there. (How long is summer in Vermont, anyway?) But since your garden center wants you to succeed and come back with cash, not a dead plant, there won’t be much of this sort of thing sold, and they are unlikely to be promoted.

Sun and Shade

Sun and Shade: plants don’t eat “plant food.” Fertilizers provide most of the nutrients plants need to grow, but the actual energy comes from sunlight. Most temperate climate plants grow best when they have sunlight all or most of the day. Some plants will tolerate fewer hours of sunlight (although they may be less vigorous with a more open growth habit and fewer flowers), and some actually require protection from hot afternoon sun in warmer areas of their range, or the foliage burns.
Sunlight exposure is graded into four types (I am taking this from the Proven Winners website since this corresponds to their labels and you will find Proven Winners for sale all over):

“Basic Light Level Definitions
• Full sun – 6 or more hours of direct sun per day
• Part sun – 4 to 6 hours of direct sun per day, including some afternoon sun
• Part shade – 4 to 6 hours of direct sun per day, mostly before midday
• Full shade – less than 4 hours of direct sun per day”

In my experience plants that are in the shade category respond better when they get at least a couple of hours of morning sun. When a plant is listed with a range of tolerances, such as Full Sun to Part Sun, it would be best to interpret it as they “prefer” Full Sun but can be grown in Part Sun, but possibly with reduced performance.

Garden Center Displays

At the garden center, you might find Part Sun plants displayed in a shade area. Remember that the garden center plants are on display tables in pots with confined root systems and need frequent watering, and in the later spring or summer may burn in the heat of the afternoon. As a customer you would logically expect everything in the “Shade Area” to be a “Shade Plant.” So it’s important to know how many hours of sun your home growing-location provides and to read the signs, labels and consult with staff to get a hold on how much sun that plant really wants. (Sometimes they will even all agree!) A perennial geranium displayed in the shade area needs a lot more sunlight to grow well than a hosta on the next table.

There are different types of shade. Evergreen trees and shrubs provide (often dense) shade year-round, while deciduous trees and shrubs provide a month or more of full sun in spring before they leaf out and then may offer dappled shade in the warmer months. In terms of growing something in the understory, evergreen shade limits you greatly. The north side of a house is shady all year; you won’t get those couple of hours of morning sun. Ed Lyon talks about the transition zone between a grassy lawn and shade cast by trees. This will often give you that morning sun, afternoon shade exposure that is ideal for many shade plants. He points out that It will look more natural if you include some shade-tolerant shrubs along with the perennials.

Soil and Moisture

Soil and Moisture: Consider how you are going to maintain your plants once they are established. In my Maryland garden I was on a modest slope, with the bottom of the yard flattening out to be the low spot for the neighbors’ storm runoff as well as that from my own gutters. In our summer thunderstorms, water raced through my heavily-planted back yard and flooded my heavily-planted lower section, and sometimes my unplanted basement. Eventually I had a dry stream installed to drain the water to a rain garden in the front. The message here though, is that soil moisture is variable in your yard and you need to take the plants’ requirements into account. Taking ferns for an example, Christmas Fern does fine in dry soil, as you can see if you walk through the woods in the summer. Ostrich Fern will dry up and go dormant, and an ugly dormant at that. Trees and shrubs compete very well with perennials for water, so unless your area collects water after a storm, you should expect that the soil is going to become dry if you aren’t irrigating.

Recommendations

Recommendations for most plants will be “evenly moist, well-drained soil.”  Since most of us don’t have this, you should try to match to your conditions and your gardening habits to those that your shade-tolerant plants will grow in. “Tolerates drought once established,” “tolerates clay soils,” “tolerates you going to the beach for two weeks in August,” and so on. You should to do some research: a terrific author is Allan Armitage. He is my go-to for perennial information—great books and readable. Online I like the Missouri Botanical Garden (MOBOT) and university websites.

If you do irrigate, water thoroughly and then let the soil dry out for a few days. The best way to water is with a hose and a water wand—a tube at the end of the hose with a breaker at the end. This lets you get the soil to the roots disperses it so you don’t wash the soil away. One of the best tools for a gardener. Only a professional should water with their thumb over the end of a hose, and then only when no one is looking.

Fertilizer

Fertilizer: perennials tend to like it “lean.” When over fertilized, they grow soft with weak, floppy stems. In my shady garden, I only removed the fallen tree leaves in autumn from lawn areas to protect the grass, otherwise, I left them in place to decay, which returns nutrients to the soil. (Within reason. Piles of leaves from the deck were hauled to the back compost pile, not left on the hellebores.) In spring or fall, I would sprinkle some organic Plant-tone in the garden, at a low rate. That system worked well for me. If you are a neat freak and remove all of the leaves each year; you may need more fertilizer. I think it’s good to get your soil tested at least once to check your soil acidity level and get nutrient recommendations. You can do this through the University of Delaware.

Doing Homework:

I already mentioned Timber Press as a good source of quality garden writing. You can never have too many garden books. Besides Allan Armitage, off the top of my head– Rick Darke, Colston Burrell, and David Culp are writers that always provide quality books. The Well-Tended Perennial Garden by Tracy DiSabato-Aust is a classic. Look for good local writers, like Adrian Higgins of The Washington Post, (retired but articles archived on the Post website.)

On the internet, I like Robert Pavlis “Garden Myths,” a Canadian who looks at the science behind internet gardening advice, and seldom finds much there. The DC/Baltimore area has many quality garden clubs, horticultural societies, and plant societies. Try attending a meeting and see if you fit in. They are always looking for new members, and they are good places to get hands-on advice, trade plants, and see interesting speakers.

In Closing (Finally):
I hope I haven’t made it too complex. Over the years I tried pretty much every sort of shade-tolerant plant that Behnke’s offered. I did water in summer dry spells. Regardless of my (low to moderate) level of care, many didn’t last very long. (Heuchera and Tiarella, I’m looking at you.) But others thrived, some for 35 years. Hellebores, hostas, wild ginger, sedges, ferns, epimedium, Japanese forest grass, perennial geraniums, astilbe, daylilies, amsonia, trillium, lungwort, ‘Phlox Sherwood Purple’ all worked well for me. I’m sure you have, or will have, your favorites as well. The good thing about perennials is that, if they don’t seem to be doing well in one spot, you can dig them up and move them to another.

Larry Hurley's Maryland Shade Garden
Looking toward the north; Hurley Garden, Bethesda; Rosa noisetliana Darlow's Enigma
Larry Hurley's Maryland Shade Garden
Hosta Blue Moon ; Hosta Elvis Lives; Polygonatum odoratum variegatum; Hurley Garden, Bethesda
Larry Hurley's Maryland Shade Garden
Bridbath with Hostas; Asarum; Hurley Garden, Bethesda

Larry Hurley, perennials specialist for Behnke Nurseries (now retired), started with Behnke’s in1984. Larry enjoys travel, food and photography. He and his wife Carolyn have visited Australia, New Zealand, Thailand, Brazil, South Korea and much of Europe. Their home is on a shady lot where a lot of perennials have met their Maker over the years.

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