Plants for Shade Containers

A year ago I blogged about the subject of my Containers that Won’t Quit lecture, which is how to compose containers that will look as good in September as they do in June. That prompted a request for a post recommending great shade tolerant plants for containers. In my area, Memorial Day weekend is when it’s considered “safe” (reliably free from frost) to plant annuals and tender perennials, so it’s often when people plant their containers. In light of that, here are some recommendations—annual and otherwise—for your shade containers.

Let me start by saying that with a little effort and a healthy dose of flexibility, you can have just as fine a container display under the cover of trees as in bright sun, but there is some fine print. I can’t devote space here to the perennial topic (no pun intended) of different kinds of shade, but you’ll find an explanation here. The plants I mention in this post should all perform well in anything up to moderate shade.

Your options for attractive compositions will expand considerably if you’re willing to use plenty of colorful foliage and not restrict yourself to flowering plants. Interestingly, many of the best plants for this purpose are things you might already know as houseplants or hardy perennials.

Second, a rule of thumb: In shade, gold rules. That is, no color shows up in the shadows better than gold—not even white. Creeping Jenny (Lysimachia nummularia ‘Aurea’) is a fast-growing plant whose long stems bearing bright, penny-shaped leaves will trail beautifully over the sides of containers. It’s sold as an annual in garden centers in spring, but it’s actually a perennial supposedly hardy to USDA Zone 3, and I can say for sure it’s hardy here in Zone 5. I’d also try cultivars of the perennial grass Hakonechloa macra, which has a lax, compact and clumping habit. ‘Aureola’ and ‘All Gold’ are two choices that will give you a bright splash of virtual sunshine to light up shady spaces.

For trailing plants, don’t forget those two old standbys, ivy (Hedera) and vinca vine (Vinca major). Both come in variegated forms, with a true plethora of choices among the ivies. I happen to like the duckfoot ivies, whose sharply lobed leaves offer an additional point of interest.

Five wonderful houseplants for container use are asparagus fern (Asparagus densiflorus, usually ‘Sprengeri’), Southern maidenhair fern (Adiantum capillus-veneris), polka-dot plant (Hypoestes), peace lily (Spathiphyllum) and Schefflera. The first two will add a feathery, delicate texture to your container combinations, while I often use the last two as solitary specimens filling an entire container on their own.

Peace lily is one of the very best performng plants for very low light situations because it has attractive, glossy, lance-shaped leaves in profusion and it produces showy white flowers continuously. Schefflera comes in a gold-variegated form made all the more attractive by the fact that no two leaves have the same coloration. As an added benefit, both can be overwintered easily in a bright spot indoors and then returned to outdoor containers year after year. The lovely Southern maidenhair fern, in contrast, needs such high humidity during the winter months that I simply discard it in fall and buy new in spring.

Finally, little polka-dot plant, a common windowsill adornment, is a nice filler at the edge of a container where it can peek out and provide a cheerful splash of pink or white.

In light shade, and still considering foliage plants, try tropicals such as Alocasia and Colocasia. Depending on the selection, both have the potential to get quite large, so generally speaking these will be choices for larger containers. They’ll give you a lushness that will stand out in a northern landscape.

For a similarly tropical look but a naturally more compact habit, you can’t beat Caladium and Syngonium. Few people seem to know the latter plant, which is a caladium lookalike, but it’s usually sold as a houseplant. The most common form has mottled, apple green leaves with a fresh appearance. Caladiums can range from the fairly subtle to the almost garish. ‘Candidum’ types have a tasteful, green-and-white simplicity, while others are heavily splashed with bright red and pink. (Click here to see a number of containers featuring several of the tropicals mentioned above.)

And of course I can’t neglect to mention coleus (Solenostemon). In the north, most coleus actually need brighter conditions than their reputation suggests, but they’re great plants for spots with morning sun or bright but indirect light. Some of my favorites are ‘Kingswood Torch’, ‘Festive Dance’ and ‘Butter Cream’.

The selection of flowering plants that will bloom all summer in northern shade is slim. For lighter shade, you can get away with fuchsias (I recommend two upright types: orange ‘Gartenmeister Bonstedt’ and pink ‘Mrs. J.D. Fredericks’—see above) and trailing wishbone flower (Torenia). The Summer Wave series of torenias will produce a waterfall of flowers in shades of purple, blue, rose and even pale yellow.

In deeper shade, you’re really limited to begonias and impatiens, but I would use the dragon wing begonias for better disease resistance and denser growth than their alternatives (non-stop and wax-leaf begonias) and and Fusion series impatiens in addition to Impatiens walleriana. For a strikingly different begonia, try one of the new selections of Begonia boliviensis that have only been on the market for a couple of years. Their trailing habit makes them especially welcome on the scene, because few flowering plants for shade are pendant.

I mentioned that many perennials also make great container plants, with the added benefit of being able to overwinter them in the ground outdoors and then replant them in your containers in spring.  You might even find that they overwinter in your containers just fine, eliminating that extra step.

Virtually any hardy fern that’s the right size and shape for your container would be an excellent choice for shade. Hostas, too, are a good choice no matter the size of your container because there are hostas ranging from miniatures to monsters.

The drapey dead nettles (Lamium) such as ‘White Nancy’ will provide both flowers on and off throughout the summer and good frosty foliage.

Finally, many selections of the perennial Heuchera (coral bells) have been introduced in the past few years with mouthwateringly beautiful foliage. Tantalizingly, selections in the Dolce series are all named after foods! ‘Key Lime Pie’, ‘Peach Melba’ and ‘Blackcurrant’ will spice up your shade containers with colors to rival those of any flowers.

A Spring Thing: Flowers in the Shade

Here we are at the start of June. By the time summer arrives in three weeks, the majority of perennials in northern shade gardens will already have finished blooming. Is that surprising? You may never have realized it, but most shade tolerant perennials bloom in spring.

Think about it: hellebore, lungwort, violet, nodding mandarin, epimedium, Solomon’s seal, old-fashioned bleeding heart, most primroses, globeflower, Siberian bugloss, twinleaf, woodland phlox and many other shade standards are already done flowering. False Solomon’s seal, rodgersia, columbine, spotted geranium, bigroot geranium and mayapple are in bloom now, but they’ll be finished by late June, too. Foamflowers are fading (although if deadheaded they’ll put up more flower stalks), and the fruits of baneberry and goldenseal are already fattening up! Yup, flowers in the shade are mainly a spring thing.

What’s left to please the eyes of shade gardeners through the coming months? Goatsbeard, astilbe, hosta, bugbane, Japanese anemone, toad lily and woodland aster are all yet to come. There are more, of course, yet the fact remains that most shade perennials bloom very early in the year. I’d guesstimate 75% of them have wrapped up their flowering by the summer solstice.

There’s a good reason for that, of course. We tend to forget that plants don’t flower to please us. They have their own agenda: reproduction.

In our mostly deciduous temperate forest, the woodland is a full sun environment from November through April when the leaves aren’t on the trees. Most of that time, it’s too cold for perennials to grow, but in March and April, it’s just warm enough for them to shoot up quickly and do energy intensive things like flowering and setting seed while there’s plenty of sunlight to fuel the process. When the trees leaf out in May, many woodland perennials are winding down and looking forward to doing what we all would do if we could get away with it: lounging about all summer.

The tendency of woodland plants to flower in spring is the main reason why shade gardeners are often advised to stop focusing on flowers and instead rely heavily on exceptional foliage plants: ferns, hostas, sedges, and variegated plants such as (to name just one example) Brunnera macrophylla ‘Variegata’. Flowers will come and go in weeks, but foliage is season long.

Annuals can also help keep color going through the warm months, but the choices for shade in the north are severely limited. Begonias and impatiens are two obvious answers, and they’re readily available at low cost. Gardeners who have grown bored with wax-leaf begonias can try the dragon-wing types for some variety. These grow larger than wax-leaf begonias, are extremely floriferous and make more of an impact, but they also cost more since they aren’t available in 6-packs but have to be purchased in 4-inch pots.

Caladiums are another great choice for summer color in shade gardens, although once again the color is coming from leaves, not flowers. Caladiums are not cold hardy in the North and won’t survive winter in the ground, but they can be dug and stored, dormant, and regrown the following year if you have a bright, warm spot to start them indoors beginning in February or March. Be sure not to put them in the garden too early because they are very sensitive to cool nightime temperatures. Even here in southern New England, I’ve learned not to plant them outdoors until the first week of June. If you do get ahead of yourself with caladiums and they get whacked by an extra-cold night, they should spring back quickly as the weather warms even if their foliage dies back completely in the interim.

Don’t forget that lots of those spring blooming shade plants I mentioned earlier also have great foliage that will contribute to the beauty of your garden right up until the first frost. Rodgersia, epimedium, hellebore, Solomon’s seal and twinleaf are just a few examples of plants that would be worth growing even if they didn’t flower! So, when designing your shade garden, consider each plant’s total contribution to the effect through the whole growing season, not just the loveliness of its flowers, its most ephemeral aspect.

Breathtaking Bluebells

Virginia bluebells (Mertensia virginica) are nothing less than the royalty of spring ephemerals. Large, showy, and colorful, they put on one of the very best spectacles of any spring blooming plant, with all the rich costuming you’d expect in the court of a queen.

Virginia bluebells break ground very early in spring. Their tightly furled leaves look like tiny burgundy cabbages when they first emerge, but as they grow they quickly morph into medium green, fleshy oblongs that resemble the leafy green vegetable sorrel. Seemingly in no time they produce profuse clusters of dangling blue bell-shaped flowers on 18″ stems, blooming for several weeks in May. (They also come in a white-flowered form that is uncommon but possible to find.) Once flowering ceases, and almost before you have time to notice, they close up shop. Their leaves yellow rapidly, and the plants have gone completely dormant by mid June. They’ll spend the remainder of the year as inscrutable, seemingly dead but really just dormant roots nestled just below the soil surface. Incredibly, their entire aboveground life cycle is barely two months long.

The sheer rapidity of their growth and “demise” along with their large size and showiness make Virginia bluebells very border friendly. Their leaves do not need to hang around the garden for months to store enough energy to ensure flowering the following year. They put on their spectacular display and then vanish—a gardener’s dream!

Virginia bluebells are excellent interplanted with other blue-flowering plants such as perennial woodland phlox (Phlox divaricata). This phlox flowers just as the bluebells fade, so the segue from one to the other is seamless, and because the phlox spreads into a non-competitive groundcover, the bluebells will continue to arise through the mat of phlox foliage year after year. Biennial forget-me-not (Myosotis sylvatica) also makes a great companion, as shown in the photo above.

Virginia bluebells’ sky blue flowers are also an effective counterpoint to yellow daffodils. Gardeners with borders in both sun and shade can take best advantage of this artful duo, planting the sunny areas with clumps of daffodils and the shady ones with masses of bluebells. The result will be breathtaking!

Another natural companion is old-fashioned bleeding heart, whose brilliant pink or clean white flowers reach their peak simultaneously with those of Virginia bluebells, although the latter plant will go dormant months before the former. If you try this combination, use hostas, ferns or other late-emerging plants to fill in the areas occupied by the bluebells in May.

Virginia bluebells spread readily by seed, moving outward from an original planting at a speed of a foot or two a year. In autumn, be careful working in the parts of your garden where bluebells are established, since it is so easy to dig into and accidentally destroy dormant roots at that time of year.

It’s not too late to have Virginia bluebells this year. Nurseries often stock them in April and early May since they’re one of the few plants that can be sold in full bloom at such a chilly time of year.

Sun/Shade needs: Half sun to moderately deep shade; full sun with adequate moisture
Hardiness: Zone 3
Size: 12-18″ tall; 8″ wide
Native status: Native to most of eastern North America, but not all of New England

 

Bloom times and other life cycle stats are accurate for northwest Connecticut. In milder areas all aspects of a plant’s life cycle may occur earlier in the year, and in colder areas, later.

March, 2010: Update!  The good folks at GardenSMART took a shine to this article and reprinted it at their website. You’ll find this post (and many other interesting items) in the Articles section.

Signs of Spring

At 7:44 AM on March 20 the Sun crossed the celestial equator heading north. In common parlance, that translates to: spring is here!

It didn’t take long for wildlife to answer the call. Two days later, I awoke to the sound of a red-breasted robin singing at 6:00 AM. The cardinals have been getting redder and redder and going great gangbusters for weeks with their impressions of distant car alarms, but they’re here year round. The robin was the first migrant I’d heard stretch its vocal cords this year.

While the robins celebrated spring by completing the last leg of their long journey, I was out in the garden performing one of the first jobs necessary to the season: uncovering my epimediums. (They have a common name—bishop’s hat—but somehow I just can’t bring myself to use it. They’ll always be epimediums to me.)

Along with hellebores and lungworts, epimediums start growing actively in March long before many of us have gotten out to remove the leaves that blew into the garden late last year after the rake had been put away for its long winter’s nap. (Or was it the gardener determined to nap? Tools can be convenient excuses…)

If you live on a lot with many trees, no matter how much you raked and blew last fall, you might find a lot of leaves staring up at you from the garden when the snow melts. Many plants can benefit from that cozy little coverlet, but for others it’s a problem.

While hellebores and lungworts are sturdy plants that can withstand the inevitable manhandling that occurs when you peel away sopping wet mats of oak leaves, epimediums are delicate little things with fragile stems all too easily snapped off. Wait even a week too long to clear them of leaf litter, and you may not be able to do it without surgical tools. (I exaggerate, but not by much.)

At left is a picture of a curled epimedium flower stalk taken on March 20 just after being uncovered. This happens to be a patch of E. ‘Silver Queen’, a large-flowered white variety. In just a few weeks, it will put on a display to rival the extravagant bloomer E. x youngianum ‘Niveum’ shown in the picture above.

As careful as I tried to be when I removed the errant leaves, I wasn’t careful enough. Below left is a photograph of a stalk that I clumsily damaged. It takes almost no force to snap the top off these little guys, and that’s one spray of flowers less for me, the bees and everyone else this spring.

Some epimediums have fairly persistent stalks that don’t disintegrate on their own over winter. While you might not have to groom ‘Niveum’ at all, most others aren’t as accommodating. E. x perralchicum ‘Frohnleiten’ has perhaps the most evergreen leaves of any epimedium. This is both a plus and a minus. In snowless winters, they’re something to look at. But snow or no snow, in spring they’ll require cleanup. A pair of hedge clippers is the tool for this task. They do the job quickly and with all the precision required. You could just leave last year’s foliage alone, and new growth would come up through it and eventually conceal it, but most epimediums look better with a figurative shower and shave.

Unless you mulched last autumn, have some light, compost-based mulch handy to spread on your epimediums as soon as you uncover them. Otherwise, the soil around them will dry out quickly. At this time of year the sun is surprisingly intense, although most of us aren’t aware of it because air temperatures haven’t climbed yet. But I’ve learned that when I come out of my winter semi-hibernation and start working outdoors up to eight hours a day in March and April, I’d better wear sunscreen! New growth of shade-loving plants should also have some protection, not from the sun itself, but from the soil dryness it can cause.

Of course, even if I didn’t remove the leaves from my epimediums, they’d grow right up through their brown blanket and bloom anyway. But I prefer the look of a clean bed with a dressing of compost as a nice backdrop. Knowing that the job of removing those leaves without damaging the epimediums becomes harder with each passing day is enough incentive for me to get outside in mid March no matter what the weather. Ironically, as intolerant as they are of mishandling, fresh new epimedium growth will have no problem withstanding freezing nights.

Spring Blooming Shade Plants: Hellebores

In a typical year, hellebores will be the first ornamental perennial to bloom in the Northeast. Although there are several species that can be grown in this region, especially in milder areas such as the coast and the lower Connecticut River Valley, one of the hardiest remains my favorite: Helleborus x hybridus (formerly and sometimes still known as Helleborus x orientalis).

Here in northwest Connecticut, hellebores send up their flower buds first, in March, before their leaves unfurl. As the month goes on, these succulent and tender looking shoots grow taller and taller, until they finally open up around April 1 to reveal clusters of 2″-wide, pendant blossoms. The species H. x hybridus is quite variable, with a range of subtle flower colors including creamy white, apple green, pale pink and burgundy. Its flowers often have striking speckled markings and prominent yellow anthers that are showy for about a week until the stamens fall off.

At first, hellebore flowers look a bit undressed because the plant’s leaves don’t come along until a few weeks later. When they do make their appearance, however, they are exceptionally attractive—leathery, glossy, palmate (arranged like fingers around the palm of a hand) and semi-evergreen.

Everything about hellebores is long lasting. Instead of dropping off after 2-3 weeks, hellebore flowers slowly fade to a pale green or buff color in much the same way hydrangea flowers do. They look good (although subdued) right up to the point when the seeds mature and are dispersed, usually in the latter half of June. Deadhead them before that point unless you want seedlings the following spring. In most gardens, the leaves will remain disease free and unblemished all season long, and will still be looking good when the first snow flies.

Shade tolerance: High
Hardiness: Zone 5; other species may differ
Size: Medium sized, with a height and spread of 15-18″
Native status: non-native to any part of North America

 

 

Growing Tips

• Don’t cut back hellebore foliage in fall, even if you clean up the rest of your garden then. Why? Hellebores come up so early in the year, they are subject to damage from late frosts. These frosts won’t kill the plants, but they will kill the flower buds. As the plant’s shoots begin to emerge from the ground, last year’s leaves will provide some protection. After the new shoots have grown taller than last year’s leaves, you can groom them, cutting off the old foliage at ground level. Be careful not to accidentally cut off new growth—it’s easy to do. For a few more weeks after you groom them, it’s a good idea to keep some pine boughs or an equivalent handy to gently arrange over the new growth at night if a hard frost is in the forecast.
• Hellebores have to be several years old before they are mature enough to flower. A nursery plant in a 5-pint pot is probably only two years old, so don’t be surprised if it doesn’t flower its first (or even second) year in the ground. As long as the plant grows well and looks healthy, flowering should start when the plant is ready. A plant that fills a one-gallon pot should be old enough to flower its first spring after planting.
• H. x hybridus is often sold in a mix of undifferentiated colors. In other words, if the tag in the pot with your plant does not specify a flower color, but just says H. x hybridus, it could be any of the flower colors listed above. There’s no way to know which color you’ve got unless you buy the plant in bloom very early in the season and the plant is old enough to be blooming in the first place. In recent years, some growers have also offered hellebores in designated colors. I like the way the mixed colors look in the garden when hellebores are massed, but gardeners with color-theme gardens might prefer to purchase all of one kind.
• Hellebores have no special needs, but they don’t like excessive moisture. If put in exceedingly dank locations or planted in soils that drain poorly, rot of the crown may result.
• Hellebores self-sow moderately. Their seeds are large and heavy, so they don’t usually travel very far. If you don’t deadhead your plants before they drop their seeds, you’ll probably find a “skirt” of seedlings around their feet in spring. Move these to a nursery bed to mature or give them away to friends.

Bloom times and other life cycle stats are accurate for northwest Connecticut. In milder areas all aspects of a plant’s life cycle may occur earlier in the year, and in colder areas, later.