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When gardening, how to beat the beast of dry shade

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This is what you learn in gardening, eventually: If you wait to do something until you think of it, it’s usually too late. By the time the rosebush stirs in April, the season for pruning has passed. The foxgloves of May are planted the previous fall. The turnips of November (singularly delicious) are sown in August.

So now, while the leaves are falling and the ground is wet, it’s time to think about dry shade. Really. Dry soil and darkness afflict pockets of most gardens. It’s one of the real challenges of gardening because most of the plants we are drawn to hate the combination of shade, which robs plants of energy, and dryness, which denies vital moisture.

In dry shade, plants wilt and are stunted and simply do not convey that green, lush vigor that imparts a primal sense of well-being — in flora and us. Dry shade is most obvious when weather patterns turn droughty, but if you tend to brood about your garden, it’s a condition that never leaves you.

Anytime is a good time to plan a fix; now is also a good time to effect one. Garden beds can be worked and planted until the ground freezes. Shrubs and ground covers would much rather endure the trauma of planting in November than in the gathering heat of May. Our desires are secondary.

Walls, eaves and fences conspire to create dry shade, but for most of the garden, the condition is found beneath trees, both deciduous and evergreen.

One approach is to install irrigation. This is not as simple as it seems. Overhead sprinklers waste water, contribute to foliar diseases and aren’t very efficient; shrubs and trees tend to block the jets of water. In his new book, “Planting the Dry Shade Garden,” Graham Rice suggests the use of soaker hoses or drip irrigation, an efficient way to water roots without troubling the rest of the plant. My advice: Pay close attention to irrigated soil, because excessive watering can harm trees even if the hostas and ferns just lap it up.

The standard advice is to try to get more light into the dark garden by removing lower limbs of trees and thinning out branches that are crossing, dying or just growing the wrong way. This fine pruning takes some finesse: Use someone you trust. You can also remove a good percentage of trees from a backyard woodland without losing the effect. Scrawny and self-invited specimens are obvious candidates for the chipper. The third leg of this tripod is to pick the right plants for the woodland floor.

Rice, a British plantsman who also gardens in Pennsylvania, devotes much of his book to recommending suitable plants. I am nodding in agreement with most of his choices, because I have been dealing with the phenomenon for 17 years. The following ground covers work: epimediums, lamiums, sweetbox, various hellebores, pachysandra and the euphorbia known as Mrs. Robb’s spurge. Plant them small and water them once or twice a month until the root systems get established, in about 18 months. In hot, dry spells, water them weekly.

In one of the sunnier openings in this edge of the garden, I have gotten three fig trees to grow 15 feet at the base of a red oak. They clearly love the free-draining soil, though the fruiting suffers from the shade.

One thinks of hostas as being thirsty devils, but Rice says certain types establish well in drier conditions. “In general,” he writes, “choose vigorous, unvariegated cultivars and avoid very small, very slow-growing types.” I grow robust upright hostas in such conditions, of a blue variety named Krossa Regal. They look great as long as you have never seen them growing more robustly in full sun.

Heucheras, or coral bells, are popular shade perennials and demand free-draining soil. There are now a million varieties; some do better in our heat than others. I’ve seen Montrose Ruby flourishing at the foot of a great oak.

One of the quickest ways to kill yews and boxwood is to drown them. This foible makes them fine evergreen shrubs for the dry woods. I would avoid the fussy English box in favor of some new high-performing varieties. Rice likes, among others, Green Velvet, Green Beauty and the upright Graham Blandy.

I was in the Tidewater garden of bulb expert Brent Heath last week and asked him to show me a dry border under three old willow oaks. Here, he has planted the hypericum Brigadoon, the cranesbill Rozanne, a lovely low-growing cranesbill named Orkney Cherry and the stonecrop Angelina, which would need the brightest area in the shade garden. Most bulbs love dry soil, especially in summer dormancy, but not all of them like the shade. In the shadow of American hollies, my grape hyacinth and glory of the snow are weak and poor flowering.

Heath says I should be trying winter aconite, various crocus species and the yellow woodland tulip (Tulipa sylvestris). He says I should also try the three-cornered leek (Allium triquetrum), named for the way its stem forms a triangle in cross section.

If I had a little more light, I would go to town with hardy cyclamen. Both Cyclamen coum and C. hederifolium have varieties with gorgeous heart-leafed foliage, mottled green and silver.

Planting in dry shade also takes patience. Things grow more slowly. After years of struggling in the worst spot, a group of St. John’s wort (Hypericum calycinum) is now growing merrily.

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