Tuesday, October 4, 2011

Dry Shade Dependables

In the Evergreen State, we have a lot of dry shade. Yes, it rains often, but we get a bad rap on the amount of rainfall. We typically get about the same amount of rainfall per year as Columbus, OH and Dallas, TX according to the average annual rainfall from 1949-2006. However, our annual rainfall is spread out over 155 days while Texas receives their rain over just 79 days. So, the areas beneath our huge Douglas firs, Western Red Cedars and Hemlocks get very dry. We all want to be good stewards of the water we have, so it is helpful to be acquainted with some plants that thrive in dry shade.

One of the best, hands down, is Epimedium. This great plant comes to us from two very different origins. The Asian varieties are choice plants, dainty and exquisite shade lovers, but they require moisture-they are not fIMG_0042or dry shade. Mediterranean varieties, however, are very drought tolerant once established. These tough, hardy ground covers are evergreen, bloom in early spring, often with magnificent new leaves with bronze, copper and red tints. Epimedium x perralchicum has sprays of golden flowers and Epimedium x warleyense has orange blooms. Cut the old growth to the ground in early spring before the bloom stalks emerge to showcase the flowers and then enjoy a fresh flush of foliage.

Solomon’s Seal (Polygonatum) has waxy, white bells drooping from lovely arching stems. The varieg2011_4 053ated version is particularly effective in the shade. The foliage turns a pleasing golden yellow in the fall. Lenten Roses (Helleborus) are terrific evergreen workhorses with exotic, frequently speckled, sometimes double blooms in the off season. They may bloom from February to May. Most asters languish in the shade but Aster divaricatus (aka Eurybia divaricatus) is native to the dry, open woods of the Eastern US. It is sprawly, with small but abundant white daisy flowers.

IMG_0074Goatsbeard (Aruncus) is commonly known as a large architectural plant topping out around 6’. Aruncus aesthifolius is a charming dwarf, with feathery leaves that combine wonderfully with larger, glossy leaves such as Hellebore or Asarum, a groundcover with glossy heart shaped leaves. The cream flower spikes dry on the plant and look attractive through frost.

Some hardy geraniums are suitable for dry shade such as G. phaeum and G. pretense. Geranium macrorrhizum, which is too vigorous for my garden, but somewhat more constrained in dry conditions.IMG_0601

Red twig dogwood (Cornus alba; C. sericea) is deciduous, but shines in the winter with dramatic red stems. The newer stems are more colorful, so you will want to cut 1/3 of the old stems to the ground each year to encourage new growth. The variegated C. alba ‘Elegantissima’ lights up the shade with white rimmed leaves, but other varieties may have more vibrantly red stems.

One of the most fragrant shrubs, Sarcococca confusa, is a shade lover. It gets 3-5’ tall and wide, has glossy evergreen leaves-wonderful for arrangements-and a vanilla /honeysuckle scented flower in winter. The flowers are insignificant in size but magnificent to smell. S. c. may require some extra water, but his little brother, S. hookeriana var. humilis, can take it dry. This is a 12-24” tall groundcover that spreads by underground stolon and shares the same tiny but fragrant IMG_0607bloom.

Climbing hydrangea (Hydrangea anomala var petiolaris) is a wonderful, bloomingIMG_0609 woody vine that will climb 60’ up a Douglas fir. Golden hops (Humulus lupulus ‘Aureus’) is slow to get started but once it is established it will glow in the dark.

Don’t let the dry shade intimidate you! You can turn it into something truly beautiful.

Monday, October 3, 2011

Defining Shade

In the Pacific NW, shade is something gardeners must learn to love. I’m from Texas and I can tell you that in other parts of the country, shade is something devoutly to be wished. People go to unbelievable lengths to produce a bit of shade to make their summer more endurable. Even in the cloudy and brisk climate of maritime Washington, a shade garden can be an elegant and serene counterpoint to a rowdy summer border. Aug 189

Shade is a multifaceted condition. Typically, shade describes an area that receives less than 4 hours of direct sun a day. A full shade plant prefers less than 4 hours of sun; you must consider not only the length of time in the sun, but also the position of the sun. A full shade plant that receives only 2 hours of direct sun-but in the middle of the day-will not thrive and may die. Learning how the sun moves across your site will help you to estimate what type of shade you have.

Aug 155Bright shade areas may receive dappled shade all day; or direct morning or late afternoon sun; or they may be bright, but not sunny. A wide variety of plants will thrive in these conditions.

Frequently, deciduous trees produce a mixture of sun and shade referred to as dappled shade. The shade area created will be larger than the tree canopy because of the movement of the sun. Usually, you will find full days of sun filtered through the leaves, but little to no direct sun. Woodland plants are ideal for these situations Aug 160

Plants that are labeled “Full shade” will not grow in the dark-all plants require some light. Full shade plants will do well in dappled shade conditions and may even grow in reflected light from a light colored wall or fence. I have an area on the side of my house that receives only reflected light for a majority of the year where I am able to grow many varieties of plants.

Dense shade can be defined as areas that get limited light-too dark to be considered dappled shade-and no direct sunlight. Frequently, these areas may have complicating factors such as surface roots and evergreen canopies. There are few plants that will bloom in such IMG_0016conditions, but you can rely on full shade shrubs and foliage plants. Variegated plants can provide variety and light up the dark space. Because tree roots compete for the moisture and nutrients, you may not be able to plant densely. Woodland flowers, sometimes known as ephemerals because they disappear after blooming, can provide delightful color. These plants emerge and bloom in spring before the trees leaf out completely.

Sometimes dense shade can be improved. Trim off the lower branches to allow more light to penetrate under the canopy. Substitute an openwork barrier for a solid fence. Select companion plants that will tolerate dry shade. Consider a sitting area, hammock, water feature or garden art in an area that doesn’t support as many plants as you would like.

Shallow rooted trees make planting anything difficult. Creating a raised bed is tempting, but will likely weaken and possibly kill the tree by burying the roots too deeply. Tree roots are naturally quite shallow growing. When root systems are buried, less soil oxygen and water is available.  An oxygen level of 25% of the soil volume is considered good for root development. At a 5% oxygen level growth stops, and at 2% roots decline and die1. If you are able to build a bed that doesn’t smother the roots, the roots will eventually grow up into the new soil, duplicating the existing problem you are trying to solve.

If you have evergreens with branches only a foot or two above the ground you should probably forgo planting and mulch for weed prevention. Use no more than 2-4” of mulch; more than that will have the same deleterious effect as too much soil piled on the roots.

1 Ohio Department of Natural Resources, Division of Forestry