If you have property that has lots of mature trees you may be considering a garden that features woodland plants. Woodland gardens are gardens where humans manipulate the understory plants- the plants which tolerate conditions of shade and competition from larger plants and fill in the space under them. You may be thinking of a wooded glen full of native wildflowers or of a place to showcase hosta, heuchera and other shade plants. There are many plants that will grow in the shade of other plants but not every shade loving plant will grow in any shaded area.
When you are considering developing a garden in a wooded or shaded area there are several considerations. One is, of course, the light available for a garden. There are very densely shaded areas under trees that won’t be suitable for most types of understory plants. The best areas for woodland gardens are where there is filtered light, with a light tree canopy and shifting patterns of sunlit spots. In nature this occurs at the edges of woodlands and around areas where trees have fallen or died. A path or road through your woodlands may provide these conditions on either side of it.
The shade from deciduous trees (trees which lose their leaves in the winter) is different from the shade under evergreen trees. Deciduous wooded areas offer the chance for many understory plants to grow and bloom in the early spring to early summer period, before the trees have heavy leaf coverage. Many native wildflowers fall into this category and are called ephemeral flowers. They grow and bloom early in the season then die back and go dormant until the next spring. There are also a few plants that bloom in autumn, after the leaves begin to fall.
In contrast when shade is from evergreen trees plants have to adapt to a continuous level of low light. These areas can support good woodland gardens if they are thinned and “limbed up” to allow some light to penetrate. This is generally easier to achieve under pines, which tend to lose their lower branches as they grow anyway and still maintain a pleasing look when lower limbs are removed. In contrast spruce and firs tend to look a bit odd when lower limbs are pruned to allow more light to penetrate under them.
Very densely planted stands of evergreens such as those in windbreaks and abandoned Christmas tree farms will need a lot of thinning and pruning, including the removal of whole trees, if you want to plant a woodland garden under them. Some deciduous stands of trees may also need thinning and pruning before a garden under them is attempted. If you have property like this and want to put in a woodland garden you may want to consult with and or use the services of a registered arborist or forester. They can advise you how to correctly thin and remove trees.
Competition for water and food
The area under trees often has drier soil than other areas. While shade helps keep moisture from evaporating from soil as quickly as in a sunny area, the trees that cause the shade also prevent some rain from ever hitting the ground under them. And when rain does hit the soil beneath the trees it is quickly soaked up by the trees roots. Moisture levels under trees can be a limiting factor as to what plants will grow there. Some areas turn out to be quite dry. Areas under deciduous trees may have more moisture in the soil because at times of the year rain and snow can reach the ground readily.
Tree roots also grab soil nutrients. Some trees have many surface roots that make planting understory plants under them difficult. The soil characteristics such as soil fertility and soil pH under trees can vary just as it does anywhere else but it is harder to amend these things than in an area not under trees. It’s a good idea to get a soil test done before beginning a woodland garden. Then you may have a better idea of what plants will do well there.
Usually soil under wooded areas has a lot of organic matter in it from rotting leaves and needles. Most woodland plants really appreciate this. But in some cases the property owner has removed leaves or needles every year and the soil is low in organic matter. While some organic matter can be worked into soil at planting time no more than 3 inches of soil or organic matter such as compost or wood chips should be put over tree roots each year. Adding more may cause stress or death to the trees.
Some tree roots may actually give off chemicals that interfere with the growth of plants near them. Black walnut trees and Tree of Heaven, (Ailanthus altissima), for example, stunt the growth or kill plants growing near their roots. Other trees which may have allopathic (suppressant ) factors include Sugar maple, Black Locust, Eucalyptus, Sassafrass, Red oak, Black Cherry, and Sycamore. There are plants which will grow near these species but your selection will be more limited.
If you are willing and able to use some irrigation and supplemental feeding you can grow many species of woodland plants that might not grow in your woodland area naturally. If you want your woodland garden to be completely self-sustaining you’ll have to carefully select plant species that suit your conditions.
Deciding what to plant
After you have determined light, soil, moisture and nutrient conditions of your woodland area you’ll need to decide just what type of plants you want to grow- and can grow- in those conditions. You can choose to grow only plants native to your area. You can use plants that are native to your area with a few “wild flowers” from other places with similar climates and conditions. You can use only cultivated shade species such as heuchera, hosta and similar plants. Or you use in your woodland garden any kind of plant that will grow well in your shade conditions, including annual plants and tropical plants during the summer.
Make sure that you research the zone hardiness and specific cultural requirements of plants that you select for your woodland garden just as you would for other gardens. Some woodland plants such as violets and sweet woodruff can spread quickly so keep the invasive qualities in mind as you choose plants too. Some species of plants have varieties that have different requirements for light. Certain hosta varieties, for example, need more light than others to do well, so pay attention to specific variety requirements.
Don’t just count on flowers
In any garden it’s important to plan on plants whose foliage, form or texture, are as important as the flowers. In woodland gardens it is even more important because most woodland plants only have a short blooming period, which tends to be concentrated in the spring, and when they do bloom the blooms may not be very conspicuous. Some woodland plants may disappear altogether once summer arrives.
Plants with gold or white variegated foliage, blue or red foliage can add color without flowers. Light colored foliage, especially in the golden range, brightens dark areas and is very effective in small amounts. Don’t overdo such color spots though- it will not look natural in a woodland setting. Varying the texture; ferns, broad leaved hosta, Japanese Forest grass, and form; ground covers, upright, arching spreading and so forth of plants is also more pleasing than plants that are all of one size and shape.
If you observe your wooded area carefully you may notice areas where “spotlights” of sun fall at least part of the day. These areas may support plants that more evenly shaded areas won’t. These areas are also great for a “focus point” perhaps an exuberant basket of tuberose begonias or a cluster of fuchsia. They are also good areas to locate a water feature in the shade garden as the light is reflected off the water.
Below are some species of plants that can grow in shade.
Bulbs and small spring plants for woodland gardens
Crocus, snowdrops, wood hyacinth, cyclamen( spring blooming), anemone, Shooting Stars (Dodecatheon species) Helleborus species, Lily of the Valley, Blood root, Hepatica species, Erythronium( Trout Lilies), Trilliums, Arisaema species( Jack in The Pulpit), Corydalis, Arum, primula, violas and violets, Bleeding hearts, Epimedium, Tiarella, Uvularia, Chionodoxa ,Hyacinthoides( English Bluebells), Scilla, Eranthis, Fritillaria
Summer and fall blooming
Astilbe, Aralia, Aconitum, Kirengeshoma, cyclamen ( fall blooming), Trycyrtis (Toad Lilies), Cranesbill geraniums, Hypericum, Siberian Iris, Lobelia( some) Polemonium (Jacobs Ladder), Cypripedium ( Lady Slipper orchids), Autumn Crocus.
Sweet Woodruff, Bunchberry, Pachysandra, Ajuga, Lamium, Chrysogonum, Liriope, Phlox stolonifera, Phlox divaricate, Asarum ( Wild Ginger),
Foliage (some also bloom)
Hosta, heuchera, heucherella, Brunnera, Aruncus, Cimicifuga(Snakeroot), Mukdenia, Rodgersia, Ferns (various), Hakonechloa (Japanese Forest Grass), Solomon’s Seal, Pulmonaria, Goldenseal, Paris Polyphylla, May Apple
Larger plants for wooded areas
Japanese Maples, rhododendrons, azaleas, Calycanthus, Dogwoods( some) Clethra, Fothergilla, Daphne, Itea, Hydrangea (some), Schizophragma (vine) Viburnum,( some)
Your woodland garden will probably evolve a bit through the years as you discover what species do well and where you need more color, form or interest. Being open to adding non-native plants or supplementing with annuals and tropical plants will often provide the most pleasing and interesting woodland garden. Many woodland native plants are now available through garden stores. New shade plants are being discovered and new varieties being developed from older ones each year. You can have a soothing, pretty garden even under trees.
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