More light under trees

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Trees are light hogs.
They can spare some of what they've hogged, for your garden

 

Keys to growing a good garden under trees:

 

Overcoming low light,
Alleviating water shortage and
Finding a plant mix that has the fewest inter-species antagonisms.

 

We always think about the light, first.

 

You must wrest some light energy from the tree(s), which will otherwise monopolize every sunbeam. Your garden plants need light or they have no energy to grow. Plants in low light also photosynthesize very slowly so that they don't draw up much water even if it's available. (It's the loss of water through the leaves -- loss to evaporation and to breakdown during photosynthesis -- that creates the vacuum that pulls water into the roots and up the stems.)

In shade, pruning is never done. We can't reach the oak and hackberry that rise above this mulberry. That calls for professionals in climbing gear or bucket trucks. However, we can reach the mulberry. It's fast growing so must be clipped every year or the naturally weeping branches descend so far they block the low angle afternoon sun -- the only light our garden has. Here, volunteer Adopt-a-Gardeners Phil Gigliotti and Ward Varns use pole pruners to do the job 

Start by pruning to elevate the tree and thin the canopy.

The objective is "high shade" -- trees that have no branches within 15 or 20 feet of the ground.

Elevating and thinning is best begun when the tree is young, then touched up throughout its life. Then there are no huge wounds that leave the tree weak during the years that pass before they close over. Yet it can be done later in a plant's life without causing unsafe situations or compromising the tree's health. A well trained arborist is the key.

Unless your trees are saplings or miniatures, pruning must involve an arborist. Shop around. Choose certified tree care people who've invested the time in learning scientific, safe methods. Ask for and check references from people who've had work done by that person, crew or company over several years.

 

Plan to prune again every 3 to 5 years.

More often if the trees are very fast growing species.

Remove unnecessary shrubs and small trees. Gardening under a single layer of light-straining branches is a challenge. Trying to grow in the dim light left after sun's filtered by two or three layers is much more difficult.

Increase light through ingenious design

Finagle and recycle light, too. Replace solid fencing with materials that admit light. Paint essential solid surfaces white, or cover them with crinkled aluminum or place mirrors at the back of the garden so available light bounces back through the area. Don't amplify afternoon sunbeams this way because those can burn on redirect.

We had an arborist elevate the big maple in this yard, then we used fencing with openings and light-reflective paint, and we planted, watered and waited. It's far more shady than the photos suggest -- the pictures were taken in late afternoon when light does reach in for two hours. Otherwise the yard is shaded by the building or the maple all day. The shrub is a leatherleaf viburnum (V. rhytidophylloides 'Alleghany'). Japanese painted fern (Athyrium japonicum 'Pictum') fared well at its feet. Four growing seasons passed between photo.

Be flexible in placing plants

Recognize subtle variations in light level. Buy several small pots of each new perennial and place each one in a different situation, because what fails in one spot may succeed just five feet away. Start small so you will more quickly see which plants are increasing or dwindling, then move them all to the best location.

This article is Sponsored by: Pat Fix

 

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Related links

  • Essential shade garden
  • Failures tell tales
  • Wringing water from trees
  • Choosing shady plants