Deep Shade Garden — Native Plants

A large part of my property is in deep shade from a mix of aging cottonwoods, 20 to 30-year-old big-leafed maples, and a smattering of conifers:  one red cedar, one very large and beautiful douglas fir, and a couple of young grand firs.  In the 4 1/2 years we have lived here, we have removed 99% of the english ivy that had killed most of the understory plants and was working on the trees.  Besides picking at the remaining 1% or so of the ivy as it tries to re-grow here and there, we are trying to replace the understory that had been destroyed.  Since we are always short of cash, most of this has to be accomplished by bringing in a small number of plants and waiting for them to multiply naturally.  I have also gotten seed and sown it in likely spots with mixed success.  I am also lucky to have family interested in native plants and been able to get cutting and divisions from them.   

Naturally, I am always looking for new ideas and suggestions, and yesterday I was at the King County, WA, Native Plant Guide.  I hope more governments invest in similar sites — it has lots of useful information.  However, I was disappointed with their sample landscape plan for dry shady areas.  In my experience, the plants suggested don’t all grow in the same conditions and so wouldn’t work together as the plan suggests.  So — here’s my version of what to grow in dry shady gardens along the west coast from Washington to northern Vancouver Island.

The determining factor in what you can grow seems to be what is causing the shade.   I think the critical factor is the number of conifers.  I presume that this is because the shade is year-around, and because conifers create an extremely acidic duff with chemicals not present in the forest duff under deciduous trees.  In any case, the understory species are quite different in a largely coniferous forest than they are in an area with few conifers and mostly deciduous broad-leafed trees.

For areas with deciduous trees and few or no conifers:

Saying the area is “dry” is a seasonal thing — everywhere here on the coast is wet in winter.  In the summer, however, unless you irrigate or live where you get coastal fog, or have a natural water source like a stream or lake, the summer will be dry.  Here, except in a few areas close to the river, the soil gets somewhere between extremely dry and barely moist beginning sometime in July.   The native plants (other that the trees with deep roots) have adapted by going dormant, usually some time between June and August. 

Here’s what grows under the high canopy of cottonwood, maple and an occasional conifer in my mixed forest (links are to my Flickr photostream or photos I have donated to E-Flora BC):

Shrubs and small trees:

Hazelnut:  Makes nice golden fall colour and provides nuts for the wildlife.  Mostly growing in the lower area where their roots can reach the water table, but there are a few young ones coming on the bank.

Indian plum: Grows everywhere, arches gracefully to about 8-10 feet, except where a large branch has knocked it down, persistent grower through tough conditions.  There are both male and female plants.  They put on a pleasant show of white in the spring, with the male plants being slightly more showy.  The female plants produce a good crop of berries that begin orange and darken to purple, and are very popular with the birds.  For a good crop of berries, though, the plant needs to be in a clearing or along the edge of the forest where it can get some sun.

Tall Oregon grape (Mahonia):  This grows here and there and, left to its own devices, makes an awkwardly lanky plant, especially in deep shade, with brilliant yellow flowers.  Along the edges and in clearings it is more compact and bears blue fruit with a whitish powdering outside.  They are good for jam, etc., are popular with birds, and kids will sometimes eat them, although I find them fairly bland and seedy.  Mahomia is used in commercial landscaping here, and is generally pruned to keep it compact, sometimes as a hedge.

Snowberry:  I do not recommend you plant this anywhere EXCEPT in deep shade.  In brighter conditions it can be an awful weed, and will out-compete anything under 4 feet tall.  In deep shade, however, it grows sparsely and makes a pretty, light brush with pretty white berries that look attractive in the winter rains.

The orange trumpet honeysuckle meanders its way through the taller shrubs and small trees here and there.

If you have some nicely rotting logs or stumps, you can grow red huckleberry and western mountain ash.  They are both pretty, airy shrubs, with the huckleberry growing to about 6 feet or so and the mountain ash to maybe 10-15 feet.  In soil with more moisture they don’t need the logs (although huckleberry seems to prefer it), but I think the logs and stumps hold water in really dry areas.

In slightly wetter spots, down near the river, I have red osier dogwood and ninebark.  There is also some gooseberry that doesn’t fruit — or perhaps the birds get to it first.  It is pretty scraggly — I think it would like more sun.

Under the shrubs I have:

All seasons:  lots of sword ferns — they survived the ivy, although we have noticed that they have become taller and lusher since the ivy has gone.  I strongly recommend sword ferns provided you have space for them.  They are tough and disease-free, and as far as I can tell, virtually immortal — certainly I expect mine to outlive me, short of a natural disaster.  There are also some sedges in the damper spots and on rotting logs.  The moss is gradually coming back on the logs that the ivy had covered.  I have come to value moss.

First in the spring, and dormant by some time in July:

  • Erythronium (fawn lily) — masses of it.  This won’t grow under conifers or evergreen groundcovers, but here it grows like crazy.  It survived the ivy until the ground covering got too thick.  Erythronium are remarkably tough, and their single requirement seems to be at least partial sun and some water during the spring when they are above ground.  Here they are growing from the top of a south-facing bank which is not watered in the summer to the riverbanks that are flooded in the winter.  But they won’t grow under conifers, salal or other evergreen groundcovers more than 8 inches high.
  • Trillium:  This was almost wiped out by the ivy but it is coming back well from the few survivors.
  • Licorice fern:  growing on stumps and the lower trunks of maples — this survived on trees with light ivy infestations.  Heavy infestations killed everything, even moss
  • Fringecup is semi-evergreen and new leaves appear early — it had survived in a few places and is spreading ike mad.

Next up:

  • The fringeup is growing lushly and starting to flower.
  • Vanilla leaf appears — the patch is spreading slowly — I suspect it would prefer a bit more moisture, but it flowers and sets seed.
  • Bleeding heart — does really well — I got a bunch from a neighbour to supplement the few survivors of the ivy, and they are doing well
  • Western meadowrue grows really well — it had survived in a few places and has spread like mad since the ivy went.
  • Starflower — is spreading slowly, but seems well
  • Foamflower (I introduced this a couple of years ago and it is doing well)
  • Both false solomon’s seal and star-flowered solomon’s seal — both where here before, and both are spreading.
  • Hooker’s fairy bells is getting common — the first year there were two plants down by the river.
  • There is cow parsnip in one damp spot.
  • The slightly damper spots have wild lily of the valley and Trautvetteria (I refuse to call that false bugbane — what an ugly name!!).  I had one surviving patch of Trautvetteria and moved some to other similar spots — it has survived, but is growing slowly.  I think it could use a litle more sun as it flowers infrequently.
  • This year I had one Columbia lily!!  I’m not sure where is came from.  There are some just downriver from here, so it could be a wild seeding.  I also bought some seed four years ago — I thought none had made it, but perhaps one did.

By August all of the above ground covers and bulbs are either dormant or looking yellow.  Of the shrubs, indian plum is looking wilty and the leaves are yellowing and dropping off.  Snowberry sometimes does that as well, but seems to hang on better.  Tall Mahonia is evergreen, although when stressed and in the fall the older leaves go bright red.  Hazelnut probably has its roots down and doesn’t seem to turn colour until fall when it makes a bright spot in an otherwise barren landscape.

In the fall I am starting to get mushrooms.  So far nothing exciting, but the first year I saw only three species, and each year there are more.  I am thinking about introducing things like oyster mushrooms to some of the dead stumps and logs.

What doesn’t grow in my mixed/deciduous forest — I’ve killed them all  ;-(:

  • Salal — I couldn’t believe that salal wouldn’t grow, and it took five dead plants over three years to convince me.  I know now that it needs to be on the edge of a coniferous forest.
  • Ocean spray — except around the edges — it needs sun
  • Low Mahonia — well, technically it will grow, but not well.  And it would out-compete the Erythronium in time, so it is just as well.
  • Creeping dogwood
  • Twinbell
  • Willow — even down by the river
  • Evergreen huckleberry

If you have similar of differing experience, I would be glad to hear your stories.


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