The trials of dry shade

Gaultheria mucronata and Luzula sylvatica, 2 plants that are actually succeeding in this tough area.

I have a long border at one edge of the garden, sitting between the lush shade garden area where the ground retains moisture through much of summer and a very dry stand of woods. The naturally mesic zone stops just a foot or two short of the edge of this border in places. In summer you can see the division clearly, where the grass (weeds) suddenly turns from green to brown. This border is very dry, though something else seems to be going on with the soil, as well, because even with water, most things grow poorly. In the undisturbed area behind the border, further under the trees, little grows except for moss and some sparse salal (Gaultheria shallon). And it's not because the shade is too dense under the trees. It's quite nice, dappled sun/shade. In the last 5 years or so, more weedy grasses and vetches have moved in, and a handful of native shrubs and small trees, such as Vaccinium parvifolium, Amelanchier alnifolia, and Corylus cornuta, have grown up from the stubs the deer kept shorn to the ground, but they grow much more slowly and sparsely than in other parts of the property.

As you can see, not much is growing in this border, and even behind it, there isn't a lot other than some fairly stunted salal.

 Yeah, it can't even be called a border, really. More like the border that never was. So, I've tried many different plants in this area and even with water, many have failed. Camellias, though said to be tolerant of dry shade, became chlorotic here. Aucubas always developed black, necrotic leaf spots and shoot tips, ultimately killing the plants. Oxalis oregana has mostly fizzled out. Iris foetidissima survives, but is slow and chlorotic. Helleborus x hybridus survive and even bloom, but tend to look yellow and a bit crispy by the end of summer (though not so bad this year). Helleborus foetidus failed to establish and died out. Two Garrya are surviving, if only barely. They weren't in great shape to begin with and I know I didn't water them well enough when I first planted them 3 or 4 years ago. Still, they should have made more progress by now. Several Frangula californica are clinging to life. They were in very poor shape to begin with, but others elsewhere in the garden that started out similarly have recovered. Mahonia nervosa and aquifolium need far more water to establish than I can supply in this bed. Two dwarf Umbellularia californica may be having the same problem, insufficient water to establish. Even Euphorbia amygdaloides ssp. robbiae struggles here.

Probably the healthiest Euphorbia and one of the few remaining Oxalis oregana remaining in this bed.

Even the ironclad Polystichum munitum struggles here. The fact that there are no volunteer ferns in the woods behind this border should have clued me in. There are plenty around, so if they could grow here, they would. They pop up most everywhere else.

Garrya. Well, at least it's alive. 

So what has worked in this bed? Remarkably, one Rhododendron 'Fastuosum Flore-Pleno', near the wetter end of the bed, is growing tolerably well, though it would like more water. Luzula sylvatica does well, but again would prefer a bit more water (possibly more nitrogen, too, or at least better access to it). Gaultheria prostrata grows and spreads surprisingly well, though it's too short and thin to smother weeds. A Lyonothamnus floribundus ssp. aspleniifolius has done ok, but gets leaf spots in this area, so I plan to move it to a more open location. Grevillea miqueliana is doing well so far. One Mahonia eurybracteata hybrid is doing well, though another had to be moved before it died of dehydration. Vaccinium ovatum shows promise. One died after having grown quite well, but the others seem fine, if a bit slow. They do manage to make little berries. Osmanthus fragrans and x fortunei seem to establish quickly in this bed (which seems to be the main issue for most plants in this area) and show much promise, though it's too soon to tell how they'll perform long-term. Arctostaphylos x densiflora 'Harmony' (or maybe 'Sentinel') and Arctostaphylos stanfordiana 'Twin Valley' are doing well, though the stanfordiana are small and need more attention to keep the weeds from smothering them. Heuchera cylindrica looks ok, if a little drought-stressed, but is too small to smother weeds. Same with Lonicera crassifolia. Holodiscus discolor, planted just behind the border, are doing well, though young yet and slow. Perhaps the plant which has performed best so far in this troublesome bed is Gaultheria mucronata (pictured at the top of this post), also known as Pernettya mucronata. It's even begun to spread. It looks healthy, if not as dense as plants grown in full sun with more water. It also needs a male pollinator to produce more than a handful of the showy berries the species is known for. I only have the one clone and am in the process of locating others.

The best-looking part of this bed, believe it or not. Rhododendron 'Fastuosum Flore-Pleno' and Luzula sylvatica (a touch crispy) plus a couple epimediums that are only a little chlorotic.

A young Grevillea miqueliana shows promise.

Most of the Vaccinium ovatum look healthy.

An Osmanthus x fortunei seedling planted a year or 2 ago shows promise.

I had been moving in a more west-coast native direction for this bed. However, the poor performances of the Garrya, Frangula, Mahonia aquifolium, Mahonia nervosa, Ribes speciosum, and several other natives I've tried makes me think another direction is needed. The Arctostaphylos are doing well enough, and I could plant more of them, but I would like the plantings in this bed to become dense enough to block out the weedy grasses and vetches which are currently overrunning it. Arctos will tolerate some shade, but will grow more open and need more air circulation to grow well. Not to mention there will be more shade here as the trees in the rest of the garden grow. 

Arctostaphylos stanfordiana 'Twin Valley', too young to tell if it might eventually outgrow the weeds, particularly the vetch that seems capable of growing through and over anything.

Arctostaphylos x densiflora. I forget which. Perhaps 'Harmony'? It's growing well and isn't all that thin compared to a plant in full sun, but as yet is too young to outgrow the vetches.

Now another little story. I had to divide a bamboo I keep in a pot because it's a potentially rampant spreader, Sasaella masamuneana 'Albostriata'. I was rather lax in watering it this summer and between becoming rootbound and my lazy watering, it suffered a bit. But since I only watered it once a week at most, and more often every 2 weeks or less this summer, I'm frankly impressed it survived and looked as good as it did! I also noted another bamboo, a bit of a mystery but tentatively identified as Pleioblastus humilis, growing in a bed off the patio, would curl in the late morning sun, but was otherwise undamaged by drought. The little bed it's in only gets water from whatever drains from the pots on the patio next to it, and I watered those VERY little this summer. Maybe there's moisture under the patio I don't know about. Maybe not. Either way, this also appears to be a resilient little bamboo.

Pleioblastus, perhaps humilis? This is actually regrowth from just a couple little rhizomes left after I dug most of it out last year. I decided to leave them. Just one growing season and not much water.

What does this have to do with that dry shade bed? Well, noticing the apparent drought tolerance and resilience of those bamboos, and having to divide the one, I decided, "why not try bamboo in the dry shade border? They'll tolerate even fairly deep shade as the surrounding trees grow, and the dry conditions in that bed will reduce their vigor, so they won't run as much. They won't go back into the woods where there's absolutely NO summer water, at least not much, and it will be easy enough to cut them off along the front of the border so they don't invade the rest of the garden. 

A division of Sasaella masamuneana 'Albostriata' planted into the dry shade border on a whim was the spark of inspiration. The yellow leaves are partly seasonal, as this bamboo does drop a few leaves in fall, but mostly due to drought stress over the summer.

That little spark of inspiration caused me to plan up a whole new planting for this bed, naturally involving bamboo. I've been running out of space for new bamboos, so of course I'm eager to work it in anywhere I can. Yushanias, the semi-running relatives of Fargesias, are reportedly more drought tolerant thanks to their deeper root systems, and I've had my eye on Yushania maculata for some time. Pseudosasa japonica, the Japanese arrow bamboo, is one of the most drought-tolerant hardy bamboos. I see it occasionally in rural yards around here, with no summer water, even in full sun, though they look best in partial shade. You'll see it often in coastal communities, as it tolerates salty coastal winds better than most bamboos. I have my eyes on 'Akebono-suji', with variegated leaves. 

I plan to incorporate these bamboos, along with several of the ground cover types I already have, into this bed to test them all. Along with the bamboos, I'll plant more of what I know works: Osmanthus, Grevillea, Vaccinium ovatum, Holodiscus discolor, Gaultheria mucronata, and Luzula sylvatica. Part of me would prefer to use more natives, but the pragmatist in me tells me to use what I know works, and the bamboo addict in me just drools at the thought of more boos. 

Part of this plan involves installing a better irrigation system, along with most of the rest of the garden. One of my main priorities this winter is figuring that out. This bed has a set of microsprinklers, which don't cover the whole bed as they were just a handful bought to test them out. I could buy more of them to give the bed full coverage, but the fine spray also blows in the wind quite a bit in summer, so I'm thinking drip line would be better. Then again, if the plants grow well enough, wind won't be as much of an issue. Overhead sprinklers are supposedly better for promoting ground cover spread, which would be good for the smaller bamboos.

Another issue is the amount of weeds that has amassed in this bed. Except for the dandelions and a few grasses with deeper roots, they're all pretty much growing in a few inches of old mulch on top of the soil. I could eliminate many of the weeds by scraping that layer off. However, I'd also be removing much-needed organic matter from this bed. So, I think what I'll do is simply cover the existing weeds with a generous layer of fresh mulch, because this bed will need more mulch either way, and plant. If successful, the new planting will smother the weeds as they fill in, particularly the ground cover bamboos.

Vetches germinating in the fall rains, along with some of the grasses and other weeds I'm dealing with in this bed.

Most gardens have at least one challenging area. They can remain eyesores for years, as we attempt to figure out what to do with them, but they can also be hotbeds of ideas. When we finally make these challenging areas work and look good, they can be some of the most rewarding parts of the garden, having put so much effort into them. Well, that's what I hope for this bed, at least.