I have this tricky garden area on the eastern boundary of my yard. It has a huge oak tree. It has a lawson cypress. The trees shade out an eastern and southern exposure until about two o’clock when the hot afternoon sun blasts through. Then all hell breaks loose. It’s the most difficult area of my yard in which to garden. A shaded sunny border.

A Heavy Wet Soil Baked in the Sun

Part of the problem is a massively tall oak tree grows along the fence in this part of the garden. The tree isn’t all that healthy. It’s old, it has dead branches, broken limbs, but the squirrels and birds make their nests in it. Plus, it gives us a pleasant screen of privacy. I don’t have good reason to remove it.

The problem is because the tree’s old and established, its roots have sucked much of the nutrients from the soil. There’s a vast network in its dripline below. Also, the soil there is very heavy, clay-like and clumpy. Buttercups often grow like wildfire. Most of my yard has sandy soil but not here along the fence. It’s all silty clay.

A Shaded Yet Sunny Border Situation

Also, because of its dense canopy, most of the plants sit in heavy dappled shade before receiving a heat scourge for about four-six hours until the sun fades.

This has created a dilemma. I have dappled shade in the morning and full hot sun in the afternoon. What grows well in half-day sun? Some plants do and I’ve had success with some, but others not so much. At the very back, I’ve planted hydrangeas and rhododendrons, shade plants that are happy and healthy. But sunny perennials toward the middle have struggled. I thought they would receive enough sun but they didn’t. Part-shade plants in the middle struggled as well. I thought they’d receive enough shade but they didn’t. And so the border is a constant work-in-progress.

I’ve had success with the ‘Halcyon’ hostas and Japanese forest grass and fuchsia magellanica near the front edge. But the acanthus struggle in the August sun, as do the astilbes. My bugbane does well for awhile and then declines. My heuchera ‘Plum Pudding’ and ‘Forever Purple’ are pretty much success stories but they’re out of scale with what I already have planted.

Ideas for the Future

So this is what I’m thinking. Move the hostas and acanthus back, a few feet deeper where the shade lasts about an hour longer than the rest of the border. Moving the acanthus will be tricky as its tubular roots like to break off and regrow big new leaves. But if I can relocate those workhouses, I may be able to arrange the heucheras and forest grass into a scheme of half-day sun perennials. I’m also considering tiarellas and daylilies and lady’s mantle for the front edge.

Lastly, I know I’ll have to fluff up the soil with some compost. And to get the best results, I’ll need to mix it into the clay soil. By the way, a lot of newbie gardeners think that mixing in sand, the most porous kind of soil, would be the way to lighten up the clay. But the opposite is true. If you mix sand with clay, you will get cement. The particles are all small and of similar size, locking them tightly together. It makes the soil extra heavy and non-porous. To lighten clay soil, you have to add particles of varying sizes with organic matter. That mix will attract insects and worms and keep the soil aerated and healthy.

I’ve been putting off this project because there’s an overwhelming amount of work to do. But’s time. I’m ready for a renovation. So my question to readers is what other plants should I use? What ideas do you have? Let me know by sending me a tweet on Twitter!