I need to prune down my tall nandina, but don’t want to lose berries for next winter’s holiday decorating. How do I do that?
Nandina requires a bit more thought these days. Nandina berries are highly toxic, and reports are surfacing of flocks of birds dying from consuming them. In particular, cedar waxwings have gorged themselves, ravenous from migrating. (Nandina are not native.) Reported deaths are considered the tip of a much larger incidence that goes unwitnessed. Since nandina berries are not normally a bird favorite, it may be that birds’ other food sources have vanished.
Homeowners can step up by planting native trees and shrubs that berry copiously. To beef up a bird-friendly landscape, plant black chokeberry [pictured], winterberry, sumac, American or inkberry holly, and crabapples whose fruit persists into winter.
Spring is the best time to prune nandina. The pruning rule of thumb for shrubs is to remove no more than 1/3 at a time. A few old nandina stalks can be cut to the ground. You could remove all the berries at holiday time, and dispose of them in the trash, not the compost, afterward.
My planting beds are mostly clay. I already covered them with a layer of bagged topsoil and a layer of mulch. What can I do to prepare a healthier growing environment to plant flowers and shrubs this spring?
Plants do better when soils transition gradually from one type (clay, for example) to another (like top soil), as opposed to distinct layers of soil types, which is known as lithologic discontinuity. This facilitates movement of water (rain) and roots from one layer to another. It also promotes better colonization by micro and macro organisms.
So, when establishing brand new beds, it's beneficial to mix up the top 6-8” of soil with organic matter (not mulch), plus lime or fertilizer if a soil test recommends that, before planting.
On the other hand, in older beds with established plants, you won't want to disturb plants and injure roots. In that case, try to promote the principle above by using the original soil to backfill planting holes, with a minor amount of organic matter added. This makes the planting hole soil similar to the surrounding soil. As time passes, soil organisms will do the mixing as they go about their tunneling and daily lives. Freezing and thawing, plus rain, will further mix your soil. Later, decomposed mulch and top dressings of organic amendments will filter down and enrich your topsoil.