I have noticed rhododendrons blooming in some older neighborhoods in Raleigh. Is there a particular variety that does well in this area? Under what conditions will they grow the best?
I hear all the time that rhododendron do not grow well in the Southeast. But my experience, and as you’ve noticed, shows that simply isn’t true. Many of the large-leaf rhododendron have been bred in very cold climates to withstand winter temperatures; however, others will do well in the Southeast. All rhododendrons prefer a moist, but well-drained, spot in the garden with acidic soil. Most of our soils are acidic but they are often poorly drained when wet and rock-hard when dry. For best results, grow your rhododendron in beds, which are well amended with organic matter, and located under some shade. Plant your plants a bit higher than the surrounding soil or on a slope where excess water will drain away and mulch your plants well. There are new hybrids especially bred for the South called the Southgate series that appear to do very well. Also, the “yak-type” rhododendron seem to be very good performers for our area.
Any nonchemical cure for caterpillars?
This caterpillar and many of his friends are chewing up my basil plants. How can I keep them away without chemicals that are toxic to humans?
It is always difficult when pests want to eat the same plants as you. I recommend avoiding chemicals as much as possible in general and certainly on food crops. For a short-term solution, you can use Bt (Bacillus thuringiensis), which is a nontoxic naturally-occurring soil bacteria. You can find it at most good garden centers. For the long-term approach, encourage birds in your garden by putting out feeders and birdhouses and otherwise making your garden welcoming to our feathered friends. They do a wonderful job of keeping the caterpillar population down.
What is killing my ajuga?
I have four patches of chocolate chip ajuga in my shaded backyard. Last year, an apparent fungus attacked one of the patches, and it came back sparsely this year. Sadly, the other three patches have been victims this year.
Can you please let me know if there is anything that can be done to salvage my ajuga? I have tried spraying it with Daconil fungicide, but to no avail. If not, could you recommend a heartier alternative groundcover? Perhaps pachysandra?
It is always hard to diagnose issues from images, but it looks like your ajuga or bugleweed could be suffering from Southern blight. This fungus affects a wide range of plants and so I would dig out the soil along with the plants and throw it away and bring in some new topsoil for that area. As an alternative evergreen groundcover for shade, pachysandra is certainly a good possibility. I also like ‘Quicksilver’ wild ginger and many of the great new sedges like ‘Everillo’ and ‘Everlime.’ Another easy and lovely groundcover is Mrs. Robb’s bonnet or Euphorbia amygdaloides var. robbiae.
Mark Weathington is the director of the JC Raulston Arboretum at N.C. State University in Raleigh. Info: jcra.ncsu.edu. Please send your garden questions, your full name and the city where you garden, to: firstname.lastname@example.org.
Common name: Mrs. Robb’s bonnet
Botanical name: Euphorbia amygdaloides var. robbiae
Family: Spurge (Euphorbiaceae)
Category: Evergreen perennial
Primary uses: Shade gardens, groundcover
Dimensions: 8 to 12 inches tall by 24 to 36 inches wide
Culture: Part sun to shade. This spreading perennial will become a groundcover quickly if planted in a loose, moist, well-drained soil. Once established it is quite drought-tolerant but will not spread to form patches very quickly in drier spots. Cut back flowering stalks in late summer.
Bloom time: Spring
Color: Lime green
General attributes: This vigorous, evergreen perennial sends up stalks topped with whorls of dark, glossy green leaves. In early spring the stems erupt with pale green flowers that contrast well with the dark foliage. The bracts from the flowers dry on the plant and are ornamental for an extended period of time. To keep the plant tidy, cut those spent stalks back to the ground in mid- to late summer. Once established, Mrs. Robb’s bonnet can be a quite effective groundcover even in deep shade.