Garden Doctors: Why boxwoods turn orange

Stephanie G. of Sebastopol asks: My boxwood foliage turns an orangey color every winter and doesn’t look healthy, but then turns green again when spring comes. Is this normal?

Some boxwoods lose some of their green color in winter if they are growing in full sun. With this loss of green color, an orange cast develops. The green color comes back fairly quickly when it starts warming up in the spring. There is really nothing that you can do to prevent this color change except planting it where your boxwood will eventually have a bit more shade. Don’t spray an anti-desiccant, because that will not help to preserve the green color.

Joan B of Santa Rosa asks: Can I transplant a large azalea now? And if so, how should I do this? It’s outgrown it’s spot and I want to save it.

Azaleas, like rhododendrons, have very shallow root systems, which means even large plants may be successfully transplanted. Don’t worry about digging too deep into the soil, since most of the roots will be near the surface. But it is important to start digging a little past the drip line of the plant; don’t start too close to the trunk. The best time to do this is early spring or early fall when the weather is cool. Prepare the new planting site by incorporating a shovelful or two of an acidic type soil amendment into the hole and mix it in with some existing soil. Make sure that the root ball is somewhat damp before you start digging up the plant. You can lift it onto a tarp and then use the tarp to drag the plant to its new location. Be sure not to plant the azalea too deeply and water it thoroughly after transplanting.

Lori K of Windsor asks: There’s this black, powdery substance on the leaves of my camellia plant. It seems to be concentrated in one area, but looks like it’s spreading. I can rub it off with my fingers. What is this?

Sooty mold is a black colored fungus that can grow on the leaves, fruit and stems of all plants. The fungus is easy to identify by its “sooty” appearance. Hence the name, “sooty” mold. Light infestations may begin at the base of leaves and move toward the tips. Heavy infestations can cause the entire plant to appear black.

Sooty mold is caused by aphids, mealybugs, scale, whiteflies, and other sucking insects. These insects suck out the plant juices and secrete a sweet substance known as honeydew. The honeydew drips on plant surfaces and over time, a bacteria grows into this specific mold.

Since almost all plants are susceptible to these insects, you could say that almost all plants are susceptible to sooty mold. You’re most likely to find sooty mold in the landscape in spring and summer, when the insects are the most active.

To control these insects, you can blast the plant with a strong spray of water from the hose, use insecticidal soaps or your own home-made soapy water. You need to be persistent and keep a watchful eye out for any areas that missed getting sprayed. It will take more than one application. After spraying, recheck the plant in one week to see if you can spot any remaining live insects. Continue this process until the insects are eradicated or reduced to a manageable level. The soapy water and strong spray of water should also help remove some of the black soot mold.

Dana Lozano and Gwen Kilchherr are garden consultants. Send your gardening questions to The Garden Doctors, at pdgardendoctor@gmail.com.