My girlfriend gave me a large-thorn “Dragon” orange tree a few years ago, and it has survived nicely outside. This year, it even produced oranges, but they were very small and sour with nothing but seeds on the inside. Is there a fertilizer or gardening technique I can use next year to plump up the oranges so maybe they will taste better?

John Drake

I’m pretty sure what you have is Poncirus trifoliata or Flying Dragon, a hardy citrus shrub that is grown more for its looks than its fruit. A happy Flying Dragon will develop into an 8- to 10-foot-tall twisted, contorted maze of 1- to 2-inch-long green thorns, and fruit that will be about the size of golf balls. And that is about as big as they get. The minuscule fruits are only a sideshow – its emerald green stems and menacing “claws” are the main attractions.

However, I would still harvest the fruits – not to use in a puckering contest but to tame this plant’s need to breed. ‘Flying Dragon’ is considered invasive in many parts of the country because of how easily it reseeds. Picking the mature fruits and disposing of them will help slow this botanical creature’s creep.

How to test soil

I would like to have the soil in my small vegetable garden tested. How do I go about it? What kind of container do I need? Where do I send it? I live in Apex, but before that I lived in New Jersey, and I had to add lime.

Gerry Werner

There are quickie soil test kits available at most garden centers, but they only give minimal useful information.

Your best bet is to pick up a soil test box (it comes with instructions) at your Cooperative Extension County Center, which in Wake County is on 4001-E Carya Drive in Raleigh. They do not mail boxes. The Agronomic Division of the N.C. Department of Agriculture and Consumer Services will do the testing, andit will be thorough.

The soil test is actually free if you turn it in before Nov. 25. After that, each test is $4 until March 31, 2015, when it is free again. But by that time, the Agronomic Division going to be in the thick of springtime rush, and they will be swamped!

If you think you need to add lime, this is another reason to have a soil test done now rather than later. Lime helps neutralize Carolina clay soils, which tend to run on the acidic side. But lime takes its time to become chemically incorporated into the soil, so the sooner this amendment is added, the better.

Mold on crepe myrtles

I have been having a problem with my crepe myrtles. Seems like the trees start off doing fine, then lots of flying things get on them and turn the leaves a black sooty color. I consulted someone at Lowe’s about the problem, and they called it black mold. What can I do about it?

Christine Talley

The problem is actually called sooty mold, and being a mold, you would think something like a fungicide would take care of such nastiness, but in this case, treat the source from where it came – the back end of a bug.

Leaf-sucking insects such as scales, white flies and aphids are no strangers to crepe myrtles, and while dining on leaves, they secrete a gooey substance called “honeydew,” which sticks to the plant’s foliage and turns black, becoming sooty mold. Thoroughly spraying the crepes during the growing season with neem oil, horticultural oil or insecticidal soap will slow this problem down, but you may have to spray several times over thespring and summer to put an effective dent in the bad bugs’ population.

Also, in the next month or two, think about applying a dormant oil on the crepes to smother any overwintering insect eggs. Any big box home improvement store usually carries this insecticide, which can also be found in garden centers. Save gas and let your fingers do the walking by calling around.

L.A. Jackson is the former editor of Carolina Gardener Magazine. Send your garden questions, including the city where you garden to: askthegardener@newsobserver.com.