Photo by Howard Garrett

Q:  I had a green ash (not the best choice for our soil) in my front yard for over 10 years. It went into decline and, in spite of professional care, it died. I heard that mushrooms growing under a tree can be a sign of root rot. This tree did have mushrooms growing under it.  It’s been more than five years since the tree was removed and the stump ground to below the surface. There is a healthy red oak on the other side of the yard. Is it safe to replant another tree in this area? I’ve had conflicting advice. B.C., Flower Mound

A:  The mushrooms are just a sign of decaying organic material in the soil, not a contagious disease. Use my online organic planting recommendations and plant the new tree so that the trunk flare is above the ground grade.

Q: I have just been introduced to organic gardening and want to get a head start with the proper information. What are beneficial nematodes and when do I put them out? J.R., Dallas

A:  Beneficial nematodes are microscopic roundworms used to control pests in the soil. Nematodes enter the insect pest through the mouth or other body openings. Once inside the host, they feed and reproduce until the food supply is gone. Next, huge numbers of nematodes emerge in search of new victims.

Early applications prior to heavy pest infestations, followed by monthly follow-up applications, are best. Therefore, spring and fall are the best times to apply them. In spring, beneficial nematodes control thrips that are about to hit your roses, young ticks in the soil, fleas, grubworms, termites, fire ants, roaches and other pests that have at least one of their life cycles in the ground. This is an annual application I recommend. The other beneficial organism I recommend for all gardeners is trichogramma wasp, to be released as the foliage emerges in the spring. These microscopic wasps control many caterpillar pests.

You can order them from online sources, but many garden retailers stocking organic products also will sell beneficial nematodes and the wasps starting in spring.

Q:  I am looking into producing organic potting soil to sell to the public. It would be a one-man operation to begin with, based on your guidelines. Any advice or direction you could give me would be greatly appreciated. G.B., Flower Mound

The potting soil ingredients that I do not recommend include peat moss, perlite, pine bark and washed concrete sand. The ingredients that I believe work much better to grow healthy plants include compost, coconut fiber (coir), lava sand, basalt sand, granite sand, zeolite, diatomaceous earth, cornmeal, wheat meal and dry molasses. The percentages can vary but here’s the most recent formula that I have used:

60 percent compost (compost, humate, coconut fiber, coffee grounds)

30 percent rock (lava sand, diatomaceous earth, zeolite, granite)

10 percent sugar (cornmeal, dry molasses, wheat meal)

This mixture is not currently available, that I know of, but I look forward to you solving that problem.

Q:  We thought our azaleas had a fungus, but we are not sure. Do you think it could be a fungus or stress from the drought? We have acidic soil. Do we need to do foliar feeding of Garrett Juice to save them? Also, is there a type of azalea that will tolerate some sun? D.S., Dallas

A:  Yours could be more of a nutrition problem. Azaleas need to be planted in solid organic matter rather than soil. If they have been planted properly, foliar feeding and drenching the soil with Garrett Juice will definitely help. If not, they should be lifted and replanted before spring.

My favorite mix is 50 percent compost and 50 percent cedar flakes or coconut fiber. Adding lava sand and greensand to the mix also is beneficial. Use 5 gallons of lava sand and 1 gallon of greensand per cubic yard of mix. Most azaleas will grow in full sun and flower better than when growing in shade, but only if they are planted correctly.

Q:  I have a question on planting potatoes. The instructions say to coat potatoes with sulfur or fireplace ashes and allow to callous. Please explain “callous” and how that would look. M.H., Denton

A:  The term refers to a hardening and drying of the cut surface. Commercial growers have told me that this procedure may not be worth the effort. On the other hand, it won’t hurt anything either.