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GARDENER'S MAILBAG: Best potting soil for tomatoes

By Neil Sperry
Special to the Herald Democrat

Dear Neil: What potting soil mixture would you suggest for growing tomatoes in 5-gallon nursery pots? (What proportions of each?) And what varieties are best?

First of all, a 5-gallon nursery pot is actually more like 4 gallons in size. That’s too small for a standard tomato plant. I use 7- or 10-gallon pots, and I find that I have much better success. The smaller pots dry out really rapidly when it starts to get warm in late spring, and blossom-end rot becomes a terrible problem for the developing fruit. My potting soil mixture might vary each time that you ask me, but it will usually be something like 50 percent sphagnum peat moss, 30 percent finely ground pine bark mulch, 10 percent horticultural perlite and 10 percent expanded shale (for ballast, to help keep the plants from tipping over). I wouldn’t be opposed to someone decreasing the peat and bark by 5 percent each and using compost as an additional ingredient. I use a high-nitrogen, “complete” (all three major nutrients) water-soluble fertilizer with each watering to supply nutrition. As for varieties, stay with small and medium-sized types such as Super Sweet 100, Red Cherry, Fantastic, Early Girl, Roma, Celebrity and Better Boy. Avoid the large-fruiting types like Big Boy and Beefsteak. They do not set fruit well once temperatures climb higher than 90 degrees.

Dear Neil: This is a 3-year-old dwarf apple tree. As you can see in the photo, all of the growth is on one side of the graft line. The opposite side has no bark. Do I have to leave the tree staked? My concern is that I’ll come out some morning and find the tree broken off.

Apple graft

Unfortunately, it looks like the tree’s trunk has originated from the rootstock, beneath where a graft would have been made. I’m not sure that you have a good apple variety. What you have growing is whatever dwarfing rootstock was chosen in the process. And the tree looks very weak. It’s only a matter of time (probably months) until the tree will snap. You’ll have apples many years sooner if you’ll start a new tree right away.

Dear Neil: My copy of your 1991 book with the gorgeous cowboy boots is a fixture on my coffee table. It calls for Diazinon or Dursban for the control of fire ants. Is either of those still available? We are in a rapidly developing area and I don’t want to use anything that would be a problem for my neighbors.

When I decided to do my newest book, Neil Sperry’s Lone Star Gardening (available only from my website), it was because information in that older book was becoming obsolete. Those insecticides are no longer available to consumers. Texas A&M’s recommendations have shifted toward area-wide baits and, where necessary, individual mound treatments. You can find their latest recommendations by searching “Texas A&M Entomology fire ant controls” online. On a personal note, I have been very satisfied with the results I’ve gotten using the area-wide baits for the past 12 or 15 years.

Dear Neil: Do you have any idea why our Obsession nandinas have not grown? They were planted two years ago. We came back four months later and filled in with two more. We have used drip irrigation and supplemented with a hose, and I have used a slow-release fertilizer. Any suggestions?

obsession nandinas

Obsession is one of the newer tall-growing nandinas. As such, the plants in your photo look very small for the “big world” they have found themselves growing in. It’s roughly equivalent to over-potting a container plant. It’s difficult for the small plant with its limited root system to take up water and nutrients properly. I would suggest switching over to a water-soluble, very high-nitrogen fertilizer and using it every time that you water the plants this spring and summer. Use a long-handled water wand and water breaker to soak their soil deeply with the diluted solution of fertilizer, and never let their soil get dry to the feel. It is very difficult to water small plants in a bed setting like this properly. In future plantings, you’d be better advised to buy larger transplants and to set them into the highest quality landscaping bed mix that you can possibly prepare. Hope this helps. Good luck with turning these around!

Dear Neil: We’ve had St. Augustine successfully for 40 years beneath a massive live oak. Two years ago, animals started digging for grub worms. I treated for grubs and eliminated them, but now the replacement sod dies soon after I plant it. I do not have grub worms any longer, but I can’t get grass to grow where the grubs killed the grass originally. What could the cause be?

The new grass is starting with two strikes against it. First, it has been dug at the sod farm with the loss of most of its roots. That sets it back. Then it is planted into heavy shade (all sod farms are in full sun, and that is St. Augustine’s preference). It just can’t get over those two hurdles. I’ve seen it happen hundreds of times, including in my own yard. Like it or not, as long as the shade is that heavy, you’re probably a candidate for a shade-loving groundcover like mondograss, English ivy or ferns. I’ve never been so pleased as I was when I finally made that decision myself. The thinning St. Augustine about wore me out.

Dear Neil: Every year I try to grow squash, but the plants die before producing their fruit. What am I missing?

Without a few more key facts, I’m going to just list some possibilities and let you do the research. Most people are growing either summer crookneck or zucchinis. Your plants may be being ruined by squash vine borers or squash bugs, or if only the fruit is dying, it could even be something as simple as failure to be pollinated due to lack of bees. You might have to do the pollinating yourself by daubing pollen from the male flowers onto the female flowers. Female squash flowers have swollen bases where the fruit will form. Male flowers obviously have pollen attached.

Have a question you’d like Neil to consider? Mail it to him in care of this newspaper or e-mail him at mailbag@sperrygardens.com. Neil regrets that he cannot reply to questions individually.