GARDENER's MAILBAG: What do you suggest for environments with a lot of dust, heat?

By Neil Sperry
Special to the Herald Democrat

Dear Neil: Our city’s Chamber of Commerce tries to keep flowers in large 30-inch round pots that are 24 inches deep at each of the four corners of major intersections in our downtown area. We have volunteers to water most intersections twice a week, but the dust and heat from the road makes it all difficult. What suggestions would you offer?

I have tons of thoughts. I’ll try to pour them all out. First, consider selling sponsorships of each pot individually and them affix a small marker that denotes the person or company underwriting the pot. It can be flat and flush so that it doesn’t detract from the looks of the show, but it assigns responsibility for that watering. If you don’t have someone watering every pot uniformly two times per week your display will never look right.

Pride Of Barbados

You should use the same group of plants across the entire city. Each pot doesn’t have to be the same, but the same 10 to 15 species should be consistent throughout for a unified look.

You mentioned “flowers,” but don’t overlook foliage. Many of our finest sources of warm-season color come from leaves.

Prepare the best possible potting soil. It should be highly organic (probably no native soil) and lightweight. I prefer a mix that is 40 to 50 percent sphagnum peat moss, 20 percent finely ground pine bark, 10 percent well-rotted compost, and the balance equally split between horticultural perlite and expanded shale. You can buy pre-mixed soils used by commercial growers.

Use a high-nitrogen, water-soluble fertilizer each time that you water the plants. Choose one that does not have a dye that would stain your walks.

Angelonia Pots

As for some of the species you might want to consider for the summer, I’ll throw out a few. I’m sure I’ll miss some good ones, but these come quickly to mind. For flowers, include lantanas, angelonias, pentas, fanflowers, salvias, Gold Star Esperanza, Pride of Barbados, firebush, Profusion zinnias and Cora periwinkles. For hot-weather, full-sun foliage include copper plants, firebush, sun-tolerant coleus, alternantheras, purple fountaingrass, purpleheart and sweet potato vines. For winter, consider pansies and violas, pinks, ornamental cabbage and kale, Red Giant mustard and sweet alyssum.

Gold Star Esperanza

Dear Neil: Last February’s cold wiped out our pittosporums. We replaced them with hollies after being told they would spread and fill in the spaces. They haven’t, but they seem to be healthy. Are we doing something wrong, or do we just need to give them more time?

Yaupon With Dropped Leaves

Your plants appear to have gotten marginally too dry at least once. Both the yaupon holly and the dwarf Burford holly have lost significant numbers of leaves that now carpet the soil. That leaf drop normally happens in early spring, just as new growth is being produced. Drought is the only thing that would cause it in the fall. Keep watering the plants when you don’t get rains and apply an all-nitrogen lawn food (no weedkiller included) monthly starting in late February. You should see a flush of new growth come spring.

Dwarf Burford With Dropped Leaves

Dear Neil: I have climbing roses in a raised bed. I am constantly pulling grass runners out of the bed. Mulches haven’t helped. Is there a herbicide that would do the job, yet be safe around the roses? Or should I plant a groundcover to crowd out the grass?

My bet would be that you have bermuda coming into the bed, and no groundcover is going to crowd it out. You can apply a glyphosate-only weedkiller spray directly to the grass to kill it during the growing season. The glyphosate-only materials are not active in the soil, meaning that they do not enter plants through their roots. They must be applied to green, active growth. I’ve done what I’m describing many times. If I’m concerned about the spray drifting onto desirable green tissues such as a rose trunk, I’ll temporarily protect it from the spray with a wrap of aluminum foil. Buy a trigger spray bottle next spring when the grass is growing actively again. I think you’ll be pleased with the results. Just be certain the product contains no other active ingredients.

Dear Neil: When can overgrown azaleas be pruned back? How much?

Trim spring-flowering shrubs and vines immediately after they finish flowering. In the case of azaleas, use lopping shears and hand pruners, not hedge shears. You can remove probably 20 percent of their growth without hurting the plants, but do so one branch at a time so you can maintain the plants’ natural form.

Dear Neil: I saw a magazine story on a lilac variety that had been selected to grow in the hot Southwest. What are your feelings?

In 51 years of public horticulture in Texas, I’ve seen that claim made many times. For northerners who have found themselves in Texas, each has later confided that they were very disappointed in these plants’ performance compared to northern lilacs. My personal preference is to grow other types of better-adapted southern fragrant plants.

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.