NEIL SPERRYGardener's Mailbag

Dear Neil: You mentioned in a recent column that the time to treat for grub worms is mid-to late June. What do I do if I find them at this time of year? Should I apply the grub treatment now and again at that time?

A: No! The short version of the life cycle is that the June bugs (adult form of the larval white grub worms) emerge, fly and mate in late spring and early summer. The small grubs hatch in mid-summer, and that’s the reason for the treatment at that time.

You want your insecticide to be there when they are small and quite near the surface of the soil. They feed actively mid-summer through mid-fall. The ones you see in winter and spring will pupate to become beetles from this point on, so there is absolutely no reason to apply insecticide now. They have finished their feeding for this generation.

NO IRIS BLOOMS

Dear Neil: We bought some “cemetery” iris four years ago. They bloomed well initially, but it looks like I’ll get nothing this year. Is the soil wrong, are they too crowded or are they planted too deeply? I’d like to make them productive again.

A: I can’t really answer from the facts given. You didn’t mention the sunlight — they do need full sun. It would be odd for them to be too crowded that quickly, but perhaps you planted them too closely together. If you planted the rhizomes more than 1 inch deep, perhaps you did get them too deep.

Hopefully you mixed a good bit of organic matter (several inches of a blend of peat, compost, finely ground bark, rotted manure, etc.) and perhaps, if you have a clay soil, 1 inch of expanded shale. If you didn’t prepare the soil that way, do so in late September and replant the rhizomes at that point.

PRE-EMERGENTS AND TREES

Dear Neil: What pre-emergent and post-emergent herbicides can be used around trees?

A: Most pre-emergents will be fine within the drip lines of trees since their impact on weeds is on germinating seeds and not on established plants. Atrazine is one in particular, however, that will do damage to existing shade trees. I have chosen not to recommend it because I’ve seen it kill even mature trees, most notably large southern magnolias.

TOO HIGH

Dear Neil: I have Tif bermuda. I’ve never had this kind of grass before. I’m told it should be mowed short, but my lawn care people leave it at 4 inches. It has grown tall and stringy. How high should it be cut and how often?

A: The phrase “Tif” refers to grasses that were bred in Tifton, Georgia, at the turfgrass breeding station. They are hybrid bermudagrass varieties, and their recommended mowing heights are all over the map. Most of the ones used for turf in Texas, however, were bred for golf courses and athletic fields and are mowed at 1 inch or shorter. A couple can be mowed at 1-1/4 inch. This is a good time to scalp the lawn by dropping your mower way down to the recommended height. Collect the clippings and use them in the compost or send them to a recycle center (not a landfill). Mow on 5-or 6-day turnarounds all season once the grass starts growing actively.

EXCESSIVE SUNLIGHT

Dear Neil: I have a planting of variegated agaves in a sunny location. I frequently get leaves with browned, rotted sections. Is this due to a nutrient shortage? Should the leaves be cut just below the browned areas? Should the plants be dug and thinned?

A: The browning may be due to excessive sunlight, especially if water collects on the leaf surfaces and stands there while the sun is shining. Yes, trim off the dead portions. You’ll probably have to use a machete, because agave leaves are extremely fibrous. Heavy gloves are also called for.

Hopefully the bed drains perfectly. Be sure that irrigation is from ground level and not overhead, again to keep water from collecting on the leaves.

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. Photos submitted with letters must not come from previously published material and may be used for publication. Neil regrets that he cannot reply to questions individually.