Beneficial insects are gardener's good friends

Q: The trunk and two large branches of my 20-foot orchid tree are covered in a fine, silky web. Is this damaging, and what can I do? I have never noticed anything like this before, and we started the tree from seed eight years ago.

A.P., Houston

A: Your description meets that of the webbing of beneficial bark lice. The insects create this covering to protect them while they clean bugs and fungi from our trees. I've also seen the stockinglike web on crape myrtles, maples and oaks.

Let the bark lice do their work, and eventually they and the web will disappear.

Q: After a long, unending and depressing battle with weeds, I surrendered and installed a weed-shield fabric in areas of my garden with numerous roses and camellias. According to product information, water and oxygen pass through the fabric. But what about fertilizer? Must I move the shield material aside to fertilize with a granular material or will the fertilizer dissolve and effectively pass through it?

S.B., Houston

A: It would be best to pull back the fabric or cut splits in it to apply granular fertilizer. Your best bet is to apply a soluble formula with a sprayer and apply as evenly as possible. If the fabric allows water to penetrate, the soluble fertilizer should seep through.

Permeable landscape fabrics are certainly better than black plastic since they allow water and air in but block some light, discouraging weed seed germination. But if organic matter collects on top of the fabric, seeds will have a chance to sprout.

Q: When I purchased my newly built home in 2008, there were several flower beds installed by landscapers, and I also made some in my backyard. All are fine except the flower bed that lines the back of my house. Oleanders, hibiscus and annuals that I have planted there have shriveled up and died. The plants will look OK for a month or so, then start a slow death.

The flower bed is on the northwest side of my house and gets direct sun in the afternoon, but I am more inclined to think that it's the soil. It is very heavy, compacted clay and perhaps junk from construction. I have tried adding soil each year when I plant, but that doesn't seem to help.

I am wondering about digging up the soil in the fall and replacing a lot of it. Should I bother with this? If so, how much should I dig up? What should I replace it with?

M.Z., North Shore

A: Perhaps poor drainage and soil makeup contribute to the problem. If plant roots sit in soggy soil, they'll suffocate. And construction debris can create overly alkaline conditions.

I would send a soil sample to Texas A&M University to identify imbalances and deficiencies and determine what amendments might help. See instructions at soiltesting.tamu.edu.

Adding a generous amount of compost will improve soil nutrients and friability. But depending on test results, it may be best to replace existing soil with a quality, well-draining, organically enriched mix. There are bag products convenient for filling smaller spaces. To fill larger areas, you can buy in bulk at a business that sells soil/mulch products.