Tulip Intrigue: When Good Bulbs Go Bad

Question: All of my bulbs have grown and flowered, but not the tulips. When I dug up a few of the bulbs, I found they had turned into black mush. Any idea what went wrong?

--V.J., Valencia

Answer: The bulbs rotted, not an uncommon occurrence, especially in California, where we must plant tulips deep (up to 8 inches deep), and sometimes in heavy soils that can stay soggy. Next year, at planting time, try placing each bulb on an inch-thick cushion of washed builder’s sand, placed in the bottom of the hole.

Many tulip fanciers I know swear by this technique. After a few years of adding sand to each hole, and then tilling the soil after the tulips come out, you end up with a sandier, more bulb-friendly soil as a bonus.

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Q: I need an easy and inexpensive way to keep cats out of my flower bed. What do you recommend?

--N.J., Westchester

A: I have found only one sure-fire way to keep neighboring cats (or even your own) from digging in garden beds, and that is to lay branches across the empty dirt until plants fill in and cover most of the soil.

I save woody, pruned branches from hedges, trees and shrubs and then simply lay them flat on any bare soil. They don’t have to be that close together, just close enough to discourage digging and squatting. I suspect you’ll find the slightly untidy look--although branches can be arranged quite artfully--preferable to the smell of cat poop.

I know of several gardeners who use this simple method in their raised vegetable beds, but it also works in flower beds. You also might consider planting more densely so there is less exposed soil.

Nurseries and mail-order companies sell dog and cat repellents, but I’ve never heard of any getting rave reviews from gardeners.

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Q: I purchased a neem oil product (Safer BioNEEM) to use on my vegetables and citrus, but the label says not to use it on food crops. I’ve heard it’s organic, so can I use it anyway?

--L.G., Torrance

A: It’s against the law and not a good idea to disregard label instructions, even on so-called “organic” products.

Peaceful Valley Farm Supply, a large organic mail-order company in Grass Valley, faxed me a label for Safer BioNEEM that shows it is registered for a great variety of edible crops, from citrus to tomatoes. You apparently have a bottle with an old label, from the days before it was registered in this state.

It would be very surprising if neem weren’t labeled for fruits and vegetables, since it has a very low toxicity for pets and humans. For the record, neem is less toxic than aspirin or even the biological control B.t., and rates only a “Caution” on its label.

Neem is derived from the neem tree in India and comes two ways--as neem oil and as neem extract. Both have extremely low toxicity because neither is a poison.

Neem oil smothers and kills pests as well as some fungus diseases, including mildew and rust, which is why Green Light markets it as Rose Defense. For diseases it’s used mostly as a preventive and is apparently quite effective; it also smothers and repels pests such as mites and, to a lesser extent, whiteflies and aphids.

Green Light makes a similar neem oil product that it calls Fruit, Nut and Vegetable Spray, and food crops are on its label. Don’t spray when bees are about, however, since it can kill them.

Neem extracts are more powerful products that, while they do nothing to diseases, work better on pests. Safer BioNEEM is an extract, aimed at pests ranging from hornworms to sawflies.

The neem extracts work as insect growth regulators and repellents and work best on insects that go though all stages of metamorphosis. It usually takes three to 12 days before you notice that the insects are dying. Extracts can also harm beneficial insects, so use with restraint.

Robert Smaus’ column is published Thursdays. Write to Robert Smaus, SoCal Living, Los Angeles Times, Times Mirror Square, Los Angeles, CA 90053; fax to (213) 237-4712; or e-mail robert.smaus@latimes.com.