Dr. Hort: Avocado tree still green but won't grow

Avocado/Persea americana

Courtesy of Pat Naegle

Avocado/Persea americana

Tree stays green but just won't grow

Q: When we bought our South Tampa home two decades ago, there was an avocado tree in the back yard that continued to grow and bear fruit. Unfortunately, it was killed in a freeze.

Two years ago, we planted a new, 5-foot-tall tree in a different but sunny spot, following the planting directions. We water it regularly, especially during dry times, and fertilize it three times a year. It gets full sun and is in a spot away from other trees, although we do have oaks in our yard. It has grown only about 4 inches and has few new leaves and has never bloomed.

I see smaller trees in nurseries that are already blooming and producing fruit. Ours looks healthy, I think, and I don't see anything on the underside of the leaves. Can you tell me why our tree doesn't grow or bloom?

Pat Naegle

A: Your avocado, or alligator pear as it is sometimes called, Persea americana, looks great in the photo. A common cause for plants not to grow but stay green is the root ball being set too low in the hole at planting. Dig around the base of the tree next to the stem with your hand in search for the first lateral (horizontal) root coming off of the stem: It should be at or near the soil surface.

If it is down an inch or more, re-dig the plant and set it where the first lateral root is at the existing soil surface (at grade) or an inch higher than grade.

Water it into the hole, then backfill with no amendments (peat, Black Cow, fertilizer). Create a soil saucer 6 inches high around the outside of the hole with no mulch in the well and fill with water every other day for six weeks. Fertilize, then cut back watering to two days per week for six weeks. Then one day per week for six weeks. Then it is on its own.

It should gain 2 to 3 feet this coming growing season.

Getting rid of caterpillars

Q: I've got green caterpillars on my carrots and tiny brown ones on my tomato plants. Will neem oil help get rid of those pesky caterpillars? If not, what would you recommend I use on my veggies?

Jean Pelak

A: When caterpillars are small, Bt (Bacillus thuringiensis), a bacterium sold as Dipel or Thuricide, works wonders. It is organic and kills only caterpillars, but it must be on the plant continually to kill them as they begin to feed as babies.

Another bacterial product contains spinosad, is sold as Naturalyte Conserve and kills caterpillars and other damaging insects on contact. Both are labeled for use on veggies. Be sure to read and follow the label directions!

Need help? Dr. Hort (Greg Charles) answers questions about garden problems. Email him at drhort@tampabay.rr.com or mail questions to HomeLink, Features Department, Tampa Bay Times, P.O. Box 1121, St. Petersburg, FL 33731. Describe problem in full, and include your name, city of residence and contact information. If possible, include a good-quality photo. Fuzzy ones won't do. Photos cannot be returned. Please do not send plant samples.

Dr. Hort: Avocado tree still green but won't grow 03/23/13 [Last modified: Thursday, March 21, 2013 5:54pm]

    

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