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Ask Dr. Hort: warm weather weeds, African violets, citrus leafminer, pampas grass

How to prevent warm-weather weeds

Q: The weather is warming up and the weeds are ready to pop out of the ground. Is pre-emergence a good remedy and where do I buy it? Is it liquid or use a spreader?

A: You are right on time for pre-emergent weed control for the summer weeds are getting ready to sprout. Common pre-emergent chemicals such as Preen or Pre-M work quite well for most annual weeds. If you want to go organic, consider products that contain corn gluten such as Amaze, but more than one application will be necessary.

As with any chemicals, follow label directions. These products are available at your local garden center except the gluten products, which you may have to order online.

Container-grown tomatoes won't ripen

Q: I wonder if you can give me some insight to a problem I had with my container tomato plants. I bought plants specifically designed for containers, planted them in the late fall, gave them substantial sunlight, watering and fertilizing. The plants grew quite tall and produced abundantly. I staked them and waited for them to ripen. I waited for several months and they never ripened. The cherry tomatoes took on a strange hue and dropped off. The other plant kept producing tomatoes that never ripened. I picked all those off and put them in brown paper sacks and only two out of the bunch ripened enough to eat. What do you think gives with these tomatoes?

I have planted container tomatoes before and got tomatoes that were edible, so I wonder what I am doing wrong. One year, I had to fight off squirrels and now this. I should note that the squirrels did not seem interested in these tomatoes, even green. Lyda Graser, St. Petersburg

A: Timing is everything for the ripening of tomatoes. Right now is the time to plant for the spring garden. It takes about 50 to 60 days from fruit set until ripening and they like temperatures of 65 to 84 degrees to accomplish this feat. It is at these temperatures that tomatoes produce lycopene and carotene, the pigments that turn them red. Temperature in the soil also plays a role; ripening slows above 80 degrees.

Another possibility is too much fruit. Your tomato plant must have enough leaf surface to produce enough energy to support ripening. Sometimes thinning fruit will help in gaining fruit color.

Lastly, tomatoes need a large enough container, 5 to 7 gallons for cherry tomatoes and a moist, well-draining potting mix to produce enough root system to support the ripening of an abundant fruit set. It is best to use a peat-based potting mix, not soil, such as Fafard, Promix or Miracle Gro Potting Mix for optimum results.

African violet has white fuzzy spots

Q: I have several African violets on my east-facing kitchen windowsill. One has developed white fuzzy spots on the leaves and stems. I believe I've read that this indicates an infestation of some sort that should be either sprayed with water or other spray. I know not to get the leaves of African violets wet, so what do I do? The others seem uninfected. This has happened before, and I threw it in the trash. Should I pitch this one, too? Lucy Brenner

A: A common pest of African violets, (Saintpaulia ionantha), is mealybug, a small one-sixteenth- to one-eighth-inch critter covered in white wax and being slightly mobile on the plant. For slight infestations, dabbing with a cotton swab with 70 percent isopropyl alcohol is an effective control. For heavier infestations, Neem Oil is effective, as well as Safers Insecticidal Soap applied weekly — making sure to cover 100 percent of the plant. Wetting the leaves is not harmful if products are applied according to label directions. If the problem is severe, it might be easier to pitch it in the trash as you mentioned.

Lime and lemon trees look diseased

Q: I need your help in verifying the problems on my lime and Meyer lemon plants. The nursery I bought them from said I cannot do anything to help the plants and said to just let them outgrow it. But they look terribly diseased. Also, they are about 2 years old but no fruiting yet. Dr. James Lin

A: It appears that the main problem on your lemon or lime is citrus leafminer, which curls up the new growth. Products containing Spinosad will control the problem if applied to flushes of new growth. Fertilize with a quality citrus fertilizer now to push a healthy flush of new growth and don't worry about fruiting yet. Grafted trees usually bear fruit when 2 to 3 years old where seedling trees don't begin fruiting until 4 to 7 years old. Concentrate on good cultural practices, water, fertilizer and pest control to grow a healthy tree and the blooms will come.

Cut pampas grass?

Q: Should I cut down my pampas grass as I do my muhly grass? Paul Herrick

A: Commonly, pampas grass, Cortadieria selloana, doesn't need the same cultural care as muhly grass, Muhlenbergia capillaris. Dead thatch can be cut from the clump at any time you wish or not at all, but you don't need to chop the clump down like muhly grass. Be careful though, the edges of pampas grass leaves are like tiny saw blades and will do a number on your arms. It's best to wear a long-sleeved shirt.

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.

Ask Dr. Hort: warm weather weeds, African violets, citrus leafminer, pampas grass 04/28/12 [Last modified: Saturday, April 28, 2012 4:30am]
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