Urban Gardening

June Q and A

Many types of tomatoes can be grown in pots as long as you're willing to provide extra care.
Many types of tomatoes can be grown in pots as long as you're willing to provide extra care.

Question: I live in Lake Forest, Illinois, and last year a few of my annual flower beds had terrible whitefly infestations. I treated them with insecticide, but I think it was too little too late, as their populations were enormous by that point. Are there any preventative measures we can take this year to minimize the problem? If we have another infestation, what is the best control?

Answer: I discussed your question with my friend, Tom Tiddens, manager of Plant Wellness at the Chicago Botanic Garden. We agreed that outdoor whitefly infestations are rare in our climate. Your whiteflies probably arrived with your plants.

You're right in thinking that the key is to catch them early and treat plants on a regular basis until the pests are under control. Thoroughly inspect all shipments of annuals. If you find pests of any kind, sequester infested plants and treat them before transplanting. Mechanical methods of whitefly control include vacuuming or hosing them off the plants. Insecticidal soaps and sprays with garlic or neem oil are effective pesticides.

Question: I am having no luck growing my tomatoes in pots. We live in downtown Phoenix where it is hot and dry, and sometimes very windy. I've placed the pots near the side of the house where the sun is less intense, but they still won't grow. What can I do?

The best time to divide overgrown iris is in late summer.
The best time to divide overgrown iris is in late summer.

Answer: Tomatoes perform best when high temperatures do not exceed the 80s during the day and the 60s at night. In the southwest and deep south, gardeners often grow tomatoes as a winter/spring crop. Peppers or okra might be better choices for a summer crop in Phoenix. I also recommend heat-tolerant varieties like 'Solar Set' and 'Heatwave'.

Question: My iris have had a growth spurt and I need to divide them. I live in Indianapolis. Should I divide them this spring or wait until fall?

Answer: Iris are easy to divide. The best time is in August, when summer heat begins to wane and conditions for root growth improve. Dividing in late summer also gives the iris time to recover and develop next year's buds before winter. Use a sharp knife or pruners to divide the clumps. Discard any shriveled or soft rhizomes. Snuggle the rhizome divisions into the soil so they are just beneath the surface, tuck the roots into the ground, and water.


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