Question of the Month

October 9, 2000 - 23:00

Each month the editors select and publish particularly interesting or topical questions from the Onhort.com "Ask the Experts" Web page. We invite you to visit www.onhort.com to check out the other posted questions or to ask a question of your own.

 


Q:

What bedding plants can be grown in an enclosed greenhouse with tomatoes, cucumbers, and green beans?

A:

Most of the traditional bedding plant crops can be grown with greenhouse vegetables; however, they will tend to be "soft" and leggy. Cool night temperatures enhance plant quality and most greenhouse vegetables require warm nights. One major thing to remember, however, is disease and pest management. The insect population tolerances for a vegetable crop are considerably different than for a bedding plant crop. While you can tolerate a small white fly population on greenhouse vegetables, especially if you are using predacious insects to control your pests, your tolerance level on a commercial bedding plant crop is zero. So the vegetable crop will serve as a major incubator for insects and diseases. Also, the pesticides that are labeled for greenhouse vegetables are not the same as for greenhouse bedding plants. My recommendation is to segregate the crops if possible. Otherwise, use systemic pesticides such as imidicloprid (Marathon) on your bedding plants for long-term control and manage your vegetables as normal.

 


Answered by Steven Newman, one of GPN’s Onhort.com Web experts and an associate professor with Colorado State University.

 


 


 


Q:

I am growing impatiens in a greenhouse under 50 percent shadecloth with open ends and a large fan on one end to help remove warm air and improve the air flow. I started the plants approximately four weeks ago from 512 plug trays. My problem is that the foliage wilts during the middle part of the day regardless of the soil moisture. I have overhead irrigation which sprays a fine mist. My question is would it be beneficial to the plants to mist them during the heat of the day to reduce wilting? Also, I have been using 20-20-20 at 150 ppm at each watering. Could this be contributing to the wilting problem?

A:

There are three possible reasons why a plant may wilt on a sunny day even when the media is moist: 1) root rot, 2) high soluble salts, or 3) excessively high temperatures. I would recommend that you check your roots first. Brown root tips would suggest either root rot or high soluble salts. If root tips are completely healthy, cooling the leaves down with mist would help. However, I believe that your problem is probably related to root rot or high salts. Test your media to see if salts are high. If salts are high, leach for 5 to 10 minutes and reduce the level of fertilization. Also, consider allowing plants to leach a little each time you fertilize. If salts are not high and roots appear damaged drench with a fungicide solution that will control both Pythium and Rhizoctonia. Also, consider drenching again in a month. Also consider using a lighter mix.

 


Answered by John Erwin, one of GPN’s Onhort.com Web experts and associate professor with the University of Minnesota.


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