Every now and again, you are sure to run into a problem with your plants. This is just a simple fact of any type of gardening. The key is to act quickly, armed with quality knowledge.
Nitrogen deficiency will cause yellowing of the leaves, especially in the older leaves. The growth of new roots and shoots is stunted. In tomatoes, the stems may take on a purple hue.
A phosphorous deficiency is usually associated with dark green foliage and stunted growth. As in nitrogen deficiency, the stems may appear purple. But since the leaves don’t yellow as they do in nitrogen deficiency, the whole plant can take on a purplish green color.
Iron deficiency results in yellowing between the leaf veins. In contrast to nitrogen deficiency, the yellowing first appears in the younger leaves. After a prolonged absence of iron, the leaves can turn completely white.
This condition can be caused by environmental factors or disease (usually caused by Fusarium). Nutrient and media temperature can be adjusted to remedy wilt. However, if Fusarium has taken hold, the chances that your plants will survive are slim.
If wilting is due to environmental causes:
Try to spray the plants and roots with cool, clean water to rejuvenate them. If this hasn’t helped them by the next day, try it again. If the plants respond, top-off the nutrient solutionand check the pH. If the plants don’t respond to the misting, empty the tank, move it to a shadier spot, and refill with cool, fresh nutrient solution. Don’t reuse the old solution – start with fresh water and nutrients.
–Charles E. Musgrove
If wilting is due to a system blockage of nutrient:
I have seen tomato plants that have been so dehydrated due to a nutrient supply blockage that they were lying flat and for all the world looked stone-cold dead. When the nutrient flow resumed and the plants were given the less stressful environment of nighttime, they rebounded so well that I wondered if I had dreamed the previous day’s “disaster.” The moral of this story is to always give plants a chance to revive, even when the situation looks hopeless.
See also pests and diseases.