tomato and zuchini crop failures

(Question)

Hello, I have a 22 year old south facing veg garden about 20 x 5′. I add 4 bags of sheep manure every spring and plant tomatoes, zucchini, lettuces, eggplant, herbs, etc., and rotate the tomatoes each year. For the first, time I have few flowers and no zucchini and the tomato plants, from Home Depot and Superstore withered and died soon after planting. I planted 3 more and 1 grape tomato survived to produce some fruit on a spindly plant. Lettuces and chard growing like mad. Is the tomato problem a fungus and the zucchini problem too much nitrogen or something else? What should I do for next year? Thank you very much!

(Answer)

How disappointing it is to suddenly experience problems growing tomatoes and zucchini squash. You are clearly an experienced veggie gardener; you are aware that adding manure and/or compost to the beds each year is important–tomatoes and squash are heavy feeders. It is doubtful that your tomatoes “withered and died” from any fungal wilt disease; you rotate your tomatoes each year and the fungal diseases generally show up after the plant has set fruit.

The problems that you have experienced with your plants are probably due to weather conditions and possibly a lack of moisture. When did you plant the tomatoes and squash plants? Although seedlings are usually available to buy in May, planting them before the soil and air temperatures warm up can be stressful for the plants. They are warm weather crops–“cold soils at planting time can stunt growth and delay or eliminate flowering.” http://www.missouribotanicalgarden.org/gardens-gardening/your-garden/help-for-the-home-gardener/advice-tips-resources/visual-guides/tomato-fruit-problems.aspx. Planting the tomatoes too soon for the conditions may have contributed to their withering and dying.  [Lettuces and chard are cool-season veggies].

The problems with your zucchini may also be due to the weather conditions (cool temperatures and lack of moisture). Zucchini produce both male and female flowers; the male flowers usually appear before the female flowers and can be affected by cooler temperatures. Since male flowers do not produce fruit, the lack of female flowers may be one explanation as to why your zucchini have no fruit. If the plants have both the male and female flowers, then lack of pollination may be the cause–bees are simply not being attracted to the flowers. If you can distinguish between the male and female flowers, then you might consider pollinating them by hand. The following website provides excellent pictures as well as further explanations about the effect of cool temperatures and lack of moisture.

http://www.omafra.gov.on.ca/english/crops/facts/00-031.htm –“Low temperatures also have an adverse effect on flowering and fruit set. Cucurbits are monoecious plants – that is, each plant produces both male and female flowers. Normally, several male flowers form before female flowers develop. During periods of cool temperatures (below 22°C, 70°F) most pumpkin and squash cultivars respond by producing primarily male flowers. Male flowers do not form fruit. By contrast some cultivars of summer squash appear to form mostly female flowers in response to cool temperatures. Without male flowers to provide pollen, however, the female flowers do not form fruit.

Summer squashes are especially susceptible to drought because the fruit develop and are harvested within a few days of pollination. Lack of sufficient moisture often results in poor or irregular fruit development”.

We all look forward to getting things planted in our gardens, especially after the cold winters that we’ve had for the past couple years. In southern Ontario, we seem to experience fluctuating temperatures that occasionally rise above 20′ C. during May; even though the air temperature may be warm, the soil may actually not be warm enough to successfully plant tomatoes and squashes. If you have raised beds, the soil will warm more quickly. However, covering your soil with black or clear plastic sheeting in the early spring will help to raise the temperature of the soil. http://umaine.edu/publications/2752e/

Patience is the key to making sure that your warm-season vegetables have the right conditions for planting.