Here are some of the most common problems vegetable gardeners see:
Tomatoes, peppers, and eggplant drop their blossoms and fail to set fruit.
If the plants are otherwise growing well, adverse nighttime temperatures -- either below 60 degrees F or above 70 degrees F -- are frequently to blame. Blossom-drop is seldom caused by heavy use of nitrogen fertilizer or sprinkler irrigation.
Tomatoes and peppers get a big black rotten spot on the end opposite the stem.
This is called blossom end rot. It is caused by a calcium deficiency that develops when soil moisture fluctuates (drought followed by heavy rains or vice versa) or too much nitrogen fertilizer has been applied. Avoid over-fertilization, use mulch to help keep soil from losing moisture, and water to make up for rainfall deficits. Some varieties are more susceptible than others.
New leaves on cucumber plants suddenly wilt.
Leaves may also show dead areas and the fruit may be mottled. The most likely cause is cucumber mosaic virus, a common disease. Bacterial wilt and root rot can also cause wilting. Plants usually recover quickly from wilting caused by a sudden rise in temperature or depleted soil moisture when the temperature falls or moisture is replenished.
Lettuce and spinach "go to seed."
This is also called bolting, when plants elongate and start to flower. It is normal for these crops when the temperatures rise and days get longer. Plant early in spring and choose varieties that resist bolting when possible. If you don't want to save seed, remove the plants and plant another crop for summer or fall harvest.
Kernels develop irregularly on sweet corn ears.
This is often caused by inadequate pollination. Planting sweet corn in blocks of several short rows rather one long row should help.
Snap bean flowers fail to develop.
Daytime temperatures above 90 degrees F sometimes cause this. Flowering usually resumes after the weather cools down.
Tomato fruits are rough and misshapen.
This is often associated with low temperatures (50 degrees F to 60 degrees F) while flowers are forming. The problem is worse on some varieties. The first fruits on a plant are often the most misshapen, while fruits that develop later when it's warmer are normal.
Cucumbers are off-shaped (crooked or nubbins).
This often occurs because of low soil moisture or cool temperatures at the time of flowering. Another possibility is poor pollination because of a lack of bees or a low number of male flowers.