Grit Blogs > The Creative Vegetable Gardener

Weathering the Elements

Weathering The Elements 

Nature’s peculiarities often alter the growth and quality of homegrown vegetables.  Temperatures that are too high or too low, summer hail, and too much or too little sun may damage crops.  While we can’t control Mother Nature, we can learn to co-operate or compensate so that our gardens have a better than even chance.

Germination Wisdom 

Most vegetables germinate seed, grow, and set fruit within a surprisingly narrow temperature range.  Each vegetable seed has individual requirements regarding soil temperature.  Lettuce and onion, for example, tolerate soil temperatures down to 32° F; germination at such low temperatures is slow, but the seed will survive and will sprout as the soil temperature warms up.  Bean and sweet corn seeds, on the other hand, will rot if left in the ground more than a few days at temperatures below 55-60° F. 

Vegetable seeds also cease germinating when the temperature rises too high—somewhere between 86 and 104° F, depending on the vegetable.  During hot weather, surface soil temperatures often climb far above this range.  Even if the seed has germinated, the seedlings (especially carrots and beets) can die of heat injury at the soil surface.  Gardeners can aid germination and seedling survival during hot weather by spreading 2 inches of organic material (such as compost) over the soil after the seeds have been planted.  This protective layer reduces soil temperature and holds in moisture.

Soil temperatures for Vegetable Seed Germination 

Vegetable               Minimum      Optimum      Maximum 

Asparagus                   50                    73                    95

Beans (lima)                60                    80                    85

Beans (snap)               60                    85                    95

Beets                           40                    85                    95

Broccoli                       40                    85                    95

Cabbage                     40                    85                    95

Carrots                        40                    80                    95

Cauliflower                  40                    80                    95

Celery                          40                    80                    95

Cucumbers                  60                    95                    105

Eggplant                      60                    85                    95

Endive                         32                    75                    75

Lettuce                        32                    75                    75

Melons                        60                    95                    105

Okra                            60                    95                    105

Onions                         32                    80                    95

Parsnips                      32                    70                    85

Peas                            40                    75                    85

Peppers                       60                    75                    85

Pumpkins                    60                    95                    105

Radishes                     40                    85                    95

Spinach                       32                    70                    75

Squash                        60                    95                    105

Sweet corn                  50                    85                    105

Swiss chard                 40                    85                    95

Tomatoes                    50                    85                    95

Turnips                        40                    85                    105


To ensure good seed germination, plant vegetables when the soil is within the proper temperature range.  A soil thermometer is a handy tool to have.  In addition, vegetable varieties have individual temperature ranges.  Early varieties require a smaller amount of heat to mature than midseason varieties.  Most miniature vegetables need less cumulative heat than other vegetables.

If you live in an area of cool summers (below 70° F), you can grow crops that require a longer or hotter season (such as melons) by planting the earliest varieties.  Those with the fewest days to maturity have the lowest heat requirements.  (Visit for early varieties)

Fruit Set 

Eggplant, peppers, tomatoes, beans, and peas start to form fruit when the male parts of their flowers successfully pollinate the female parts.  The success or failure of this pollination depends greatly on the temperature.  The determining factor for such vegetables as peppers and tomatoes is the nighttime, not the daytime temperatures.  To set fruit, most tomatoes require temperatures above 55° F for at least part of the night.  Night temperatures above 75° F inhibit fruit set and cause blossoms to drop.

Misshapen tomato fruit and puffiness can result from high or low temperature extremes, which interfere with the growth of pollen tubes and normal fertilization of the flower’s ovary.  In addition, catfacing (puckering and scarring of the blossom end of the fruit) can occur when cool weather at flowering time makes the blossom stick to the small fruit.  Many of these problems can be averted by placing clear polyethylene covers over the plants when temperatures fall below 60° F.

© Copyright by Karen Newcomb