Consuming Temperature

It is July 24, 2008. Yesterday the high temperature was 65°, not the normal temperature of 76 °; that is 11° cooler than usual. The low temperature, 53°, three degrees cooler than the normal low of 56 °. The weather forecast predicts highs in the 60’s for a couple of days then getting hotter, into the 70’s. The nighttime lows will stay in the mid-50’s. In the wee hours of the morning, such as 3 a.m., you can see your breath. This is July - that's just wrong.

This is awful weather for food plants. Two major factors regulate plant growth: sunlight and soil temperature. While air temperature is important, soil temperature is the determining factor.

To provide a wider variety of vegetables throughout our 20 week CSA season, we plant sequentially. That means that we really have three gardens that should provide four gardens of food (the first garden is replanted). Plants germinate and grow all summer long. This year, we are transplanting more than ever before to ensure that our plants have a good start. We are direct seeding, too, but not as much as is economical. Here is why we are spending more time, which equals money, on transplanting.

Let us consider the Broccoli plant. The soil temperature for germination must reach 70°, but not exceed 80° to 90°. Seeds take 3 to 8 days to germinate, and reach maturity in about 70 days.

Next, let us consider the Cucumber. The soil temperature. for Germination must be between 70° and 90°F. It takes 7 to 14 days to germinate, and they mature in 70 to 85 days.

Finally, let us consider lettuce. For this year, it is the best. The soil temperature for germination has a wide range, from a low of 40° for some varieties, extending up into the 50s for many other varieties. The top high temperature ranges to 80°. For many varieties, when the air temperatures suddenly increase, for example go from the mid-60s into the high 70s, they bolt, that is rapidly produce seeds. Depending upon variety, it takes 40 to 65 days to mature. This means, however, that when temperatures exceed 80°, lettuce dies.

Sounds quite predictable, but not this year. Soil temperatures are in the 60s. That means that our little broccoli and cucumber seeds had to be planted in the green house, hardened (a process of acclimating the plants to the cooler temperatures outdoors), and transplanted. We even transplanted hundreds of heads of lettuces. There is no guarantee that the transplants will survive.

This spring the air temperatures did not rise above highs of 45°, which means that the soil temperatures were several colder. Not even lettuce would germinate.

The temperature for germination really tells the temperature range in which the plant will survive. The Cucumber survives between 70° and 90°F. A more mature plant can survive and grow in temperatures ten degrees cooler or warmer, but the progress towards maturity will be adversely affected at either end of the range.

When you hear of cold temperatures in the Pacific Northwest, or extraordinarily hot temperatures in other areas like New York, that means that the crops are stressed and may under produce or simply die.

For this reason, climate change directly affects our food crops. We are told by those who visit many farms in the whole Puget Sound Area, that our crops are doing marvelously, considering the weather. We have more of everything. It is taller, more mature, and more abundant. This is due to our diligent Co-farmer, Brad, and his workers, Lesley, Allison, and Kathy. Still, our crops are slow: perhaps six to eight weeks behind. Pray for a long season.