Predicting and Preparing for Frost in the Garden

When is the first frost date? What about the last? How long is the growing season here? Well, that depends on who (and how) you ask.

According to data published by the Texas State Climatologist at Texas A&M University, the average first frost date in Fayette County based on mean compilations between 1971 and 2000 was Nov. 23. The average last frost date based on the same data was Feb. 26. That results in a growing season of 269 days.

The Old Farmer’s Almanac calculates first and last frost dates differently. Their current dates, calculated using 1991-2020 climate normals from the National Oceanic and Atmospheric Administration, are based on a 30 percent probability of freezing temperatures. For La Grange, the Old Farmer’s Almanac predicts a first frost date of Nov. 15 and a last frost date of March 12. That results in a 247-day growing season.

I reached out to the Lower Colorado River Authority for temperature data they collect for La Grange. LCRA Meteorologist Bob Rose replied with a chart he compiled based on two different sets of weather data – one collected by a local weather observer for the National Weather Service with a date range of 1962-2012, and another based on readings at the Fayette Regional Air Center from 2010-the present. According to Rose’s chart, the earliest first freeze recorded was Oct. 20, 1989. The latest first freeze was Jan. 17, 2016. That’s right – it didn’t freeze until after the New Year that winter.

When the frost does finally come, it’ll kill any warm weather crops still growing. The cold weather freezes water inside plant tissue. Ice expands and ruptures the cell walls, leading to cell death. The physical damage kills the plant. Cool weather crops have some resistance to cold weather – up to a point.

Some folks might have a tomato patch still going right now. Occasionally, we get a frost followed by a week or two of warmer weather. For a long-established crop this time of year, like tomatoes, it might be worth it to cover them up for the first frost. You could get a week or two of more production out of them.

Plants can also gain two to three degrees of frost protection with repeated applications of seaweed extract. Liquid seaweed contains natural compounds that act as a sort of antifreeze inside the plant cells. Mix it at a rate of one ounce per gallon. Apply it as a foliar spray, to the leaves, using a pump-up sprayer. It’s best to spray in the morning when there is still dew on the leaves. Repeat the application every week to week-and-a-half.

Seaweed can also help cool weather crops survive extra-cold temperatures. Cabbage, for example, has a cold tolerance somewhere between 20 and 25 degrees F. If the temperature happens to drop to the high teens, those regular seaweed applications could save your crop.