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The Garden Plot for September 07, 2007
3:55 PM - 4:00 PM
[Program Website]
Today's Highlight: “Fall Season Extension”
It’s been a tough growing season for many vegetable garden crops. We had the latest frost I’ve ever seen in the Bitterroot (June 25), followed by one of the hottest, driest July months on record. Kalispell also had a frost on June 26. Missoula was spared that frost and didn’t get another freezing night after a last frost on May 6. The result is that warm season crops such as tomatoes, peppers, and eggplants did not do well in many western Montana gardens, except Missoula. Warm season vegetables like squash, tomatoes, peppers, and snap beans can be injured when temperatures drop below 40 ْ F and killed at frosty temperatures below 3ْ 2 F. Tomato and pepper blossoms can be killed at temperatures over 90 F.
Ironically, smoke from the fires shaded plants some, and now many of the recalcitrant, slow to ripen plants are finally setting nice crops of green tomatoes and miniature peppers. The problem is that it could be a bit late. If the universe were fair, we would be granted a late fall frost since many of us were victims of a late spring frost. However, the average first fall frost date is looming. In most of western Montana, we can expect a frost any time after September second.
So it’s time for some season extension. Start slowly pulling back on the water. Irrigate less frequently and for a shorter duration. If you are still feeding your plants with liquid fertilizers, such as fish fertilizer, compost tea, or Miracle Grow, STOP IMMEDIATELY! It’s too late for plants to be putting on leaves, they don’t need any fertilizer. They need to switch over to ripening mode.
Next, pay attention to night-time temperatures. If temperatures below 40 F are predicted, make sure you have frost protection on hand for frost susceptible plants. Row cover can be used to protect warm season crops. Row cover comes in several thicknesses; it can weigh from 0.5 to 1.25 ounces per square yard. The heavier the fabric, the more frost protection. Row cover for frost protection works best if it does not touch the plants, but instead allows air movement through and around plants. In fact, in one experiment, we compared row cover to clear and white plastic tunnels, and found that tomato plants survived temperatures of 27-28ْ F best under row cover. You can use wire or PVC hoops to keep row cover off of plants. If you are ambitious, you can start using row cover now to warm plants as night temperatures cool. Cover plants before dark and uncover them when the sun comes up the next morning.
You can further encourage ripening by heating up garden soil with plastic mulches. Black plastic is the most common, but researchers have experimented with colored (especially red and green) plastic mulches designed to increase the yields of specific warm season crops. Green plastic is called IRT, or infrared transmissible. We compared tomatoes grown without plastic mulch to tomatoes grown in black and green plastic. In our climate, black plastic warmed the soil almost as well as green plastic mulch and tomatoes ripened just as quickly.
So, don’t give up on warm season crops just yet, despite the cold weather that may be coming soon. Season extension can help stretch a few more weeks of ripening out of warm season crops. For more information on season extension methods, contact your local county extension agent.
Helen Atthowe's new short program of gardening tips
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