(11/4) Years ago I read an article about gardening weather problems in different areas of the US. The Baltimore area was rated by that author as having one of the most frustrating problems of all – short springs and autumns with unpredictable weather. Here in Central Pennsylvania, we share this particular climatic phenomenon with much of the Middle Atlantic: maybe cool and sometimes wet in April and May, followed by hot, dry June, unless it’s not. And we often enjoy pleasant fall temperatures with nail-biting uncertainty until the first frost and first freeze. I’m not griping, really. I’m scratching my head, wondering how to garden more productively.

Spring can be short and possibly followed by a fast-warming June, making it difficult to get the most out of spring vegetables. So, I plant some spring favorites in the fall, too. The hardy vegetables we plant in late March and early April are the ones best suited for fall. Some of them, like cabbage, Brussel sprouts and carrots, reach maturity over two years. If we don’t harvest and eat them when young and tender, they overwinter, flowering and setting seed the next spring. Fast maturing radishes, spinach and many lettuces are also cool-loving vegetables that give the gardener a quick treat before winter.

After the first heavy frost, look over your garden; you’ll find some vegetables survive better than others. The summer plants – tomatoes, squashes, beans, etc. – have limp, watery leaves. The cell membranes of these cold intolerant plants can’t maintain their structure at low temperatures, making them leaky and no longer able to maintain their cell contents. If the water in the cells freezes, the ice crystals also pierce those cell membranes.

On the other hand, the cold tolerant plants are still alive. Their cell membranes are made of tougher stuff; they maintain their integrity when exposed to cold. They also have a chemical trick. Earlier in the year, photosynthesis produces sugars which the plant turns into starch for efficient storage. As the temperatures cool through the fall, the starches become sugars again.

You know that water with dissolved chemicals freezes at a lower temperature than pure water, and the more chemical you add, the lower you can push the freezing temperature. That’s why salt keeps ice from forming when applied to wet roads and sidewalks in winter. Likewise, when starch reverts back to sugars, the freezing point of the cell sap is lower, protecting the plant and making these winter vegetables taste sweeter, too.

We can protect plants, grabbing a few more days or weeks out of the season, and maybe extending the season of summer favorites. One trick is planting location. I can hide lettuce between tomato plants to keep it shaded in the summer, but this also protects it from a cool autumn wind. When pumpkins and winter squash are planted within a block of corn, the stand of now-dried corn forms a microclimate trapping warmer air close to the ground and protecting the vines from frost. Planting on higher ground or on the south and west sides of walls and buildings is also protective.

Another means of protection for all your fall plants is covering them. If you are growing brassicas, you likely covered them with row cover already to deter the white cabbage butterflies. This covering is not expensive and can protect sensitive plants to a temperature of 28oF. Row covers can protect cold tolerant plants down to 24o or lower. Cloches and cold frames can be used to protect small plants, too. Cloches can be made by cutting the bottoms from gallon milk jugs. Be sure to remove them in the morning!

Building ‘low tunnels’, structures akin to knee-high hoop houses, extends the season into colder temperatures. They are formed by covering the supports you use for row covers with clear, greenhouse plastic to create a very warm environment. In fact, you need to be careful to open the ends of the tunnels on sunny days to keep the interior from getting too hot. Excessive heat can stimulate disease and/or cook the veggies. For both the row covers and the low tunnels, be sure to use supports that lift these covers high enough so they don’t touch the plant. Otherwise, the plant will freeze where it contacts the cover.

These are methods that worked for me, but there are consequences. Don’t forget to water if there is little precipitation. Winter annual weeds, like dead nettle and chickweed, thrive in the warm environment you created. Some insects linger much longer undercover, too. And the worst pests in my book, voles, look at the low tunnels as warm, predator-free larders, giving them great winter homes.

There are on-line resources that list many of the winter vegetables and their cold tolerances in unprotected settings. A list of plants and plant varieties for fall and winter gardening in Pennsylvania can be found at https://extension.psu.edu/season-extenders-and-growing-fall-vegetables. You might also have neighbors who can tell you what they found to be the best varieties for your location as well.

For fall vegetables, then, we want plants that can take the cold, ones adapted in their physiology and chemistry to dealing with near freezing and below freezing temperatures. If we work within the cold tolerances of the vegetables and add a few tricks, we can deal with Jack Frost when he comes around.

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