As spring advances and weather warms, the urge to plant the summer garden becomes almost overwhelming. Knowing which crops can stand a bit of cooler weather and cooler soil can help us make good choices about what to plant when we just can’t wait any longer.
Understanding the last frost date
Most of the garden vegetables that we grow in summer are frost tender, which means that they won’t survive freezing weather. This is why most seed packets use the “last frost date” — the expected date of the last freezing temperatures — as a marker for when to plant summer crops.
Where I live, the average date of the last frost in spring is in mid-April. The date is not exact; we estimate the date based on the dates of the last frost in previous years. Annoyingly, we won’t know the exact date of the last frost for this year until we are well past it. Some years, the last frost in my yard is in March, and one year my yard had a frost on April 23rd.
The role of soil temperature
Part of finding the best time to plant vegetables is knowing the best temperature for seeds to sprout and for plants to grow. Texas AgriLife Extension points out that these two temperatures are not necessarily the same. For example, bean seeds may sprout best at a soil temperature of 85 degrees F, but that temperature isn’t best for plant growth and productivity.
The AgriLife article lists reasonable, “compromise” soil temperatures for planting many crops:
- cucumber (64°F)
- cantaloupe (68°F)
- okra (73°F)
- pumpkin (75°F)
- squash (70°F)
- watermelon (72°F)
- beans (72°F)
- beets (45°F)
- tomato (55°F)
- turnip (50°F)
- corn (55°F)
From the list, you can see that beets and turnips (cool-season crops) can do well in cooler soil, corn and tomato plants slightly warmer, and cucumbers and cantaloups a bit warmer still. This information can help in planning your schedule.
Recommended date ranges from University Extension programs
UGA publishes a Vegetable Planting Chart that shows suggested planting dates for garden vegetables. The dates are for middle-Georgia (a line through Macon across the state), which means that the dates need to be adjusted for areas north and south of that line.
For my area, just north of Atlanta, I would add about two weeks to the ranges in the UGA planting chart to get a reasonable planting date range for my garden.
North Carolina State University Extension publishes a planting chart for Western North Carolina. The dates are similar to those that I would use for my garden.
You may notice that the recommended date-ranges in the linked publications for spring planting can be quite large – up to six weeks for some vegetables. The whole range of dates might be good theoretically for a particular crop; however, for organic home gardens, there are some good reasons for choosing to plant either at the early end of the range or the late end.
Reasons to consider dates at the edges of the recommended ranges
For both bush beans and pole beans, I usually plant as early as I think the plants can survive the experience. The early planting — as early as the first week in April, if the weather forecast looks ok — means that I start harvesting beans before the end of May. By the time the Mexican bean beetles show up to demolish the plants, I will have harvested plenty of beans.
I also choose an early planting date for cucumbers, squashes, and melons. Those plants all are attacked by mildew diseases in late summer and an assortment of pest insects in mid to late summer. Early planting allows a larger harvest, before the plants are affected by whichever problem attacks first. For these crops, planting seeds in the first week in April, or transplants a week or two later (when the soil is warmer), can make a big difference in how much food I can harvest before the plants die.
Okra and sweet potatoes are two crops that I plant at the later end of the recommended planting date range. Both of those two crops grow slowly in cool weather, and I have found that keeping ahead of the weeds, which grow faster, is more work when these two crops are planted early. When okra and sweet potatoes are planted later, in early or mid May in my yard, they grow fast enough to shade the ground sooner, and weeds have less chance to take hold.
Tomatoes are another crop that I plant later than almost every other gardener I know. My experience is that later-planted tomatoes, like at the end of April or early May, are less troubled by blossom-end rot than earlier-planted tomatoes. They also are more likely to survive whichever soil-borne wilt disease is in my yard, and infection by the ever-present early blight disease is usually less severe.
Organic gardeners won’t use the chemicals that are available in garden centers to control all the above problems. Instead, we have be a bit wily about getting around the diseases and pests that can reduce the productivity of our organic home gardens. I have found that adjusting my planting dates to the edges of the date ranges, for some crops, is all the “control” I need.
Of course, keeping a good attitude about the vagaries of the natural world also helps.
Amy’s planting schedule
In case you are curious, this is when I plant the standard summer crops, most years, in my garden, zone 7B, just northwest of Atlanta:
- first week in April – plant seeds for bush beans and pole beans if forecast is ok; if a freeze is in the forecast, I start these in a flat or tray, to transplant to the garden after a couple of weeks. I also start squash-family plants – cucumbers, zucchini, winter squashes, melons – in little pots this week, to transplant to the garden when the soil is warmer.
- mid-April – plant corn, if any is planned. For me, that is usually popcorn. Early planting for corn reduces problems with corn ear-worm. Later plantings almost always have more ear-worms. Plant the transplants (beans, squash family plants) when the first true leaf is a couple of inches across.
- late-April – plant pepper plants, and seeds for Swiss chard (if planned).
- early May – plant tomato and eggplant transplants, seeds for okra.
- mid-May – plant sweet potato slips.
- mid-summer – plant Southern peas when one of the earlier crops comes out of the garden (bush beans or cucumbers are usually the first to go). After bush beans have been gone from the garden for a couple of weeks, if there aren’t any pole beans also in the garden to harbor more Mexican bean beetles, plant a new patch of bush beans.
What the above schedule doesn’t show is that I start tomato and pepper plants from seed, indoors, in early March. It also doesn’t include annual herbs, like basil or borage, or flowers, like nasturtium and Zebrina hollyhock, that I plant most years.
Protecting early-planted crops from frost
The summer crops are frost-tender, but I plant some of these crops early enough that the risk of frost is high. A couple of different strategies can be used to protect your crops.
The first strategy is the use of transplants to allow an early start for some crops, like beans and cucumbers. This strategy takes some planning, and it takes space in your house. It also, though, protects plants from cooler weather, since they are indoors. The plants can be planted into the garden when the risk of frost is lower.
The second strategy is the use of row covers to protect tender crops in the garden from a light frost. If a hard freeze happens and the row cover does not fully protect a crop, some replanting might need to be done. The good news here is that most seed packets contain enough seeds to replant a small home garden.
For further reading, my older post about planting seeds in the garden contains reminders about planting depth and plant spacing that might be helpful.
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