Gazette Gardener: Early-season outdoor gardeners get frosty reception

Last week's regionwide frost damaged early-season plants of gardeners trying to get a head start.

As I write this, my kitchen table is covered with plants. Last Thursday, the temperatures in our region dropped to 28 degrees. The “girls” — all annual plants — would die if left outdoors in those temperatures. In fact, most would be damaged if left out in 40 degree temperatures.

Unfortunately, I heard from quite a few readers who already planted tender annuals such as impatiens, tomatoes and basil in the ground. Encouraged by the warm summerlike temperatures in April, they purchased plants early and set them out.

“The leaves are black. Will they come back?” was the question.

No. If the leaves and stem are wilted and black, the plant is gone.

I was going to continue with the second half of the growing plants in containers article this week, but that will be next week’s column. Let’s talk about the weather, how to determine when to plant, and how you get plants off to a good start.

All about timing

In our area, the last frost date is generally around May 20. If you live north or in the hill towns around the Capital Region, it can be a week or two later. Because the frost date is based on averages, a hard frost can hit up to two weeks before or after the average last frost date.

Planting early is a gamble I understand thoroughly. My green thumb twitches in eagerness to get the season growing. I go to the flower and garden shows and get inspired. I see photos at the end of March of cherry blossoms in Washington, D.C., and get zone envy, and it is all I can do to lead with what my head knows about gardening in upstate New York and not with what my heart wishes were true.

If you absolutely must get an early start, you can protect seedlings in a cold frame or cover them with a jar or cloche at night. Using a cloche helps against light frost but it’s not going to do much to protect if the temperatures dipped into the 20s.

Or, you can shuttle the plants indoors at night and out in the day, which is what I do.

When to plant outdoors

I use Memorial Day weekend as the time I put my tender vegetables and annuals into the ground. Even then, I watch the weather. If the temperatures are cool, I’ll wait.

As I plan and plant in the weeks leading up to planting date, I use an arbitrary date of May 25 as the day I want plants to be ready for the garden.

Just like kids are not the same, not every seed is the same. Those fast-to-mature vegetables that like to be cool are usually best planted out of the house and directly into the soil. I’m talking about spinach, lettuce, radishes, beets and peas. My peas were planted in the ground mid-April as soon as the snow melted. Spinach and lettuce were sown in large containers the end of April.

Those plants can tolerate a light frost but I still would throw a sheet over the soil if the forecast was for heavy frost. Or, even better, drag the containers into the garage for the night. My sweet peas, bachelor’s buttons, and larkspur are cool-weather annual flowers that were sown directly in the soil in April.

Warm-weather Plants

There are short-season warm-weather plants and long-season warm-weather plants.

These are plants that need warm weather conditions to survive. They don’t like to be rushed. They want warm soils.

The short-season plants are quick to mature and do best when sown directly into the garden because they don’t like to have their roots disturbed with transplanting. Beans, corn, and sunflowers fall into this category. For those plants, wait to plant until after the last frost date.

The long-season plants include many of those whose taste inspire us to garden in the first place, such as tomatoes. Tomatoes need a long, warm growing season, which is why we either start these as seeds indoors in March or we buy them as transplants. Other plants that fall into this category are peppers, eggplants, petunias, ageratum, and impatiens.

They will not be planted outside until Memorial Day weekend, if the forecast is right. If the weather calls for heavy rains, I will wait. Seedlings can’t be expected to take a pounding rain.

Hardening OFF

This weekend, I will begin to harden off the seedlings of sunflowers, zucchini and zinnias that I have started. To get around the difficultly sunflowers have being transplanted, I have grown them in peat pots and will set the whole pot into the ground in a few weeks.

To acclimate seedlings to outdoor conditions, I will bring them out for longer and longer periods of time over the course of the next couple of weeks. First, I set them out in the shade and gradually over the course of a week move them into ever increasing sunlight until they are in full sun from morning to sunset.

This step is very important. If you don’t harden off seedlings, they will be stressed, suffer sunburn and have a setback. Some will die if treated harshly. After all the nurturing you did, don’t be tempted to transplant directly into the sun.

Happy gardening.

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