Getting Started at PPCG (Part 2): Our Growing Season

Our growing season is short here in New England, which means that if you want to fit in a few successive crops, you have to plan carefully. You can try to extend your growing season by using tunnels and other frost protection. These lettuces that I planted out on April 1, our opening day at PPCG, survived a few bouts of temperatures down in the 20s under a grow tunnel.IMG_20180423_075227139.jpg

Other plants like tomatoes can suffer setbacks, if they survive at all, for the rest of the growing season if they’re exposed to cold temperatures.

Take a look at this handy chart from URI for a guide on when to start specific crops indoors or plant them out in the garden. URI bases their chart on a final spring frost date of May 15, which is a good guide for us as well.

Cool season crops, planted in spring, include onions, leeks, chives, lettuces, spinach, kale, broccoli, and peas. These plants not only thrive in the cool weather, but in many cases won’t grow well in the heat of summer. Broccoli, for example, can bolt to seed before you harvest any florets if the weather warms before the plant has produced. Here’s a blog post with a more complete list and some growing tips.

Warm season crops include tomatoes, peppers, potatoes, cucumbers, corn, eggplant, melons, and squash. You’ll need to start these crops indoors (if you’re growing from seed) at around the time that you’re planting out your cool weather crops.

Check your plant tags and seed packets for growing information, paying careful attention to ‘Days to Maturity.’ Since our growing season is on the shorter side, think about selecting varieties that mature more quickly.   Johnny’s Selected Seeds is a great resource for growing information. Browse through their online information and request a catalogue. Seed Savers is another good resource. UMassAmherst offers a wide range of fact sheets.


Part 3: Garden Design

Part 4: Plant Choices

Part 5: Planting

Part 6: Garden Maintenance

In case you missed it…

Part 1: Organic Gardening and Soil

Playing the Odds with Frost Dates

Here in Massachusetts, I’ve often gone by the rough guideline of waiting until Memorial Day weekend to put out all but my cold-tolerant plants. It’s not a terrible guideline, but the date of Memorial Day does vary from year to year, from as early as May 25 to as late as May 31. It’s also too late for certain cool weather crops and can unnecessarily cut short your garden’s growing season.

Official frost dates are often given as a single number, such as this date given on the Old Farmer’s Almanac website.

farmers alm frost date

Here, the frost date is listed as April 16, which is quite a difference from the Memorial Day guideline.

A few things can be noted about this chart. (1) It uses weather data from South Weymouth.  And (2) it calculates a spring frost date at which there is still a 50% chance of a later spring frost. (Update: Old Farmer’s Almanac now uses 30% odds, which moves the frost date back to April 22.)

How lucky are you feeling at 50-50 odds? (Or the updated 30% risk of frost?)

I’d definitely feel okay about putting out kale at this time, which says nothing about my feelings toward kale. (It’s all right.) Kale can take the cold weather.

For a better sense of frost dates, I like this chart from (Click here to see the full chart; excerpt is below.)

Temp (in Deg F) 10% 50% 90%
Last 16 Mar 25 Mar 10 Feb 24
Last 20 Mar 31 Mar 19 Mar 8
Last 24 Apr 12 Mar 30 Mar 17
Last 28 Apr 27 Apr 15 Apr 4
Last 32 May 15 Apr 30 Apr 16
Last 36 May 25 May 13 May 1

According to this chart, there’s only a 10% risk that temperatures will drop below 32 degrees F after May 15. Now we’re getting closer to the old rule of thumb. But note that there’s still a 10% risk of 36 degree weather after May 25, which could set back members of the nightshade family (e.g., tomatoes, potatoes, eggplant, peppers). Warm weather crops don’t just need frost protection, but also warmer growing conditions to fully thrive. (Side Note: For a number of reasons, your garden may experience colder temperatures than those measured at local weather stations. Using the dates associated with 36 degrees gives you a little bit of insulation from frost.)

Click here if you’d like to see another chart, but don’t get too bogged down in the numbers. We’re looking for guidelines based on data, not one proven date.

Bottom line? “Frost date” is better expressed as a range of dates and probabilities.

Also think about…

  • How cold-tolerant your plants are.
  • How much risk you can handle and how sad you would feel if you froze that one special tomato plant variety you can’t get anywhere else.
  • How willing you are to take some extra measures to protect your plants if a frost bogey threatens crops in late spring/early fall.
  • How long you can hold your young plants in their containers. They’ll take some time to recover if they start to get pot bound before you put them out, which is another kind of risk.