Timing For Vegetable Planting on Cape Cod

When to put seeds and plants in your garden.

In late April and early May we frequently have warm days that call us to get into the vegetable garden and start planting. Some crops can be put in now, but others don’t do well in the cool night temperatures we have on Cape Cod through most of May. Here is a guideline of what plants and seeds you can put in the ground now, and which varieties need to wait.

Plant these seeds directly in the ground now.

You can sow peas, carrots, lettuce, mustard, arugula, beets, and the cole crops (broccoli, kale, cauliflower, Brussels sprouts, cabbage), chard, and bok choi seeds directly into the garden at this time. Keep the soil moist after sowing and when the seedlings are small.

Plant these plants outside in the garden now.

You can put peas, lettuce, mustard, arugula, broccoli, kale, cauliflower, Brussels sprouts, cabbage, and collards plants in the garden now. One way that you know what’s safe to plant outdoors is to see which vegetables we have displayed outside in the garden center. If you see the plants on the benches outdoors, it’s safe to put them in your garden.

Wait until later in May to put these seeds in the garden.

When the soil is too cold, these seeds often rot before they sprout, and if the night temperatures are falling below 50° the young plants will sulk, become stunted, or die. So wait to plant squash (summer and winter), cucumbers, beans, and basil seeds until you see that the nights are reliably going above 50 degrees. You can still plant carrots, beets, lettuce, mustard and arugula seeds later in May as well.

Wait until late May to put these plants in the garden.

We get some six-packs of vegetables such as peppers and tomatoes in early at Hyannis Country Garden because some people like transplant them into larger pots and grow them on indoors. But the nights (and many days!) are too cool to put these outdoors. Although most planting instructions talk about last frost dates, that isn’t as important for plant survival as soil and overnight temperatures. On the Cape we frequently won’t have a frost in May, but vegetables that like warm air and soil won’t thrive in our typically cold spring weather. Wait until late-May to place peppers, tomatoes, basil, squash, and cucumber plants in your garden.

If you purchase six-packs now, transplant the seedlings into six inch pots filled with a good potting soil. If seedlings are kept in the small packs for too long the plants can stop growing, and these often become stunted or take longer to grow once they’re planted. Once they’re in pots, grow them in the sunniest windows you have, or under grow-lights. On days when the temperatures are above 60 you can place these outside, leaving them in full sun for a short period of time at first so that they will get “hardened off” without being sunburned. Bring the pots back indoors around 4 PM before the temperatures drop.

Plants grow quickly once the air and soil warm up.

Don’t worry that waiting until late May or early June will mean that your plants will bear later in the summer. Once the soil and air are warmer vegetables grow quickly, and by early July most plants look very similar no matter when they were placed in the garden. I’ve planted seeds and plants as late as July 1st and by the end of that month my garden looked just as mature as others that were planted much earlier.