Advice on Planting Warm-season Vegetable Crops

The peas are up in Marjorie’s Garden, as are the shallots, and the October-planted garlic is knee high.  We planted asparagus crowns on May 19.  Onion transplants planted three weeks ago wait for warmer weather while dandelions bloom on the fringes of the garden, the golden flowers swarming with honeybees, mason bees, and bumblebees.  I am surprised to see so many honeybees as scarce as they’ve been in recent years and as finicky as they can be about cold and rain.

Soil temperatures in Marjorie’s Garden have yet to reach 60 degrees.

With Memorial Day approaching I find myself having to go against my own advice.  The soil’s temperature has not reached 60 ºF, the recommended minimum for transplanting seedlings of warm-season crops such as cucumbers and tomatoes, while 70 ºF, the minimum for transplanting squash seedlings, is still days away, yet transplants of all these crops are growing out of their pots.  They need to be in the ground!

I got into this pickle when I decided to combine my transplant needs with those of a schoolyard garden that must be completely planted by early June.  The school greenhouse environment was very effective in pushing growth.

The seedlings are ready for planting even if the weather is not.

So now what?  Do I go ahead and plant, hoping that the soil will rapidly warm?  Should I invest more time and money in shifting the squash seedlings to larger pots?  I can hold the smaller tomato, tomatillo, and basil plants for one more week, but I’ve decided to plant the squash and cucumbers on Memorial Day and hope for rapid warming.

At the same time, we will transplant seedlings of cosmos, calendulas, sweet peas, and nasturtiums.  Some of these annuals will go in pots, others in garden beds, all for the enjoyment of gardeners and pollinators.

On the cusp of the gardening season, here are a few suggestions for northern New England gardeners from someone who does not always heed his own advice:

Harden off transplants before setting them out.  Whether home-grown or purchased from a greenhouse grower, transplants will need gradual acclimation to the full sunlight and wind that they will experience in the garden.  We use our sunny porch railings and steps for this task, extending the length of exposure to full sun and gentle wind from one hour on the first day to all day by the end of the week, bringing them into a protected spot if unseasonably cold temperatures arrive.

A tomato seedling planted with a newspaper cutworm collar.

Use cutworm collars around all transplants.  I like to use plastic yogurt cups with the bottoms cut out.  They slip easily over most transplants and should be pushed an inch into the ground around the seedling.  Or you can wrap the base of each seedling with a collar made from strips of newspaper several pages thick, again making sure the collar extends at least an inch below ground.

Crows and jays will make a game of pulling corn seedlings out of the ground and devouring the sprouting seeds.  They watch from nearby trees as you sow, then check daily for the first shoots to emerge.  You can derail their efforts with a lightweight row cover (the kind used to keep cabbage butterflies off the broccoli), keeping the seedlings covered until they are several inches tall.

Speaking of broccoli, buy yours from the farmer’s market and use your garden space for other crops.  It’s nearly impossible to keep determined cabbage butterflies from laying their eggs on broccoli plants.  Row covers do work if they remain secured against the ground, but there is always that one rip in the fabric that goes unnoticed.

Transplant seedlings into moist soil.  Water dry soil the day before planting and water the transplants a few hours prior to setting them out.

Let the soil warm after planting before mulching around transplants.  After a few days of sunny weather, apply a mulch of shredded leaves or straw between the plants to help hold water in the soil and reduce weed growth.

Vegetable scraps tossed on the compost pile may keep the slugs out of the garden beds.

If you are plagued with slugs, try surrounding planting areas with wood ashes, pine straw, or other rough-textured material.  At the same time, place shallow containers (small aluminum pie plates work well) of cheap beer or yeast solution in strategic locations.  Armed with a flashlight, make midnight forays into the garden in search of slugs that have breached your defenses and dispose of those you find – I throw them into the woods with hopes that there are hungry toads lurking about.  As a last resort, put kitchen vegetable scraps on top of the compost pile and hope that the slugs convene there instead of in the garden beds.

Beans seeds rot in cold soil.  Wait until the soil temperature has reached 60 ºF before sowing pole beans or bush beans.

Late May or early June is not too late to sow seeds of carrots and beets.  These root crops do best when soil temperatures have settled above 50 ºF.

Wait until late August to sow spinach.  You’re lucky to get more than one or two picking of spinach leaves from a spring-sown crop before the plants bolt (flower).  A sowing in late August will keep producing leaves until frost.

Keep weeding!  Let no weed go to seed.

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About Reeser Manley

I was born in Laramie Wyoming but moved to the southeast at an early age. I was educated through my B.S. in Biology in the Columbus, Georgia area, then crossed the Chattahoochee River to earn my M.S. in Botany at Auburn University. For the next ten years, I worked as Horticultural Manager for the George W. Park Seed Co. in Greenwood, S.C. At 40 years of age, I decided to return to graduate school and in 1994, I earned a Ph.D. in Horticultural Science from Washington State University, Pullman, Washington. Fast forward through 10 years at university (7 at UMaine, Orono) and you find me teaching high school science in Eastport, Maine, the edge of the world, and writing a weekly garden column for the Bangor Daily News. My new book, The New England Gardener's Year, a Month-by-Month Guide for Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, Connecticut, and Upstate New York”, will be published later this year by Cadent Publishing. You can learn more about the book by visiting its Facebook page: