Let’s talk last frost…

In a nutshell, your last frost date is NOT a green light to go outside and plant your entire garden. All it simply is, is an estimated date that predicts the winding down of nighttime temperatures dipping below freezing level. And it is only an estimate. So that means that it can very well be extremely cold or even snow after that date (in fact, it snowed here as late as Mother’s Day last spring).

This shot on the left is the garden last Mother’s Day in May. On the right is the following day with sun shining.

Over the past few weeks, as we begin sowing seeds, we’ve also begun to mark down the weeks until this last frost date. I exclaimed with glee the other day on Instagram that we’re just four weeks out from our last frost date here in Maine (zone 5b—estimated last frost date is May 2nd). I got a whole lot of folks surprised that our last frost date is “so early” and how “where we live we can’t plant that early”. Based on some of these repeated messages, I’m guessing that people are getting confused by exactly what their last frost date represents.

What that date does not represent is the kick-off to go out to your garden and plant everything. What it does represent is the time to focus on your cool weather crops and flowers. Crops like cauliflower, spinach, beets, peas and such are cool weather crops that need the chillier temperatures to properly germinate, grow and thrive. If started later in the season when the weather warms up, some of these crops won’t produce much at all, rather they’ll just bolt in the heat. Many of these crops prefer their temperatures to stay below 70ºF.

Here is a listing of some Cool Weather crops:

asparagus
beets
broccoli
Brussels sprouts
cabbage
carrots
cauliflower
celery
endive
kale
kohlrabi
lettuce
onions
peas
potatoes
radishes
spinach
Swiss chard
turnips

Now, some of these crops are very hardy to the cold (like the brassicas), while others are semi-hardy. The way to gauge when to soil or transplant your cool weather crops is to take the temperature of your soil. On the backs of many seed packets, it lists the ideal soil temperature that your specific variety needs to germinate/grow.

Just because these veggies are spring-friendly, does not mean that they can necessarily survive a hard frost. So, plan to offer protection when needed on super cold nights. At my place, I use everything from fleece row covers to tapestries to milk jugs and bubble wrap to keep my seedling babies warm.

In regard to flowers, there are many varieties that prefer to be directly seeded into the garden “as soon as the soil can be worked”. It’s still frigid around here right now, but the soil has thawed enough to be called “ready to work”, so outside I’ll directly sow flowers like Poppies, Larkspur, Clarkia, Foxglove, Ammi, Love in the Mist, etc… One of the other reasons that it is preferable to direct seed these flowers is because they all detest having their roots disturbed, hence not a fan of transplanting.

So, above is pretty much where all of my garden activity will be for the next several weeks. It is not until Memorial Day, or the very end of May, beginning of June, that I begin to sow and transplant my Warm Weather crops.

My heart breaks each time I see excited people walking out of the local nursery in early May proudly carrying their pots of tomatoes that they immediately go home to put in their garden, only to have Mother Nature stomp their tomatoes dreams into the dirt. Warm weather crops, like tomatoes, need not only warmer air temperatures to grow, but even more importantly, they need warmer soil temperatures and warmer nights to live. And many seeds, like white-colored bean and lettuce seeds, won’t even germinate unless the soil is warm enough (darker-colored seeds are more tolerant of cooler soil/temps).

Here is a listing of some Warm Weather crops:

beans
corn
cucumbers
eggplant
melons
peppers
pumpkins
summer squash
tomatoes
winter squash

And finally, can’t leave without a little bit about herbs. Fortunately, many herbs are fairly cold-tolerant, but I also err on the safe side and don’t transplant the majority of mine out into the garden until mid-May. But the one herb you definitely want to wait until warmer weather arrives for planting is Basil. Basil is a very tender herb and is best transplanted or sowed directly when the soil and air temperatures have warmed up. Traditionally, I transplant my basil outside on the same day I transplant my tomatoes.

One last quick note—do not forget to take the time to properly harden-off your plants before transplanting. I’ll chat more on this soon.

A very happy April everyone! It’s SOW exciting that Spring is here!

Let's talk last frost dates and what that means