Get Your Heat-Loving Garden Vegetables Off To A Great Start (Timing is Everything)

Create your own common wisdom

Gardening wisdom comes in many forms, but it abounds in rush of getting the heat-loving vegetables into the ground. The best, as far as I can tell after 30 years of growing food, is to take all of it “with a grain of salt”. One person’s “fail safe method” is another person’s disaster. The trick always comes down to finding what works for you, in your garden, based on the type of late spring you are experiencing.

So how do you distill the volumes of when-to-plant-what information now at your finger tips on the web?

Most of finding what works for you and your garden boils down to a few key problem-solving steps that you can apply for a great start to the heat-loving gardening season.

Follow the trends, but not blindly

Most gardening advice has been distilled over the years by averaging temperatures to determine when the last frost free date for an area will be. This is how the USDA plant hardiness zone map gets built, and a similar one for Canada, and you can usually look up your zone by your postal code.

But these long term averages, even though based on extremes, are only a starting point when determining if it’s “safe” to plant your tender little starts, or direct sow heat loving crops. And unfortunately for most of us, any one year may not be average in what you are seeing when you step outside.

The key thing to remember is that heat-loving plants still require the minimum 10C (50F) no matter what the daytime highs reach. It’s the night temperatures that are the killer.

The rule of thumb to live by is 10C (50F) at night, every night, for the heat-lovers.

All the heat loving vegetables - tomatoes, peppers, eggplants (aubergine), cucumbers, corn, many of the squashes, etc - all need a minimum of 10C (50F) to thrive and grow. Some might survive a short dip below that, but that drop below minimum usually comes with consequences like shocking, stunting growth, delayed or dropped flowers, and the potential for disease due to a weakened plant.

Tomato Seedling (Photo by Olga on Unsplash)

Conventional wisdom where I live is that it is “SAFE” to plant your heat lovers after the May long weekend (which is May 25th)). Others say, after the May full moon (which May 12th this year).

I did find a pretty cool “average last frost date map for BC” in my search which does display a May 10-20 zone for my area - so that’s interesting. But it is no guarantee in any one year - and we’ve had more than a few where the temperatures were still menacing in early June. If you are curious for your area, just google “frost free dates” and insert your specific location, state, province or country and see what comes up.

But again - this is a starting point - not a guarantee. To be successful you need to keep in mind these steps:

Know which plants are heat lovers

You can grow all the cold-loving plants much early - some even before the frosts are done with. But the heat-lovers need that 10C (50F) nighttime minimum.

You can read all about cool season plants here.

Pepper seedlings (Photo by Amber on Unsplash)

Let nature be your guide

Bioindicators is a term used to describe plant (or animal) cycles that help you predict what is happening on a seasonal basis, in real time. In the spring, plants bloom at a certain time of year and in a certain order, not because the calendar says it’s May, but because they have accumulated enough heat and light which enables them to start growing fast and bloom.

You don’t need to live on a large property to take advantage of bioindicators. City parks, street trees, and natural spaces usually provide enough flowering trees, shrubs and plants to give you the data you need. All you have to do is become a keen observer of nature, and tune into seasonal trends. It’s fun, and a great way to enjoy nature.

You can read more about bioindicators and how to use them here.

Eggplant seedling (Photo by Francesco Gallarotti on Unsplash)

Get an indoor/outdoor thermometer

You don’t need a fancy weather station to figure out the safe planting zone in your garden, yard or on your patio. A simple indoor/outdoor thermometer sold at a hardware store will do the trick. Just put the outdoor sensor in a sheltered place outside (not in direct sun) and then you can easily read the values on the little monitor in your house.

Simply get in the habit of checking it first thing in the morning. What does it say?

Compare that to your local weather reading off the internet. Usually I am either on track with the local weather station reading for Lillooet (my nearest station), or within 2 degrees. But 2 degrees colder at this time of year is a BIG DEAL.

So start watching the weather as you are getting ready for the big garden plant out of heat loving veggies. And don’t get fooled by stunningly hot days because if the nights are still dropping, it is still too cold.

Use protection

In some years, mother nature toys with us gardeners brutally. Just when you think the trend for summer weather has arrived - surprise! Here’s a zinger of a cold night.

That’s why season-extending tricks are so popular. If you are just not sure, then floating row covers, draping plastic over hoops, thermal retainers like hot caps and special water-filled insulators like wall-of-water, can all get you passed that dreaded time where it is still dipping to +8C (46.4F) overnight despite lots of heat during the day.

It can be so disheartening, especially if you’ve gone through the effort of starting your heat lovers from seed indoors, or dropped a ton of money at the market for big starters, to plant them out and see them zapped by a one-off cold night.

Avoid transplant shock

And so transplanting heat-lovers into the garden - whether your own or the kind you buy - also requires you to take some effort to avoid shocking them. Even if the night temperatures are in the right zone, day time temperatures in full sun can be enough to burn the leaves brown on seedlings not yet used to life in the great outdoors.

It is totally worth the effort to baby your starts at first. Move your plants outside but into the shade for a day or two. Or place them somewhere such that they get only a few hours of morning light at first. Then after a couple of days, put them into the garden in full sun. And of course if it is still dropping at night, then they need to be covered or brought back in. . . . a pain, but worth it if you want extra early food this year.

As they say, timing is everything

There is so much you can get away with when gardening, but ignoring minimum temperatures for heat-lovers isn’t one of them.

I am right on this edge of it being almost warm enough, but not quite. And as I debate my strategies for timing, I know I am very blessed with a “normal” kind of year for once in a very long time. This spring so far is like the ones I remember when I first moved here years ago.

My strategy may well be to plant out a couple “sacrificial” starts to see how they do. If they do great then I will enjoy some extra early cherry tomatoes! But if they fail, then I haven’t risked my entire crop all at once. Seems like the plan for now.

Do you have any other tips for getting the heat-lovers timing right?

Happy growing!

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The Naturalized Human is about growing food, creating wellness, and bringing together the science and human experience of the mind-body-food connection. Stay tuned for a re-organization coming to the newsletter website that will make it easier to find topical information without scrolling through all the posts. I’ve nearly got the Seed Saving section revised.