Cool-Season Versus Warm-Season, and Why It Matters Here
Okay. New module, new set of decisions, so let's start with the one that trips up almost everybody I've ever taught.
Vegetables split into two camps. Cool-season crops want to grow when it's chilly, some of them actually prefer a light frost. Warm-season crops want heat and will sit there sulking, or die outright, if the ground and air aren't warm enough. Here in Utah County, with our short season and our habit of dumping to freezing on a clear night in what should be spring, that split matters more than almost anything else you'll decide.
The two camps
Cool-season: peas, lettuce, spinach, radishes, carrots, broccoli, cabbage, kale, most root vegetables. These want to go in the ground early, while it's still cold enough that you're wearing a jacket to plant them. They'll germinate in cool soil, and a lot of them actually get sweeter after a light frost. Lettuce that's been through a cool snap tastes better than lettuce grown in July heat, which surprises people every single time I say it.
Warm-season: tomatoes, peppers, squash, cucumbers, beans, corn, melons. These need warm soil to even germinate well, and they will not tolerate frost at all. Not "struggle through it." Dead. One cold night and they're black and mushy by morning.
I learned that one the hard way, and I've told this story in another lesson already so I won't repeat the whole thing, but the short version is: don't trust a calendar date for warm-season crops. Trust the soil and the sky.
Why this matters more here than it would somewhere warmer
Our last frost date can slide into late May some years. Our first frost in fall can show up in late September. That gives you a real season, but it's not a long one, and it's bookended by cold on both sides. If you plant warm-season crops too early, a late frost gets them. If you plant cool-season crops too late, the summer heat makes them bolt, bitter, or just quit.
So the trick isn't memorizing a list. It's matching the crop's personality to the actual weather happening in your yard, not the average weather for the county, not the date on the packet.
A practical way to sort your seeds
Here's what I actually do, and what I'd tell a beginner to do their first year.
- Sort your seed packets into two piles before you plant anything. Cool-season pile, warm-season pile. Most packets will tell you which they are if you read the back instead of just the pretty front.
- Plant your cool-season pile as soon as the soil can be worked, which around here is often in March or even earlier some years if we get a mild stretch. Peas in particular can go in shockingly early. I've had peas in the ground while there was still frost in the shade.
- Hold your warm-season pile until the soil has genuinely warmed up, not just until the calendar says it's fine. This is where your cheap max/min thermometer from a couple lessons back earns its keep. If your bed is still dipping into the 30s overnight, your tomato transplant is going to sit there in shock even if it doesn't die outright.
- Plan a second round of cool-season crops for fall. A lot of people plant lettuce and spinach once in spring and call it done. You can often get a second crop going in August for a fall harvest, before the real cold shuts things down. I didn't figure this out until my second year and I felt a little silly about the wasted bed space in year one.
Where I actually learned to trust this
I want to be honest that I didn't work all this out alone in a book. I almost skipped a ward activity one summer, wasn't in the mood, went anyway mostly out of guilt. That's where I met Brittany and Bailey. Brittany still texts me photos of her garden all the time, bugs mostly, asking "is this bad," and going back and forth with her over a season taught me more about explaining this stuff plainly than any gardening book did. She'd ask me why her lettuce turned bitter in July and I'd have to actually think through why, in words that made sense, instead of just knowing it in my hands the way I'd learned it. Teaching someone forces you to understand it better yourself. That's the honest version.
The opinion I'll stand behind here
Ignore the seed packet dates. They're written for somewhere warmer than us. A packet that says "direct sow in April" was written by someone who doesn't know our last frost can sneak into late May. Read the packet for which camp the plant is in, cool or warm, and then plant to your own yard's actual conditions, not the envelope.
Before next time
Go through whatever seeds or transplants you're planning to buy and sort them into your two piles, cool-season and warm-season, before you buy a single thing. It'll change what order you plant in, and it might save you a tray of tomatoes.
- D