Tomato Patch: Hello, Cool, Breezy World

Starting to "harden off'

My tomato seedlings are growing well, thank you. If you recall from earlier Tomato Patch postings, I planted my tomato seeds in cups on April 25 and the first sprouts appeared four days later. Two weeks later, on May 9, I planted seeds in the cups where the April 25 seeds failed to germinate. From April 25 until today, all the cups have been under shop lights with cool-white fluorescent bulbs in our utility room, where the temperature is about 73°F.

Today—May 20—three and a half weeks after I planted the seeds and three weeks after the first tomato plants began reaching toward cool, white light, I introduced all the plants—even those that grew from the more recent sowing—to real life in the cool, breezy world with its warmer days and cooler nights.

Life was near ideal in our utility room for the young plants. The temperature was uniform. No spring downpours pounded the seedlings to the ground. No thunderstorm whirlwinds bent them at 90° angles over the edges of their cups. No frigid nights gave them the shivers. No crows played pranks and pulled them up to die of root exposure.

Today I moved all the cups from the trays in which they sat for three weeks into three plastic storage bins—minus tops, of course. I watered all the cups well with my squeeze bottle, to which I had added a quarter teaspoon or so of Miracle-Gro, a water-soluble fertilizer, and then arranged the cups in the bins and set them on our front porch, which faces due east.

Seedlings at 3.5 weeks

Welcome, to the real world, young tomato plants. Don’t be alarmed at that force pushing on you slightly from the northwest. That’s our prevailing breeze—gentle compared to the gusts that have blown through during the last week—and it will help you develop sturdy central stems. And, yes, that light is bright. It’s the sun. It peeks over the pines about seven each morning. It will help you grow robustly over the next two weeks. Just after noon, however, the shade of the house will keep you from getting sunburned while you’re getting used to the sunshine.

Putting young plants that have been grown inside under lights outside for increasing hours over a week or two before they’re set out in the garden is called “hardening off.” It’s my way of avoiding rubbing sun block on all those tiny leaves. (Yes, that last sentence is attempted humor.) Every two days I’ll move the bins another six inches or so farther from the house, so they’ll get a little more direct sunshine.

In addition to watering the plants every morning, I’ll keep an eye on forecasts while my plants are hardening off. If a springtime thunderstorm threatens with gusts that could upset the bins, I’ll give them some protection by moving them up against the wall of the house, or into the house if severe weather threatens. If I were still working and weren’t here to move them, I would put a brick or two into each bin to thwart the wind.

If temperatures soar, as they may next week, I’ll check the plants during the early afternoon to make sure they don’t dry out, wilt, and die. If I were still away at work during the day, I’d add water to each bin so the level goes about a quarter-inch up the sides of the cups—just to make sure the plants don’t dry out. Different brands of starting mixes have slightly different formulas, and some dry out faster than others. I’m using two different mixes this year, and I’ve noticed one dries out faster than the other, so I’ll be sure to check the cups morning, noon, and night.

You may wonder why I fertilized the plants. One of the starting mixes I’m using contains a small amount of fertilizer, but the other doesn’t. So I’m just being “sure” that all the young plants have enough. Really, though, the plants probably would do well even if I didn’t give them a shot of nitrogen.

I did some rearranging when I moved the cups into the larger bins. After just three weeks of growing, seedlings of some of the varieties are several inches taller than those of other varieties. Also, the later-planted seeds were much shorter. Since I had coded each cup with a permanent marker when I planted the seeds, I don’t have to worry about identifying the plants when I go to plant them or give them away. Every “J” is a Juliet, and every “ByR” is a Brandywine Red.

In another 10 days to two weeks, when I’m fairly certain the temperatures won’t dip below 50°, I’ll transplant my growing tomato plants into our garden. Yes, some gardeners have already set out their tomato plants, but when the warm days and warm nights come, all tomato plants will grow quickly, and by mid-July it will be hard to distinguish those set out on May 15 from those set out May 30, or even later.