Want a Huge Crop of Tomatoes in August? Do This in May.

May is graduation month for most tomato plants. If you're growing in a temperate climate, this is probably when you're moving your seedlings from their coddled life indoors to the rugged reality of the garden. It can be a little daunting.

But don't worry! As long as you follow a few simple rules, you can send your tomatoes out into the world with confidence. Here are six absolute must-do's for tomato care in May if you want a bumper crop come August.

1. Harden Off Seedlings

This one comes first, no matter what. Whether you've started seeds indoors yourself or you've bought seedlings at a nursery, your little plants are likely used to the cushy indoor life. That means no wind, no bright sun, and especially no cold. If you plant them straight in the ground, all that sudden change is going to give them a rude awakening.

Will it kill them? Unless it frosts, probably not. But it will shock them, and they'll spend the next several weeks struggling to recover when they could be putting down roots and shooting out leaves. It's best to avoid it.

Here's how to harden off seedlings:

1. Place seedlings outdoors in a shaded, sheltered spot for 2 hours during the day.
2. Bring them back indoors.
3. Repeat, increasing outdoor time by 1-2 hours each day, gradually exposing them to dappled sunlight and then direct morning sun.
4. Keep up the process for 7-10 days.
5. As long as temperatures are consistently above 50 F (10 C), you can move them outside permanently.

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2. Dig Deep and Transplant

Once your tomato seedlings are hardened off, they're ready to transplant... as long as the soil has warmed to at least 60 F (16 C). Don't try to sneak them in early! Just like with hardening off, cool soil won't kill them, but it will set them back.

When you do transplant tomato plants, dig deep! Tomatoes and other nightshades have a unique ability that lets them develop roots anywhere along their stems. That means that whatever part of the seedling you bury, it will sprout roots.

If your seedlings are a bit leggy, that's totally fine. Just snap of the leaves on the bottom two thirds of the plant, and bury it so the remaining leaves are a few inches above the soil line. If the stem is extra long, you can try trench planting. Dig a long angled trench, and lay the seedling along it so its leaves are poking up above the soil line, then fill in the trench. The plant will benefit from having more roots close to the surface, where the soil is warmer and water is more readily available.

3. Add Support

It happens to the best of us. We plant our tomatoes, and we swear we'll add a cage as soon as we get to it. Then life happens, and weeks go by, and by the time we finally get to it, the plant is huge and it's impossible to fit a tomato cage around it without breaking some branches and dislodging some fruit. Or we stab part of the now-expansive root system and damage the plant. I know I've done it.

Learn from my mistake: add support to your tomato plants the day you put them in the ground!

4. Mulch Mulch Mulch!

Tomatoes are notoriously susceptible to soil-borne diseases like early blight and Septoria leaf spot. These spores live in the soil and ride up to your tomato's leaves in drops of water that splash onto them. If a seedling is surrounded by bare soil, every rain or watering is going to be an opportunity for splashback.

Keep spores from splashing by laying down 2-3 inches (5-7.5 cm) of mulch. I like to use straw mulch for all my vegetables.

5. Fertilize, and Keep It Balanced

Tomatoes benefit from an application of fertilizer when they're first planted, but it's important to keep it balanced. Too much nitrogen now, and they'll have a growth spurt much too fast. Too much phosphorous and they'll focus on making flowers when they should be growing leaves. A balanced fertilizer like this from Amazon will give them a good start.

Though it's tempting, don't put fertilizer in the hole with the seedling – it'll burn any roots it comes into direct contact with. Side dress them, or dilute it in water and drench them with liquid feed.

6. Prune, and Be Ruthless

If you're growing indeterminate tomatoes, you'll probably notice suckers – these are the small shoots that develop between the main stem and a branch. Pinch these suckers off to improve airflow.

If your plant is less than 12 inches (30 cm) tall and it starts to produce flowers, you should pinch them off, too. It feels like a crime, but it forces the plant to invest that energy into its root system, leading to a much higher yield later in the summer.