Grow-How: Sprouting In The Summer Heat

by Isabel Vinton

In the Northeast, we spend most of the spring dodging frosts and keeping germinating seeds cozy indoors. Now that summer is here, the problem becomes just the opposite: how do you encourage seeds to sprout and grow when the sun is so strong? While plants love (and need) warmth and sunlight, they can suffer if the heat is too extreme. Luckily, there are several easy routines and remedies you can use to keep growing all summer long.

1. Shade: Yep, that's right--if your plants are getting too much sun, give them less of it. There are several techniques that can help with this. If possible, choose the shady sections of your garden for planting during this time of year. You can also intercrop shorter plants (like herbs and lettuce) with taller plants (like sunflowers) so they can naturally benefit from their surroundings. Another option is to cover newly-sown seeds and transplanted seedlings with row cover, or create a barrier of shade cloth. Not only do these options reduce the intensity of the sun, they can also block wind which can make water evaporate from your soil faster. The key with these options, however, is to make sure not to lock in too much moisture--that can lead to damping off.

2. Water: Seeds need a steady supply of moisture in order to germinate, and in hot weather, you may need to water more frequently. Check your seeds twice a day, and if the soil is dry, water. The best times of day are the morning and evening; if you water in the heat of the afternoon, most of it will go straight back into the air instead of to the roots of your plants. For transplants, it can be useful to dig your hole a little deeper to create a slight bowl shape that will catch and retain moisture for seedlings.

3. Depth: In summer, not only can you plant seedlings deeper--you can do the same with seeds. Since the surface of the soil heats up and dries out quicker, a few extra layers of soil can keep them moist and safe. Consult the planting instructions on the pack and don't go too much deeper than that--just enough to give the seeds an edge.

4. Mulch: If your soil isn't retaining moisture well, consider sprinkling a thin layer of straw mulch over your seeds or around your seedlings. The key is not to make the layer too deep--otherwise it could encourage rot and damping off, making it harder for seeds to grow, and create a habitat for pests.

5. Soil: During this challenging season, plants can really benefit from having the proper soil. Help your soil do its important work by adding compost or fertilizer when needed, and using techniques like cover cropping and crop rotation.

6. Timing: We've already discussed how morning and evening are the best times to water. Unsurprisingly, those are the best times for you, too. If you need to be out working in the garden, you'll be a lot more at ease if you can beat the heat. Transplant your seedlings in the evening too; that way they'll have the night to rest and adjust before the onslaught of the next day.

7. Thin: Over-sowing is great insurance if germination rates end up low, but as seedlings grow and compete for moisture, water stress becomes a big issue. Make sure to thin your seedlings to the recommended spacing and remove all but one plant from the cells of starter trays before transplanting.

8. Selection: As with any season, the choice of what to plant is key. Vining plants like beans and cucumbers can be a good option if trellised since they shade the soil, block weeds, and hold moisture once they’re mature enough. Heat-tolerant crops, like brassicas, corn, and summer squash will also do well this time of year. However, using the tips above, you'll find you can also grow many seeds you thought were just for spring like lettuce and spinach. For a full list of what to plant in July, click here.

Now that you know how to sow in summer, you can even starting looking towards the fall. Now is the perfect time to take a look at our fall planting schedule and be fully prepared for the rest of the growing season. Hot, humid days make it harder to get outside, but the rewards of a perpetually-giving garden are just too good!