STOP Salad Crops Failing in Summer (Beat the Heat!)

13 July 2025, written by Benedict Vanheems

Bolting in Salad Crops

Summer might be a time of plenty for many vegetables in the garden, but with heat, water stress, and long days all working against them, fleshy-leaved salads can struggle. One of the main issues in summer is bolting (flowering and going to seed prematurely), which renders the leaves bitter-tasting.

Salads bolt a lot sooner in hot summer weather, which means they do need to be replaced a few times over the summer months. Once the first lot have begun to bolt, pull them up and throw them on the compost heap. Then it’s time to get the next generation going.

Plant Summer Salad Crops

The great joy of sowing salads is their lightning speed of growth. No-one needs to hang around for long with these guys! But if you don’t fancy sowing seeds, you can always plant ready-to-go plug plants.

Clear the bed to remove any weeds, then top up soil fertility with a little extra organic matter such as compost, spread to around an inch (2 cm) thick. I also like to add a handful of blood, fish and bone, which is a general-purpose organic fertiliser that helps give young plants a strong start.

Thoroughly soak the pots or plugs before planting to ensure they don’t struggle if the soil is drier than is ideal while they settle into their new home. Don’t forget to water them in once planted too.

Keep on top of watering as they grow and, if it gets very hot, offer some shade too. If you don’t have much natural shade in your garden, improvise with shade cloth. Shade, together with regular watering, will keep salads much happier, and you can expect to begin picking your first leaves before long.

Tips for Summer Salad Sowing Success

It's easy to grow salads from seed too, sown straight into the soil where they’ll grow. But in hot weather, germination can prove tricky because these are cool-season crops that germinate best in cooler temperatures.

Start by marking out a drill (row) for the seeds, a little under a half inch (1cm) deep. Water into the drill, let it drain through, then water again. This should create a nicely moist and cool environment for our seeds.

Take a pinch of seeds and sprinkle them along the drill, aiming to avoid clumps of seeds in one spot. Then cover the seeds back over with soil and water again to settle them in.

Next, lay a plank of wood over the sown row. This will shade the row to keep it consistently moist and a lot cooler, which will make for a far less hostile environment for your seeds to sprout. Peek beneath the plank every day and, as soon as the seedlings have started popping up, remove it so they can get enough light. This simple trick can also be used for other cool-season, summer-sown crops such as carrots or salad onions, and should dramatically improve your success.

Sowing Salad Crops in Containers

Another option to dodge the heat is to sow or plant into containers. It’s easy to move containers into the shade or even indoors where it’s cooler to get them started.

Salads such as rocket and Oriental leaves are absolutely perfect for growing this way, and because they’re shallow rooted, they can be grown in just about any container. Sowing in the latter half of summer is ideal for these crops because they’re much less likely to bolt at this time of year. They’re both members of the brassica or cabbage family, and like many brassicas, have a habit of trying to flower in response to increasing daylength. But with midsummer behind us, they’re far more likely to give lots of luscious leaves, not flowers – which is exactly what we want.

To fill your container you need nothing fancier than a standard, multi-purpose, peat-free potting mix. Break up any clods between your fingers, and pat the surface level. If growing in terracotta pots, be aware that you’ll need to water them more regularly than plastic pots because the material is slightly porous and moisture will wick away from the potting mix. Or, to counteract this wicking effect, line the inside of the pot with plastic. This should keep your plants so much happier in hot, dry weather. Just be sure to make a hole in the bottom of the plastic that corresponds with the drainage hole so excess water can still drain through.

Sow your seeds quite thinly across the surface, cover them with a smidgen more potting mix, and water them in. Bring the container indoors or into a shady area to sprout, then once the seedlings have germinated, they can go outside into a mostly shaded spot to continue growing.

If your garden regularly sees scorching temperatures, try to choose somewhere to grow that’s not only shaded but also gets plenty of breezy airflow, away from areas that hold heat like concrete and sunny walls.

Sowing Salad Crops in Seed Trays

If you’d prefer to start off your seeds in seed trays and then plant them into the garden, you can do that too. Fill trays right to the top with potting mix, then lightly press the it down so it’s just below the level of the top of the tray.

Sowing is the same as for containers – lightly sprinkle a pinch of seeds over the surface, cover, and water. Don’t forget to label the tray so you remember what’s growing there, especially if you’ve never grown it before.

The first watering can be from the top, with a watering can or spray mister, but once the seedlings are up you can switch to watering from the bottom. Fill larger containers with water then sit your trays of seedlings in the water until they’ve absorbed what they need.

This next step isn’t essential, but you can also cover the seedlings with clear glass or plastic to raise the humidity and help to speed up germination. Do keep the tray out of direct sunlight though, as we don’t want this to act like a greenhouse and start raising temperatures too much! The moment you see the first seedlings, remove the cover, because its job is done.

Keep your seed trays somewhere nice and bright but out of direct sunshine, so the trays won’t overheat, then once they’re big enough you can transplant them into their own individual plugs and pots to grow on further, or plant them out into the garden.