Need some inspiration on what to grow in your greenhouse and garden this June? Our handy guide gives you all the best plants and vegetables to grow at this time of year.
The Gardening Year
19 / 05 / 2025
What to grow in your greenhouse and garden in June
The summer is here, and June can be a delightful time in your garden. The flowers and crops you have been tending since the early spring are coming into their own, and your garden is heading towards abundance.
By now, you have probably hardened off and planted out much of what filled your greenhouse over the past few months – but that doesn’t mean your greenhouse shelves need to stand empty. June is a great season for sowing and transplanting heat-loving crops, getting your late sowing salads in the soil and starting your autumn and winter veggies.
Heat loving crops to sow in your greenhouse in June
Tomatoes
It’s not too late to sow tomatoes in your greenhouse. You may well have already tended your tomato seedlings, hardened them off and planted them out – but getting another round of seeds in the soil now will extend the succulent tomato season and fill your plates into the autumn.
Remember that you’re planting in warmer conditions, so your water schedule needs to be regular, and you’ll need to prevent overheating and scorching through judicial use of ventilation and shade.
Some gardeners keep tomatoes in greenhouses all summer rather than planting out, in which case, think about your support structures for the vines as they get larger. You will also need to be a bit more actively involved in pollination when your tomato plants bloom, because insects won’t be doing their important pollen-carrying work. You can gently shake the plants when they’re flowering, to move pollen around, or use a soft brush to transfer pollen from one flower to another, to ensure a bumper crop.
Remember that tomatoes need feeding, so keep and eye on them and be ready to add nutrients if you spot yellowing leaves.
Sweet Peppers & Chillis
Another heat-loving crop to plant in your greenhouse in June is peppers – of both the sweet and spicy varieties. Seeds you plant now will be ready to harvest in the Autumn.
In the heat of a summer greenhouse, certain varieties will thrive, so make sure you choose pepper and chilli seeds that really love the heat.
Keep your seedlings well-watered, and look out for pests as you tend them through the peak of summer.
Cucumbers
Cucumbers will be plentiful throughout the summer if you sow them in your greenhouse in June. Seeds tend to germinate in 5-10 days, and the seedlings will thrive in a propagator or under cover to retain moisture. As the seedlings mature, transplant them into pots in your greenhouse or outside in your veg patch.
Basil and Other Herbs
Since we’re filling our plates with delicious salad treats well into the autumn, June is a great time to sow basil, coriander, parsley and other tender herbs, adding wonderful flavours to your recipes. Some herbs, such as basil, offer benefits beyond their lovely taste: they make great companion crops for tomatoes, because they discourage aphids.
Your herbs will love the warm and stable conditions of your greenhouse, but will rapidly let you know if they’re not getting enough water. With some thought and planning around light and shade, airflow and moisture, your herbs will thrive in your greenhouse this summer.
Melons
If you’re looking for something sweeter, why not try growing melons this summer. Cantaloup and Honeydew melons will thrive in the summer months in your greenhouse. These trailing plants love the heat and humidity of your greenhouse, and will do well in a container or growbag. With the right care, they will produce up to six delicious fruit per plant.
Autumn and Winter vegetables to sow in your greenhouse in June
As well as your late-sown summer crops, June is a good time in your greenhouse to think ahead to how you want to fill your plate towards the end of the year.
Here are some ideas for vegetables to sow in June for autumn and winter:
Leeks
Sow late-cropping varieties of leeks now to harvest in winter and early spring. Leeks can be harvested at any size, and as long as they don’t bolt, can be left in the ground during cold months – ideal for adding flavours to winter stews and soups.
Brussels Sprouts
We know it’s WAY too early to mention jingling bells and turkey dinners, but it’s ideal timing to think ahead to the Brussels sprouts you want to serve up when Yuletide does arrive.
Kale
While kale is generally a cool-season crop, with the right care and ventilation, you can sow kale in June to grace your plate (or soup bowl) in the winter. You’ll need to prevent bolting during the heat of summer, so keep your kale shaded and in a well-ventilated spot.
Cabbage
June is the perfect time to sow your winter cabbages. Make sure to pick a late-sowing variety when you choose your seeds.
Broccoli
You can also sow broccoli seeds in your greenhouse this month, for delicious harvest at the end of the year. Again, check the variety you’re choosing, and make sure to keep seedlings well-watered and pest free.
Tips for June Greenhouse Care
We spend so much of the year keeping our greenhouses warm enough and not letting the precious heat out, but now the season of managing high temperatures is upon us. This June, here are some things to think about to help keep your greenhouse plants thriving:
Ventilation: As the days get hotter and the weather improves, make sure the airflow to your greenhouse is adequate. On hot days, open your vents and doors to keep air circulating and stop temperatures from getting too high for your plants. It’s also worth considering a louvrematic automatic louvre, as this will open and close in line with the weather, to ensure your crops get the ventilation they need 24/7.
Shade: As the summer gets into full swing, strategic shade will be important to help prevent scorching in your greenhouse. Take a look at different shading methods, including shading paint, mesh and investing in greenhouse blinds.
Watering: Just like the rest of your garden, timing your watering to avoid evaporation is the key to keeping your greenhouse plants thriving. Water early morning before the heat of the day rises, or in the evening once the sun has passed, so that your plants are nourished by the water before it evaporates in the heat.
Pollination: if you’re growing plants that will stay in your greenhouse until harvest, make sure you have an eye on pollination, because those helpful bees and bugs may not find their way into your greenhouse. Read up on how to pollinate the different types of fruit and vegetables you’re growing, to make sure your harvest is as bountiful as possible this year.
Pest Watch: Summer heat means summer pests, and greenhouses can make all-too-cosy homes for critters. Keep an eye out for the telltale signs of aphids, whitefly and spider mites, and be ready to take action with organic pest control as soon as you notice them settling in, rather than waiting for them to take over.
Enjoy the summer months ahead if your garden and greenhouse!
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