What to Grow in a Greenhouse in September: Fruit, Veg, Exotic Plants & Flowers
As the days shorten and temperatures begin to dip in September, a greenhouse becomes an invaluable sanctuary for gardeners. It offers a protective environment to extend the growing season, start winter crops, and experiment with more exotic varieties that might otherwise struggle in the cooler months. But what exactly should you be planting or tending to in your greenhouse as summer turns to autumn? In this post, we’ll explore a wide variety of fruits, vegetables, exotic plants and flowers ideally suited for greenhouse cultivation in September. We’ll also look at how mist irrigation systems can help maintain ideal growing conditions as the weather changes.
Why September is a special month for greenhouse growers
September sits on the cusp of two seasons — late summer and early autumn. The weather can still offer warm, sunny days, but nights begin to cool quickly. This transitional period is ideal for both finishing off summer crops and sowing new plants that will flourish over winter or be ready for early spring harvest. A greenhouse helps moderate these temperature shifts and protects delicate plants from early frosts.
Vegetables to grow in your greenhouse this September
1. Winter lettuces and salad leaves
As outdoor temperatures decline, your greenhouse becomes the perfect place to keep a steady supply of fresh salads going. Varieties such as ‘Winter Gem’, ‘Arctic King’, and ‘Valdor’ lettuce are well-suited for cooler conditions. You can also sow hardy oriental greens like pak choi, mizuna, and mustard leaves. With the protection of the greenhouse, these can keep producing well into the colder months.
2. Spinach and chard
Fast-growing and cold-tolerant, spinach and Swiss chard are ideal for sowing in September. They’ll establish strong roots while it’s still mild, ensuring healthy growth through winter. Cut-and-come-again harvesting means you can enjoy fresh greens regularly.
3. Carrots and beetroot
Quick-maturing varieties of carrots and beetroot can still be sown in early September. Growing them in the greenhouse gives them a fighting chance against cold snaps and keeps them away from carrot fly, which can be a nuisance outdoors.
4. Spring cabbage and kale
Sow spring cabbage and hardy kale varieties now to get young plants established before winter. They’ll overwinter in the greenhouse and provide an early spring harvest when there’s little else fresh to pick.
5. Radishes and turnips
These quick-growing root vegetables can be sown successionally through September for a steady supply. They benefit greatly from the slightly warmer, sheltered conditions of the greenhouse.
Fruits that thrive under glass in September
1. Strawberries
Now is the time to plant strawberry runners into pots or grow bags in the greenhouse. Protected from frost and heavy rain, they can establish strong roots and may even produce an early crop in spring.
2. Figs
If you’re already growing figs in your greenhouse, keep an eye on their water needs and prune lightly if required. For new growers, September can be a good time to pot up young fig plants to overwinter under glass.
3. Grapes
While September is more about harvesting than sowing grapes, it’s a great time to tidy up your grape vines, remove diseased leaves, and start planning for pruning once the plants go dormant.
4. Citrus trees
Lemon, lime, and orange trees appreciate being moved into the greenhouse around September to avoid the first chills of autumn. Keep them in large pots so you can shift them outdoors on warm days.
Exotic and tropical plants to enjoy
A greenhouse isn’t just practical — it’s also the perfect place to indulge in growing plants that bring a touch of the exotic to your garden.
1. Chillies and peppers
Although these are technically vegetables, many varieties have stunning ornamental qualities, too. If you’ve started them earlier in the year, September is when fruits ripen and colour up beautifully in the warm, sheltered environment.
2. Orchids
September is a great time to refresh orchid displays. Phalaenopsis and cymbidiums can benefit from the stable humidity levels in a greenhouse, especially if you’re using a mist watering system (more on that shortly).
3. Passionflower (Passiflora)
These stunning climbers thrive in a greenhouse, where you can protect them from harsh autumn weather. September is a good time to tidy up growth and check for pests.
4. Bananas and other tropical foliage plants
Dwarf banana varieties and other architectural tropicals like canna lilies or bird of paradise can move into the greenhouse now, ensuring they’re protected from cold nights.
Flowers to brighten your greenhouse in autumn
1. Winter pansies and violas
Plant these in pots and hanging baskets in the greenhouse now. They’ll establish quickly and provide colour even as the weather outside becomes grey.
2. Cyclamen
These elegant flowers bloom in cooler weather, making them perfect for autumn and winter in the greenhouse.
3. Sweet peas
Sow sweet pea seeds in September in root trainers or deep pots. Kept in the greenhouse, they’ll develop strong root systems ready to be planted out in spring for early blooms.
4. Primulas and polyanthus
Sow these now to bring cheerful colour to your greenhouse and later to the garden in spring.
The role of mist watering and irrigation in September
As the season changes, managing humidity and moisture levels becomes even more important in your greenhouse. A mist watering system — also known as mist irrigation — can help create a balanced environment, especially for seedlings and humidity-loving plants like orchids, ferns and tropical exotics.
Benefits of mist watering in September:
- Helps maintain consistent humidity levels as external air dries out.
- Prevents delicate seedlings and leafy crops from drying out quickly.
- Reduces the need for heavy watering, which can encourage fungal diseases in cooler weather.
- Keeps foliage cleaner and healthier, which is particularly important for ornamentals and edible crops alike.
If you’re installing a mist irrigation system, consider using it during the warmer parts of the day, as damp conditions combined with cold nights can increase the risk of mildew. Timers and sensors can help automate the process and avoid overwatering.
On all our value models the mist irrigation system is a additional item which can be purchased separatley or on the classic models it is included within the frame. (Excludes the westminister frames as it too narrow.)
Tips for greenhouse gardening success this September
1. Keep the greenhouse tidy and ventilated
Remove fading summer crops, dead leaves, and spent compost to reduce pest and disease risks. Open vents on sunny days to keep air moving.
2. Use insulation wisely
Bubble wrap or fleece can help protect tender plants at night as temperatures drop. Consider lining parts of your greenhouse or using horticultural fleece over plants.
3. Feed sparingly
Growth naturally slows in autumn, so reduce feeding to avoid encouraging soft growth that could be damaged by cold.
4. Watch for pests
Greenhouses can shelter pests like aphids and red spider mites over winter. Regularly inspect plants and act quickly if you spot a problem.
5. Plan ahead
Use this quieter month to clean pots, sharpen tools and order seeds for late autumn and winter sowing.
Final thoughts
September marks a new chapter in the greenhouse calendar. While it may seem like the end of the growing season, it’s actually the beginning of many exciting opportunities. From sowing winter salad crops and spring cabbages to nurturing exotic tropical plants and colourful autumn flowers, your greenhouse can stay vibrant and productive long after summer ends.
By using mist watering systems to manage humidity, keeping a close eye on temperature changes, and choosing the right varieties to sow now, you can enjoy fresh produce and floral displays through the coldest months of the year. With thoughtful planning and care, September can set the stage for a stunning and fruitful greenhouse garden well into winter and beyond.