That is the time when days become shorter and nights get colder. Although many gardeners only use greenhouses to grow Tomato plants in summer and produce seedlings in spring, it can offer many uses in fall and winter. Don’t be surprised – September is a busy month for a greenhouse grower!
Many plants are still actively growing but the colorful summer display slowly fades away. It is right about time to bring frost-sensitive plants from the garden to the greenhouse and start preparing for winter. The cucumber season finishes in September and you need to remove most Tomato plants.
So, what to grow in a greenhouse in September?
Plant winter salads like lettuces, rocket, pak choi, mizuna, and spinach. Moreover, plant herbs such as chives, parsley and mint in September. Sow broad beans and peas for crop earlier in spring. Pot up spring bulbs and force them to bloom for Christmas time.
Keep reading to find out what plants flowering plants should be on display in September. I am also going to talk about the general tasks that you have to perform this month. Finally, at the end of this blog post you will find a list of all plants that you can plant in September. Let’s dive in!
What flowers are in bloom in September?
- Abutilon
- Aphelandra
- Begonia
- Beloperone
- Bougainvillea
- Capsicum
- Carnation
- Cobaea
- Exacum
- Fuchsia
- Gloriosa
- Gloxinia
- Habranthus
- Impatients
- Ipomoea
- Lapageria
- Passion Flower
- Pelargonium
- Petunia
- Plumbago
- Saintpaulia
- Stephanotis
- Streptocarpus
- Thunbergia
What should you do in the garden and greenhouse in September?
Task #1 – Carefully control temperature
It is very important to control temperature inside the greenhouse this month. If is it still hot where you live, then make sure to open all the ventilators and keep the door open to prevent overheating. However, if you are based in the UK, then you have to close all vents.
You have to aim to keep the temperature in the 50 – 70°F range. To achieve this range, I recommend closing vents early in the evening to capture most in the sun’s heat during the day. Get accurate temperature readings every time with a digital thermometer which you can buy on Amazon.
Task #2 – Reduce damping down
If you are not familiar with the term ‘damping down’, it is basically wetting the floor and benches inside the greenhouse to cool it down. It is a cheap and easy technique to reduce heat inside a greenhouse on a hot day. I always recommend to wet floor and staging at least 3 times a day.
However, in September you have to reduce damping down and most of the time stop doing it completely. Only wet the floor and shelves on warm days once and make sure to complete the task by midday. Along with damping down you have to stop ventilating your greenhouse.
Task #3 – Keep the watering to a minimum
As temperatures start to fall, soil stays moist for longer and plants are not growing as actively. That is why you need to reduce the frequency of watering. Skipping this step will lead to muddy soil that can provoke fungal diseases.
Task #4 – Remove shading
It is a must to remove any form of shading from your greenhouse structure to maximize all available light. That is more important than heat control. Didn’t know that a shade cloth can help to heat a greenhouse? Then have a look at an ultimate guide on a shade cloth to learn everything about its benefits.
However, if you are growing some shade-loving plants like ferns, then you have to keep some form of shading. Click on this post to learn about my favorite ways to shade a greenhouse. Use any of the 4 ways of shading to shade an area where shade-lovers are growing.
Task #5 – Clean your greenhouse
September is a perfect month to deep clean your entire greenhouse structure! Take your time and harvest your Cucumbers and Tomatoes at the beginning of the month. Then you will notice that you have a gap in the middle before you need to start bringing frost-sensitive plants from outside.
Follow my greenhouse cleaning routine to use your time efficiently and to make sure that your structure stays clean for longer. I also want to point out that there are different cleaning techniques based on the materials your greenhouse is made of.
If you have a greenhouse made of wood, it needs more maintenance than an aluminum frame. Learn how to keep your wooden frame in a good condition for longer here. For an aluminum greenhouse owners I put together an article on how to clean aluminum frame.
September greenhouse planting guide
Although fall is a busy time for harvesting Cucumbers and Tomatoes, you can still plant spring bulbs and sow hardy annuals for spring bedding in the garden. I put together an ultimate list of plants that you can grow in a greenhouse in September:
Bulbs: Tulips, daffodils and hyacinths. Pot them up and keep in a dark spot outside for six weeks. You can cover them with a layer or peat or ashes. Then bring into the greenhouse to encourage blooming in time for Christmas!
Annuals: sow seeds of hardy annuals like Sweet Pea and Pansy for spring begging in the garden.
Vegetables: Sow Carrots, Lettuce, Radish, Endive and Mustard and Cress.
Save this PIN to your gardening board on Pinterest so you can always come back to this post later!
Also, have a look at the planting guide for October where I am talking about cool-season crops and winter-hardy vegetables that benefit from cold winter temperatures.
Let me know what are your go-to plants to grow in September in the comments section down below. What are the gardening tasks that you carry out this month?
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Happy Growing 🙂
