What to grow in a greenhouse?

Once you’ve built your greenhouse, deciding what you want to grow can be a bit of a daunting task. The entire vegetable kingdom lies before you, but how do you decide what to pot and what to continue picking up at Tesco? Not to mention, when do you grow it? Tomatoes planted in December may be possible but it’s far from the best way to start your growing journey.

At Dunster House, we’re strong believers in year-round use for your garden buildings so we’ve got you a guide for What to grow in your greenhouse that covers the whole year! We’ve also given a suggestion for beginner easy level plants and some more difficult vegetables you can shoot for.

No time like the present to start growing those veggies!

Spring (March – May)

Spring has sprung and it’s time to start growing in earnest! There’s a reason this season is most closely associated with growing, as the temperature starts to warm but rain continues to fall, you get the best environment for growing and makes it the best time to start working on your crop! This is the ideal time to be sowing seeds ready for Summer.

What to Grow:

You can start with planting some seeds for summer. These won’t be ready for harvest until the next season but they’re also the most popular for many growers. It’s the best time for you to start seeding warmth loving plants like peppers, chillies, cucumbers, aubergines, and the champion of Greenhouse projects, tomatoes! All of these can be sown in late spring.

You can also grow some leafy plants like lettuce and spinach quickly and these can be harvested quickly as well. If you really want to get a jump on things, for early spring/late winter you can start some especially hardy plants like onions or leaks before moving them outside as the weather warms up.

Easy vs. Difficult:

• Easy: Spinach and lettuce are fuss-free and grow rapidly.
• Difficult: Aubergines and peppers are slow to germinate and require consistent high heat (often needing a heated propagator).

Summer (June – August)

Summer is where a Greenhouse will really shine and also where ventilation will become most important as temperatures continue to climb. You will have quite a few options to choose from and any Mediterranean crops you’re looking to grow are going to be most viable around this time of year. The only thing you need to be wary of is “sunscorch” and making sure that conditions are perfect for you to regularly harvest and engage in succession planting for your leafy greens.

What to Grow:

While you’ll start to see harvests coming in, you can continue to grow your plants from spring for maximum yield as well as opening the door to some other difficult plants like melons. Summer is the peak season for a number of plants and this is where your tomatoes will really begin to come in but you can also look at growing Aubergines, Basil and Climbing beans!

You can sow a few autumn plants as well in the form of Kale, French beans, and Brussel Sprouts for autumn and winter harvests, as well – with all the heat and humidity on offer, the sky’s the limit for summer growing.

Easy vs. Difficult:

• Easy: Cherry tomatoes are more resilient and faster-fruiting than larger beefsteak varieties which makes them the ideal way to start your summer growing journey.
• Difficult: Melons require high humidity and manual pollination to succeed in the UK so if you want a challenge this is the one to aim for.

Autumn (September – November)

You can use what heat remains to keep plants going but it’s going to be the start of winter plants and cleaning up what you’ve got left over from summer as the season gets autumnal. Planting out your winter crops is going to be the name of the game as the greenhouse growing season winds down but there’s still plenty to be getting on with if you make the most of the heat you have left.

What to Grow:

You can start with the hardier greens like winter lettuce, pak choi, as well as Kale, French beans, and Brussel Sprouts for autumn and winter harvests. If you’re up for something a little different, you could see about getting your Christmas potatoes ready. While potatoes are usually the vegetable equivalent of the Terminator and will grow even without soil, avoiding a cold snap is essential as frost can wipe them out.

It’s also the right time to start moving outdoor plants into the greenhouse so they can have somewhere warmer to overwinter. Peas is a good contender for a plant you can keep going in your greenhouse before transplanting again in the spring.

Easy vs. Difficult:

• Easy: Kale and winter salads are extremely hardy and handle light frosts well.
• Difficult: Christmas potatoes must be kept frost-free; if the greenhouse is unheated, they may fail during a cold snap.

Winter (December – February)

In an unheated greenhouse, growth is going to slow significantly as the heat being caught will be greatly reduced. Despite this, you can still produce hardy greens and if your greenhouse is heated you’ll have a few extra options for what you can grow (although you’ll still likely be having a wind down period.

What to Grow:

Root vegetables are always a contender but can be a good way to keep your greenhouse growing in the colder climates, along with the classic winter crop of Microgreens. Add into this winter salads and hardy herbs like Rosemary, Oregano, Arugula and lamb’s lettuce. You can also make a start on those hardy plants we mentioned for early spring in the late winter such as onions and leaks.

Easy vs. Difficult:

• Easy: Microgreens are the easiest winter crop, ready to harvest in under 15 days and can continue into spring.
• Difficult: Growing tomatoes or cucumbers in winter is nearly impossible without significant supplemental heating and artificial lighting, but if you don’t have anything else you want to grow and are up for some real difficulty…

Essential Greenhouse Tips

Whatever the weather, there are a few things you can do to help your plants to thrive by keeping these essential tips in mind

• Planning: Working out what you’re going to plant ahead of time will help you keep your growing plan on track.
• Watering: Always water in the morning to allow foliage to dry before evening, which prevents fungal diseases like grey mould.
• Ventilation: In summer, keep doors and vents open to prevent temperatures exceeding 30°C, keeping your plants safe from damage.
• Insulation: On the flipside, in winter, you can use bubble wrap or horticultural fleece to retain heat without using expensive electricity.
• Pollination: For indoor crops like cucumbers and melons, you may need to hand-pollinate or find a way to let bees inside.