April Greenhouse Gardening: Your Complete Guide
April is an exciting time for gardeners! We’re finally past that uncertain phase of wondering, “Is it warm enough?” or “Will there be another frost?” The clocks have gone forward (yay), and with longer days and rising temperatures, it’s the perfect moment to start many plants under glass. Your greenhouse becomes an invaluable space this month – providing protection from any late frosts while giving you a head start.
It’s definitely time to dig out those seed packets! Some gardeners are already ahead, with strong seedlings well on their way, but I personally like to wait until early April before sowing tomatoes, cucumbers, and other warmth-loving plants. These can be a little sensitive to chilly nights, so I find this timing gives them the best start.
If you haven’t already, now’s the time to check your greenhouse setup – clean the glass to maximise sunlight, make sure your ventilation is working, and organise your staging for an efficient growing space. Whether you’re sowing your first seeds or potting on young plants, April is all about setting yourself up for a successful growing season! ☀️
Pruning and Plant Care
If you haven’t already, take care of the pruning and plant preparation:
- Remove any remaining dead winter growth
- Prune overwintered plants to encourage robust spring growth
- Inspect plants for early signs of pest activity
- Gently remove any yellowing or damaged foliage
Vegetables to Start in Your Greenhouse
Tender Crops
April is the perfect time to sow heat-loving plants that need a long growing season:
- Tomatoes – Choose varieties suited to your space, but also ones that you will enjoy to eat through the summer months. We like Shirley as salad tomatoes, roma for cooking and ‘Bloody Butcher’, which go well with mozarella, basil and olive oil.
- Chillies and aubergines – Late April is the final opportunity to start these from seed as they need a long season to produce well.
- Courgettes, squashes and pumpkins – Sow in individual pots for planting out after frost risk passes.
- Cucumbers and gherkins – Start in individual pots toward the end of the month.
- Sweetcorn – Sow in modules for later transplanting.
- French and runner beans – Sow under cover for planting out in 4-6 weeks. I tend to plant my green beans in pots and set them along the side of the greenhouse, on the outside. They offer valuable natural shade to the greenhouse, keeping the tomato plants on the inside with some shade.
Salad Crops
- Lettuce – Start in seed trays to give them a head start against slugs and snails.
- Herbs – Basil and other tender herbs benefit from an early greenhouse start.
Flowers to Grow Under Glass
Annual Flowers
- Cosmos and field poppies – Perfect for filling gaps in borders.
- Sunflowers – Easy to grow; start indoors for early blooms.
- Marigolds – Sow in warmth for summer bedding.
- Zinnia, salvia, and ageratum – Final chance to sow these summer bedding plants. My established Salvias are moved into the greenhouse over winter, so now is the time I look to move them back out.
- Nasturtiums – Start in pots; plant in poor soil once frost passes for best flowering.
Climbing Plants
- Sweet peas – Continue sowing at the base of supports. I plant mine in a large planter with canes. They’re quite effective once they flower and can be moved around the garden.
Summer Bulbs
If you can provide frost protection, start:
- Lilies
- Freesias
- Gladiolus
- Crocosmias
Fruit to Start in Your Greenhouse
- Strawberries – Start plants in pots, hanging baskets, or prepared to plant out. They’ll fruit within weeks.
- Melons – Surprisingly easy to grow from seed with greenhouse protection.
Essential Greenhouse Management Tips
- Ventilation – Open roof glass on warmer days to prevent overheating and reduce disease risk.
- Watering – Check plants regularly as they’ll dry out more quickly as temperatures rise.
- Propagation – Use heated propagators or mats to speed up germination.
- Pest control – Keep an eye out for aphids and other pests that become more active in spring.
- Hardening off – Begin acclimatising seedlings to outdoor conditions 2-3 weeks before planting out.
What to Plant Outside in April
While your greenhouse is essential for tender crops, many plants can now be sown directly outdoors:
- Root vegetables – Carrots, beetroot, radish, and parsnips
- Peas – Direct sow in prepared soil
- Potatoes – Plant second earlies and maincrop varieties
- Onions, shallots, and garlic sets
- Leafy greens – Spinach, Swiss chard, and kale
- Hardy annuals – Wildflower mixes can be sown directly
By utilising your greenhouse effectively in April, you’ll ensure a productive growing season ahead with earlier harvests and stronger plants. Remember that proper timing is crucial – tender plants should remain protected until all risk of frost has passed.
Final Thoughts
We absolutely love April! The lighter evenings make such a difference – there’s nothing better than coming home from work and still having time to potter around in the greenhouse. Whether it’s sowing seeds, pricking out seedlings, or just checking on your plants, those extra daylight hours make greenhouse gardening so much more enjoyable and relaxing.
The temperature shift is also really noticeable inside the greenhouse. On sunny days, even if there’s still a slight chill outside, stepping into a warm greenhouse makes all the difference. It’s the perfect time to start hardening off plants, getting summer crops established, and watching everything burst into life.
If you haven’t already, we highly recommend investing in a small radio or Bluetooth speaker – it’s amazing how much of a difference a little background music or a good podcast can make. Pair that with the soothing sounds of watering your plants or the scent of freshly turned compost, and you’ve got yourself a true little haven. Gardening isn’t just about growing plants – it’s about creating a space that brings peace, joy, and a real sense of accomplishment. ☀️
