Greenhouse tips & facts

Velt shares the following tips

What is Velt:

Velt (Vereniging voor Ecologisch Leven en Tuinieren) is the association for everyone who wants to garden and cook in an environmentally friendly way. For more than 40 years, we have been promoting healthy living in tune with the seasons, with respect for nature.

Velt is the go-to association for anyone who wants to adopt eco-friendly practices in the garden or kitchen. With Velt you learn not only how to grow delicious vegetables organically, but also discover everything about beautiful eco-gardens, keeping chickens in an animal- and eco-friendly way, and preparing wonderful dishes with freshly harvested seasonal vegetables.

Greenhouse itch in January

De dagen beginnen te lengen, maar de moestuin ligt er bij gebrek aan licht en warmte nog wat verlaten bij. Heb je een serre of kas, dan kun je vroeger toegeven aan de tuinkriebels. Jos Van Hoecke, auteur van het boek Achter Glas, vertelt wat hij tijdens deze wintermaanden doet in zijn serre.

• In part of my greenhouse, I sowed green manures in autumn. They have grown well and form a colourful mix of phacelia, rye and vetch. At the end of January I dig them in shallowly. Then I spread five litres of fine compost per square metre on top of the soil.
• The rest of the greenhouse is still full of lamb's lettuce, cut-and-come-again lettuce, rocket, winter purslane, chervil and chicory. These can of course remain until their harvest is finished.
• As soon as it stops freezing during the day, I sow the first seeds and the vegetable garden year begins for me. Saxa is my favourite radish variety for greenhouse growing. From now on I sow small batches of radishes every three weeks to have a constant supply until April, when I continue growing outdoors.
• Sow fresh spring leaves now! Cut-and-come-again lettuce is a fast grower that you can already sow in the greenhouse. Witte Dunsel is my earliest favourite: a fast grower that I sow both in the greenhouse soil and in the seed tray. Rocket, Osaka Red, Tokyo Bekana, Serifon, turnip greens, mizuna and Purple Frills are all brassica leaves that I sow every three weeks in rows 30cm apart. I mix all those lovely leaf seeds together so that the harvest is naturally spread out. Vroeg Reuzenblad is my favourite spinach variety, as it copes well with the cold.
• From mid-February I sow one or more winter leek varieties (Blauwe Luikse Winter, Avano, Sint Victor and Blauwgroene Mechelse) in the seed tray and in the greenhouse soil. Leeks germinate with a cute green shoot that forms a hook at the tip. By April those hundreds of young plants are as thick as a knitting needle and I plant them out in the open ground. At the same time I sow onion seeds in the greenhouse. Good varieties are Sturon and Stuttgarter.
• If you want to harvest peas in May, pre-sow them in the greenhouse now. That way you can plant sturdy seedlings outside from mid-March and reduce the risk of caterpillars in your peas. Sugar Snaps do not germinate in cold soil but germinate readily in the greenhouse.
• In the second week of February I sow cauliflower for the first time. Alpha, Mechelse Vroege, Vier Jaargetijden and Odysseus are recommended. Three weeks later I sow again to spread planting and extend the harvest.
• In the conservatory at the end of February I pre-sow chilli peppers and sweet peppers, as they need around 22°C during the day and 18°C at night to germinate.

Almost summer in the greenhouse! (August)

From mid-May everything takes off in the garden, as the Ice Saints are finally over. All frost-sensitive plants can now go into the greenhouse and outside. It gets so busy that even Jos Van Hoecke forgets to sit in his greenhouse chair and enjoy the sun and the wonderful activity in the garden.

• The last spring vegetables leave the greenhouse for the table, making room for the tomatoes. After planting them out you need to tie them up straight away — Jos uses sturdy string, but stakes work too. Remove side shoots regularly while they are very small: the wound stays small and heals quickly. Opinions differ on watering tomatoes. The rule of thumb is: definitely not too much, and always at the base of the plant so the leaves stay dry. Jos waters two to three times a week with five to seven litres. Some gardeners water only once a month, even in the greenhouse — this encourages the roots to go deeper.
• Sweet peppers, chilli peppers and aubergines that you have raised indoors or in the conservatory should be gradually acclimatised to the temperature in the greenhouse. When the first flower buds appear on the young plants, transplant them — either in the greenhouse soil or in pots. With pots, remember that you need to water regularly.
• Melons can now go into the open ground too. If space in the greenhouse is limited, grow them vertically, for example on a structure of stakes and wire netting. Pinch the main shoot of young melon plants after the fifth leaf has fully developed. This produces side shoots, which can also be pinched after the fifth leaf. In a greenhouse, melons often need hand pollination to produce really good fruit.
• Gherkins and cucumbers are fast growers. Train them best on a trellis of sturdy poles or on strings. Harvest the fruits young: that is when they taste best and the plants keep producing abundantly.
• Do not leave the greenhouse soil bare — mulch with a growing layer of organic material. This keeps moisture in the soil and gives unwanted plants no chance. A mix of horsetail, tansy, comfrey and nettle (without seeds) works very well as ground cover, as these plants provide good nutrition to the soil life — and therefore to your plants — as they decompose.

Extend the seasons in your greenhouse (November)

As the days shorten, nature and the garden slow down. But with a greenhouse you can extend the seasons. Jos Van Hoecke proves it: while harvesting the last fruiting crops, he stores his chicory roots and starts planning the new growing season. These five tips will help you get more out of your garden too.

• Sweet peppers and chilli peppers are in large pots in my greenhouse. The advantage is that in autumn, when frost threatens, you can temporarily move them inside or to the conservatory. In November, space the pots a little further apart. This gives the plants more light and air, helps them dry out faster and reduces the risk of fungal problems — a simple trick for enjoying pot peppers longer. In this way I usually pick the last sweet peppers and chillies well into November.
• In November I bring the dug chicory roots into the greenhouse. I cut the leaves back to 3cm — wonderful feed for chickens and rabbits. Then I bury most of the chicory roots vertically, frost-free. Every four weeks I take out about forty to force. I do this using what is called 'cold forcing'. I dig a trench in the greenhouse, removing about 20cm of soil. In early November I place around forty chicory roots in it. In December I make a second trench. I pour a bucket of water per square metre into the trench and let it slowly soak in. Meanwhile I trim the roots to 20cm. When placing them, I stand the roots upright against one side of the trench — a whole row, one root against the next, their feet in the mud. Then I add a thin layer of moist soil between the roots. A second row of roots goes up against the first. I continue like this until the trench is full of roots. I cover them with two layers of jute sacks. If you start forcing at the end of November, you can harvest in February–March.
• If you continued sowing in late summer, you can now harvest abundantly from your winter purslane, lamb's lettuce, chervil and rocket. Water regularly.
• If winter temperatures drop to -10°C or colder, I cover the vegetables stored in the greenhouse with extra jute, hay or straw.
• And then it is already time to draw up the greenhouse growing plan for the new season. A great help is my annual garden diary. I write down all the small and larger tasks in the greenhouse and garden. My diaries provide me with a wealth of information over the years and support my memory.