On Friday 23 January 2026, a coach load of AHS members plus guests, visited
Growing in a Glasshouse by Shannon Thaden
We welcomed Shannon Thaden, from Organic Lea Community Farm in Chingford, to hear his talk about Glasshouse Growing. It was a wet and windy January evening but our hardy AHS perennials turned up in numbers, a receptive audience, to learn about the challenges and successes of growing in a glasshouse.
Shannon explained that Organic Lea had evolved organically, of course! From allotment space on the edge of the Epping Forest in the River Lea Valley in 2001 and the adjoining Waltham Forest plant nursery which became vacant in 2007, providing an extensive glasshouse area for growing.
The glasshouse covers half an acre and was originally the site of the council nursery, growing all their street trees and public spaces plants. The economics of this changed and the Council gave up the Hawkwood nursery site. The land had a covenant allowing it only to be used for horticulture so a serendipitous opportunity arose and Organic Lea expanded its operation.
Under the concrete is the soil and so this proved. The glasshouse concrete floor was excavated and 25 growing beds were created by adding compost and developing the soil structure.The soil is London clay, which has the advantage of retaining nutrients and water. High value crops are grown on a 5 year rotation with the soil nourished by compost so no added nutrients are needed. In summer it is: tomatoes, cucumber, aubergines, green beans and peppers, with green manure in the growing gaps. In the winter it is spring garlic from small cloves, full size garlic, broad beans, and winter salads such as endive, lambs lettuce and rocket. Some watercress is grown in damp soil, and hops and lemon verbena are small sidelines.
The glasshouse allows for extensive seed sowing, with the trays laid out on a sandy bench, heated by snake like piping in parts, to help with germination. Crops like chilli need a good head start in the cool, varying light conditions in the UK and this warming helps.
One of Organic Lea’s USPs is collecting their own seeds, and nearly all their plants are grown from saved seeds. Organic Lea have 2 big plant sales, in April and May, so well worth a trip up to Chingford to buy local good quality organic plants. They also produce compost and green manure.
As organic growers they are not allowed to heat the greenhouse because of the carbon footprint. Temperature control is through tweaking the venting which is mechanically operated. The roomy height of the glass house allows climbers like cherry tomatoes to grow to impressive heights and lengths, up to 7 metres on a diagonal, allowing a bigger crop. Overhead wires run the length of the greenhouse and jute string hangs down from the wire, single strands paired up with a plant, and the string end settling into the hole made for the new plant.The plant can be easily trained around the string without having to use individual ties. Irrigation is with seep tubing, and a sprinkler system is used to keep cucumbers and aubergines foliage moist as they like these conditions.
Pollination is promoted by planting marigolds and other flowers that attract insects, wind pollination occurs naturally and some of the plants self pollinate. Pests are kept down with biological controls and by encouraging predator insects.
White fly is predated by a parasitic wasp that lays its eggs in the white fly larva and then eats its way out. Bit of an alien theme !
Ladybirds eat white and black flies and when there is an outbreak then the ladybirds respond in numbers. Nettles are grown at the glasshouse entrances providing a happy home for the ladybirds.
Blue spider mite is a fairly unusual indigineous pest that appeared about 5 years ago and sucks sap from the plant and it has been a particular problem on winter salad crops especially endive. Shannon thought it had peaked now and that natural predators may be finding it and reducing numbers.
The seed trays are covered with a layer of recycled cork waste to retain moisture and provide a deterrent to egg laying pests. Previously vermiculite was used but Organic Lea are trying this more sustainable material. Something to consider for your houseplants.
Expanding undercover growing has been a 2025 project and Shannon has assembled a mobile polytunnel structure to use on outdoor beds. Organic Lea are experimenting with crops to grow in the polytunnel.
Organic Lea have a local reach. Their veg box scheme is delivered to St Gabriels Church Hall for collection. They are a food distribution hub for organic products to serve their veg boxes and they source from farms in Suffolk, Norfolk and Kent to supplement what they grow.
Do check them out: www.organiclea.org.uk
As well as their plant sales they run courses and have an active, well organised volunteer programme and the site is quite special to visit. Shannon also mentioned a side hustle he runs in Leytonstone when we were talking about growing spaces, which is Church Lane Community Garden, Harold Road, E11 4QY, usually opens Mondays and Saturdays. Again worth a visit and on our doorstep.
Tips of the month – December
December is the first month of winter with the shortest days and it is often fairly mild. Despite what some think, there are a lot of lovely garden tasks to do this month, so make the most of dry days to do any final tidying. And if the weather turns wintry, retire into the warmth, plan next year’s display and tend to your festive houseplants.
Fruit and vegetables
Manure and mulch: if you haven’t already, add manure and mulch to protect the bare soil surface from rain and to benefit soil structure.
Brussels sprouts: harvest as needed starting from the bottom and removing lower leaves. Earth up stems and support with canes if necessary.
Leeks, parsnips and root vegetables: can be harvested as needed. A good sign that your root vegetables are ready is when their shoulders peep out of the soil. The leaves of parsnips also start to turn brown.
Asparagus: if you haven’t already, cut down dead asparagus foliage, and cover the bed with a thick layer of well rotten manure.
Fruit trees: December is the perfect time to prune fruit trees to maintain an open, balanced structure and encourage fruit production. The exception is plums, cherries and other stone fruits that should not be pruned until the summer to prevent silver leaf fungus. Use clean, sharp secateurs to avoid damaging your trees
Blackcurrants: winter prune established blackcurrants bushes. They fruit best on strong, young growth, so remove old, thick stems a the base to leave a structured open bush with 6 to 10 upright shoots.
Raspberries: plant raspberry canes while they’re dormant. To prune established raspberries, it is best to wait until the end of the winter. Look out for the February tips for details on how to prune raspberries.
Rhubarb: divide established clumps of rhubarb, to renew the plant’s vigour. Sections taken from the outside of the plant are better than those from the centre. Plant the new plant section in a well-prepared soil with plenty of organic matter. They are hungry feeder.
Flowers
Tulips: they will still do well planted this late in the year, provided there is no frost. December is the end of the spring bulbs planting season and there is always a big sell-off with some good bargains. Check out the November tips to find out how to protect your bulbs from squirrels.
Wisteria: winter—prune your wisteria, cutting back weeping summer side shoots to 2 or 3 buds.
Climbing roses: prune now, removing diseased or damaged growth and tying in any new shoots to their support. Prune older flowered side shoots back by two thirds of their length.
Hydrangeas: leave the faded flower heads until spring as they provide frost protection to the swelling buds further down the stems.
Dahlias: if you have stored your dahlias tubers (check November tips on how to store dahlias tubers), keep an eye out for rot.
Cut down and clear away: Cut down perennials that look too untidy. Cut off damaged hellebore leaves. Regularly nip off the spent flowers of cyclamens and winter pansies, to prevent the plants from setting seeds and to extend their bloom.
Christmas decorations: making your own Christmas decoration from natural materials is a satisfying way to add a festive flair to your home. Even the simplest, barest branch or handful of pinecones can be transformed into impressive decorations. They are many eye catching materials in our gardens and neighbourhood: evergreen foliage, twigs, branches, berries, seed heads.
Don’t forget
Consider winter protection: it is your last chance to bring into a frost-free location plants that need protection. Potted plants can also be protected by wrapping hessian and/or bubble warp around the outside of their pot to help protect their roots from frost. Cover roots of tender plants with dry thick mulch and wrap sensitive soft growth with biodegradable fleece.
Greenhouse: tend to plants overwintering in your greenhouse, removing faded leaves and watering them sparingly to keep them just moist. Excess moisture can contribute to disease spread. Ventilate the greenhouse on warmer days to reduce humidity and the risk of disease.
Get ready for spring: clean and organise your pots and seed trays. It will also help reduce the rick of fungal diseases.
Watch out for wildlife: Look out for lichens and leave them in place. They are harmless and colourful composites organisms beneficial to their hosts and especially elegant in the frost.
Don’t forget to stock up feeders to keep birds fed and to provide water. When refilling feeders, clean them to prevent disease.
Don’t turn over compost heaps and rotting leaves as it may disturb hibernating grass snakes, slowworms, frogs, toads and hedgehogs.
Have a fantastic and festive December