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.