Growing tomatoes at Gosberton

Growing tomatoes at Gosberton

My name is Frank Gundry-White, I’m the head grower for the Seed Co-operative and I’m going to go through how we grow tomatoes at Gosberton Bank Nursery, just one way of many! Tomatoes are a very rewarding crop to grow and I am always trying to improve how I do it – it’s not set in stone.

I sowed our tomatoes on the 22nd of February, they germinated four days later, as of today they are pretty much all up as you can see from the photos.



We have a heated bench that has heating cables buried in damp sand. There is a thermostat and a control box that regulates the temperature. I have it set to 26 degrees and though there is some fluctuation between night and day time temperatures that seems to be within the tolerance of the seedlings. I may have to open up the germination bench on sunny days if the temperature becomes too high. I have created hoops with blue plastic pipe, and covered the bench with horticultural bubble wrap (big bubbles!), that has been UV stabilised.


I keep a watering can full of water in the germination area to warm up the water so I don’t shock the seedlings too much when I need to water them.

When they are big enough to handle they will be transplanted into bigger pots and kept in the warm protected conditions until the general temperature is suitable to remove them from the protected area into a covered bench that's not directly heated.

I have some lights on in there to avoid the small seedlings becoming too leggy, to make up for the fact the bubble wrap and the plastic cover are excluding some light.

We will keep the tomatoes in pots until they are big enough to plant out, and we plant them out after the main threat of frost has passed. Last year we had some late frosts and some of our tomato plants were damaged.

This year we are growing six varieties of tomato; five indoors and one wild tomato outdoors - Black Cherry, Marmande, Matina, Golden Currant, Golden Queen and Yellow Submarine. They are mostly indeterminate or 'standard' tomatoes except the sprawling Golden currant which is a ‘wild’ tomato closer to the original landrace from South America. The others we grow in the greenhouse, in rows and up strings, spaced 70cm apart. We give our tomatoes quite a lot of space as I prefer to have more elbow room to move between plants when they are fully grown. With between 80 to 100 plants of each variety we will easily hit our target weight of seed before October. We will train them upwards leaving the main top growing point and taking out the side shoots that form in the leaf joints. We may start to take off some of the lower leaves later in the season when they begin to yellow in August and September.

Tomatoes can be prone to lots of diseases so we need to be careful to give them the optimum conditions and the best start in life. The one I’m most concerned with is the tobacco mosaic virus, so any smokers are banned from our glasshouses! The other big one is blight which may transfer from local potato fields; it seems to arrive in Lincolnshire by late summer but we have never had any serious problem indoors so far. Our glasshouses are kept quite dry and there is quite a low risk of blight as we water them by drip line. In fact we needed to import blight from a research station to infect our own outdoors, blight resistant tomatoes in our tomato breeding programme!


When the fruit is ripe we begin to harvest and process the fruit into seed. We prefer to have the fruit ‘over ripe,’ that means it would be riper than a normal market garden would harvest at. There is a risk of splitting but we try to time our harvests on the days before we water to avoid having to take seed from split fruit. We open the fruit, remove the seeds, separate the seeds from the flesh using our hands, hoses and sieves, then we set the liquid and seed from the fruit to ferment for a few days to remove the jelly like coating on the seeds. We add a little yeast to make sure we get them going in a regular and prompt fashion. After a few days we wash the seeds using sieves and buckets to separate whatever pulp is remaining and the seeds are then ready to dry.


Golden Sunrise tomato - seed harvest

 We try to actively dry the seeds and move them about whilst they start to dry to avoid them sticking together - we don't dry them on paper as they will stick to it! We instead use cotton tea towels which make it easier to remove the seeds from when they do stick. We also, before drying give them a short treatment in vinegar solution which, by law we are obliged to do to prevent the spread of certain seed-borne diseases.

One of the reasons we are growing so many tomatoes, aside from loving them, is that we are now facing more certification protocols being instituted by the government and need to provide a plant passport to all of our tomatoes. We need to send seeds to be tested for diseases, and we need to submit to an inspection of the crop when it’s in production. This increases the workload but also the cost of seed production and to consolidate our passport responsibility and streamline the inspections we are keeping all the tomatoes and peppers here with us this year and for the foreseeable future. We do have the growers’ network, but it makes sense to us to have a one stop shop for the passporting visits.

Growing at home

You can start germinating tomatoes at home now if you have a warm, sunny windowsill for an early crop of tomatoes for summer salads. You don’t need to have a polytunnel or greenhouse to grow your tomatoes; there are some types which like to grow outside and are more resistant to blight which develops in warm, humid weather. I can recommend the Golden Currant ‘wild’ tomato for beginners, as it can be grown almost anywhere, in pots or in a small bed. It can still grow well without much compost and it produces lots of small sweet fruits over a long period. It can have a sprawling habit so has a tendency to take over, but you can always cut if back a bit and try support it a bit if it gets out of control.










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