Around the beginning of June 2013, Monty Don showed us his visit to a tomato grower named Peter Sanford.
Peter grows tomatoes in small terracotta pots, just half full of compost – and with excellent results!
Monty updated us this week in the Gardeners’ World Tomato Growing Trial on the progress of his plants. His aim was to see which tomatoes have the best taste out of those growing in grow bags, large plastic pots and small terracotta pots.
Unfortunately, this link has now expired.
The tomatoes in the grow bags are doing well because grow bags contain about six weeks of fertiliser. They also have a large surface area so roots can access air more easily.
Large Plastic Pots
The tomatoes in the large plastic pots look a bit sorry for themselves, probably because of over watering, soil compaction and very little air in the root zone.
Small Terracotta Pots
The tomato plants growing in the small terracotta pots have been starved of nutrients because they have been six weeks in compost containing about a week’s supply of food.
In the first video it was mentioned that Peter Sanford’s success at growing tomatoes in small pots was mainly due to feeding at every watering. In Monty’s trial the plants in the terracotta pots have gone about five weeks without being fed.
Tomato Root Systems
These plants will have tried to develop a large root system in search of food and become pot-bound.
About Tomato Plant Roots and Container Size
Tomato plants grow large root systems in search of food and water. However, if you give them all the nutrients and water they need, their root systems won’t grow as large and they’ll be better able to cope with smaller pots.
I have to say that I do like Monty Don and especially his dog Nigel!
Tomato Taste – Nitrogen to Potassium
The trial was to find the best tasting Gardener’s Delight tomato from three different growing containers – grow bags, large plastic pots and small terracotta pots.
However, it will take more than comfrey tea to get the plants grown in small pots back to full health.
Comfrey tea and liquid seaweed extract are both great as a potassium feed.
Potassium increases tomato taste, colour and shelf life.
Nettle tea and fish emulsion are great as a nitrogen feed.
Nitrogen based food is best given before flowers appear. Too much nitrogen after fruiting starts, can produce watery tasting tomatoes.
Blossom End Rot
Being told to water frequently to avoid blossom end rot without saying why, is one reason I started this website!
We know that BER is caused by calcium deficiency, but there is a connection between transpiration (see previous newsletter), watering and mineral deficiency – calcium deficiency in this case.
Plants release moisture through their leaves especially in hot, light and dry conditions.
As moisture is lost, water is taken in through their roots, with dissolved nutrients from the soil, and into the plant.
If water is only available on an infrequent basis, nutrients and especially calcium will be too.
We mentioned translocation in a previous newsletter. This happens when upper leaves are able to take nutrients from lower leaves when there aren’t enough nutrients being absorbed by the roots. Top growth always gets priority.
The problem with calcium is that it can’t be moved around a plant like many other nutrients can – it can’t be translocated. So when the fruit need calcium to form the fleshy wall, if it isn’t immediately available in a plant’s system, from the roots, the dark brown leathery patch appears.
A way to avoid the transpiration/translocation problem and blossom end rot, is to foliar spray the leaves with calcium – see previous newsletter.
Containers and Hot Weather
I’ve noticed that the tomato plants in air pots and fabric pots are doing well in this heat.
This is because heat can escape through the sides of the pots as well as the roots absorb the extra air needed for the faster growing conditions.
I hope your plants are doing well and your tomatoes are getting bigger each day!