SCHOOL VEG GARDEN OUTPACES ALLOTMENT

For the last six or seven years I´ve been running the Belleville School veg garden. When I took over my Garratt Parl allotment I bought some trays of veg seedlings from Homebase as I hadn´t had the time to grow seedlings myself. I planted them out at Belleville School and the allotment at the roughly same time, and a month or so later the differences between the two sites is incredible. Whereas the Belleville crops have grown enormously (I´ve just harvested twenty lettuces of various varieties) the crops at the allotment have really struggled to get going.
Compare the carrots and parsnips below:

Allotment

Belleville

Allotment

Belleville

The tomato plants are stuggling a little at both sites thanks to the unseasonally low temperatures, but once again, the Belleville plants are way ahead:

Allotment

Belleville

The allotment tomato is a Radiator Charlie grown from seed and the Belleville plant is a Gardener´s Delight shop bought by a parent. The Radiator Charlie was quite a lot larger than the Gadener´s Delight when planted out.

Perhaps the most dramatic example are the red cabbages:

Belleville

Allotment

So what´s behind these variations?
Temperature 
Well the first thing that springs to mind is the fact that the school veg plot is sited near buildings and was built in a sheltered corner of the playground on top of tarmac. These factors probably combine to create a bit of a suntrap.
The allotment is on quite an open windy site near the Wandle River and I imagine the there´s a bit of a difference between the average temperatures at the two sites.
Soil
At Belleville the raised beds are over a metre high and filled with a slightly clay like soil delivered from a site near Heathrow airport. To be honest it wasn´t of the highest quality, but since then we´ve added quite a few bags of compost to top it up and enrich the soil.
The allotment soil is quite a sandy loam that has been well worked over the years. It´s possible that many of the nutrients have been removed from the soil over time.
Noise
At Belleville the children make a racket in the playground.
The allotment is nice and quiet.
Maybe Prince Charles was right all along?

The Belleville Veg Garden

If anyone has any other thoughts or suggestions please leave a comment in the box below.
Thanks!