Potting On Brassicas

Sunday afternoon turned out quite nice, actually some sunshine! However, I'm still limping around and anything heavy is out of the question. Which brings me to my brassicas.

I've got a number of cauliflowers, cabbages, Brussels sprouts and calabrese sitting in pots. Most could go into the ground now but I've no ground prepared for them. In a perfect world, I'd have prepared the ground last year but since we weren't here then not really possible.

I've bought myself a few weeks by potting them up. The calabrese had been sown in modules, 15 to a seed tray. Once they had germinated, I'd thinned to one plant per module. These have gone on to square 3" pots.

The rest of the brassicas were in 3" square pots and they've gone up to 5" pots. Some years back, I bought 200 square pots. There are two reasons I went for the square pots rather than the round ones. Firstly, they waste less space. You can rack them side by side and 8 just fit into a seed tray, which makes carrying easy.

Secondly the root system is different in a square pot. In round ones the roots can go round and round which makes it hard to spread them out when planting out or potting on. If you just plant out from a round pot you can find the roots just keep going in circles and development is poor.

Now for most things in pots I just use a good quality multi-purpose compost but brassicas are different. They like a high pH – neutral soil and they need, being leafy plants, a lot of nitrogen.

So I put the compost into my potting bench tray about 3" deep and then sprinkle lime over the top. A bit like dusting icing sugar on a sponge. This raises the pH a bit as multi-purpose compost tends to be a lower pH which is optimum for nearly all vegetables apart from brassicas.

Now multi-purpose compost should contain enough nutrients to keep the plants going for 4 to 6 weeks but brassicas are hungry plants and need a lot of nitrogen. But it's generally not a good idea to add lime and fertiliser at the same time. The way around this conundrum (love that word!) is to add nitrate of chalk. This is a high nitrogen fertiliser (NPK 27:0:0) and contains lime.

The cabbage I'm growing is a dwarf called Hispi. It's good for small spaces and I can actually get them to maturity in the pots. So, if need be, I can leave them in there. After 4 weeks I'll give them a weekly liquid feed with something high in nitrogen or a general purpose liquid feed plus added prilled urea or sulphate of ammonia.

If this all sounds a bit chemical, then substitute dried blood for high nitrogen feed. Only thing I've found with dried blood and with fish, blood & bone fertiliser is that they attract too much interest from carnivores like cats and foxes.  Foxes will sometimes dig up plants looking for a buried body if you use fish, blood & bone.

Hopefully, weather, back and leg permitting, I'll be able to prepare a brassica bed before the cauliflowers and sprouts are pushing out of the bigger pots.