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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.

Posted in Allotment Garden Diary
10 comments on “Potting On Brassicas
  1. David says:

    I would get your self checked if I were you. The same thing happened to me out of the blue walking down the allotment path. I didn’t take much notice and by 9.00 in the evening my left leg had swollen up due to the fact that it turned out I had a blood clot. After visiting the local A&E dept. they treated it as a blood clot until tests carried out and it was a blood clot so I was on wafarin for three months with no other ill effects.

  2. John says:

    Thanks for your advice, David. However, I’ve had back problems on and off for a few years now and there’s no swelling of my leg. It’s just a pulled muscle.

  3. Su says:

    Interested in the info on cabbages.am trying them this year, mainly over winter. What can I substitute for blood f ‘n b? My daughters is vegetarian and I do try and respect this when growing veg. Have not managed to get my head round fertilisers yet. Ok with soil and acid and alkaline and ok with tomatoes. Can I use chicken manure pellets?( have a shorter and more descriptive term we use, but had better be proper!) or comfrey? Are they good for nitrogen?

    Also many thanks to you both for all your help these last few years, since I got my plot. For example; Looking for info on drying apples. Googled it and up you popped! Should have known better and gone straight to your site to start with! Su

  4. John says:

    Chicken manure pellets are high in nitrogen, comfrey not so much, so good for cabbages that like a lot of nitrogen. Instead of Fish, Blood & Bone just go for Growmore. It’s basically the same thing but artificial.

    For brassicas an extra dose of Nitrate of Chalk which is a straight nitrogen fertiliser but with lime is beneficial.

    There are articles in the advice section about fertilisers that should help make it clear.

  5. Allan says:

    Growing veg for a vegeterian ………..maybe the use of chicken manure pellets goes against the grain so to say…….vegeterian and chicken derived fertiliser …… dosent seem right to me but hey thats just my opinion.

    keep up the good work John

  6. Jen says:

    The chicken MANURE pellets are not derived from chickens, they are the poo.

  7. John says:

    I think Allan clearly knows they’re manure – which are a by-product of chicken keeping. However, many vegetarians eat eggs and milk which involves the death of the unproductive males. Get ready for an ethical debate!

  8. Stephanie says:

    one thing I would say that when planting brassicas over winter be a little careful how much nitrogen you use in any form as it stimulates leaf growth which is great summer months but not so great winter months as the new growth is affected by frosts.
    I have been informed that a slow release fertiliser is best.

    • John says:

      @Stephanie: That’s a very good point – but there’s not a lot of difference between adding fertiliser in small amounts frequently or a slow release in one go except slow release may not be balanced as you want for the particular crop. Certainly less bother though!

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