Growing Brassicas: A Lesson in Ingenuity

I must admit that there are few things more satisfying than the taste of freshly grown sprouting broccoli or the tremendous feeling of pride you get when hauling a huge head of cabbage home from the garden. Because of these rewarding moments I have endeavoured to grow brassicas, despite the numerous challenges this group of veg presents to an allotment gardener.

Our first year on the plot I was so excited to get growing. The allure of full heads of calabrese and ripe buds of Brussels sprouts presented an easy way to get my plot started – or so I thought. I had heard the occasional warning from fellow growers about cabbage moths or club root or cabbage root fly or root rock, but I figured it was just one of those things that might present itself. Hopefully, it was just something that happened in theory rather than in practice. As with most of my growing experiences, I was very quickly proven wrong!

It turns out our site is inundated with cabbage moths. Within a few short days, my entire crop of broccoli and Brussels sprouts were wiped out – and I mean, annihilated by these greedy little insects. I quickly started researching these flying destroyer of plants and found out that, when presented with a delicious member of the brassica family, cabbage moths (also known as cabbage whites) lay their eggs on the underside of the broad leaves so commonly associated with this plant. The eggs then hatch and the little larvae consume the leaves for sustenance. If you have a really bad infestation – like I did – your crop can be gone within a matter of days.

That first year we had set up the most rudimentary of protection against these moths by laying a bit of (what we thought was sufficient) netting over the crop. It didn’t reach the ground to provide complete cover and the netting ended up resting directly on top of the leaves, allowing cabbage moths the perfect opportunity to lay their eggs. ‘Next year,’ I remember thinking, ‘next year, I’ll be ready!’

Sort of.

When we went to plant next year’s crop of brassicas I reused the same netting (first mistake) but this time ensured that the netting reached all the way to the ground. I put upturned bottles on the top of the bamboo canes to keep these from sliding between the holes in the netting and placed bricks along the ground to secure the netting. While this theoretically worked (we did get a successful harvest) there were other problems that presented themselves.

The netting situation last year – it wasn’t tall enough to accommodate this sprouting broccoli and constantly removing the bricks to gain access kept ripping holes in the net.
  1. Weeds grew through the netting before I could get to them. These would then get tangled and rip the nets, creating larger holes and proving to be a sad deterrent against the moths.
  2. The netting wasn’t tall enough to protect larger crops like sprouting broccoli which ended up growing to about a metre high.
  3. We used a lot of bricks to hold down the netting, which meant that if we wanted to do anything to the crop, it would take a lot of effort to move everything just to access the brassicas beneath.
  4. The holes in the netting proved to be too wide, meaning it was almost useless against moths and butterflies. It turns out we had mistakenly bought netting that was more suited to keeping birds, rather than insects, out.

After a moderately successful crop, I was determined to not make the same mistakes this year. To combat this, I used the most powerful weapon in my gardening arsenal to ensure my brassicas would be fully protected from these flying jerks – I got my overly neurotic, hyper analytical, and cynically-minded husband involved.

Those little bastards didn’t stand a chance.

I unleashed my husband and got a brassica fortress!

We decided that the best way to grow brassicas for this year would be to address each problem individually and find the best solution. To counter the weeds that would constantly grow up through the netting, we removed the need for weeding at all by placing a sheet of black mulching plastic on the ground. In all honesty, this isn’t the most green or environmentally friendly approach, but I figured using this to ensure a good brassica crop outweighed the cons of eating broccoli that had been shipped from halfway around the world.

We bought better netting – and lots of it! Our whole allotment experience has been based on growing as inexpensively as possible – saving money is one of the many perks of growing your own – but we do occasionally spend a little if it means we’ll get a lot in return. It turns out that we hadn’t been using butterfly proof netting, so we went for a much finer and more appropriate type of barrier. We also spent some money on new wooden posts to hold the structure in place and, instead of using free bricks that we had dug up on the plot to hold down the netting, we bought metal u-shaped pegs to hold it all in place. To secure the opening, we bulk bought clothes pins from a discount store – I think it was £1 for a pack of 50. We used zip ties and string to tie everything else in place.

To make our brassica cages (or as my husband likes to call it, ‘Lydia’s Play-Pen’) you will need the following materials (please note this is to make two of them, just half it or double it where necessary if you want to make more or less):

  • Black Plastic Lining, approximately 4m x 1m in size – don’t buy the fabric kind as you will want to make holes in it
  • Box Cutter (or a similarly sharp knife)
  • Scissors
  • Six 2m wooden posts for the corners and middle
  • Thirty bamboo canes, approximately 1.5m-2m long
  • Two Butterfly Proof Nets, approximately 5m x 1m each
  • Saw
  • Sledge Hammer or Mallet
  • Zip Ties
  • Twine
  • Clothes Pins
  • Metal U-Shaped Pegs

The assembly may take up the better part of a day’s work in the garden, so set aside some time. Once it’s up, there’s very little maintenance to do afterwards.

  1. Start by clearing the area where the cage will go of all weeds and previous crops. Give the ground a good turn and rake to a fine tilth – you’ll thank yourself later for this extra step!
  2. Lay down the black plastic and place something heavy in the corners to keep it in place for now.
  3. Saw each of the 2m wooden stakes in half, so they are each 1m long.
  4. Hammer each of the stakes in place – one on each corner and two in the middle for extra support.
  5. Assemble the bamboo canes to the stakes with zip ties so that it makes a frame (see the above picture).
  6. For the more dexterous gardener, begin assembling the net (note, this will take up most of the assembly time and I found it helpful to do this on the ground and then bring it to the cage). Lay one of the nets in a u shape, so that it mimics three of the sides of the cage (the two longer sides and one shorter). Unravel the other net and place it so that the end aligns with the shorter side of the first net and the longer sides match up with the longer sides of the first net. Using the twine, ‘sew’ it so that you connect the two nets together – you will basically be making a 3D box shape from the netting.
  7. Lay the completed netting over the top of the cage so that it covers the frame (the stakes and bamboo canes should be on the inside).
  8. Using more zip ties, attach the netting to the bamboo canes and stakes.
  9. Take the metal pegs and, wrapping the bottom of the net around more bamboo canes, pin these into the ground so it makes a firm seal.
  10. Take the clothes pins and the excess netting from the unsown side and pin it closed so it can act like a door.
Another angle of the cages.

Now that this assembled, it’s time to get planting! Don’t worry – growing brassicas is much easier once you have these basics covered.

Using the box cutter or a pair of scissors, make a hole in the plastic approximately 15cm in diameter. Using a hand trowel or a fork, loosen the soil to a fine tilth, removing any stones or hard clumps of soil. Stir in a bit of compost or well-rotted manure in the hole.
Place the plant in the hole (here I’m planting cabbages) and fill the soil to just under the seed leaves. It is important that brassicas have a very firm and strong planting to protect the roots from wind. Too much disturbance to the root system can cause root or wind rock which harms your crop.
Place a ‘collar’ around the plant to protect it from cabbage root fly. I recycle 2L soda bottles for this job, but I’ve seen people use PVC pipes, pieces of agricultural felt, strong wool, carpet, or wooden frames for the same purpose.

Water your brassicas well and feed with an all-purpose high nitrogen feed every 2 weeks throughout the growing season. If you have butterfly proof netting then you shouldn’t have to worry about cabbage moths, but feel free to pop in the cage occasionally to check the underside of leaves, just in case. Also, ensure you sew up any holes and make sure there are no possible ways to get in the cage. Curious small birds have been known to get trapped in netting, so please make sure there is no way they can get in and harm themselves.

A successfully grown and moth free cabbage!

Apart from watering and the occasional feed, there is very little for you to do. The black plastic will take care of the weeds, the netting should keep out pests, and the collars will protect from any root borne problems. All you have to do is sit back and dream of cabbage!

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