Organic broccoli

The best way to grow organic broccoli

Growing organic broccoli over the winter months is very rewarding. Some varieties are faster growing than others. Some varieties form small broccolini type flower heads whilst others form large heads.

Whichever variety or varieties you choose to grow this winter. Make sure your try tasting your home grown broccoli before cooking it.   Raw broccoli is a treat and I always nibble on some when I’m pottering around the garden.

But before that, we need to know how to grow organic broccoli.


Organic broccoli likes a moist and rich soil

Brassicas like broccoli generally like a full sun position and a deep, rich, well draining soil. The soil needs to be fairly deep to ensure the growing plants have enough room for their roots to spread.   Therefore, a deep soil for broccoli is about 20cm deep.

The soil needs to be rich. That means plenty of compost for microbes and worms, well rotted manure such as horse manure and rock minerals. People speak of broccoli needing a nitrogen rich soil. In organic gardening, that means a rich soil with a nitrogen rich manure such as horse manure. But make sure the horse manure is well composted before using it.

A well draining soil is essential to ensure the roots don’t succumb to fungal diseases. For that we need water to move through the soil fairly efficiently rather than sitting in the soil for hours on end.

The watering requirements for broccoli will vary depending upon the quality of the soil and this includes its water retention capacity.

When it’s thirsty, the leaves will start to droop and they will feel thinner to the touch.

Crop rotation and growing organic broccoli

Even if broccoli is the only thing you grow: you need to understand this key and fundamental reason for crop rotation.

Growing brassicas like broccoli year after year requires a bit of planning and a number of different beds.   Crop rotation is a systemic approach to cultivating edibles. It’s based on pathogenic and nutritional theories.

Crop rotation is important for brassicas such as broccoli due to the risk of soil born pathogens. These pathogens, usually a fungus, can hibernate in the soil and affect the next seasons brassica crops. Therefore, some of these pathogens are host specific.

Therefore, due to the risk of pathogenic soil microbes accumulating year after year, it’s wise to plant brassicas in different places each year for say 3 years. So if we have three garden beds, we would plant our brassicas in bed one, then bed 2, then bed 3.

However, the reality is not this neat and clearly defined. We might choose one end of bed 1 and the other end of bed 2 for our brassicas this year, and one end of bed 3 and the other end of bed 1 in the second year…

If we only have one garden bed and we plant brassicas like organic broccoli this year, then for the next two years we shouldn’t plant brassicas at all. In stead we can plant silverbeet, legumes like peas and beans, we could try fennel as a perennial or tomatoes,

Note however that the same rule applies to tomatoes… if you grow then one year, grow them in a different place for the next two years.

The key is to make sure the roots come into contact with different soil and different microbes in successive years. Of course, as we add compost throughout the year, we are also adding more microbes and the healthier the compost the more likely any pathogenic microbes will be consumed. This is particularly the case if we’re not feeding them with more brassicas…

Nutritional theories of crop rotation suggest we plant brassicas like broccoli after nitrogen fixing plants such as peas and beans. However, this isn’t always practical mainly because most legumes such as peas and beans grow in the same season as brassicas. Secondly, if we’re growing perennials then crop rotation falters.


Growing brassicas from seed – tools we need

I’ve been growing brassicas like organic broccoli from seed for years. The time to start germination is when the weather starts turning cold. This is autumn to early winter.

This is what you need:

  1. Tube stock pots. I use 50mm tube stock pots because I had a commercial nursery and I still have heaps of pots. Many of us have small pots from previous plant purchases. We can also use the cardboard centre of toilet rolls, napkin rolls etc. If we’re using previously used pots, then be sure to sterilise them with diluted vinegar.  Many people say to use a chlorine or bleach but they’re only effective for bacteria. With pots, we’re mostly concerned with transferring fungal problems, for that we need vinegar.
  2. Seed: I use heirloom varieties. I like the variety that heirlooms provide and there are really cool ones like Broccoli Romanesco. That one forms a fractal flowering pattern.       Also, it makes sense to me to use heirlooms with organic gardens. I also like to save the seeds from key plants and I certainly don’t want a modern hybrid for that.
  3. Seed germination/raising mix: We need a compost that has a fine texture and no chunks. If it has chunks larger than say 1cm it’ll reduce germination rates. To our compost we need to add a fertiliser. If we use an inorganic fertiliser, then when we plant our brassica into our organic garden, we’ll be adding an inorganic plastic based substance that takes years to break down. So I use an organic fertiliser for all my pot plant work including seed germination. I also add some rock minerals.
  4. We may need a liquid organic soil wetter as some composts are hydrophobic.       I’ve written about soil wetters in a blog about dry pot plant and hydrophobic soil.
  5. That’s about it!


How to plant and germinate the seed

Fill the pots to the top with the seed raising compost. Gently put a bit of pressure on the top of the potting mix to firm down the mix. As you fill them, line the pots up in a container that will prevent them falling over.

Using a dibber, a screwdriver, a stick… whatever, make a small indentation in top of the potting mix. Poke the dibber into the soil about 3-5mm deep and push that soil to the side a bit.

Place one seed in each of the holes. Cover the seed with the displaced mix. So the seed should be buried under about 3mm of potting mix. I then sprinkle on some dust fertiliser and rock minerals.

Using a diluted organic liquid soil wetter, we can water them in using a watering can. Place them where they can receive morning to midday sun. This can be filtered light with up to 40% shade cloth.

Water them in the mornings and they should germinate within a week. Place them in full sun to prevent legginess. Once they have developed their fourth leaf, they’ll be ready for planting.


Harvesting organic broccoli

Depending upon the variety, our organic broccoli could be ready for harvesting in 6-9 weeks or 12-16 weeks.   It does depend on the variety. We can start harvesting when we see the flowers heads form. Depending upon the variety of broccoli we have, usually when we harvest the central flower head we can stimulate the growth of many many smaller flower heads. This can extend our harvest for a significant time.

When we start seeing the flower heads elongate that’s a sure sign that the flower heads are about to open into flowers.

Once that happens, the stems become a bit woody. Brassica flowers are delicate yellow blooms. Bees love them and I often let one or two plants go to flower just to make the bees happy.


Insects that like eating organic broccoli and some remedies

There are a number of insects that like eating our organic cauliflower. If the soil lacks nutrition we might see aphids or scale insects colonising underneath the leaves and sucking the sap of our organic cauliflower. Most often however, organic cauliflower is a target for the white cabbage butterfly, diamondback moth and other specialist herbivore insects.

One key predator to many caterpillars including the white cabbage butterfly caterpillar but also many other herbivore insects are parasitic wasps. Often we see their activity on our plants and our brassicas like our cauliflower is no exception.

Parasitic wasp cocoons on brassica

Parasitic wasp cocoons on a kale leaf.

Parasitic wasp cocoons on a cabbage leaf. Notice some of the cocoons have dots or holes in them? This indicates the wasp has left the cocoon and flown off to capture another caterpillar!

Adult wasps lay their eggs inside the body of living prey such as caterpillars and aphids. The larvae hatch and start consuming their host. In the case of this particular wasp, the larvae then group together and form a web of cocoons and down the track, wasps emerge.

So be on the look out for these cocoons and when you see them be sure to leave them. Also, given our predators need herbivore insects to feed on and to reproduce in, let’s start leaving more herbivore insects on our plants.

Land Cress (Barbarea vulgaris) is a companion plant to brassicas like organic cauliflower.  It has been found to effect the diamondback moth, flea beetle larvae and the white cabbage moth.  However, our Land Cress can work either as a sacrificial crop or as a dead end trap crop depending upon the genotype and expressed chemical compounds in the plant.

Another remedy for the white cabbage butterfly is BT or Bacillus thuringiensis v. kurstaki. This is a microbe (bacteria) that lives on the leaves of plants and consumes some leaf eating insects such as caterpillars. BT can be purchased and sprayed onto plants but dies off if not stored under say 4 degrees C (40 degrees F).


Diseases and issues with broccoli

Brassicas like broccoli are susceptible to a lot of disease issues. I’m not going to list them here. However, if we start seeing brown spots or lesions we may have a fungal problem. If the growth of our plant is leggy with small leaves we are likely to have a nutrition problem and a lack of quality organic matter in the soil.

The best remedy for diseases and nutrition issues is to get the soil right first and then plant. A healthy soil helps feed the plant with all the nutrients she needs and she can then fight off pathogens as required. If we do that, give our plants enough natural sunlight, the appropriate amount of water and rotate our crops we should be able to grow really tasty and really healthy organic broccoli.


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