Organic cauliflower white

The best way to grow organic cauliflower

Growing organic cauliflower over the winter months is very rewarding. Some varieties are faster growing than others. Some varieties form smaller flower heads whilst others form large heads. Some cauliflower heads are white and some are purple!

If you haven’t grown Cauliflower Purple Sicily you definitely need to try it. To increase the depth of the purple bud, we simply wrap some of the larger leaves around the developing flower head and shade it from the sun.


Organic cauliflower likes a rich soil

Brassicas like cauliflower generally like full sun 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 cauliflower is about 20cm deep.

The soil needs to be rich. That means plenty of compost for microbes and worms; and well, rotted manure such as horse manure and some rock minerals. People speak of cauliflower needing a nitrogen rich soil. In a natural, organic garden, that means a rich and fertile soil full of diverse, aerobic microbes and worms.

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 amount of water we supply will depend on our soil and it’s water retention capacity.

All brassicas communicate their thirst by droopy leaves.  They also respond very quickly to water.  Therefore, the best way to work out watering requirements is to get to know how our individual plant species respond to water.


Crop rotation and growing organic cauliflower

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

Growing brassicas like cauliflower 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 cauliflower due to the risk of soil born pathogens. These pathogens, are a type of microbe and they can hibernate or over-winter in the soil and affect the next seasons brassica crops. Therefore, some of these pathogens are host specific.

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 each year.

If we only have one garden bed and we plant brassicas like organic cauliflower this year, then for the next two years we shouldn’t plant brassicas at all. Instead we can plant silverbeet, or 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 them 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 (both good and bad) in successive years. Of course, as we add compost throughout the year, we are also adding more microbes (hopefully more good than bad) 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 cauliflower 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 nutrition based systems of crop rotation falters.


Growing brassicas from seed

I’ve been growing brassicas like organic cauliflower 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 or 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 reducing the risk of transferring fungal problems. For that we need vinegar.
  1. Seed. I use heirloom varieties. 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.
  2. Seed germination/raising mix. We need a compost mix 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.
  3. 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.
  4. That’s about it!

Using our compost mix we fill the pots to the top. Gently put a bit of pressure on the top of the potting mix to firm down the mix, but don’t push too much. We don’t want compacted compost. As you fill them, line the pots up in a container. This prevents 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. Therefore, the seed should be buried under about 3-5mm of potting mix. I then sprinkle on some dust fertiliser and rock minerals.

Using the diluted organic liquid soil wetter, we can water them in using a watering can. This ensures the soil in our pots isn’t hydrophobic. 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 or so depending upon conditions including the age and quality of the seed. Place them in full sun to reduce legginess. Once they have developed their third leaf, they’ll be ready for planting.


Harvesting organic cauliflower

Depending upon the variety, our organic cauliflower could be ready for harvesting in 9-12 weeks or 12-17 weeks.   It does depend on the variety.

Unlike broccoli, harvesting the main head of cauliflower doesn’t tend to stimulate the growth of more smaller heads. So once we’ve harvested the main head, the only edible part left are the leaves. I often harvest part of the main flower head rather than cut the whole head off. I harvest as I need rather than store excess in the fridge.
When we start seeing the flower heads change shape and elongate that’s a sure sign that our cauliflower is about to flower and go to seed.

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 cauliflower and their 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. Note the small dots on some cocoons? That indicates the wasp has left the cocoon and flown to catch 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 cauliflower

Brassicas like cauliflower 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 cauliflower.



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