5 Reasons Why Your Cauliflower Is Not Forming a Head

Cauliflower is a delicious veggie that has grown in popularity within the past couple of years due to its versatility in so many different recipes. But cauliflower can be a finicky crop to grow in the garden and leave you with less than ideal heads if they form a head at all.

The main reason that cauliflower does not form heads is due to stress on the plant. Common causes of cauliflower stress include nutrient deficiencies, temperature fluctuations, insect pressure, tight plant spacing, and lack of water. 

But don’t worry. I’m going to cover all of these things in detail and tell you what to do to prevent your cauliflower from becoming stressed. As a bonus, I’ll tell you the best variety of cauliflower to grow in your garden based on your hardiness zone.  

How long does cauliflower take to form?

Cauliflowers can take up to four months to reach full maturity from sowing to harvest time. Depending on what variety you choose to grow, you can expect to harvest your cauliflower between 65-100 days from when you first sowed the seeds.

If you’re someone who likes to purchase transplants, then you can expect your cauliflower to be ready between 45-85 from its planting date. 

If you started your own transplants then make sure to harden them off before planting them. Hardening-off is the process of getting your transplants acclimated to the outside world before you plant them to help prevent transplant shock.

Hardening off is as simple as taking your transplants outside during the day and then bringing them back inside at night. Do this every day for about a week and your cauliflower sprouts should be ready to face the world!

5 reasons your cauliflower is not forming a head

Cauliflower can be a difficult vegetable to grow because it’s so temperamental. Even the slightest amount of stress can cause heads not to form leaving you with lots of leaves that you can’t do much with. 

Here are some of the most common stressors to cauliflower and what you can do to help prevent some of these stressors. 

Nutrient deficiencies

Cauliflower are heavy feeders meaning that they take up a lot of nutrients from the soil. If you plant your cauliflower in soil that is already low in nutrients, then the cauliflower will have nothing to eat!

It’s always best to start the growing season with a soil test just to check and see what’s happening in your soil. The nutrients that you should be paying the most attention to are nitrogen, phosphorus, and potassium, or NPK. 

These three macronutrients are essential to the growth and development of all plants and a deficiency in any of them will mean stress and stunted growth for your cauliflower.

It’s always good practice to work in a thick layer of compost to your beds before planting to help return some of the lost nutrients to the soil. If your soil test indicates that you need more of something, then you can start applying fertilizers as well.

Depending on what state you live in, each soil test is a little different and it can be difficult to figure out what the numbers mean. Many states provide instructions on how to read your test results but if you’re still unsure, don’t be afraid to ask your local extension agent for help.

Fluctuations in temperature

Although cauliflowers are part of the brassica family, they are not as cold-hardy as some of their other brassica family members. 

Temperatures that swing too much between hot and cold will stress your cauliflower out and they will not form heads. During the transitions from spring to summer or summer to fall, the days tend to be quite warm but the nights can become drastically cold. 

To protect your cauliflower from the colder temperatures at night, you can cover them with reemay or some other kind of frost cloth. Use metal hoops to make sure that the cloth doesn’t touch any part of the plant. This can cause damage to the leaves.

Similarly, you can use shade cloth to help keep your cauliflower cool on warm days. The setup is pretty similar to how you would use frost cloth. Drape the shade cloth over the hoops that you’ve set up in your cauliflower row or bed. 

Then, find something heavy that you can use to hold the cloth in place and keep it taught. I’ve used sandbags and bricks but sometimes just shoveling some dirt along the edges is enough.

It’s also important to keep your cauliflower cool during the warm days otherwise they may bolt or go to seed. When a plant bolts, it’s because it thinks it’s reached the end of its life and quickly needs to produce seeds. 

You’ll know your cauliflower has bolted if it starts to send up flowers. You can snip these flowers off to slow down the bolting but unfortunately, once a plant has started to go to seed, there is nothing you can do to stop it.

Plants are too close together

Planting cauliflower too close together is a surefire way to cause stress among your plants. When plants are too close together, they don’t have room to spread out and grow into the big cauliflower you’re looking for. 

They will also start competing for nutrients and water. As I mentioned earlier, cauliflowers are heavy feeders so there need to be enough nutrients to go around or your plants will not form heads. The same goes for the water, which I will get to in the next section.

Good spacing for cauliflower is 24 inches, or 2 feet, apart from each other. For those working with smaller gardens, finding enough room to grow cauliflower can be tricky. But cauliflowers are actually a good option for container gardening due to their shallow root system.

Not enough water

On top of being heavy feeders, cauliflower are also heavy drinkers! Cauliflower needs soil that stays consistently moist about 6 inches deep. The soil around your cauliflower should never be dry.

If you live in a dryer climate, then staying on top of watering will be crucial to the success of your cauliflower. If you have the option, consider setting up some sort of irrigation system like a drip line to ensure your cauliflower is properly watered and to make it easier on you. 

Insect pressure

The two most common insects that affect the growth of cauliflower are flea beetles and cabbage worms. 

Flea beetles are tiny black insects that like to munch away on the leaves of many different garden plants but especially brassicas. You’ll notice spots on the foliage of your cauliflower that almost look as if someone took a needle and poked tiny holes all over the place. 

Cabbage worms are easier to spot than flea beetles simply because of their size. If you notice any green caterpillars about 1 inch in length, you’re probably looking at a cabbage worm. Check your cauliflower leaves for any holes and damage as you’re likely to find worms nearby.

Also, be on the lookout for any white moths flying around your cauliflower as these are the cabbage moths that lay eggs that hatch into cabbage worms. 

One of the best ways to treat flea beetles and cabbage worms is to sprinkle diatomaceous earth (DE) on the leaves of your plants. This powdery white substance is made of ground-up aquatic crustaceans and fossils which severely dry out the pests and make it impossible for them to digest the leaves they’re munching on.

DE is easily washed away by the rain so make sure to reapply as necessary. 

Another way to keep out insect pests is to cover your plants with mesh netting similarly to how you would with frost or shade cloth. This will especially keep the moths from landing on your cauliflower and laying more eggs. 

Best cauliflower varieties for your hardiness zone

Finding a cauliflower variety that is suitable for your plant hardiness zone is key to having a successful cauliflower harvest. Not sure what zone you live in? Check out the USDA Plant Hardiness Zone Map. 

I made this chart with variety recommendations for each hardiness zone to help you determine what variety is the best for your garden. 

Best Cauliflower Varieties by Hardiness Zone
Zone	Variety	DTM
Zone 4	Denali	70
Zone 5	Skywalker	80
Zone 6	Synergy	60
Zone 7	Snow Crown	50
Zone 8	Bishop	65
Zone 9	Twister	60

DTM = Days to Maturity from transplants

Takeaway

Hopefully, by now, you feel more confident in your cauliflower-growing abilities. Just remember to give them plenty of nutrients, water, and space and protect them from any major temperature fluctuations and insect pressure. 

Cauliflower can be a difficult plant to grow but don’t give up on it! With a little extra tender love, and care, your cauliflower will produce the big, beautiful heads you’re looking for.