Best fertilizer for Broccoli and Cauliflower

The best fertilizer for broccoli and cauliflower is blood and bone, organic liquid fertilizers like fish emulsion, aged cow manure, worm castings and compost. These fertilizers used together contain nitrogen for good leaf growth, phosphorus for good root development and calcium for stem and flower growth.

This article will explore the best types of fertilizer for broccoli and cauliflower, when to apply them and organic options for your home garden.

How to apply fertilizer to broccoli

Here are my top tips for the best way to apply fertilizer to broccoli at each timepoint in their growth.

Before planting seedlings

Before planting broccoli and cauliflower, dig aged cow manure, compost and worm castings through the soil.

Early growth

As the broccoli and cauliflower are growing add a handful of pelleted chicken manure or blood and bone around the root zone until you see broccoli heads form.

Use pelleted chicken manure or blood and bone fertilizer on broccoli and cauliflower.


Once your broccoli heads have sprouted do not apply any more fertilizer to your broccoli plant. The slow release fertilizers like pelleted chicken manure and blood and bone will support your plant for the next 2-3 months of growth.

Dig fertilizer into the soil before planting cauliflower and broccoli seedlings. These broccoli plants are around 4 weeks old.

The best natural fertilizers for broccoli and cauliflower

Aged cow manure

Dig aged cow manure through the soil before planting broccoli and cauliflower seedlings. This will add carbon rich organic material to the soil to improve soil structure and drainage. This will also attract and grow good bacteria and worms which will aerate the soil to encourage good root growth.

Pelleted chicken manure

Mix 1 handful of pelleted chicken manure into the soil for each broccoli and cauliflower seedling before planting. Add 1 handful of pelleted chicken manure around the root zone every 4 weeks as the plant is growing and water in well.  This will give your plant long lasting nutrients ready to sprout heads.

Broccoli plants will grow well with pelleted chicken manure added every 4 weeks until the head sprouts.

Worm Castings

Mix worm castings through soil before planting broccoli and cauliflower to add extra structure to the soil. The worm castings will also contain good bacteria which will feed worms in your soil.

Worm castings are great for broccoli and cauliflower as they will help the soil to hold moisture.


Homemade or purchased compost can be mixed through soil before planting broccoli and cauliflower at a rate of around 1 shovel full per plant. This will improve the water holding capacity of the soil, add nutrients and add extra nitrogen to your soil for good leaf growth.

I am making my own compost in my new compost bag out of fall leaves.

Liquid fertilizer

To boost your plants growth add a liquid fertilizer during the early stages of growth. Use a mild mix of liquid fertilizer like fish emulsion on growing seedlings to provide extra nitrogen to encourage fast growth and improve the soil at the same time.

I like to use fish emulsion on all of my plants including broccoli and cauliflower.

Blood and bone

Use a blood and bone based fertilizer every 4 weeks after planting broccoli and cauliflower until you see flower head form. Use blood and bone instead of pelleted chicken manure as both will benefit plants in similar ways. Blood and bone contains slightly more calcium so can produce stronger stems.

Check out the link from Amazon for a natural blood and bone fertilizer.

How to grow bigger broccoli and cauliflower

Choose the right size seedlings

Plant broccoli and cauliflower seedlings out when they are around 3-4 inches high. If seedlings are grown larger they will not transplant well and moving them can stunt their growth.

When buying broccoli and cauliflower seedlings from a garden center choose plant that have 2-4 true leaves. These leaves are larger than the first 2 leaves which will still be on the bottom of the stem. These will be at the perfect point to plant out in your garden.

Dig fertilizer in the soil before planting

Adding soil improvers like compost and worm castings and fertilizer like pelleted chicken manure before planting will give broccoli and cauliflower the best start. Adding fertilizer to the soil before planting will give your plants the best start.

Add extra fertilizer boosts like pelleted chicken manure or blood and bone monthly to keep your seedling growing strong until they form heads.

Mulch the broccoli and cauliflower with compost

Applying a nutrient rich mulch like compost around your broccoli and cauliflower will give them the extra nutrient boost they need to grow big heads. Put mulch around your plant as soon as you plant them out to prevent weeds.

Extra nutrients will be washed down from the compost to the plant roots when it rains or when you water. Add straw, sugar cane or hay mulch over the top of the compost layer to stop it drying out.

Water broccoli and cauliflower well

These plants love regular so make sure you keep the soil moist. Mulch will help the soil to stay moist for longer but you will need to check the soil and water by hand or irrigation regularly if the top soil is drying out.

Harvest your broccoli regularly

The best tip to keeping your spouting broccoli producing well is to harvest the stems regularly. These plants will produce a single head in the middle of the plant first. Once you harvest the central broccoli head it will send out smaller sprouts on the outside of the stem.

These broccoli stems should be picked regularly to keep the plant sending out more shoots. If the stems are left to flower, the plant will slow down and stop growing stems.

Cauliflower will grow 1 single head so you will get one harvest from each cauliflower plant. Pick the heads when they still look tight and have reached around 8 inches across. Pick the heads before the head start to spread out. This is what the head will do just before it will flower.

How to fertilize broccoli and cauliflower – Summary

The trick to growing broccoli and cauliflower successfully is to add fertilizer before planting and regularly while the plant is reaching its maximum size. Natural fertilizers are best for your garden and going organic will keep your plants happy and support your garden to find a natural balance of insects, soil microbes and worms for bigger harvests.

Happy growing.

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