Broccoli and cauliflower are quintessential cool season vegetables to grow in your home garden. Like Brussels sprouts and other cruciferous vegetables, these guys thrive in the cooler temps of spring and fall.
While broccoli and cauliflower are fairly easy to tend in the garden, they can both be what we call heavy feeders. I’ve got some organic fertilizer options to keep these Brassicas happy and healthy while they’re forming their flower heads.
Did you catch that? Broccoli and cauliflower are kind of the odd-vegetables-out when it comes to the plant part that we eat. We grow lots of things for their nutritious leaves, which are typically ready for harvest fairly quickly, while we have to wait for other things to form flowers and then develop fruit from those flowers. We grow other things still for their juicy roots, and we have to practice patience while we wonder what’s happening underground.
We don’t grow broccoli or cauliflower plants for their leaves (though these are edible and taste like salad greens!), their roots, or their fruit. We grow these two for their flower heads, which should be harvested just before the flowers open.
That means that broccoli and cauliflower plants need more nutrients to help them grow strong than their cousins like kale and arugula. We actually need to fertilize them more like we would a fruiting plant—every couple of weeks and varying based on the plant maturity.
Let’s look at ways to fertilize your broccoli and cauliflower plants while they grow to ensure you end up with nice heads for harvest.
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The Best Way to Fertilize Your Broccoli and Cauliflower Plants Is in 3 Stages
Our focus when fertilizing vegetables in the garden is to use natural products, typically things that were alive (or passed through something alive) and have broken down into nutrient-rich matter. We try to avoid any synthetic fertilizer.
Stage One: Add Compost to Your Home Garden Soil to Give Broccoli and Cauliflower a Good Start
Before you sow broccoli or cauliflower seeds or transplant seedlings to your garden, make sure to add a 1- to 2-inch layer of compost to the top of your soil. This is a great way to add a little nutritional boost for young plants at the time of planting. Moist soil is also critical for both broccoli seed and cauliflower seed germination, and compost helps to hold moisture.
Stage Two: Use a Nitrogen Fertilizer to Help Younger Plants Get Established
While your cauliflower and broccoli plants are forming strong roots under the soil and frilly-edged leaves above the soil, it’s best to feed them with a fertilizer higher in nitrogen to encourage lots of green growth. I like MicroLife Ocean Harvest, which is an organic, liquid fertilizer that can be applied every 2 weeks.
Make sure to mix a liquid fertilizer according to the directions on the bottle and apply it as you water your plants. You can begin your fertilizing schedule as soon as you transplant seedlings to the garden.
Another organic fertilizer option to use at this stage is fish emulsion. Make sure to dilute it before applying. This might not be the best fertilizer option for you if you can’t stand fishy smells, though they do sell deodorized products.
Stage Three: Switch to a Fertilizer That Encourages Flowering Once Mature Plants Begin to Form Heads
Like I said before, the broccoli heads that we typically eat are actually clusters of closed flower buds that we harvest before those flowers bloom. Same goes for cauliflower. Once the plants begin to form these central flower heads, we don’t want to encourage them to grow more leaves for us by adding too much nitrogen. Instead, we want the plants to focus on forming nice, large heads, and we can encourage them to do so with a fertilizer that promotes flowering.
I like MicroLife Maximum Blooms, another liquid fertilizer that can be applied every 2 weeks.
More Growing Tips to Help You Get a Large Main Head of Broccoli or Cauliflower
It’s not just fertilization that’ll help you grow large mature heads for your broccoli or cauliflower. Here are some other tips to make your season a success.
1. Make Sure You’re Growing Broccoli and Cauliflower in the Right Growing Season
Broccoli and cauliflower need cool air and soil to germinate, and they both continue to grow best when the temperature is below 75 degrees Fahrenheit.
Here in Central Texas, we can grow these guys as a fall crop by planting them in late September or October for a late fall harvest or winter harvest, and then we can grow them again in late January or February for an early spring harvest.
The simplest way to determine planting time for broccoli and cauliflower is to work back 4 to 6 weeks from your last frost date. This is when you can start seeds for these plants indoors under a grow light.
Central Texas Monthly Planting Guide
Take all the guesswork out of your seasonal planting.
2. Start Broccoli and Cauliflower Seeds Indoors to Get a Head Start on the Growing Season
Broccoli and cauliflower both need between 50 to 100 days to grow to maturity, depending on which variety you’re growing.
If your cool season doesn’t last a full 100 days, then it’s best to start broccoli and cauliflower seeds indoors ahead of time so that you can move seedlings outdoors as soon as the weather cools. (Follow the steps in our indoor seed starting guide to ensure success, and check out my favorite broccoli varieties and cauliflower varieties to grow from a great seed company.)
3. Or Buy Well-Grown Broccoli and Cauliflower Seedlings from Your Local Nursery
Buying a healthy plant start from local nurseries or garden centers is a great way to get a head start on your season if you don’t want to start broccoli and cauliflower seedlings indoors yourself.
Plant your transplants slightly deeper than their root ball in your garden, all the way up to the first set of leaves to give them extra support as they adjust to your space.
4. Give Broccoli and Cauliflower Full Sun
Make sure to plant your broccoli and cauliflower in a spot that receives at least 6 hours of direct sunlight each day. These plants need lots of energy to form large heads. If, however, you’re expecting warmer temperatures, you might want to give these plants some afternoon shade.
5. Grow Broccoli and Cauliflower in a Raised Garden Bed Filled with Fertile Soil
These Brassicas love more sandy soils that are rich in organic matter. They like a consistently moist soil but hate having their roots sit in a bath. The combo of a raised bed and well-drained soil mix will keep many of your favorite veggies happy.
6. Cover Broccoli with Shade Cloth During High Temperatures
“Buttoning”, or producing a smaller head than expected, occurs when broccoli and cauliflower are stressed by the heat. Cauliflower in particular has even less heat tolerance than its cousins. Use a shade cloth to keep the air and soil underneath cooler during warm days.
7. Ensure Your Plants Get at Least 1 Inch of Water a Week
Water is pretty important to broccoli and cauliflower developing those nice mature heads. If you’re not getting at least 1 inch of rain per week, supplement with a nice, deep soak from the garden hose or use drip irrigation lines.
8. Check Your Broccoli and Cabbage Plants for Pests
Cabbage worms, cabbage loopers, slugs, and snails all love snacking on your growing Brassica plants. You can protect your plants with some simple garden mesh or fabric tulle as a physical barrier. For best results, cover the moment you sow seeds or set transplants outside.
Larger pests can be picked off by hand and tossed into soapy water. If cabbage loopers are an issue (you’ll notice round holes on the outer leaves), consider using insecticidal soap and Bacillus thuringiensis (Bt) on your plants to prevent these pests from decimating your crops. Spray the back and front of the leaves.
9. Cover Broccoli and Cauliflower Plants Before a Freeze
Both broccoli and cauliflower can typically handle temps as low as 26 degrees Fahrenheit without damage, but it’s best to go ahead and cover them with some old sheets, frost cloth, or a row cover if we’re expecting a freeze. Most plants appreciate a little extra protection from extreme temps while they’re doing their thing.
10. Don’t Pull Your Broccoli Plants from the Garden After You’ve Harvested the Main Head
Broccoli plants will develop side shoots off the main stalk if the weather is still nice and cool at harvest time. These side shoots will develop into small heads you can cut and enjoy. Cauliflower, unfortunately, only ever produces the one main head.
Lettuce Help You Grow
I hope these tips help you grow the largest broccoli or cauliflower head ever! If you still need a garden space installed or if you’re looking to improve on your current setup, we’d be happy to design your garden, come do a garden check-in, or give you one-on-one advice in person or over Zoom. Just click here to grow with us!