Broccoli is a biennial crop that can typically be grown for harvest twice a year (spring and fall). It’s not particularly difficult to grow, but it does require a few simple things to have a successful crop and harvest. Here’s how to plant, grow and harvest broccoli.
How to grow broccoli
Broccoli is a cool weather crop and timing is essential to a good harvest. It can be planted twice a year in most climates, in the early spring (ensuring the harvest is before it gets too hot) and in the fall (ensuring the harvest is before a hard freeze).
It’s a fairly hardy vegetable, but it’s temperamental when it comes to timing. It will bloom too early if it is exposed to temperatures below 40 or above 75-80 too early in the process. I usually have issues with timing, truth be told. But, it’s my own fault.
Growing Broccoli as a spring crop
To grow broccoli in the spring, start the seeds indoors about 7-9 weeks before the last frost for your zone. In zone 5 (where we currently are) that’s around March 15 (give or take a few days).
You can direct sow the seeds when the soil is workable and above 40 degrees, but you’re more likely to have a better harvest if you start your seeds indoors. The optimal temperature for germination is 75˚F.
You’ll want to plant them about 1/4″ to 1/2″ down in the pod and water thoroughly. Keep your seeds covered until they germinate. You can expect germination in about 5-10 days.
You’ll want to use a grow light (or a florescent light) kept close to your seedlings for the best results. This will prevent them from becoming too leggy. Keep light on them 14-16 hours a day.
A south facing window will also do, just make sure you turn your tray daily to keep them from reaching one direction or the other.
Transplant your seedlings when they have a minimum of 2 sets of true leaves about 2 weeks before your last frost date (around May 1 here, generally) after hardening them off for about 4 days.
You don’t want your seedlings to become too mature before transplanting them or they may experience transplant shock. And you also don’t want your transplants to be too leggy or they may form small, button heads and flower early.
Growing Broccoli in the fall garden
Growing broccoli in your fall garden can be very rewarding. Unlike in the spring, the weather isn’t quite as unpredictable and you generally won’t see small, button heads due to too cold temperatures for the transplants or early flowering due to extreme, early heat.
You will start your seedlings indoors for this as well (or I recommend it). Start your seeds indoors 15 to 17 weeks before your first expected frost. You’ll start them the same way you did the spring crop.
Transplant your seedlings outside into the garden when they have at least 2 sets of true leaves, about 10 to 12 weeks before your first expected frost. The plants will mature and be able to withstand the cooler autumn temperatures and provide you with a great harvest.
If any of your seedlings are leggy, they can be planted up to their first set of leaves when transplanted to create stronger roots.
Where should you plant broccoli?
Broccoli grows best in full sun, though it will tolerate partial shade, especially if you’re planting a spring crop, it can be some much needed relief.
It prefers well draining, compost-rich, moist soil that is slightly acidic with a pH level around 6.0 and 7.0.
Add plenty of organic matter to the soil prior to planting. A good layer of well aged compost mixed into the site will provide nutrients your broccoli needs.
Take your transplants and plant them about 12″ apart at a depth slightly deeper than their container. For intensive planting, you can space your rows 24″ to 36″ apart.
Your plants will thrive in temperatures between 50˚F and 70˚F. As long as your fall crop has begun to mature before frost hits, you might be able to harvest broccoli into late November and December.
Mature plants are frost hardy down to 20˚F and the leaves will perk back up as the weather warms during the day.
Water broccoli deeply and mulch around your plants for weed and disease control and to help keep the soil cool and moist.
Companion planting your broccoli
Broccoli will yield the best flavor when it is planted near celery, onions, garlic, and potatoes.
It will also do well planted near radishes, bush beans, and beets.
To repel insects, you can interplant fragrant herbs like chamomile, tansy, oregano and mint.
Flowers that do well with broccoli are nasturtiums, cosmos, and marigolds. These plants also help repel some common pests from your broccoli and other cole crops.
Broccoli gets along well with just about everything in the garden, except for other brassicas. Since broccoli is a fairly heavy feeder, you don’t want to plant broccoli where a brassica was planted in the past season and you don’t want to plant them too near each other as they will compete for nutrients.
The brassica family consists of broccoli, brussels sprouts, cabbage, collard greens, kale, and kohlrabi. Broccoli also fails to thrive when planted near tomatoes, pole beans, sweet corn, strawberries, squash and watermelon.
Care of Broccoli
If you get the timing right, broccoli is fairly easy to grow, though it is a heavy feeder so it does require some nutrition to really thrive.
Water & Fertilization Needs
Broccoli requires about 1.5″ to 2″ of water a week. If mother nature doesn’t provide that much rainwater, you’ll have to water the plants yourself. Try to mind the rainfall with a rain gauge as overwatering can cause disease problems.
Water the plants slow and deep. If you need to water the plants with the garden hose, keep the water flow low and use the sprinkler or mist setting if you’re utilizing a sprayer.
When watering by hand focus the water at the base of the plant and not on the leaves to help prevent fungal diseases.
Broccoli is a heavy feeder, so supplementing it about once every 3 weeks after transplanting will help it.
Working compost into the soil before transplanting will help feed it for the first few weeks, then once ever 3 weeks or so until harvest. You can use fish emulsion, which is well balanced or find an organic, balanced granular fertilizer and sprinkle it around the plants.
Avoid adding any fertilizer directly to the plants or getting it on the stalks so as to not “burn” the plants.
Common Pests & Diseases
Broccoli is susceptible to a few pests and common diseases. Particularly fungal diseases.
You can help prevent a lot of these problems by ensuring your pH level is adequate and practicing good crop rotation. Do not plant brassicas in the same area more than once every 3 years.
Proper spacing to promote adequate airflow is essential to prevent fungal disease.
If your leaves are curling, you may have aphids wreaking havoc and sucking your plants dry.
You can create some soapy water with dish soap and apply it to the leaves to easily combat aphids.
Cutworms will cut young seedlings off at ground level. Seemingly healthy plants will look like someone went through and did an awful hack job in the morning when you go to check your garden.
Planting sturdy transplants as opposed to direct sowing seeds can help prevent this problem from occurring. You can also put a collar around the seedling until it matures enough.
Once in a while cutworms will bore into the leaves of mature plants, you can treat the plants organically with bT.
Like most cole crops, broccoli is highly susceptible to these cabbage worms. They are the larvae of those pretty white butterflies we often call cabbage butterflies flying around the garden.
There are ways to control cabbage worms in the garden, one is any time you see cabbage butterflies, go check the underside of the leaves for eggs. It’s a problem you have to combat early on. You can also treat with bT.
Downy mildew is caused by a wet growing season and lack of airflow. Generally it results in a fungal infection that causes yellowing leaves.
You can prevent downy mildew by not overwatering plants (if mother nature will allow it) and making sure there is good airflow between your plants. So, never plant too closely.
You can treat downy mildew by removing diseased leaves and spraying with neem oil.
This disease will result in wilting leaves and requires the entire plant, roots and all to be removed expeditiously. If you pull up the plant and the roots are misshapen, you have clubroot and it can transfer through the soil.
To combat the issue if it’s already occurred raise you soil pH to 7.2.
To prevent clubroot, make sure your soil pH is at least 6.0 before planting your broccoli.
How long does it take broccoli to grow?
Grown from seed, broccoli takes anywhere from 70 to 100 days to mature for harvest. Which is why most people start their seeds indoors or use seedlings from the nursery.
Transplants will take about 55 to 85 days to mature and harvest. So, when started indoors, you’ll be able to get your broccoli out of the garden before it gets too hot and starts to bolt.
Reasons broccoli won’t form heads
Timing is the number one reason for a broccoli not forming a head. Like I said earlier, if you plant too early or too late… your crop won’t be very bountiful.
Lack of water or nutrients can also cause lack of a head or a small, button head on broccoli.
Transplanting too late can cause no head to form due to the roots becoming root bound in the container.
Overcrowding can cause a broccoli not to head as well. While I’m all for intensive planting so that you can grow as much as possible in a small space, things still need room to grow.
Lack of patience could also be the problem. It may just not be ready depending on the variety you’re growing. Check your seed packet and see what the maturation rate is.
Can you eat broccoli leaves?
If your luck runs out and your broccoli just won’t form a head, harvest the leaves!
In fact, even if your broccoli does form a head, you can still harvest the leaves and they can actually be harvested at any time after they reach about 4″ long. Simply cut them off to harvest.
The leaves can be used in place of collard greens, kale, and chard. Though, their flavor is distinct. They do sweeten as they cook and can be cooked simply in just some butter with salt, but unlike most greens, they don’t wilt into nothingness.
When is broccoli ready to harvest?
When you begin to see a head forming in the center of the broccoli, begin checking it every day.
Most broccoli heads will be between 4″ and 7″ when ready to harvest, but this can vary greatly depending on the growing climate and season. Broccoli grown in the fall is often larger than broccoli grown in the spring, especially if it is a particularly hot spring.
Floret size is a pretty good indicator of whether or not the head is ready to harvest. If the outside florets are about the size of a match head, your broccoli is ready.
The ideal the buds will be tightly closed when you harvest. The color should be a deep green. If you start to see even a hint of yellow, harvest the broccoli head immediately, regardless of the size.
Harvesting is fairly easy. Simply take a sharp knife and cut the broccoli head stem about 5 inches below the head and remove it with a quick cut. Try not to saw at it, this can ruin your chance at another harvest.
Can you harvest broccoli more than once?
You can! Once you harvest the main head, side shoots will continue to grow off of the broccoli. You can look for the same signs as you did for the main head to know when they’re ready to harvest.
Simply harvest the side heads the same way you did the main head as they become ready for harvest. They will not be as large as the main head, typically but they are still broccoli!
How to store broccoli
Broccoli does not keep long at all once harvested and is best eaten fresh. You can store it in the refrigerator and use it within about 3 days. Do not store broccoli in a tightly covered container.
Broccoli can also be easily blanched and frozen. Once prepared, store it in a tightly sealed container in the freezer for up to one year.
Heirloom broccoli varieties to consider growing
A lot of heirloom varieties of broccoli exist and we try to stick with growing mostly heirloom varieties in our garden.
Calabrese is a great Italian variety of broccoli that produces medium, dark green heads. It’s known for its prolific side harvests after the main head is harvested and matures in 65 days.
Dicicco is another Italian variety that produces medium heads at different rates of maturity making it great for someone who wants a staggered harvest but doesn’t want to succession plant. It begins to mature in 50 days.
Purple sprouting is an incredibly cold hardy variety that produces multiple, small purple colored heads instead of one large main head. It often has the variety to over-winter.
Growing broccoli isn’t difficult after you figure out the proper timing and it produces a bountiful, healthy plant for your harvest. Some varieties can be incredibly beautiful (like purple sprouting).
Generally, you’ll want to grow about 4 plants per person to feed throughout the year. I hope you have fun with it!
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