How to Grow Broccoli From Seed
Cole crops fill temperate gardens with lush and edible foliage, flowers, and stems. Broccoli is one of the most widely grown cole crops, and for good reason! It sprouts dense, green heads with clusters of unopened flowers. Join seasoned grower Jerad Bryant in learning how to start this tasty crop from seed.
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Broccoli is closely related to other cold-loving species like cabbage, cauliflower, and mustard. It grows well during the cool seasons, performing spectacularly as a spring or fall crop. Growers in warm regions may cultivate it during the winter if there aren’t significant harsh frosts.
No matter the season you grow broccoli, you’ll enjoy harvesting its tasty, crunchy, and dense-packed heads when they’re ready. Chop them in stir-fries and sautés, steam them with salt and olive oil, or serve them fresh in salads and crudité platters.
Let’s not get ahead of ourselves—before harvesting big heads of broccoli, you must start seeds! They’re the cheapest and most efficient way to get your hands on multiple plants for the garden. Though nurseries sell starts, they’re often three to four times the price of seed packets! Save your budget and follow these steps instead.
Step 1: Find Cool Varieties
Everyone has their favorite varieties. Finding a cultivar that tastes great and grows well is crucial for success in your garden. If you don’t like eating the veggies you’re growing, you’re less likely to care for them! Start by finding a proper cultivar that thrives in your region.
Most broccolis prefer cool, moist weather and continuous access to direct sunlight. Try ‘Burgundy’ for purple-blue heads instead of green ones. ‘Belstar’ resists bolting in hot climates, growing well as a spring or fall crop in most regions.
Aside from head-producing broccolis, there are a few different ways to enjoy this tasty green! Try broccoli raab, a small head-producing form grown for its edible stems, flowers, and leaves. Stir fry the stems with your favorite veggie mix for a delicious side dish.
A final way to grow this vegetable is as sprouts or microgreens. Broccoli sprouts and microgreens are tender, crunchy, and flavorful. Their growing process is different than outdoor crops. Use a seed sprouter for sprouts or plant seeds in small flats for microgreens.
Step 2: Decide Where to Plant
Raised beds are ideal for growing this vegetable, though it’ll thrive in containers, in-ground beds, or borders. This crop needs access to full sun, consistent moisture, and regular airflow to thrive. Aside from environmental conditions, soil quality also affects your crops.
Plan on growing this veggie in an open site of your garden where there are six to eight hours of daily direct sunlight. It needs rich, fertile, and well-drained soil high in organic matter. This means excessive clay and free-draining sand aren’t good options; they’ll need amending ahead of time.
Amend soils with organic mulches like compost, leaf mold, or straw. Organic matter is anything biodegradable and beneficial for the soil. It’ll add some nutrients to the site, though its main benefits are increasing drainage, water retention, and structural integrity. The dirt grows alive the more organic matter it contains!
In particularly difficult conditions, consider using raised beds or containers. A container two feet deep and wide will work well, though larger containers can help you grow a bigger harvest. You can plant two or three plants in large pots in spring and replace them with peppers and tomatoes in summer.
Step 3: Prepare Beds or Containers
Now that you know where you’re growing broccoli, it’s time to prepare the site! You have two options when starting seeds: indoors or outdoors. Each method has its benefits and drawbacks, and some growers like to do both. Which style is right for you depends on your garden and how much space you have inside.
Indoor seed starting is best for gardeners with short growing seasons. You can start seeds ahead of time, harden the seedlings off, and put them in the dirt well before outdoor seeds germinate. Though efficient, this method requires lots of indoor space. You’ll need a bright windowsill or a shelf with grow lights to germinate seeds.
Outdoor seed starting requires less space, though you’ll have to protect the seedlings from pests, diseases, and adverse weather. Harsh frosts can zap the tender plants, while aphids, cutworms, and slugs can devour entire plantings in minutes. Protect them with row cover, or plant extra plants to compensate for future losses.
Step 4: Sow Seeds
Starting broccoli from seeds is magical; you watch tiny seeds germinate into giant plants! How to do it depends on your growing method:
Indoor Seed Starting
- Prepare small pots or flats with potting soil. Plant two seeds per pot, or sow them thickly in flats, burying them ⅛” deep.
- Water the soil well, but take care not to disrupt the newly planted seeds.
- Place the pots under bright light by a window or beneath grow lights.
- Add a small fan to encourage regular air circulation. Aim it near the seedlings, not directly at them.
- Move seedlings in flats to individual pots after they sprout true leaves.
Outdoor Seed Starting
- Plant seeds four to six weeks before your average last frost date. Bury them ⅛” deep in raised or in-ground beds.
- You may plant when soil temperatures hover above 40°F (4°C), though ideally when they’re 60-85°F (16-29°C).
- Keep the site moist, not soggy, and protect young seedlings from harsh frosts. Use a row cover or frost cloth to cover them.
- Thin seedlings so the plants have a foot or more space between them.
Step 5: Consider Light, Water, and Air
Your seeds should germinate a week or two after planting. After sprouting they benefit from continuous care to ensure they form proper heads at harvest time. Keep them well-lit, moist, and breezy.
Indoors, a small fan keeps air moving and helps the stems stay thick and strong. The seedlings resist outdoor winds better than those growing up in stale conditions.
Leggy seedlings are another curse of indoor growing! They often appear when light levels are low and insufficient. Move the plants closer to the light to help them beef up, or transplant them into containers and bury a portion of their stems so they’re less leggy.
Watch outdoor specimens to make sure they grow well. The outdoors provides airflow, water, and sunlight so you don’t have to! Step in only if natural rainfall is low and the soil dries excessively.
Step 6: Harden Off Seedlings
When you start broccoli from seed indoors, you must transition them outdoors to ensure they perform well in the garden. Hardening off is a process that’s essential for helping them adjust from inside to outside. You’ll slowly expose the plants to cold temperatures and bright sunlight to avoid shocking them.
Start by moving the seedlings outside after they have two to four true leaves and strong stems. Place them under dappled sunlight for an hour and back inside for the rest of the day. Each day, let them sit a little longer until they’re there for most of the day.
After a week, you can begin leaving them outside overnight. They’re ready for transplanting after a few nights outside. Move them back inside if you expect severe frosts, otherwise, they’ll be ready to plant in a few days!
Step 7: Transplant Broccoli Plants
Getting your crop in the ground at the right time will increase your chances of growing large, bulging heads come harvest time. Plant transplants one to two weeks before the last frost date in your area or two months before the first fall frost.
To transplant, dig holes for the seedlings’ rootballs. Make the holes as deep and twice as wide as the roots, place the plants in them, and backfill the soil until it reaches the surface. Water well, then add compost or a similar organic mulch on the dirt around the plants.
You may feed the growing plants before their heads form with an organic vegetable fertilizer. Most crops are ready for harvesting 50 to 60 days after planting, though some types may take anywhere from 60 to 85 days. Keep them moist and pest-free as you wait for the heads; they’ll start forming before you know it!
