Broccoli: Indoor or Direct Sow or Potted Vegetable
How to Sow and Plant
Broccoli may be direct sown or started indoors early for fall and spring crops, or purchased as transplants for a fall crop.
Sowing Seed Indoors:
- Start seeds indoors about 8 weeks before outdoor planting.
- Sow seeds ¼ inches deep in seed-starting formula
- Keep the soil moist at 70 degrees F
- Seedlings emerge in 10-21 days
- As soon as seedlings emerge, provide plenty of light on a sunny windowsill or grow seedlings 3-4 inches beneath fluorescent plant lights turned on 16 hours per day, off for 8 hours at night. Raise the lights as the plants grow taller. Incandescent bulbs will not work for this process because they will get too hot. Most plants require a dark period to grow, do not leave lights on for 24 hours.
- Seedlings do not need much fertilizer, feed when they are 3-4 weeks old using a starter solution (half strength of a complete indoor houseplant food) according to manufacturer’s directions.
- If you are growing in small cells, you may need to transplant the seedlings to 3 or 4 inch pots when seedlings have at least 3 pairs of leaves before transplanting to the garden so they have enough room to develop strong roots.
- Before planting in the garden, seedling plants need to be “hardened off”. Accustom young plants to outdoor conditions by moving them to a sheltered place outside for a week. Be sure to protect them from wind and hot sun at first. If frost threatens at night, cover or bring containers indoors, then take them out again in the morning. This hardening off process toughens the plant’s cell structure and reduces transplant shock and scalding.
Sowing Directly in the Garden:
- Sow in average soil in a sunny location in early spring or in midsummer for a fall crop.
- In rows 2 feet apart, sow seeds thinly and cover with ¼ inch of fine soil.
- Keep evenly moist. Water gently.
- Seedlings emerge in 10-21 days.
- Thin to stand about 16 inches apart when seedlings are 1-2 inches high.
Planting from Transplants in Fall:
- Select a location in full sun with good rich moist organic soil.
- Prepare the bed by turning the soil under to a depth of 8 inches. Level with a rake to remove clumps of grass and stones.
- Dig a hole for each plant large enough to amply accommodate the root ball. Space plants 1-2 feet apart in rows 2 feet apart.
- Carefully remove the plant from its pot and gently loosen the root ball with your hands to encourage good root development.
- Place the top of the root ball even with the level of the surrounding soil. Fill with soil to the top of the root ball. Press soil down firmly with your hand.
- Use the plant tag as a location marker.
- Thoroughly water and apply a light mulch layer on top of the soil (1-2 inches) to conserve water and reduce weeds.
How to Grow
- While small, floating row covers will help to keep pests at bay.
- Keep weeds under control during the growing season. Weeds compete with plants for water, space and nutrients, so control them by either cultivating often or use a mulch to prevent their seeds from germinating. Avoid disturbing the soil around the plants when weeding.
- Keep plants well watered during dry periods to promote rapid, uninterrupted growth.
- Monitor for pests and diseases. Check with your local Cooperative Extension Service for pest controls recommended for your area.
Harvest and Preserving Tips
- Pick broccoli when the heads have tight, firm buds. This happens about 50-60 days after transplant.
- Cut off central head along with 6 inches of stem so broccoli plants will produce smaller heads, which can also then be harvested.
- Broccoli may be frozen for future use. Cut florets and blanch them. To do this, drop into boiling water for 2 minutes, then plunge into cold water to stop the cooking, drain and store in freezer bags or vacuum bags.
- Eat the heads raw or cooked.
Common Disease Problems
Bacterial Leaf Spot: This causes brown water soaked spots on the foliage which eventually makes the foliage turn yellow. It thrives in cooler temperatures. Burpee Recommends: Remove infected plants. Rotate crops with plants in a different family. Avoid overhead watering. Do not work around plants when they are wet.
Damping Off: This is one of the most common problems when starting plants from seed. The seedling emerges and appears healthy; then it suddenly wilts and dies for no obvious reason. Damping off is caused by a fungus that is active when there is abundant moisture and soils and air temperatures are above 68 degrees F. Typically, this indicates that the soil is too wet or contains high amounts of nitrogen fertilizer. Burpee Recommends: Keep seedlings moist but do not overwater; avoid over-fertilizing your seedlings; thin out seedlings to avoid overcrowding; make sure the plants are getting good air circulation; if you plant in containers, thoroughly wash them in soapy water & rinse in a ten per cent bleach solution after use.
Downy Mildew: This fungus causes whitish gray patches on the undersides and eventually both sides of the leaves. Burpee Recommends: Rotate crops with plants in a different family. Avoid overhead watering. Provide adequate air circulation, do not overcrowd plants. Do not work around plants when they are wet.
Powdery Mildew: This fungus disease occurs on the top of the leaves in humid weather conditions. The leaves appear to have a whitish or greyish surface and may curl. Burpee Recommends: Avoid powdery mildew by providing good air circulation for the plants by good spacing and pruning. Contact your Cooperative Extension Service for fungicide recommendations.
Root Rot: This fungus causes damping off in seedlings, and in older plants, the leaves turn yellow and drop off, stunting occurs. The fungus can live in the soil for five years. Burpee Recommends: Rotate crops with plants in a different family.
Common Pest and Cultural Problems
Aphids: Greenish, red, black or peach colored sucking insects can spread disease as they feed on the undersides of leaves. They leave a sticky residue on foliage that attracts ants. Burpee Recommends: Introduce or attract natural predators into your garden such as lady beetles and wasps who feed on aphids. You can also wash them off with a strong spray, or use an insecticidal soap.
Cabbage Looper: These worms are green with a white stripe on either side, about 1-1.5 inches long. They tunnel through the heads. Burpee Recommends: Hand pick. Floating row covers can help prevent their laying eggs on the plants.
Flea Beetles: These small hopping beetles feed on plant foliage and can spread disease. Burpee Recommends: Rotate crops with plants in a different plant family. Use floating row covers to prevent damage to young foliage.
Leafminers: These insects bore just under the leaf surface causing irregular serpentine lines. The larvae are yellow cylindrical maggots and the adults are small black and yellow flies. They do not usually kill plants, but disfigure the foliage. Burpee Recommends: Remove affected foliage.
Slugs: These pests leave large holes in the foliage or eat leaves entirely. They leave a slime trail, feed at night and are mostly a problem in damp weather. Burpee Recommends: Hand pick, at night if possible. You can try attracting the slugs to traps either using cornmeal or beer. For a beer trap, dig a hole in the ground and place a large cup or bowl into the hole; use something that has steep sides so that the slugs can’t crawl back out when they’re finished. Fill the bowl about ¾ of the way full with beer, and let it sit overnight. In the morning, the bowl should be full of drowned slugs that can be dumped out for the birds to eat. For a cornmeal trap, put a tablespoon or two of cornmeal in a jar and put it on its side near the plants. Slugs are attracted to the scent but they cannot digest it and it will kill them. You can also try placing a barrier around your plants of diatomaceous earth or even coffee grounds. They cannot crawl over these.
What is the best region to grow broccoli? Because broccoli will prematurely flower if allowed to get too warm, gardeners in cooler regions grow broccoli best in spring and early summer. Gardeners in warmer regions can grow broccoli mid-fall through winter.
Why does my broccoli have yellow flowers and no broccoli? If you see flowers, your broccoli has prematurely flowered because of warm weather, OR your broccoli is over mature.
Why won’t my Romenesco broccoli form a head? Broccoli ‘Romanesco’ is really a green cauliflower. Like cauliflower, it is very sensitive to an inconsistent growing environment (fluctuations in weather, temperature and water). Gardeners in regions that have very even growing conditions can grow this variety best, as do greenhouse or hoophouse growers. This is also a very long season plant and it does not form heads until late in the season. It may not be mature enough yet.
When should I sow broccoli in the fall? If temperatures are over 85 degrees F in your area in August, start planting indoors in the beginning of August. If temperatures are consistently under 85 degrees in August, direct sown at the end of July.
My broccoli won’t form a head (blunting) or has formed a tiny head (buttoning). Why? The early development of a broccoli plant often affects head development; potted plants that were root bound before being planted out or transplants that experienced unusually cold temperatures after being planted out may blunt or button. Both experiences are considered transplant shock.