Climate
Broccoli plants require a moist, cool climate to thrive. Broccoli can be grown in cold areas, but heat tolerant varieties are necessary for people in warmer climates. Broccoli will die in the heat of summer and is not tolerant of extreme cold. This makes the timing of when to start broccoli seeds for fall important. It also means that it’s best to start your broccoli seeds indoors 6 to 8 weeks before you plan to transplant outside.
Indoor seedlings can be started in either small pots or a soil block with 5–7 seedlings per block for an even more compact and easy-to-transplant approach. To maximize germination success, cover the seeds with 1/4 to 1/2 inch of soil or vermiculite and keep them moist and warm while germination takes place. A temperature of between 64 and 75°F (18-24°C) is ideal. Once most of the seeds have germinated, reduce water application and reduce the temperature to between 60–70°F (15-21°C).
Planning
When harvesting a fall crop, it’s important to plan a few steps ahead. To produce high yields, consider the average first-frost-free date for your area and calculate the recommended number of days for the broccoli variety you plan on growing. For example, if you plan on growing a broccoli variety that takes between 70 and 90 days to mature, you will want to plant your seeds six to eight weeks before that first frost-free date. This will allow enough time for your seedlings to mature and be harvested before cold temperatures arrive.
Depending on your soil type, you should also consider adding compost or other soil amendments when planting. Broccoli prefers a sandy loam soil with a pH level of 6.0–7.0 and a soil that has been enriched with manure or compost a few weeks before planting. Add two to four inches of manure or compost and work it into the soil to the depth of six to eight inches.
Transplanting
Before transplanting, harden off your seedlings by gradually introducing them to the sun and cooler temperatures. Start by leaving the seedlings outdoors for one or two hours each day, gradually increasing the amount of time they are outside. By slowly acclimating the plants to the harsher environment outside, you will increase their chances of success.
Plant broccoli seedlings in a sunny spot with at least six hours of direct sunlight each day. Space the plants 18 to 24 inches apart, depending on the variety. Firmly press each seedling into the soil and mound the soil slightly around the base of the stem to protect the roots from the cold. Be sure to water the plants immediately after planting.
Pest Control
As with any crop, it’s important to monitor your plants for any signs of disease or insect pests. Regularly scout your garden for pests and make sure to catch pest issues early. Treatment may include row covers, hand picking, beneficial insects, or organic approved sprays.
Additionally, if birds present an issue in your garden, protect the broccoli with cheesecloth or netting. It is best to cover the plants in the early stages of growth to ensure that the netting is properly secured.
Fertilization
Fertilize your broccoli plants every two weeks or so throughout the growing season. Broccoli requires a balanced fertilizer containing nitrogen, phosphorus, and potassium. As an alternative, you can use fish or seaweed emulsion, manure tea, or compost tea to keep your plants healthy.
Also, keep in mind to avoid over-fertilizing as this can cause leaf loss and decrease the overall quality of the harvest. To avoid any nutrient deficiencies, have your soil tested and provide the necessary fertilizers during the growing season.
Harvest
When harvesting, broccoli should be harvested when the heads are tight and crisp. Avoid over-harvesting by cutting off just the heads and leaving the plants in the ground. This should result in more side shoots and an extended broccoli harvest. If the heads start to yellow, they are past their prime and should be removed. Be sure to practice proper storage techniques to maximize the freshness and quality of your broccoli.
Prevention and Protection
Plant broccoli in an area that has good air circulation to reduce the chances of mold and mildew. You can also employ preventative measures, such as spraying water and milk, to keep the plants healthy and protected. Additionally, spacing your plants further apart and staking or trellising the plants can prevent diseases caused by overcrowding.
Also, be sure to keep the soil mulched with straw or grass clippings to help retain moisture and reduce weeds. Keeping the garden tidy helps to keep pests away. If your plants start to show signs of stress, such as yellowing or wilting, move them to a shadier, cooler spot and water them more frequently.
