Understanding how broccoli grows is important to growing it. Partly, broccoli’s temperature sensitivity throughout its growth stages makes it different from other crops. Harvesting broccoli at the right time requires careful monitoring.
Broccoli flowers are similar to ornamentals, which send up a main stem with branching floral spikes. After the yellow flowers have bloomed, the broccoli becomes bitter and tough. So, harvest the broccoli when it is still in flower buds.
Broccoli is usually grown as a spring annual or an autumn one, depending on your growing zone. Keep a calendar on hand to keep track of when your broccoli variety is mature, whether you are starting from seed or transplants. The right conditions and timing are crucial for growing this nutritious vegetable.
01
Germination Stage
Broccoli Seeds
When a seed breaks its covering, a green stem emerges. Broccoli seeds germinate in 5 to 10 days at temperatures above 80 degrees Fahrenheit. Germination can be improved by soaking seeds in hot, boiled water for 24 hours before sowing.
Choose a variety that matures in your growing zone before the temperature reaches 75 degrees Fahrenheit. The maturation time varies from 50 to 70%.
Broccoli grows well in zones north of the equator with cooler temperatures during summer. Six to eight weeks prior to the last frost, start seeds indoors. Southern growers are more successful at planting broccoli in autumn. In zones 5 to 7, the typical weather patterns will determine your success. If temperatures in spring fluctuate or increase quickly, broccoli may not head up or the heads can bolt. Whether you plant seeds in flats or directly in the ground, starting them in mid- to late-summer can yield better results.
02
The Seedling Stage
Broccoli Seedling
The structure for photosynthesis and nutrient absorption begins to form during the broccoli seedling stage. The stem develops a root system and the new leaves appear. It is necessary to keep seedlings in the house for a period of two to three weeks, or until there are several sets of leaves.
Plan to plant spring-grown broccoli seeds one to two weeks prior to the last frost. Give the plants time to harden off. Transplant seedlings or seedstarts for autumn harvest when temperatures are between 65-75 degrees Fahrenheit on average each day.
03
Vegetative Stage
Young Broccoli Plant
In the vegetative phase, the broccoli plant begins to grow most actively. In the next four to five weeks, it will grow up to three to four feet tall and wide with large leaves.
The main stem develops a small head of unopened, green flower buds. This first flower bud, also known as the crown, is a common feature. From the main stem, branches start to appear. These are essentially flower stems which will also produce green buds when the plant reaches the flowering stage.
This phase of the life cycle is best suited to temperatures between 65 and 75 degrees Fahrenheit. It is important to have enough light, moisture in the soil, and nutrition because it takes energy for a flower to grow. Use fertilizers with higher levels of phosphorous or potassium. A head that is too nitrogen-rich may not form. At this stage, row covers provide protection against caterpillars as well as other insect pests.
04
Harvest (Flowering) Stage
Broccoli Harvest
The crown or stalk head of the broccoli grows larger with more green buds. The stems that branch off the main stalk start to produce green buds. They are tightly packed around crown. Keep an eye out for any signs that the flowers are about to open. In the case of broccoli bolting can happen when temperatures are above 75 degrees Fahrenheit on a daily average. Check your broccoli seed packet or calendar to determine the “days until maturity”.
The crown on top of the main stem should be 2 1/2-3 inches wide. The entire head can be up to 6 inches wide when combined with the branches.
Look for the flowerheads starting to separate from the stems. The green buds begin to swell, and then turn yellow. It only takes a few days after the process starts for the broccoli buds to turn into bitter, grainy vegetables.
Tip
The smaller florets will continue to grow from the leavestalks after the main head is harvested. These are also edible and can be harvested.
The FAQ
How long does broccoli take to grow?
Depending on the variety, maturity can range from 50 to 75 days after germination.
How long does broccoli take to develop a head of lettuce?
Temperature, nutrition and the type of plant planted are all factors that influence the heading up. Three to five weeks following planting, look for the first flower bud the size of a button on the main stalk. The plant will continue to grow until harvest. However, if temperatures are above 75 degrees Fahrenheit you should watch out for signs of bolting.
How many broccoli heads can you expect to get from a single plant?
The main stem and branches of the broccoli plant are considered a head. Each plant only produces one head. After the central large head has been harvested, new florets will continue to appear on the leafstalks. These are also edible, but they’re smaller.
