The 5 Broccoli Growing Stages

Broccoli is a cool-season vegetable. It is grown for the unopened flower heads that form a clump at the top of the plant. Some broccolis also have side shoots that grow smaller heads after the primary head is harvested.

Important Broccoli Facts

Broccoli is a biennial plant but is generally grown as an annual. We eat the unopened flower head of the plant and the stalk. Broccoli is a cool-season plant that grows best when the temperature is between 65-70 degrees F. The head is harvested when it is large enough, generally more than 2.5 inches in diameter. Waiting too late allows the flower head to open. When the flower head opens, the yellow flowers are fibrous and bitter, so the head is not good to eat then. After the primary head is harvested, many varieties will grow smaller side shoots with heads on them for the rest of the season. The primary head is ready 50-85 days after the seedling is transplanted. For seeds that are directly sown, add 30 days. 

The 5 Broccoli Growth Stages

*The exact time depends on the variety. 

The Beginning

The first stage is germination. During this stage, the coating on the seed breaks down, and the plant embryo within begins to grow. It breaks the surface of the soil and has two leaves. In broccoli, this stage takes about five to ten days when the temperature in the soil is 80 degrees. Most broccoli in the South is started inside on germination mats that hold the Temperature at 80 until they break the soil. In the North, broccoli may be directly seeded in the late summer for the fall season. The primary threat to seeds is rotting in the ground when it is too wet. Some birds or mammals may eat the seeds if they can find them, but that is rare. 

When considering what variety of broccoli to grow, choose a variety that will be harvested before the Temperature in your area reaches 75 degrees in the spring. In the fall, you can choose a variety that takes five to ten days longer to harvest because foliage grows in the heat, and the flower head grows when it cools. In the spring, start your seeds six weeks before your last frost date. In the fall, start your seeds about four weeks before the Temperature falls to 75 degrees. 

Growing Stronger

The next stage is the seedling stage. When the plant embryo breaks the surface of the soil, it becomes a seedling. If you use a germination mat to start the seeds, turn it down to 70 degrees or turn it off when most of the seeds have broken the surface of the soil. At first, the seedling has two leaves. It soon develops two more, the true leaves, at which point you can start to fertilize it with a weak solution of fertilizer once a week. Strong fertilizer will burn the baby roots and kill the seedlings. In addition to leaves, the broccoli seedling develops roots and can begin to take water and nutrients up into the plant. As the seedling develops, the stem thickens, and more foliage grows.  

The seedling grows until it is strong enough to survive outside, usually by the time it is four to six weeks old. Be sure and harden your seedlings off before transplanting them outside. Otherwise, they are unlikely to survive. In the spring, plant your seedlings outside one or two weeks before the average date of the last frost. In the fall, transplant your seedlings when the Temperature is between 65-75 degrees. The primary threat to the seedling is damping off, a fungal infection that kills seedlings that are overwatered. Space the seedlings eight to ten inches apart and the rows ten to twelve inches apart. 

Putting on Foliage

The third stage is the vegetative stage. Once transplanted, the broccoli plant begins to grow rapidly. In the next four to five weeks, the plant can grow to be four feet tall and wide. The button of the flower head develops and grows. The flowers are still tightly closed, and the head is very compact. Branches develop, which may develop other flower heads that are smaller than the primary head in the center. 

Broccoli needs temperatures of 65-75 degrees F for this phase of development. It takes a lot of energy to develop a flower head, so broccoli needs lots of water and nutrients. Use a low-nitrogen fertilizer with phosphorus and potassium in it for the best results. Too much nitrogen can cause the plant to spend all its energy growing foliage. The flower head may not develop or will be small. This is also the stage that is most likely to be attacked by insect pests and diseases. Row covers can help protect against insect pests. Planting resistant varieties can help protect against diseases. Make sure the transplants are planted far enough apart, so they have lots of air circulation. Poor air circulation leads to fungal diseases. Water enough to keep the soil moist but not soggy, which leads to root rot. 

Time to Harvest

The fourth stage is the harvesting stage. Broccoli heads are ready to be harvested 50-80 days after transplant. If you are starting broccoli from seed, add 30- 35 days to that. Broccoli heads should be harvested when they are 2 1/5- 3 inches in diameter. Waiting for the heads to get larger can cause the buds to start opening, which ruins the head for eating. If you look at the head and see a hint of yellow, harvest it immediately. Before it blooms, the flower head will also spread out. The flower buds will open when the Temperature gets to be around 75 degrees F for several days. 

Harvest the head with a sharp knife. Cut the head off with about six inches of the stalk. After harvesting the primary head, side shoots will often develop heads that are smaller but still good to eat. Cut these off and include the stalk down to the first leaves. 

Storage

Broccoli can be stored in the refrigerator crisper drawer for ten to fourteen days. Broccoli can be eaten raw and cooked. To save it longer, broccoli can be blanched and frozen. To blanch the broccoli, drop the pieces of the head into boiling water for two minutes. Immediately drop the pieces in cold water to stop the cooking. Drain the pieces and put them in plastic freezer bags, and freeze. 

Flowering Stage

The fifth stage is the flowering stage. If the broccoli head is not harvested before it opens, the plant has entered the flowering stage. Pollinators will pollinate the flowers, and they will produce seeds. Most broccoli are never allowed to reach this stage because they are harvested before the head opens. Sometimes, though, the head will bolt, or open prematurely, before it can be harvested.

How Many Broccoli Heads?

The head is the main flower head and the stalk. Each broccoli plant has one head. Many varieties will grow small florets, or small flower buds, on side shoots. These florets are smaller than the head but are edible. 

Problems With Premature Flowering

If the broccoli plant is exposed to warm temperatures, then a period of cold weather, then warm temperatures, it will bolt. This is where the flower head opens prematurely. Bolting ruins the head.

Collecting Broccoli Seeds

To collect seed, you need to allow the seed head to open. When the flowers dry on the plant, the seeds are ready to be harvested. Broccoli seeds are very small, so place a paper bag around the flower head and fasten it closed around the stalk. Cut the stalk off and turn the bag upside down. Shake it to loosen the seeds from the flower head. You should find small seeds on the bottom of the paper bag. Store them in a jar or envelope in a cool, dry place. Do not freeze them. 

In conclusion, broccoli plants go through four stages of growth between when the seeds are planted and the broccoli is harvested. Most broccoli are not allowed to reach the fifth stage, flowering, because the head is harvested first. If you want to save broccoli seeds, you will have to let the head open, which ruins it for consumption. When the flowers dry, the seeds are ready to be collected.