Today we will review all of broccoli’s growing stages to help you become a better gardener!
One of the first things a gardener does when purchasing seeds is to flip the package over and see how long it takes to grow broccoli. Knowing the growing season’s length helps decide when to get your seeds planted and your broccoli growing!
Broccoli Total Growing Time
It takes 80 to 100 days for broccoli to go from seed to being ready to be harvested. The exact amount of time can vary depending on the broccoli variety and your local climate. When you start seeds indoors and transplant them, the transplant’s growth time to harvest is typically around 55 to 85 days.
Broccoli Germination Time
Broccoli seeds typically germinate in 10 to 14 days. This germination period is measured from initial planting to the formation of its first set of true leaves rather than the appearance of a radicle (as discussed later). Broccoli seeds can be germinated outdoors or started indoors and transplanted outdoor after it germinates.
Keep reading below for details of the actual growing stages broccoli goes through.
Broccoli Growth Stages
Broccoli (Brassica oleracea) is predominantly grown in the home garden as a cool-season annual, with the broccoli plant completing its life cycle in a single growing season. In reality, though, broccoli plants are genetically designed to grow as biennial plants completing their life cycle in two years. In home gardens, broccoli plants are typically pulled up when harvesting finishes; a new crop is planted the following year.
Broccoli is a cool-weather crop — it needs cooler air and soil temperatures to germinate and grow. Most people plant broccoli in the late winter or early spring for a summer harvest; gardeners in USDA zones 8 and higher can also plant seeds in late summer for a fall or early winter harvest.
Spring Plantings: Start broccoli seeds indoors in early spring, approximately 6 to 8 weeks before the last frost date.
Fall Plantings: Direct sow seeds into the soil sometime mid to late summer, when temperatures are at the season-high, so plants mature during the cool weather of fall.
Once you plant broccoli seeds, keep the soil moist at all times. Viable seeds, i.e., seeds capable of germinating, contain both an embryo and food reserves inside the protective seed coat. Through a process call imbibition, soil moisture softens the seed coat, allowing soil moisture to enter the seed. This moisture triggers internal cells to begin respiration and metabolizing the food reserves.
After sowing your broccoli seeds – regardless if you start seeds indoors or direct sow them in the soil — you can expect germination in about ten to fourteen days, which is standard for most garden vegetables.
The emergence of the radicle, also known as the primary root, through the seed coat is the first step in germination. The radicle’s job as the first emerging root is to anchor broccoli seedlings in the soil, holding the plants upright. Once the radicle emerges, it starts absorbing moisture and nutrients from the soil to drive plant growth.
After the radicle starts absorbing moisture and nutrients from the soil, the first shoot develops and emerges from the seed. Natural gravitational forces direct the shoot to grow upward, pushing through the soil, reaching toward the sun. Once the shoot breaks through the soil surface, the plant begins to direct its resources toward developing leaves.
First True Leaf Forms
During this time, plant growth is relatively slow as the broccoli has limited resources to draw from. The newly sprouted seedling still relies on the internal food stores in the endosperm to power all of its metabolic processes, but these stores are dwindling. It’s vital for the broccoli to form leaves and start photosynthesis.
It’s now that the first true leaf appears, a smaller version of the plant’s mature foliage. Photosynthesis begins, and the broccoli seedling is capable of producing its own food.
Third True Leaf Forms
With the ability to photosynthesize, the broccoli plant’s growth picks up at a more rapid pace. Plant growth hormones found inside the seedling’s newly developed, undifferentiated cells work together in overdrive to develop new leaves, including the third set of true leaves. Each new set of leaves increase’s the rate of photosynthesis, driving growth.
Vegetative Growth Continues
With the root system developed, and plenty of leaves for photosynthesis, the broccoli plant’s focus now switches to upward and outward growth. This stage of growth between germination and flowering is known as the vegetative phase of plant development. During this stage, the plant focuses on upward growth and storing resources to use for flowering.
Main Broccoli Head Forms
Most people are unaware of this, but the edible part of a broccoli plant is actually a flower head harvested before it blooms. For the plant to produce the main head, vegetative growth slows down to almost a standstill; all resources within the plant get directed to forming the main flower head sitting atop the broccoli stalk.
It is time to harvest broccoli once the central head is fully developed, but before the individual green buds open and display small yellow flowers. At this time, the main head is tight and compact, and the florets are a deep, vibrant green color. Each floret should be about the size of a matchstick.
Side Shoots Develop
After the main head of broccoli is harvested, apical dominance breaks. Plant hormones send internal messages to the cells within the plant, encouraging the development of side shoots off the main stalk of the broccoli plant. Over time, each of these side shoots grows and develops into a smaller, harvestable head of broccoli, extending the harvest.
Harvest each of these secondary flower heads off the plants when they reach the appropriate size.
When soil temperatures begin to climb, hormones within the plant trigger cells to elongate or stretch. Florets quickly become tall or leggy. Commonly known as bolting, this process occurs as the plant nears the end of its lifecycle in an attempt to go to seed. The green flower buds open up, revealing yellow flowers.
If any broccoli heads remain on your plants, make sure to harvest them immediately once they begin flowering.
In many home gardens, the life cycle stops here, and gardeners pull plants from the soil. However, if the plants are left to grow in the vegetable garden bed, they continue through the next steps, reaching full maturation.
Formation of Seeds
Pollination of the bright yellow flowers causes seeds to form in seed pods, as carriers of the plant’s genetic information.
Once seeds form, the plant has completed its mission and no longer needs to grow — its life cycle has come full circle. The broccoli plant directed almost all of its resources towards developing the newly formed seeds, leaving little for further plant growth. Plant growth hormones induce the genes responsible for senescence, and the plant perishes.