Broccoli is a member of the Brassica family, commonly started from seed. Propagation applies to two methods of continuing its growth cycle: regrowth, which extends the yield of an established plant, and cloning, which creates a new, independent plant from a piece of the original. Understanding these methods is key to maximizing your harvest from this cool-season crop.
Extending the Harvest: Regrowth from Side Shoots
The most reliable way to continue harvesting from a single broccoli plant is by encouraging the growth of secondary heads, or side shoots, after the main crown has been removed. Once the central head is mature and harvested, the plant shifts its energy from apical dominance to lateral bud development. This physiological change causes smaller, but still edible, florets to develop along the main stalk and leaf axils.
To initiate regrowth, cut the main crown with a sharp knife, leaving four to six inches of the stalk and several healthy leaves intact. The remaining leaves perform photosynthesis, providing the energy necessary to fuel the development of new lateral buds. Consistent harvesting of these smaller side shoots will encourage subsequent flushes of growth until the weather becomes too warm.
Cloning Broccoli: Propagating from Stem Cuttings
Propagating a new, genetically identical broccoli plant from a stem cutting addresses the literal definition of cloning, but it is generally a difficult process for members of the Brassica family. Broccoli stems lack the natural rooting ability found in many other garden plants, making the success rate for this method inherently low. The technique involves selecting a healthy, non-flowering side shoot and taking a cutting that includes a few nodes, which are the points on the stem where leaves attach and where roots are most likely to emerge.
For the best chance of success, dip the base of the cutting in a rooting hormone to stimulate root formation. Place the cutting in a well-draining, sterile rooting medium, such as a mixture of perlite and peat moss. Keeping the medium consistently moist, but not waterlogged, is essential, as brassicas are highly susceptible to fungal rot. Using a hormone and a specialized medium significantly improves the odds of developing a viable root system compared to simply placing the stem in water.
Essential Care for Propagated Broccoli
Whether nurturing an existing plant for side shoot regrowth or attempting to establish a new plant from a cutting, specific environmental factors are needed to ensure long-term health. Broccoli is a heavy feeder, particularly requiring high levels of nitrogen to support the vigorous leaf and shoot growth that produces the harvestable heads. Applying a nitrogen-rich fertilizer after the initial crown harvest, or once a cutting has successfully rooted, will encourage continuous production of new florets.
Consistent soil moisture is necessary, as water stress can signal the plant to prematurely flower, a process known as bolting, which makes the head bitter and inedible. Bolting is also triggered by prolonged heat, as the ideal growing temperature is between 60 and 70 degrees Fahrenheit. Newly cut or stressed plants are vulnerable to common pests like cabbage worms and aphids. Regular inspection and preventative measures, such as row covers or organic pest control sprays, are necessary to protect the plant.