Bolting Brassicas in Winter: A Hidden Benefit for Pollinators

Starting brassicas and other cold weather crops in the fall are great fun to keep the harvesting season going after the summer bounties. There’s an even more important role these crops can play for our pollinators. We planted an array of turnips, beets, radishes, lettuce, Yod Fah (Broccoli Rabe), and Tiny Bok Choy in our vegetable bed. Some did great and others had different plans. Our brassicas - minus the brussels sprouts - decided to bolt, and rather than pull them up, we left them for our pollinators. Here’s why: 

Brassicas—such as kale, cabbage, broccoli, and mustard—are widely grown for their edible leaves and stems. Under certain conditions, these plants “bolt,” meaning they transition from vegetative growth to the formation of flower stalks and blooms which are rich in nectar and pollen. While bolting is often considered undesirable for crop production, it can provide significant ecological benefits, particularly for pollinators during winter and early spring.

Bolting occurs when brassicas experience stress or respond to environmental cues such as:

• Temperature fluctuations: cold followed by warmth (which Virginia is having more and more of on top of extremely low rain amounts) 

• Day length changes

• Nutrient imbalances

• Scarcity of floral resources: During winter, most native plants are dormant, leaving pollinators with limited food sources.

• Energy demands: Bees and other insects require nectar and pollen for survival and colony maintenance, even in cooler months.

• Early emergence: Some pollinators, like honeybees and certain solitary bees, become active on warm winter days and need to forage.

  

• Extended forage availability: Brassica flowers provide nectar and pollen when few other plants bloom. They also support early-season pollinators and overwintering bees.

• Diverse pollinator support: Pollinator diversity attracts honeybees, bumblebees, hoverflies, and other beneficial insects. It also enhances biodiversity in agricultural and garden ecosystems.

• Bridge between seasons: Flowers act as a “bridge” resource between winter scarcity and spring abundance. They also reduce stress on pollinator populations during critical periods.

• Leave some plants to bolt intentionally in garden beds or field margins. They also act as a hint of color when the landscape looks mostly empty.

• Avoid pesticide use during flowering to protect visiting insects.

• Combine bolting brassicas with other winter-blooming species for a continuous nectar supply. Mahonia, Witch Hazels, Daphnes and Winter Aconites are all great plants to have for winter color and nectar.

While bolting brassicas may seem like a crop failure, they can be a strategic ecological choice. By providing vital forage during winter, these flowers help sustain pollinator populations, which in turn support healthy ecosystems and future crop yields. Give it a try; last year we left our kale and brussels sprouts to bolt and yes, while it led to the infamous cabbage whites laying their eggs (which their caterpillars are fantastic to put in bird feeders), we saw so many different types of early pollinators feeding off the flowers.