Brussels Sprout Heritage

Brussels sprouts are part of the Brassica oleracea family (generally called “mustards”) that also includes broccoli, cauliflower, cabbage, kale, and collard greens. They are believed to be descended from wild Mediterranean kale grown in ancient Rome. Brussels sprouts, as the little baby cabbage vegetable we know today, were developed in the vicinity of Brussels, Belgium in the 13th century, becoming popular there in the 16th century. It took another two centuries for European settlers to introduce Brussels sprouts to North America in the 18th century and another couple of centuries to establish Brussels sprouts as a viable large-scale commercial crop in California in the 1900s. Today, the U.S. produces about 70 million pounds of Brussels sprouts annually.

Brussels sprouts have been cultivated and improved in the last century. Sprouts as we know them today have been bred to have higher sugar content and lower glucosinolates (i.e. sulfur smell, bitterness), making them a more appealing vegetable for the American palate.  Brussels sprouts are now often found in high-end restaurants served as an appetizer, in salads or as a side dish.

Late Season Care

Brussels sprouts may remain in the garden through October and possibly into early December in a mild winter year.  Brussels sprouts will readily survive in temperatures as low as 20 degrees but will die out when temperatures drop to 10 degrees or lower. In fact, Brussels sprouts need one or two frosty mornings before harvest to reduce any bitter flavors and concentrate the sugars in the sprouts.

To keep your Brussels sprouts healthy during the late season, follow these gardening tips:

1. Stop Fertilizing. Do not fertilize Brussels sprouts after the sprouts have started to grow in mid-summer.  You will see the sprouts growing on the stalk of the plant next to the leaf stems.

2. Mulch. Add a fresh layer of mulch around the plants to keep the ground temperature and moisture more uniform.  Leave about a 3” ring of clear ground around the stalks to reduce the chance of rot.

3. Water. Continue to water the Brussels sprouts plants until harvest.  Generally, Brussels sprouts need about an inch of water per week. However, the ground may retain water longer during cool weather so it is good to check if water is needed before watering. If the top one to three inches are dry when you poke your finger into the soil, then add water. Water around the base of the plant and avoid watering the leaves which could encourage disease.

4. Stake. Healthy Brussels sprouts will continue to grow taller and develop more sprouts along the newer stalks throughout the long growing season. Therefore, consider staking the plants in the autumn.  Staking will help support the weight of the growing sprouts. Staking will also promote air flow which can reduce the chances of disease.

5. Trim.  Commercial farmers trim leaves from Brussels sprout plants to concentrate the growth into the sprouts.  While this action is not necessary for the home gardener, trimming leaves will improve airflow and may encourage sprout growth.  Start by trimming the bottom 6-8 leaves and any yellowing leaves.  An additional 2-3 lower leaves may be trimmed each week to allow room for the sprouts that intersect those leaf stems to grow. Be sure to keep the largest and healthiest leaves at the top of the plant since they are needed to feed the plant.

6. Top Off.  Brussels sprouts mature from the bottom of the stalk upwards – i.e. the sprouts at the bottom will be larger than the sprouts at the top of the plant. To encourage the upper sprouts to develop faster, you can cut the off the top 2” to 5” of the main stalk.  Top off Brussels sprouts 20 to 45 days prior to final harvest (usually end of August or mid-September in Minnesota).

7. Wrap.  If you want to keep Brussels sprouts happy through a few freeze/thaw cycles, you could build a burlap-wrapped structure around the plants. This protection may help when night temperatures dip into the 20s, but the structure will not keep the plants alive during a longer stretch of harsher winter weather.

8. Observe.  Brussels sprouts will send you signals if they are not healthy. The plants may wilt or turn yellow during an autumn heat wave. Leaves may yellow and the plants may bolt if the plants are overwatered. Alternatively, brown spots and edges may develop on the leaves or sprouts if the plants are too cold. The newest growth will usually show signs of stress first.  Be prepared to adjust your care and possibly your harvest time to accommodate the plants’ conditions.

Harvesting and Storage

Brussels sprouts are ready to harvest when the sprouts are solid, bright green, 1-2 inches in diameter and tightly wrapped. Most of the leaves should still be green; do not wait until the leaves have turned yellow or are dying. In addition, the plants will be 2-3 feet tall and approximately 80-100 days old depending on the variety (check the seed package). Wait to harvest until after one or more light frosts which will improve the flavor of the Brussels sprouts.  Generally, Brussels sprouts are harvested mid-September to late October in Minnesota. A healthy Brussels sprout plant will yield between 60 and 100 sprouts.

Partial Harvest. Brussels sprouts start losing their flavor within a day or two of being picked.  You can retain the fresh flavor of the Brussels sprouts over a longer period by picking only some of the sprouts while maintaining the plants in the garden.  The plants will continue to grow and produce more sprouts on the new growth until the plants are topped off.  

Harvest the sprouts near the bottom of the plant first.  To pick a sprout, hold the sprout where it meets the stalk and quickly twist the sprout to snap it off. Alternatively, you can cut the sprout off the stalk with a knife. Remove the leaves left on the stalk near the sprouts you picked. Dispose of any yellow, brown or squishy sprouts and leaves. 

Dust off the sprouts but do not wash the sprouts before storing.  Store the sprouts in a perforated plastic bag in the refrigerator where sprouts should last for a week or more.  Alternatively, sprouts may be blanched and frozen for up to a year.

Complete Harvest. Harvest the entire Brussels sprouts plant when the temperature drops below 25 degrees on a regular basis.  To harvest, remove all remaining leaves and then cut the entire stalk one inch above the soil line.  Leave the healthy sprouts on the stalk but remove any sprouts that are discolored or show signs of rot.  Hang or stack the stalks in a cold storage area (e.g. garage, cellar or refrigerator).  A harvested stalk can be stored for 3 to 5 weeks at 32 degrees Fahrenheit. In fact, 32o is the temperature that keeps sprouts the freshest for the longest in storage or the garden. Avoid storing Brussels sprouts with apples, pears, or other fruits which will increase the sprouts’ bitter flavors.

After the Brussels sprout harvest is complete, it is best to remove the entire plant from the garden.  The plants may be composted or burned.  Remember to rotate crops in next year’s garden; a 3-4 year rotation is recommended for all members of the Brassica oleracea family. Then, pull out one of your favorite Brussels sprouts recipes and enjoy!

If you want to learn more about growing Brussels sprouts, please visit:

• https:/extension.umn.edu/vegetables/growing-brussels-sprouts#direct-seeding-229361

• http://yardandgarden.extension.iastate.edu/how-to/growing-brussels-sprouts-home-garden

• http://extension.illinois.edu/gardening/brussels-sprouts

• http://www.canr.msu.edu/uploads/files/brusselsprout2011.pdf

• http://www.rhs.org.uk/advice/grow-your-own/features/fascinating-facts-brussels#:~:text=The%20precursors%20to%20modern%20Brussels,crop%20in%20the%2016th%20century.

Photo credits: Cherise Skeba (1), Mollsmadeleine.blogsport.com (2)