Brussels Sprouts in Zone 7A — Mountain West

Brussels sprouts, with their nutty flavor that sweetens after a frost, are a rewarding crop to grow in our Mountain gardens. Freshly harvested sprouts taste far superior to anything you'll find at the grocery store, and they add a unique touch to fall and winter meals. Plus, you can't beat the satisfaction of harvesting your own food as the mountain air turns crisp.

Our high altitude, intense sun, and short growing season can present challenges, but with careful timing, Brussels sprouts are definitely achievable. Our roughly 173-day season means starting indoors is crucial, and knowing when to transplant is key. We'll walk you through it.

Starting your Brussels sprouts indoors is the best way to get a jump start on our short growing season. Aim to sow your seeds indoors from early to late March, about six weeks before you plan to transplant them outside. This gives them a head start against the clock.

Use seed trays filled with a good quality seed-starting mix. Keep the soil consistently moist – bottom watering is a great way to avoid damping off. A warm location and supplemental light (especially with our intense mountain sun) will encourage strong, healthy seedlings. Remember, spring can be late in the Mountains, so don't rush them outside too soon!

Transplant your Brussels sprouts seedlings outdoors from mid April through mid May, once the danger of hard frost has passed. Before planting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to our intense UV and fluctuating temperatures.

Space your plants 18-24 inches apart in rows. Our weather can be unpredictable, so watch the forecast for late-season frosts, and be ready to cover your seedlings if needed.

Consistent moisture is key to growing great Brussels sprouts, especially with our dry Mountain climate. Aim for about 1-1.5 inches of water per week, depending on rainfall. The finger test is your friend – stick your finger about 2 inches deep into the soil; if it feels dry, it's time to water.

Water deeply at the base of the plants to encourage strong root growth. Overhead watering can lead to fungal issues in some areas, but with our low humidity, it's generally not a major concern. Just try to water early in the day so the foliage can dry before nightfall.

Pay attention to your plants. If the leaves are wilting or yellowing, you're likely underwatering. If the leaves are consistently soggy and the plant looks droopy, you might be overwatering. A layer of mulch around your plants will help retain moisture and keep the soil cooler in our intense sun.

Brussels sprouts can get tall and top-heavy, especially when those sprouts start to develop. Our occasional strong winds at altitude can also cause them to topple over. Staking is definitely recommended.

A sturdy stake, like a bamboo or metal stake, works best. Install it when the plants are around 2 feet tall, driving it into the ground a few inches away from the stem. As the plant grows, gently tie the stem to the stake with soft twine or plant ties.

Pruning Brussels sprouts is pretty straightforward. As the sprouts develop from the bottom up, remove the yellowing or damaged lower leaves. This improves air circulation and directs the plant's energy to the developing sprouts.

About 3-4 weeks before your expected harvest, you can top the plant by cutting off the growing tip. This forces the plant to put all its energy into the existing sprouts, resulting in larger, more uniform sprouts. As our first frost approaches in early October, consider removing any tiny, undeveloped sprouts near the top of the plant, as they likely won't mature in time.

You can expect your first harvest from mid July through late August, about 90 days after planting. Look for firm, tight sprouts that are 1-2 inches in diameter. Start harvesting from the bottom of the plant upwards, twisting or cutting the sprouts off the stem.

Harvesting after a frost or two significantly improves the flavor of Brussels sprouts, making them sweeter and less bitter. Don't pull up the whole plant at once. Continue harvesting as the sprouts mature, and the plant will keep producing for several weeks.

As the first frost approaches in early October, harvest any remaining sprouts that are a decent size. Even if they're not quite fully mature, they'll still be delicious.

Aphids

• What it looks like: Clusters of tiny green, black, or white insects on stems and leaf undersides. Sticky honeydew residue. Curled or distorted new growth.
• What causes it: Rapid-reproducing sap-sucking insects thrive in warm weather. Ant colonies may farm them.
• How to fix/prevent it: Strong water spray knocks them off. Encourage ladybugs and lacewings. Insecticidal soap or neem oil for heavy infestations. Avoid excess nitrogen fertilizer.

Cabbage Worms

• What it looks like: Smooth green caterpillars chewing holes in leaves. Dark green droppings. White butterflies flying around.
• What causes it: Larvae of white cabbage butterflies. Multiple generations per season if we have a warm summer.
• How to fix/prevent it: Bt spray is very effective. Floating row covers prevent egg laying. Handpick caterpillars. Interplant with aromatic herbs.

Loose Sprouts from Heat

• What it looks like: Sprouts that don't form tight, compact heads. They're often leafy and bitter.
• What causes it: High temperatures during sprout development. Even our moderate-at-altitude summer heat can stress them.
• How to fix/prevent it: Consistent watering is key. Provide afternoon shade during the hottest periods. Choose heat-tolerant varieties. Mulch well to keep the soil cool.

Clubroot

• What it looks like: Stunted growth, wilting in afternoon heat, yellowing leaves. Roots are swollen and club-shaped.
• What causes it: Soil-borne pathogen that persists for years. Favors acidic, wet soil.
• How to fix/prevent it: Raise soil pH to 7.0-7.2 with lime. Improve drainage. Rotate brassicas on a 7-year cycle. Remove and destroy infected plants. Start transplants in sterile mix.

Mountain West Specific Challenges: Our intense sun can scorch leaves if plants aren't properly hardened off. The alkaline soil can also be a challenge, so amend with compost to improve drainage and lower the pH slightly. Hail can damage leaves and sprouts, so consider using netting if hail is in the forecast.

Companion planting can really benefit your Brussels sprouts. Green beans fix nitrogen in the soil, which Brussels sprouts need. Celery deters cabbage white butterflies. Onions and dill also deter pests. Potatoes don't directly help, but they don't compete for the same nutrients and have different pest issues.

Avoid planting Brussels sprouts near tomatoes, strawberries, or peppers. Tomatoes and peppers are heavy feeders and can compete for nutrients. Strawberries can attract slugs and snails, which may also target your Brussels sprouts.