Growing brassicas in your dome gives you so many choices! We are going to write about just a few: broccoli, cauliflower and romanesco.
- Family: Brassicaceae
- Botanical Name: Brassica oleracea
- Type: Annual, Vegetable (Broccoli and cauliflower can be biennial)
- Light: Full sun
- Soil pH: Acidic, neutral (6.0 to 7.5) can tolerate slightly alkaline soil
- Broccoli: variety Italica
- Zone 2–11
- Grows 18–30 in. tall, 12–24 in. wide
- Cauliflower: (Botrytis group)
- Zone 2–11
- Grows 12-30 in. tall, 12-24 in. wide
- Romanesco: (Botrytis Group) variety Veronica
- Zone 2a–11b
- Grows 12-18 in.tall,12-24 in. wide
Growing Brassicas
Growing brassicas will allow you to choose from many varieties with similar growing requirements. They are cool-weather crops that grow best in the spring and fall. In a dome greenhouse, they can continue to grow in the winter months. Nutrient-rich soil is important. Be sure to water well.
Best Location in a Dome Greenhouse for Growing Brassicas
Broccoli, cauliflower and romanesco all prefer a sunny spot in the dome.
Plant broccoli by mid-spring for a summer harvest and has a moderate growth rate.
Cauliflower does well with partial shade and has a moderately slow growth rate. Choose a location with a consistent temperature as cauliflower is sensitive to changes.
Romanesco is a cool-season crop and does not tolerate hot temperatures. The best planting location in the dome is the east zone.
Planting Brassicas
Broccoli – Plant broccoli seeds ½ inch deep. Thin the seedlings to 12-20 inches apart. Pro tip: Plants want airflow. Give them space!
Cauliflower – Plant cauliflower seeds ½ inch deep a few inches apart. Thin the seedlings to 18-24 inches apart.
Romanesco – Plant romanesco seeds ¼ inch deep. Thin the plants to 18-24 inch apart.
Growings Brassicas: Broccoli Care
Stress from heat, drought or long days may cause brassicas to bolt or go to seed. Choose varieties that are less prone to bolting and provide consistent moisture.
Broccoli plants are happiest with consistent soil moisture and that means regular watering. Water broccoli plants with 1-1 ½ inches of water at the base of the plant. Wet broccoli heads may develop rot.
The best temperature for broccoli is between 65-70 degrees F (18-21 degrees C).
Growings Brassicas: Cauliflower Care
Cauliflower prefers 2 inches of water per square foot every week with good drainage. A lack of water can cause cauliflower to taste bitter.
Some varieties are self-blanching variety and the leaves will cover the cauliflower head.
Cauliflower will grow better with a high-nitrogen fertilizer 3-4 weeks after transplanting the seedlings. If developing cauliflower heads are brown it may be a boron deficiency.
Pro tip: Cauliflower does NOT handle change well. Disruptions in temperature, moisture and other factors can force premature development. It can ruin the cauliflower head. Extreme cold may stop growth.
Growing Brassicas: Romanesco Care
Romanesco likes consistent moisture. Do not let the soil become completely dry. Fertilize after the plant is established. This will boost growth and help in the development of the complex green heads.
This plant prefers temperatures that range from the mid-60s to the mid-70s F. The best soil is high in organic matter. Note: Avoid planting romanesco in the same location. Rotating the crop location will help reduce diseases and pests.
Best Companion Plants for Growing Brassicas
Companion plants are a simple and effective way to help your garden thrive.
Growing brassicas with companion plants will help in many ways. Brassica companions are: celery, beets, dill, onions and lettuce. Dill is invasive and we don’t recommend growing it in your dome.
Broccoli companions include basil, chives, oregano, rosemary, sage and thyme.
Cauliflower companions are: beans, beets, celery, nasturtiums, onions and spinach. There are other friendlies you can plant in spring.
Romanesco’s companions include artichokes, beets, chard, peas, potatoes and yarrow.
Managing Brassica Pests and Diseases
Growing brassicas means you will be dealing with the same pests and diseases as other members of the cabbage family. Some of the usual suspects include cabbage worms, cabbage loopers, and aphids.
Lightweight row covers are an option for preventing some pests. Rosemary and sage can deter pests with their strong scent. And don’t forget the beneficial insects!
We recommend installing hardware cloth to keep rodents out of the greenhouse.
The most common diseases of brassicas are blackleg, black rot and clubroot. Rotate where you plant your brassicas each year and clean up debris at the end of the season. Keep a close eye on your plants and remove any diseased plants. We recommend soil testing each spring.
Black rot is a very common disease among brassicas. It affects the leaves, can limit your yield and is spread through water.
Blackleg fungus usually affects the stems and leaves of vegetable brassicas. Damaged stems can lead to the plant severing at the base.
Clubroot is a disease that affects brassicas. Infected plants may be stunted and wilt easily or have yellowing leaves. The root of the plant becomes swollen into thick roots with irregular shapes. Remove infected plants.
Growing Brassicas: Harvesting
Harvest broccoli between 50-90 days. The the head should be compact and tight. If the buds are open, it’s a bit late and they will be tougher to eat.
To harvest broccoli, leave about 6 inches of stalk with the head. To allow the plant to keep growing, make an angled cut. This will keep water from collecting on the cut surface and prevent new shoots from rotting.
Harvest cauliflower between 50-100 day. The head should be firm and compact. They usually grow 6 to 8 inches in diameter. Protect the cauliflower head by keeping the leaves intact.
If the heads are open, they should be harvested right away. Cauliflower with a coarse appearance is past maturity. and is best added to compost.
Romanesco are usually ready to harvest about 80-100 days after planting. Cut the entire head from the plant using a sharp knife. The leaves, stems and curd are all edible.
If growing a variety that produces several heads, harvest each individual stalk. After harvesting the main head, romanesco will not produce new shoots.
The History of Brassicas
Did you know that many of the brassicas we know and love all originate from wild mustard? Thanks to careful selective breeding we now have many different plant varieties.
Broccoli History
The word broccoli is the plural of broccolo, which means “the flowering crest of a cabbage”. Broccoli was brought to the United States by immigrants from Southern Italy.
Cauliflower History
There are competing theories about the origin of cauliflower. The French believe cauliflower was developed in Cyprus and called it Cyprus cabbage. The rest of the world believes cauliflower was growing in the Middle East throughout Europe’s dark ages. No matter what is true, cauliflower was definitely an early result of selective breeding.
Cauliflower was introduced to Italy in 1490 and spread throughout Europe in the centuries after. It was introduced to India in 1822 by the British. It was brought to North America in the late 1600s.
Collieflower Muppet was introduced to Colorado in 2016. It was a sweet, black and white, self-starting variety with a slow growth rate. You can see that this variety thrived in a pot! Collieflower muppet was soft, fluffy, playful, and boisterous. Alas, it was not edible. (Muppet was a staff pet!)
Romanesco History
Romanesco originated in the Lazio region of Italy in the 16th century. It is even named after Rome! The brassica oleracea species originated in Northeast Africa. Plants were cultivated over time and spread into Asia Minor. Farmers in Italy created Romanesco by using traditional cross-breeding techniques. Romanesco is mentioned in farmhouse booklets in the 16th and 17th centuries.
Romanesco was introduced to the United States in the 20th century as a specialty crop. It is now grown in temperate climates worldwide.
Brassica Trivia
- Some Brassica vegetables come in a variety of colors. Have you eaten purple broccoli or purple cauliflower? How about orange cauliflower?
- Former President George H.W. Bush refused to eat broccoli and made a statement about it: I do not like broccoli. And I’m President of the United States, and I’m not going to eat any more broccoli! Hmmm, how do you really feel about broccoli?
- Here’s one of the funny headlines about President Bush’s statement: “Broccoli Doesn’t Grow on Bush; Growers Steamed,” United Press International, March 21, 1990.
- Cauliflower has a strong smell. Adding celery seeds or leaves to boiling water will minimize the smell.
- If you don’t like white cauliflower, the orange variety is sweeter.
- Romanesco looks a bit like an alien vegetable with its lime green color and fractal-like shapes.
- Is romanesco broccoli or cauliflower? Neither. It is its very own cultivar. It is often mistakenly called romanesco broccoli or romanesco cauliflower.
Health Benefits of Brassicas
Broccoli is a superfood! It has nutrients that can reduce your risk of cancer, help control blood sugar, protect your gut and boost your immunity. Broccoli contains vitamin C, K, folate, potassium and magnesium.
Broccoli is thought to boost heart health by lowering triglycerides and LDL, providing fiber and reducing calcium build up on your blood vessel walls. Eat your broccoli!
Cauliflower has an impressive resume. Cauliflower contains vitamins B6, C and K plus folate, fiber, pantothenic acid, potassium, manganese and magnesium. Let’s not forget choline, choline, choline…(thank you Dolly!)
Cauliflower contains antioxidants to help reduce inflammation and fight against chronic diseases. Cauliflower is high in fiber and water and is low in calories.
One serving of romanesco provides over 100% of the daily requirement for vitamin C. Now that’s impressive! It has vitamins A, B, and K along with potassium, iron, manganese, protein and antioxidants.
Rich in fiber, romanesco helps with digestion and promotes regular bowel movements. It’s low in calories if you are dieting and helps you to feel full.
Add these brassicas to your garden for health, color, texture and for your enjoyment. Happy gardening!
