How to Plant, Grow, and Care for Romanesco Broccoli (Roman Cauliflower)
You’ve probably seen the unique intricacies of Romanesco broccoli while perusing seed catalogs and passed on them because they look complicated. But I assure you, if you’ve mastered growing broccoli or cauliflower, you’re ready for this adventurous vegetable! Join organic farmer Jenna Rich as she attempts to convince us all to grow it while teaching us how to care for it successfully.
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Is it broccoli, cauliflower, or intricate garden artwork? Romanesco broccoli is an heirloom cousin of these two brassicas and deserves a place in your garden, not solely for its unique beauty but also for its nutrition and culinary flexibility.
Even if you’ve never grown a brassica, it’s easy to learn. You can grow these beautiful babies with space, sunlight, and fertile, well-draining soil. I’ll admit to thinking this funky heirloom was a hybrid due to its color and intricacies. However, Romanesco broccoli has been grown for centuries.
Let’s explore how to plant, grow, and care for it.
Romanesco Broccoli Overview
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Botanical Name
Brassica oleracea var. botrytis
Plant Type
Italian heirloom flowering brassica
Family
Brassicaceae
Spacing
18 to 24 inches apart
Special Characteristics
Unique appearance with a nutty flavor
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Native Area
Italy
Exposure
Full sun
Height
Up to 3′
Watering Requirements
Moderate
Soil Type
Fertile, moist, well-draining, alkaline
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Pests
Cabbage loopers, diamondback moths, imported cabbage worms, flea beetles, aphids
Disease
Powdery mildew, Fusarium yellows, root rot, Alternaria brassicae, black rot, and clubroot
Maintenance
Low to moderate
Hardiness Zones
USDA 2 to 11
Days to Maturity
75 to 100
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What Is Romanesco Broccoli?
Romanesco broccoli is one of the most stunning vegetables. Its bright chartreuse color and geometric patterns often confuse consumers, leaving them wondering if this large-headed crop is a cauliflower, a broccoli, or something else entirely.
It’s an heirloom cousin of both crops, not a hybrid, as some might suspect. A cultivar of cauliflower, its texture is similar: soft, firm, and crumbly but with a nutty, sometimes spicy flavor. Its spiky, cone-shaped florets form a unique logarithmic shape, proving that Mother Nature is a true artist! Its peaked, spiraled head displays the Fibonacci sequence, a fantastic example of this pattern.
Romanesco broccoli is eye-grabbing and exciting enough to be a housewarming gift or worked into your next charcuterie board at game night. Our Botanical Interests community loves it for its hardiness and gorgeous fractals. It is sometimes called fractal broccoli, Roman cauliflower, or Romanesco cauliflower.
Brief History
This unique broccoli is believed to date back to the 15th or 16th century. Consumers are often confused by Romanesco broccoli, referring to it as broccoflower. Broccoflower, while delicious and nutritious, is a hybrid green-colored cauliflower. You’ll know you’re dealing with the Italian heirloom by its spiraled and peaked florets. Today, it’s adored by home gardeners, farmers’ market shoppers, and chefs.
Scientists recently broke the code that causes this intricate, exciting pattern. Now, the genetic code may be used to alter genes of other crops to create new cultivars.
Uses
Its uses are similar to those of broccoli and cauliflower, and it is enjoyed both raw and cooked.
- Roast it along with root vegetables and drizzle it with olive oil. Serve it alongside a protein and a fresh green salad.
- Use it in place of broccoli or cauliflower on a charcuterie board or steamed with a light cheese sauce.
- Chop it up and add it to soups, casseroles, and egg bakes.
- Eat it raw with hummus or creamy dill dip.
- Steam and sprinkle it with light salt and pepper for a healthy snack.
It contains high levels of vitamins A, B, C, and K and is a good fiber source. It also contains high levels of phytochemicals, which can reduce inflammation, control blood sugar levels, and be easy to digest. Its bright green color indicates its levels of carotenoids and chlorophyll.
Appearance
This giant chartreuse head of “broccoli” is full of spiraled fractals. The number of spirals always represents a Fibonacci number. When cut in half, the peaks resemble the tops of pine (Christmas) trees. It’s cruciferous, so its texture is soft and crumbly like cauliflower.
Each five to six-inch head can weigh up to five pounds and is encased in dark green leaves at the base. Each plant will grow to about three feet tall with a 24-inch spread.
Native Area
This Italian heirloom was once grown in Rome in the 15th or 16th century. While it’s not often seen at the grocery store, it is a popular crop among small-scale farmers who vend at farmers’ markets and local food co-ops.
How to Grow
Grow Romanesco broccoli in the ground, in greenhouses, or containers. Proper fertilization is crucial to their success, and caution should be used in peak summer to prevent plants from going to seed prematurely.
Light
Plant it in an area that receives full sun. Some afternoon shade or dappled sunlight will be appreciated in extreme summer heat or drought-like conditions. Utilize shade cloth to prevent bolting during times of high heat.
Water
Water consistently after transplanting, allowing the water to dry out between sessions. Water-logged soil increases the risk of fungal disease. Watering in the morning keeps water from sitting on the foliage.
Deep water to ensure water gets to the roots and stays off the foliage. Schedule sessions for the morning to avoid wet foliage heading into cool nights. Water plants every other day or less based on the finger test, and more during drought conditions. The finger test suggests putting your fingers into the soil several inches. If there is no soil on the bottom two inches of your fingers, it’s time to water. If there is, plenty of moisture is present in the soil for now.
Soil
Provide fertile, loamy soil high in fertility. Broccoli takes a long time to mature, so ample fertilization is necessary for proper growth and nutrition. The preferred pH is slightly alkaline, between 6.0 and 7.5.
Temperature and Humidity
Broccoli, including this marvelous type, thrives in cool weather, preferring temperatures between 65° and 75°F (18° to 24°C). The soil should be above 50°F (10°C) before transplanting. Growers using greenhouses or low tunnels have more flexibility because of the increased temperatures they offer. Work this information into your sowing schedule when planning your sow and transplant dates.
While most broccoli is very cold-hardy, young spring seedlings are still vulnerable to damage. When newly transplanted, use a row cover to protect them. You may also select a shorter season variety and delay your planting. Established plants can tolerate frost and colder temperatures in the fall, tolerating 20°F (-7°C). Hard frosts may damage flower heads, so look to future forecasts and plan your harvests accordingly.
Shade cloth may be necessary in peak summer to reduce bolting, and more water is needed to keep the plants from entering a stressed state.
Fertilizing
This attractive brassica requires a long time to mature, so fertilizing appropriately is crucial to its success. Add bone meal at transplant for a nitrogen and phosphorus boost, which will help the plants establish a robust root system and above-ground foliage. Aged compost will add organic matter. Provide plenty of nitrogen, potassium, and phosphorus throughout its growth and feed every three to four weeks.
Pro Tip: Perform a soil test before planting to ensure proper nutrients are available.
Pruning
Pruning is not necessary or recommended. The entire plant works hard to produce one main head and does not provide side shoots. Remove any lower, dried or diseased leaves to provide more airflow.
Mulching
In cooler growing zones, add a thick layer of straw, leaf mulch, or grass clippings in the spring to keep the soil at a consistent temperature, suppress seeds, and retain moisture. Remove it in warm regions when temperatures increase and move it to the paths. This organic matter will break down and add fertility to your soil.
Harvesting
When the head has tight spirals, and before they form flowers, it is ready to harvest. The flavor may be bitter if flowers are present or the head has begun to separate, and there should be no discoloration. Use a sharp, clean harvest knife to cut the head, leaving two inches of the stem attached. Trim it up before cooking it, using all parts of the stem, leaves, and head.
Fun Fact: Romanesco’s edible head is the plant’s flower.
Popular Varieties
Traditional Romanesco broccoli is a bright chartreuse, but white hybrids are available.
‘Veronica’
This organic option has extra-pointed pinnacles and performs best when planted in the summer for fall harvests. Its bright flavor is deeper and nuttier than that of the white options.
‘Puntoverde’
Ready in about 78 days, ‘Puntoverde’ performs well in all seasons, sans extreme heat, although this cultivar can handle more stress than others without adverse effects. It can be planted earlier in mild areas where winters aren’t harsh.
‘Whitaker’
This hybrid matures in about 80 days and is uniquely white. It resembles traditional cauliflower even more than its chartreuse sisters. Stress may cause some hints of green.
Propagation From Seed
For summer harvests in mild zones, start seeds indoors six to eight weeks before your last anticipated spring frost and about four weeks before the last frost in cold regions. Start them in deep cell trays or 72-cell flats. If your sowing area is outdoors, use a heat mat and set it to 70°F (21°C) until germination, then lower it to 60°F (16°C).
For fall harvests, select all-season, mid-season, or storage varieties. Start seeds in May and transplant in June or July to ensure a mature head before a hard frost.
For spring harvests in areas that don’t receive freezing temperatures or frost, sow seeds in late summer or early fall for a September through February transplant.
Pro Tip: Harden off seedlings for five to seven days to ensure they can tolerate outdoor conditions before transplanting.
Planting
Transplanting is recommended over direct sowing.
Transplanting
Seedlings are ready to transplant after being hardened off and are about four to six inches tall, with no woodiness on the stem. They will be ready to transplant four to five weeks after germination. Add compost to the transplant holes or some to the top layer of the bed or container.
Use a trowel to dig a hole about the size of the seedling and break up any bound roots before placing it into the hole. Fill the hole with native soil and tamp it down. Water immediately using drip lines or soaker hoses.
Pro Tip: Avoid waiting until seedlings are rootbound or the stem is woody. This is a sign that the plant is too mature and won’t perform as well. If there is any purpling, this is a sign of maturity unless it’s a purple variety.
Location
Ensure plants receive six to eight hours a day of sunlight to allow for proper head formation.
Spacing
Transplant seedlings so they have enough space to spread to their estimated maturity width, which is about 18 inches to two feet. Play around with your spacing; closer proximity may help suppress weeds and cool the soil. However, closer spacing may result in smaller heads. Cultivate tiny weed seeds while plants grow and bush out to reduce competition for water, sunlight, and nutrients.
Common Problems
Like most brassica family members, pests love Romanesco broccoli. Here are a few to watch out for and safe ways to prevent them from destroying your plants.
Pests
If you’ve grown brassicas before, you know how incessant pests are when attacking these delicious cruciferous plants. Romanesco broccoli is no exception in terms of their preferred garden vegetable snacks.
- Cabbage loopers are the larvae of the cabbage moth, better known as those pesky green caterpillars that seem to blend into all your gorgeous greens, destroying them right before your eyes. Having no legs in the middle section of their bodies, they move similarly to an inchworm.
Spray your Romanesco broccoli with the bacterium Bacillus thuringiensis (Bt) or the pesticide Spinosad, which doesn’t adversely affect the good guys. For tips on safely using Spinosad, refer to the National Pesticide Information Center fact sheet. - Diamondback moths are easily camouflaged by their mottled combination of browns. They lay their eggs within the florets of cruciferous veggies like cauliflower and broccoli, hidden out of sight—Scout early for their fuzzy, white cocoons.
Their green caterpillar larvae feed on the underside of leaves, giving leaves a “windowpane effect.” While their damage can seem insignificant compared to other pests, plants cannot perform correctly if the populations are high enough and damage is extreme.
Pro Tip: Avoid leaving mustard plants to overwinter. The moth will lay eggs here in the spring, causing early-season trouble. - Imported cabbage worms are the larvae of the cabbage butterfly and can cause mass damage to your early spring greens and brassicas. Preemptively spray young greens with Bt if you experience damage every season to prevent them from feeding on your crops.
- Flea beetles can be most damaging in the early spring when there are few other food options. Young transplants are most vulnerable; they can chew them down overnight without proper protection. Dust plants with Diatomaceous Earth or kaolin clay or plant radishes nearby to trap them. Transplant them rather than direct seeding, as established plants can ward off pests more effectively than newly germinated ones. Spinosad can be used in extreme infestations.
- Aphids crawl deep into the tight spaces between florets, and sometimes, unfortunately, you’re unaware of their damage until it’s time to harvest and cut inside. Many organic growers assume they have them and blast their plants with strong streams of water occasionally, which may cause them to fly away if they have wings. This isn’t a permanent solution, but it will deter them temporarily.
Soapy water solutions (insecticidal soaps) dissolve their protective outer layer, causing death. Another option is releasing lacewing eggs. Adult lacewings are ferocious aphid feeders that can help control the population.
Delayed planting in spring and fall may help you avoid some of these pests. If the plantings don’t align with the pests’ life cycle, they’ll have moved on to greener gardens if they don’t have enough food. Delayed planting with the addition of insect netting or row cover decreases the risk of pest damage even further.
Remember to control your weeds, which can harbor pest eggs and diseases, overwinter, and be ready to strike next season. Keep your garden beds and paths free of debris and properly dispose of potentially infected plants to a burn pile rather than letting them linger in a compost pile. Doing so will help prevent future outbreaks and re-infection.
Diseases
- Powdery mildew may occur when plants don’t receive proper circulation or go to bed with wet leaves. Avoid this by spacing out plants properly, adding fans, if possible, in indoor or patio grow areas, and avoiding watering in the evenings. Remove any damaged leaves as they crop up. Spores may survive the winter, so remove any infected plants quickly, clear the space of debris throughout the year and at the end of the season, and rotate crops to avoid future infections.
- Fusarium yellows is best avoided by growing resistant varieties like ‘Veronica.’ The spores can live in the soil for up to seven years. The disease infects crops by entering through a wound or root openings and traveling into the stem, causing wilting, drooping, curling, yellowing, and eventual death. Solarize soil or allow it to lie fallow where Fusarium has been present.
- Too much moisture and sitting water increase soil-borne bacteria, causing root rot. This is typically a death sentence for plants, although plants can bounce back and survive if caught early enough. Avoid this issue by providing plants with well-draining soil and taking swift action when you notice symptoms like wilting, leaf drop, stunted growth, and gnats at the soil surface.
Romanesco broccoli is at risk for diseases that others in the Brassicas family, so look out for the less common but possible Alternaria brassicae, black rot, and clubroot. Ensuring proper growing conditions is your best bet for preventing these diseases.
Key Takeaways
- Romanesco broccoli is a member of the cauliflower family and a cousin of broccoli and cauliflower.
- Diseases and pests that affect broccoli and cauliflower are shared with this vegetable.
- It grows best in cool regions; most varieties perform best when planted for a fall harvest.
- Provide lots of rich soil and fertilize plants often.
- Transplanting mature or stressed seedlings will not result in healthy yields.
