Vegetable · Brassicaceae
Romanesco
Brassica oleracea var. botrytis
Give it a cool fall season and this brassica rewards you with a head that spirals into tidy green fractals.
Full sun
Every 5–7 days
50–70°F · 10–21°C
75–100 days
Overview
If Romanesco looks intimidating, take heart, because underneath those green spirals it grows much like a cauliflower. Each head is a pattern of lime-green cones that repeat smaller and smaller toward the tip, and it belongs to the cabbage family alongside broccoli and cauliflower. Italian gardeners have raised it for generations, and it tastes like cauliflower with a gentle, nutty sweetness, so you are in good company growing it.
It is fair to call this the most demanding of the brassicas, but demanding does not mean out of reach. What it really asks for is steady moisture, rich soil, and cool weather while the head fills out. Summer heat is the one thing that trips it up, turning the curds loose and grainy, so most gardeners raise it as a fall crop and let the harvest land on cooling days. Time it that way and half the work is already done.
Get the season right and the rest feels easy. Give it full sun, even water, and a little elbow room, keep the usual cabbage pests off the leaves, and cut the head while it is still firm and tight. Even a first try can hand you one of the most beautiful things to come out of a garden bed, and a slip here or there is usually recoverable.
Care
The short version: give it full sun, rich soil kept evenly moist, and a feed every couple of weeks, all timed so the head matures in the cool of fall instead of summer heat. Do that and you are most of the way there.
Light
Romanesco loves full sun and leans on every hour of it to bring the head to its proper chartreuse. A touch of partial shade will not ruin things, but resist the urge to tie the leaves over the curds the way you might with white cauliflower, since shading them only mutes that lovely color.
Water
Aim to keep the soil evenly moist, about an inch of water each week, and try not to let the plant dry out. Patchy watering is the usual cause of buttoning and rough heads, so a little consistency goes a long way. Watering in the morning lets the leaves dry off, which keeps disease at bay.
Soil
Plant into fertile, well-drained ground enriched with compost or well-rotted manure, soil that stays moist without turning soggy. A pH between 6.0 and 7.0 keeps it happy, and that slightly sweeter range gives you a bonus by helping hold clubroot in check.
Temperature
Cool weather is the heart of it all. Romanesco is happiest between 50°F and 70°F (10°C to 21°C), and the head needs that coolness to set firm and tight. Let the days push into the mid-80s and the curds start to loosen and go grainy, so lean on the calendar to keep things cool.
Humidity
Everyday outdoor air suits it just fine, so there is no number to chase here. What matters more is good airflow, since leaves that stay crowded and damp invite the diseases brassicas are prone to. A bit of breathing room does the trick.
Feeding
This plant likes to eat. Feed it every two weeks with a balanced or low-phosphorus fertilizer chosen from a soil test, and give it a side-dressing of nitrogen such as calcium nitrate once the plants reach about 4 inches tall. Regular meals keep it growing without any stressful checks.
Pruning
There is really no shaping to worry about. Leave the head uncovered so the sun can build its color, and the only leaves worth pulling are those that turn diseased or get nibbled by pests. Beyond that, let the plant be.
Size & spacing
Expect plants to stand 2 to 3 feet (60 to 90 cm) tall and spread 18 to 30 inches (45 to 75 cm) wide. Give each one that full width so air moves freely among the big outer leaves, which quietly keeps disease from settling in.
When to plant
Timing is the kindest thing you can do for Romanesco, since the head really wants to fill out in cool weather. Start seed indoors 6 to 8 weeks ahead, then set the plants out in cool early spring or, better still, in mid to late summer so the crop heads up as fall arrives.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: Start seed indoors 6-8 weeks before the intended transplant date.
- Plant: Transplant in cool early spring, or (preferred) in mid- to late summer for a fall harvest; Romanesco is best grown as a fall crop.
- Harvest: Cut the head when it is full-sized, firm and tight, before the fractal spiral curds begin to separate or loosen.
Hardiness
USDA hardiness zones: 3–10
Temperature: down to -40°C
Troubleshooting
Almost every Romanesco worry comes down to the same root: a stall in steady growth or a burst of heat at the wrong time. The head and the leaves show the first signs, so keep a gentle eye on them. Find your symptom below and act early, and most troubles never get the chance to take hold.
No firm head, or one that goes loose and ricey
Heat is almost always behind this, since the curds pull apart once daytime temperatures climb past 86°F (30°C) while the head is forming. A shortage of boron can also brown the curds and stop them staying tight. The kind fix is to time the crop for a cool fall finish, and to correct boron only if a soil test asks for it.
Fix:
- Time the crop so heads mature during cool weather
- Correct boron deficiency per soil test
Wilting, stunted plants with swollen, knotted roots
Lift a struggling plant and you may find the swollen, twisted roots of clubroot or maggots working through the root zone. Sadly an infected plant cannot be saved, so pull it and get rid of it. Nudging the soil toward neutral pH holds clubroot back, and a long rotation away from brassicas keeps it from building up over the years.
Fix:
- Remove and destroy affected plants
- Raise soil pH toward neutral to suppress clubroot
A little head shows up early on a small, stalled plant
This is buttoning, and it tends to follow any stumble in growth, whether from transplant shock, a hungry plant, or a dry stretch. Seedlings that go out too old or after a cold spell are the usual reason. The fix is gentle: keep the soil evenly moist and well fed, and move young transplants out at the right moment so they never stall.
Fix:
- Maintain even moisture and adequate fertility
- Avoid transplanting overgrown or cold-stressed seedlings
Chewed holes in the leaves with green caterpillars at work
Soft green cabbageworms and cabbage loopers do most of the chewing, while tiny hopping flea beetles leave shot holes in young seedlings. Picking the caterpillars off by hand is easy and effective, and slipping floating row covers on early keeps the whole crowd out. For a heavy run of caterpillars, Bacillus thuringiensis clears them without harming anything else.
Fix:
- Handpick caterpillars
- Use floating row covers
- Apply Bacillus thuringiensis for caterpillars if needed
Toxicity
Good news for a worried gardener: Romanesco is a food crop and safe all the way through. Nothing in the leaves, stems, or head will harm people or pets, so plant it freely wherever cats, dogs, rabbits, or chickens roam. The only small note is that a lot of raw brassica can leave some animals a little gassy.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Perfectly safe around cats, since there is nothing toxic in the leaves, stems, or head. A curious nibble might bring a touch of gas, and that is about the worst of it.
Dogs None
Dogs have nothing to fear here either. A few plain cooked florets make a nice treat, though a big helping of raw brassica can leave a dog a little gassy.
Horses Safe
Not poisonous to horses at all. Brassicas just are not part of their usual diet, so offer only small amounts and their stomachs will stay settled.
Rabbits Safe
The leaves and florets are safe for rabbits and make a welcome green. Bring them in slowly so a bunny's gut has time to adjust.
Livestock Safe
Safe as forage, with no toxins to worry about. The one thing to keep an eye on is heavy, steady grazing of brassicas, since the natural goitrogens can add up over time.
Birds Safe
Backyard poultry are welcome to it, pecking happily at the leaves and curds. No part of the plant will do them any harm.
People Safe
A wholesome vegetable to enjoy raw or cooked. The whole head and the tender leaves are all good eating, with nothing to worry about.
Safe to handle and grow around pets and children. Note that brassica glucosinolate goitrogens are mainly a concern for heavily-grazed livestock, not household pets.
Varieties
You will only meet a couple of Romanesco types in most seed catalogs, and both give you that lovely spiral. Here is how to tell them apart.
Veronica
A well-loved hybrid that reliably gives you uniform lime-green fractal heads with crisp, clearly cut spirals.
Romanesco Italia
An open-pollinated heirloom that carries classic apple-green pointed spirals on tall plants across a long season.
How to propagate
There is only one way to begin Romanesco at home, and happily it is a simple one: seed. It will not root from cuttings, so every plant gets its start in a tray on a windowsill.
SeedModerate
Sow indoors 6-8 weeks before transplanting; transplant when seedlings have 4-5 true leaves. · About 4 weeks from sowing to transplant-ready seedling, then 75-100 days to a mature head.
Romanesco comes from seed and is not cloned at home, so a simple seed packet is where each of your plants begins. Start the seed indoors 6 to 8 weeks ahead of transplanting, and set the seedlings out once they hold 4 to 5 true leaves, roughly 4 weeks on. After that comes the patient part, a stretch of 75 to 100 days before a head is ready to cut, and it is worth every day.
Myths
Romanesco heads have to be blanched by tying the leaves over them, just like white cauliflower.
That old habit belongs to white cauliflower, which needs shade to stay pale, and Romanesco works the other way around. Its chartreuse curds need full sun to color up, so leave the leaves untied and let the light pour onto the head. You get a brighter, prettier result for doing less.
Romanesco is a lab-made cross of broccoli and cauliflower.
It is really a traditional Italian cultivar of Brassica oleracea, sharing the same cauliflower and broccoli group as its relatives. It is an old heirloom, not a GMO, and gardeners have grown and saved it for generations, so you can plant it with an easy mind.