Imperial

Family: Brassicaceae Vegetable

Planting Schedule

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Velvety, deep-blue green curds form a tight, regal dome on sturdy stems—lush to the eye and richly flavored in the garden.

Imperial delivers a dense, fine-textured head with a pleasing snap, plus dependable side shoots for extended harvest. Ideal for roasting, steaming, and turning into creamy sauces, this is a standout broccoli for gardeners who want bold color and consistently satisfying texture from one planting.

Light: Full SunMaturity: 68 DaysHabit: Rosette

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Imperial Planting Dates by USDA Zone

Estimated US hardiness-zone windows for sow, transplant, and harvest. Enter a US ZIP above for exact local dates, or open a zone below.

Zone	Start Indoors	Sow / Transplant	Harvest
Zone 1a	Protected Environment Only
Zone 1b	Protected Environment Only
Zone 2a	Apr 27th	May 25th	Aug 1st – Aug 29th
Zone 2b	Apr 17th	May 15th	Jul 22nd – Aug 25th
Zone 3a	Apr 17th	May 15th	Jul 22nd – Sep 1st
Zone 3b	Apr 21st	May 19th	Jul 26th – Sep 21st
Zone 4a	Apr 17th	May 15th	Jul 22nd – Sep 24th
Zone 4b	Apr 15th	May 13th	Jul 20th – Sep 27th
Zone 5a	Apr 10th	May 8th	Jul 15th – Sep 30th
Zone 5b	Apr 6th	May 4th	Jul 11th – Oct 5th
Zone 6a	Apr 3rd	May 1st	Jul 8th – Oct 10th
Zone 6b	Mar 28th	Apr 25th	Jul 2nd – Oct 16th
Zone 7a	Mar 23rd	Apr 20th	Jun 27th – Oct 20th
Zone 7b	Mar 13th	Apr 10th	Jun 17th – Oct 28th
Zone 8a	Mar 4th	Apr 1st	Jun 8th – Nov 5th
Zone 8b	Feb 23rd	Mar 23rd	May 30th – Nov 12th
Zone 9a	Feb 6th	Mar 6th	May 13th – Nov 26th
Zone 9b	Jan 12th	Feb 9th	Apr 18th – Dec 9th
Zone 10a	—	Oct 1st	Dec 8th – Feb 28th
Zone 10b	—	Oct 1st	Dec 8th – Feb 28th
Zone 11a	—	Oct 1st	Dec 8th – Feb 28th
Zone 11b	—	Oct 1st	Dec 8th – Feb 28th
Zone 12a	—	Oct 1st	Dec 8th – Feb 28th
Zone 12b	—	Oct 1st	Dec 8th – Feb 28th
Zone 13a	—	Oct 1st	Dec 8th – Feb 28th
Zone 13b	—	Oct 1st	Dec 8th – Feb 28th

Crop Details

Trait	Value
Days to Maturity	68
Sun Requirements	Full Sun
Growth Habit	Rosette
Support Needed	None
Planting Depth	Normal
Germination Temp (°F)	45
Min Soil Temp (°F)	40
Min Night Temp (°F)	32
Harden Off (days)	6

Culinary Notes

Chef's Note

Imperial’s dense, fine curd holds its shape under heat—so it roasts up browned and crisp at the edges instead of collapsing into mush. The mild brassica bite turns sweet and nutty with butter or olive oil, making it especially persuasive in roasted florets or a blended creamy sauce.

Best Uses

roasting on high heat so the florets caramelize before they go soft
steaming and finishing with browned butter for a nutty, creamy gloss
making a silky broccoli-cream sauce (blend warm with stock and cream)
quick sauté of side shoots for a crisp, bitey side dish

Flavor Profile

sweet-broccoli earthiness tight, fine-textured curds clean snap with tender interiors slight brassica bite that sweetens with heat

Kitchen Pairings

lemon garlic parmesan browned butter olive oil smoked paprika

Frequently Asked Questions

What pest or disease is most likely on Brassica oleracea var. italica (calabrese/“imperial”) and how do I manage it?

Watch for cabbage worms (imported cabbageworm/diamondback larvae) because they chew irregular holes in the curd and leave frass behind. Hand-pick small larvae early and spray an appropriate Bacillus thuringiensis (Bt) product as soon as you see feeding—repeat per label after 5–7 days if activity continues. Also check leaves regularly for downy mildew/black rot symptoms (yellowing that turns dark and spreads along veins) and remove infected plants early to prevent the spread.

How often should I water during the main growing phase for Brassica oleracea var. italica, and what soil moisture level should I keep?

During head (curd) formation, keep soil consistently evenly moist—aim for the top 1 inch to stay damp, not soggy. Water deeply about 2–3 times per week depending on heat and rainfall, and reduce frequency only if the soil is staying wet longer than a day. Uneven watering can lead to loose, stressed curds and increased susceptibility to diseases.

How can I tell when Brassica oleracea var. italica (“imperial”) is ready to harvest?

Harvest when the curd is firm and tightly budded, with the individual florets still compact—before the surface starts to separate and yellow. Typical timing is around 68 days from transplanting/seedling establishment; in practice, harvest at the first clear window of tightness rather than waiting for size alone. Cut the main head with 6–8 in (15–20 cm) of stem, and keep an eye out for smaller side shoots that can be harvested after the main cut.