What hardiness zones is Brassica oleracea 'Long Island Improved' suitable for?

Brassica oleracea 'Long Island Improved' is an annual vegetable reaching 20-24 inches (50-60 cm) tall with a spread of 18-24 inches (45-60 cm) and an upright, single-stemmed, compact habit—shorter and more compact than most Brussels sprout cultivars. An American heirloom developed on Long Island, New York, in the early 1900s, it produces firm, round, medium green sprouts 1-1.5 inches (2.5-4 cm) in diameter along a stocky stalk—typically 50-100 sprouts per plant. The compact stature makes it suitable for smaller gardens and windy sites without staking. Days to maturity 90-100 from transplant—faster than 'Diablo' (110-120 days). Open-pollinated—saves true to seed. Flavor improves after frost.

Native Range

Brassica oleracea (gemmifera group) descended from wild cabbage native to coastal Europe. 'Long Island Improved' was developed on Long Island, New York, in the early 1900s.

Suggested Uses

Grown in vegetable gardens for culinary use—roasting, sautéing, steaming. Compact short plant for small gardens. 50-100 sprouts per plant. Open-pollinated—seed saving. Fastest Brussels sprout 90-100 days. Long Island NY heirloom. Frost sweetens flavor. Not suitable for warm-winter regions or where hybrids with larger sprouts are preferred.

How to Identify

Distinguished from 'Diablo' by the shorter, more compact stature (20-24 versus 24-36 inches), the faster maturity (90-100 versus 110-120 days), and the open-pollinated (versus hybrid) breeding. Distinguished from cabbage by the multiple small sprouts along a central stalk. Long Island Improved—compact short stature, fastest Brussels sprout, open-pollinated, Long Island NY early 1900s.

Appearance

Size & Dimensions

Height1'8" - 2'

Width/Spread1'6" - 2'

Colors

Flower Colors

yellow

Foliage Colors

blue

Fall Foliage Colors

no change

Bloom Information

Yellow four-petaled flowers if overwintered. Harvest sprouts before bolting. Plant in spring for fall harvest.

Detailed Descriptions

Flower Description

Yellow; four-petaled; bolting only

Foliage Description

Blue-green; fan-shaped; above medium green sprouts on stocky stalk

Growing Conditions

Sun Requirements

Full Sun

Requires 6-8 hours of direct sunlight daily

• Full Sun: 6+ hours of direct sunlight

• Partial Shade: 3-6 hours of direct sunlight

• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range6.0 - 7.5(Neutral)

357912

Soil Types

loam

Drainagewell drained

Water & Climate

Water Needs

High

Frost Tolerance

hardy

Time to Maturity

90-100 days from transplant

Care & Maintenance

Care Guide

Start seed indoors 10-12 weeks before first fall frost. Transplant into rich, moist, well-drained soil (pH 6.0-7.5). Consistent moisture and heavy feeding. Compact enough for small gardens—no staking needed. Days to maturity 90-100 from transplant. Top the plant 3-4 weeks before final harvest. Harvest bottom-up when sprouts reach 1-1.5 inches. Frost improves flavor.