Costata Romanesco Zucchini

Cucurbita pepo

Also known as: Roman Zucchini, Ribbed Roman


The Roman ribbed zucchini — a traditional Italian heirloom with pronounced ridges running the length of the fruit, so each slice comes off as a small green star. Skin is pale green with darker striping between the ribs, and the flesh is dense, nutty, and richly flavoured — the variety many Italian cooks and chefs consider the finest-eating zucchini there is. Yields are lower than a commercial bush type but the flavour is on another level, especially grilled, where the ribs char handsomely and the flesh keeps its shape. The plant is also generous with male flowers, ideal for stuffing and frying as fiori di zucca. Open bush to semi-vining habit — a little more room than a standard zucchini.

Days to harvest 50–65 days from sowing
Fruit size Long ribbed fruit, best picked young at 15–20cm
Sowing depth 15–20mm
Germination 6–10 days at soil temperature 21–30°C
Spacing 90cm–1.2m between plants — larger than a standard bush zucchini
Aspect Full sun; moist, well-drained soil rich in organic matter
Frost tolerance Frost-tender — sow after last frost only

Growing notes

A warm, sunny position with room to spread suits it best. Costata Romanesco is a bigger, more open plant than a supermarket bush zucchini, and the trade-off for its lower yield is exceptional flavour — worth the extra square metre.

Soil preparation: Well-rotted compost and aged manure worked in before sowing. Zucchini are heavy feeders, so build the bed generously.

Sowing method: Sow 2–3 seeds per station 90cm–1.2m apart, either direct into warm soil or into large pots for transplant, then thin to the strongest seedling per station.

Support: None strictly needed, though the semi-vining habit responds well to a low stake or short trellis to lift the plant off the ground and keep fruit clean.

Containers: Suits a large pot of 50L or more. Keep water and feed consistent, as pots dry out faster than beds and zucchini are thirsty croppers.

Watering & feeding: Deep, consistent watering at the base — like other summer squash, susceptible to mildew, so keep water off the leaves. Side-dress with well-rotted manure or a balanced liquid feed once flowering starts.

Harvest: Pick every two to three days once fruiting begins, cutting fruit at 15–20cm for the tenderest eating. Larger fruit stay usable for longer than a standard zucchini — the dense flesh doesn't turn seedy as quickly — but pick regularly anyway to keep the plant productive. Male flowers can be harvested in the morning and used fresh the same day for stuffing.

Timing: First fruit ready 50–65 days from sowing.

Key features

  • Distinctive ribbed fruit — sliced rounds are star-shaped
  • Dense, nutty, richly flavoured flesh
  • Widely regarded as the best-eating zucchini
  • Excellent for grilling — holds shape and chars beautifully
  • Generous male flowers for stuffing as squash blossoms
  • Italian heirloom with a Roman-garden pedigree

Short season tips


Direct sow into warm ground from mid-spring to early summer once frost risk has passed. In Coonabarabran and similar inland zones, that means mid-November onwards. If time is tight, start seed indoors in large pots 2–3 weeks before transplanting — cucurbits resent root disturbance, so handle carefully and move on with the root ball intact. Costata Romanesco takes a little longer than a standard bush zucchini to hit full stride, so a hoop tunnel or cloche buys useful early days.

  • Spring
  • Summer

Annual

  • Corn, climbing beans, nasturtium, borage, marigold
  • Potatoes, other cucurbits within cross-pollination distance if saving seed


A traditional Roman zucchini kept in continuous cultivation across central Italy for generations, bred and refined for flavour rather than yield in an era before that trade-off tipped decisively toward the commercial. Carried outward through the twentieth century by Italian seed-savers and cooks, it has become the standard-bearer among heirloom zucchini for eating quality — a reminder that older cultivars often won their reputation for reasons a supermarket shelf can't quite carry.