Italian Large Leaf Basil

Italian Large Leaf Basil Seeds

Basil ‘Prospera Italian Large Leaf’ F1 (Ocimum basilicum — Prospera Series — Genesis Seeds / Johnny’s Selected Seeds)

In recent years an epidemic of downy mildew caused by the pathogen Peronospora belbahrii has caused severe damage to sweet basil crops all over the world. The disease was first discovered in basil in Switzerland in 2003 and spread throughout the world via fresh material transport, infected seeds, and airborne spores. For home growers and commercial producers alike, the appearance of downy mildew — recognized by yellowing upper leaves and a characteristic grey-purple spore layer on the leaf undersides — meant that a crop that had always been considered straightforward to grow suddenly required constant vigilance and frequent replanting.

Genesis Seeds, specialists in seed manufacturing and cultivation including basil, joined researchers at Bar-Ilan University develop a breeding programmed aimed at transferring downy mildew resistance from wild Ocimum species into sweet basil varieties. This collaboration produced hybrid plants that are both downy mildew resistant and fertile — a genuine breakthrough that had eluded breeders for years. The resulting Prospera series, developed and commercialized with Johnny’s Selected Seeds, represents the most significant advance in commercial basil breeding of the past two decades.

The breeder’s pre-commercial variety reference code for this variety is (ILL2) — ‘Italian Large-Leaf 2’ — which may appear in university trial reports or other research resources. The Italian Large Leaf type is distinct from the compact Genovese type: the leaves are longer and broader, the plant habit is taller and more open, and the flavor profile is slightly sweeter and more anise-forward than the more herbal, peppery character of Genovese. This makes Italian Large Leaf the preferred basil for torn-leaf applications — caprese, bruschetta, grilled vegetable garnishes — where the visual impact of a large, whole leaf matters as much as the flavor.

An important note on disease resistance: downy mildew-resistant cultivars have been commercially available since 2018, but observations of isolates overcoming resistance were reported after each new introduction. The rapid development of pathogens overcoming genetic resistance suggests the evolution of new races under selective pressure. Prospera Italian Large Leaf carries intermediate resistance — it provides meaningful protection under normal growing conditions but is not immune. In Kuwait’s hot, dry climate, the low humidity of the outdoor growing environment significantly reduces downy mildew pressure compared to humid greenhouse or indoor conditions where the disease is most destructive. Good air circulation, avoiding overhead watering, and growing outdoors in the cool season are the most effective practical measures alongside choosing a resistant variety.

Variety Details

• Botanical Name: Ocimum basilicum
• Series: Prospera
• Variety: Prospera Italian Large Leaf DMR (ILL2)
• Commercialized by: Johnny’s Selected Seeds (USA)
• Seed Type: F1 Hybrid
• Plant Type: Annual
• Disease Resistance: Intermediate resistance to Downy Mildew (Peronospora belbahrii) and Fusarium Wilt
• Related variety: Nufar (predecessor — no downy mildew resistance)
• Certification: USDA Certified Organic seed available

Key Features

• Breakthrough F1 hybrid combining Italian Large Leaf quality with downy mildew resistance
• Large 10 cm leaves — substantially bigger than standard Genovese basil
• Sweet aroma with anise notes — classic Italian basil flavor profile
• Intermediate resistance to downy mildew and Fusarium wilt — meaningful protection under normal conditions
• Highly uniform plants — consistent leaf size and habit across the planting
• High yield — suitable for continuous leaf harvest and bunch harvest
• Suitable for field, garden, and greenhouse production
• Very similar to Nufar — the most trusted Italian Large Leaf basil — with added disease resistance
• Note: DMR designation indicates intermediate resistance, not immunity — good air circulation and dry-foliage watering remain important management practices

Plant Information

• Height: 60–75 cm
• Spread: 30–40 cm
• Plant Type: Annual
• Habit: Upright, well-branched, vigorous
• Leaf Size: Up to 10 cm long
• Leaf Colour: Medium green, slightly glossy
• Aroma: Sweet, with anise notes — classic Italian basil profile
• Days to First Harvest: 60–70 days from sowing

Germination Instructions

• Sow seeds 6 mm deep, 2–3 seeds per position, in rows 45 cm apart.
• Firm the soil over the seeds.
• Thinning is not necessary, but a final spacing of 10–20 cm apart produces healthy, full plants.
• For transplanting, sow indoors 6 weeks prior to setting out.
• Keep at 21°C for best germination.
• Transplant to the final position when seedlings have 3–4 sets of leaves, spacing 10–20 cm apart.
• Days to germination: 5–10 days at 18–21°C.
• Keep the growing medium consistently moist throughout germination — do not allow to dry out.
• Basil is cold-sensitive; do not sow outdoors or transplant until temperatures are consistently above 18°C.
• Germination is inhibited below 15°C.
• For Kuwait: sow in March to April for summer production, or October for cool-season production.
  October sowing benefits from warming soil temperatures and produces the most vigorous plants through November and December.
• Avoid sowing in the hottest months — basil under severe heat stress above 40°C will bolt rapidly and produce fewer leaves.

Growing Tips

• Grow in full sun to part shade in moderately rich, moist, well-drained soil.
• Basil is not drought tolerant and can be damaged by heat stress — regular moisture throughout the growing season helps ensure a good crop.
• Water consistently at soil level — never overhead — as wet foliage creates ideal conditions for downy mildew even on resistant varieties.
• Ensure good air circulation between plants by maintaining adequate spacing of 15–20 cm. Begin light harvesting after plants are established — best done in the early morning when the temperature is cooler and leaves are less likely to wilt.
• A full harvest should be completed just before plants start to flower. Cut the entire plant 10–15 cm above the ground to promote a second growth.
• Pinch out flower buds as soon as they appear to keep the plant producing leaves — once basil is allowed to flower fully, leaf production slows significantly and flavor quality declines.
• Do not store harvested basil below 10°C as cold temperatures blacken and damage the leaves.
• To minimize downy mildew risk regardless of variety, reduce relative humidity around plants through good air circulation, avoid wetting leaves when watering, and grow outdoors where natural airflow is available.

Gulf Planting Season

• Sowing outdoors (direct or transplant): October to November and March to April
• Peak production season: November to February (cool season) and March to May (spring)
• Avoid: June to September — extreme heat above 40°C causes rapid bolting and poor leaf quality
• Note: Unlike most ornamentals in this catalogue, basil is a warm-season herb that grows in Kuwait’s cool season as well as the mild transitional periods of spring and autumn.
• October is the optimal sowing month for the first cool-season crop — soil temperatures are still warm enough for fast germination while air temperatures are beginning to moderate, producing vigorous, productive plants through the winter months.
• As temperatures rise above 35°C, plants will begin to bolt regardless of variety — harvest fully before flowering begins to retain the best flavor and leaf quality.

Culinary & Garden Uses

• Prospera Italian Large Leaf is the basil of the Italian kitchen — its large, broad, sweet-scented leaves are the classic choice for any application where a whole basil leaf is presented as a visual and flavor element rather than chopped or processed.
• Torn over ripe tomatoes with good olive oil, layered in a caprese, placed on grilled auberge, or used as a wrap for small morsels of mozzarella, the 10 cm leaves of Italian Large Leaf provide a visual generosity and aromatic presence that smaller-leaved Genovese basil cannot match.
• For pesto, both types work well — Italian Large Leaf produces a slightly sweeter, more anise-forward pesto compared to the more complex, peppery character of Genovese.
• In the Gulf kitchen, the large leaves adapt naturally to regional uses — as garnish for mezze platters, torn over grilled fish, or infused into vinegars and oils for longer-term flavor capture.
• In the garden, the tall, upright plants provide structure and aromatic foliage that works well alongside fruiting vegetables — basil is a renowned companion plant for tomatoes, where it is believed to deter aphids and improve tomato flavor when grown in proximity.