Parris Island Cos (Romaine) Lettuce

Lactuca sativa

Approximately ~ 200 seeds per packet

Packed for 2026

Botanical Origins and History of Domestication

Parris Island Cos is a classic American romaine, or “cos,” lettuce belonging to the family Asteraceae. Cultivated lettuce (Lactuca sativa) ultimately traces its ancestry to wild lettuces of the Mediterranean region and Southwest Asia. Lettuce was cultivated thousands of years ago, including in ancient Egypt, and over centuries selection transformed earlier forms into plants grown primarily for tender edible leaves. Romaine or cos lettuce became one of the major cultivated forms, characterized by elongated leaves that grow upright and develop into tall, somewhat cylindrical heads.

Development, Spread, and Diversification

Unlike ancient romaine lettuces generally, Parris Island Cos is a distinctly American cultivar developed in South Carolina around 1950–1952. Clemson sources identify it as an heirloom named for Parris Island, South Carolina, while historical seed accounts associate its development with Clemson College's agricultural breeding work. It was selected for uniform upright growth, quality, resistance to tipburn and lettuce mosaic virus, and better tolerance of warm conditions than many lettuces. It was introduced commercially in the early 1950s and became widely grown by home gardeners and commercial growers, particularly in the eastern United States.

Parris Island Cos represents the continued diversification of Lactuca sativa into specialized lettuce types such as loose-leaf, butterhead, crisphead, and romaine. Its combination of dependable head formation, crisp texture, disease tolerance, and adaptability helped establish it as one of the best-known American romaine cultivars. Cornell describes it as a cos/romaine suitable for both baby-leaf and mature-head production.

Appearance and Characteristics

Parris Island Cos produces attractive, upright heads generally reaching 10–12 inches tall. The outer leaves are medium to dark green, elongated, slightly crinkled or savoyed, with prominent crisp ribs. Toward the center, the leaves become progressively lighter, forming a tender pale-green to creamy-white heart. The plants are vigorous and relatively uniform, producing the tall, narrow head characteristic of romaine lettuce.

Its flavor is mild, sweet, fresh, and somewhat richer than many commercial romaines, while its leaves combine a tender texture with a pronounced crunch. Parris Island Cos also has useful resistance or tolerance to tipburn and lettuce mosaic virus and has moderate resistance to bolting, although prolonged heat can still cause plants to send up a flower stalk and develop bitter leaves.

Culinary Uses

Parris Island Cos is particularly well suited to Caesar salads, where its sturdy leaves and crisp midribs stand up well to rich dressings. It is equally useful in mixed green salads, sandwiches, wraps, burgers, tacos, and chopped salads. Whole leaves can serve as edible cups for vegetables, grains, beans, chicken, or other fillings. Young plants can also be harvested as tender baby lettuce, providing a milder leaf for spring mixes and mesclun.

Growing Tips and Growing Zones

Parris Island Cos is a cool-season annual that can be grown throughout USDA Zones 2–11, although planting dates rather than winter-hardiness zones are most important for lettuce. In colder and temperate regions, grow it primarily in spring and fall; in mild-winter climates it can also be grown during fall and winter. Lettuce performs best when temperatures are relatively cool—Clemson Extension gives approximately 55–65°F as an optimum growing range. High temperatures encourage bolting and can make the leaves bitter.

Choose a location receiving full sun during cool weather. Partial or afternoon shade becomes helpful as temperatures rise. Plant in loose, fertile, well-drained soil rich in organic matter and maintain consistent moisture, since alternating dry and wet conditions can reduce leaf quality. For full-sized heads, thin plants to approximately 8–12 inches apart. Succession sowing every two to three weeks during suitable weather can provide an extended harvest.

Sowing Depth and Planting

Because lettuce seed is small and benefits from light for germination, it should be planted very shallowly. Sow Parris Island Cos seed on the soil surface to approximately 1/8–1/4 inch deep, gently firming the soil and keeping the seedbed consistently moist. Clemson notes that lettuce seed needs light for good germination, so avoid burying it deeply. Seeds commonly germinate in about 5–10 days under favorable conditions.

Direct sow outdoors about two to four weeks before the average last spring frost, or start seedlings indoors four to six weeks before transplanting. For a fall crop, sow while enough cool growing weather remains for plants to mature before severe freezing conditions. In hot climates, germination may improve when seed is started indoors because lettuce germinates poorly in excessively warm soil.

Days to Maturity

Expect approximately 60–70 days to maturity for full-sized heads, although growing conditions and the desired harvest stage can shift this range. Baby leaves can be harvested considerably earlier—often around 21–30 days. Some commercial seed listings give approximately 68–72 days for mature heads.

Harvesting Guidance

For baby greens, begin clipping individual outer leaves once they are large enough to use, while leaving the central growing point intact so the plant can continue producing. For mature romaine, harvest when the upright leaves overlap to form a firm but not excessively tight head, generally around 10–12 inches tall. Clemson Extension describes mature romaine as having elongated, overlapping leaves forming a partially tight head.

Harvest preferably in the cool of the morning, when the leaves contain the most moisture and are at their crispest. Cut the entire head just above soil level with a clean, sharp knife, or selectively harvest the larger outside leaves for an extended picking period. Do not wait too long once warm weather arrives; plants beginning to elongate vertically from the center are preparing to bolt, after which leaf quality and sweetness decline.