| Variety | Relative Maturity/Disease Tolerance | Head Size and Color/Butt or Leaf | Notes | Description |
 Butter Lettuce: Harmony |
50-70 days | Large, Dark, glossy green | Ideal for organic and conventional production; excellent internal quality. | A remarkably uniform variety that produces glossy, very dark green heads; its large size and good weight ensures a good packout; the leaves have smooth margins and the texture is moderately thick with slight blistering; ideal for early and late season productions or year round in temperate areas; resistance to Downy Mildew (pathotypes I-VI) and Lettuce Mosaic Virus. |
| DMR 1-6, LMV. | Leaf: Slightly blistered | |||
 Butter Lettuce: Rhapsody |
50-70 days | Large, Gark Green | Ideal for year round organic and conventional production. | A very attractive and high yielding butter; it produces large, heavy heads that make it especially suited for the prepared salads market; its leaves are glossy, dark green and have smooth margins; the leaf texture is moderately thick and mildly blistered; ideal for year round organic and conventional production in temperate areas; superior tipburn tolerance compared to other varieties in its class; resistance to Downy Mildew (pathotypes I-VI) and Lettuce Mosaic Virus. |
| DMR 1-6, LMV. | Leaf: Slightly blistered | |||
 Butter Lettuce: SSC 2835 |
0-0 days | , | SSC 2835 is Shamrock’s newest development in butter lettuce; it produces uniform heads with an attractive light green external color and a buttery, yellow interior; the heads have excellent size and weight and they have a nice, tall-round shape and a very smooth, flat butt; short cores, very good tip burn tolerance and high mildew tolerance complete this outstanding variety. DMR I-VIII. | |
| Leaf: | ||||
 Iceberg Lettuce: Acrópolis |
70-80 days | Large, Dark green | Remarkable uniformity and consistent performance; tipburn & bolting tolerance. | A sure-heading, hot season variety with remarkable uniformity and consistent performance; produces large, dark green plant frames that provide good head protection; reliably makes flattened-round heads with a very smooth shape; large size and thick, crisp texture ensure high yields; very good internal quality due to its tipburn and bolting tolerance. (Utility Patent #7,102,606) |
| Tipburn. | Butt: Smooth, flat | |||
 Iceberg Lettuce: Blockbuster |
80-110 days | Large, Dark green | Big Vein resistant; large heading under cool growing conditions; for spring harvest. | A vigorous, Salinas type lettuce for the early season; consistent production of large, heavy heads with a full-round, symmetrical shape and a flat butt; heads have a medium-large butt, a short core and flat ribs; its large, bright green plant frame offers excellent head protection; excellent size in sandy and decomposed granite (DG) soils; suited for carton and processing markets; Big Vein resistant. (PVP #200500183) |
| Big vein. | Butt: Smooth, symmetrical | |||
 Iceberg Lettuce: Champion |
0-0 days | , | Extraordinary resistance to mildew is what sets Champion apart. In our field trials it has held up to mildew better than other varieties that are DMR I-VIII / BL 1-25. It’s a vigorous variety that produces large plants with good head cover. Its large heads have good weight, good texture and a fresh green color. It will yield shapely heads with short cores when grown in the proper slot. Resistant to DMR I-VIII, CRR. | |
| Butt: | ||||
 Iceberg Lettuce: Colossus |
98-105 days | Large, Dark green | Attractive, large heads; early maturity; Big Vein tolerant | A lettuce variety that has distinctive advantages over standard Winterhaven types; amongst its advantages are better uniformity, earlier maturity and stronger Big Vein tolerance; Colossus produces attractive, large heads with a round shape and dark green color; relative maturity is 98-105 days; DMR llB, lll, IV. (PVP # 200400011) |
| DMR 2b, 3, 4. | Butt: Medium | |||
 Iceberg Lettuce: Cornerstone |
80-110 days | Large, Medium green | A mildew resistant variety for early season. | A mildew resistant variety for early Spring production; it produces a uniform crop of large heads protected by a large plant frame; its heads have a smooth, round shape and very crisp leaf texture; resistant to Downy Mildew (pathotypes I-VI). (PVP contemplated) |
| DMR 1-6, corky root. | Butt: Large, smooth | |||
 Iceberg Lettuce: Excalibur |
65-80 days | Large, Dark Green | Very uniform size and maturity; for summer harvest in temperate areas | A very sure heading variety for main season production in coastal areas; it is very uniform for head size and maturity; its smooth, round heads are a medium green color and have crisp texture; produces heavy heads in the 24's size range; highly tipburn and bolting tolerant; resistant to DMR I-VI. (Utility Patent #7,326,829) |
| DMR 1-6. | Butt: Smooth, symmetrical | |||
 Iceberg Lettuce: Spartacus |
0-0 days | , | A variety with very uniform head formation; it produces heavy heads with good size; the heads have a smooth, round shape, clean butts and a short core; it makes an ample plant frame that ensures head protection; in addition, the heads sit off the bed resulting in a lower incidence of bottom rot; tipburn and bolting tolerant. (Utility Patent #7,960,617Plant Breeder's Right pending) | |
| Butt: | ||||
 Iceberg Lettuce: SSC 1962 |
0-0 days | , | A hot season, desert variety similar to Spartacus; SSC 1962 is a sure heading variety with good uniformity that consistently produces smooth 24’s; it has a nice plant frame with slightly thicker leaf texture compared to Spartacus; SSC 1962 is tip burn and bolting tolerant. | |
| Butt: | ||||
 Iceberg Lettuce: Trophy |
0-0 days | , | Trophy is a sister line of Champion and has the same extraordinary level of mildew resistance. In our field trials it has held up to mildew better than other varieties that are DMR I-VIII / BL 1-25. It’s a vigorous variety that produces large plants with good head cover. Its large heads have good weight, good texture and a fresh green color. It will yield shapely heads with short cores when grown in the proper slot. Resistant to DMR I-VIII, CRR. | |
| Butt: | ||||
 Romaine Lettuce: Kessler |
65-95 days | , | A variety with dense, blanched centers; ideal for romaine hearts. | Kessler is an ideal variety for romaine hearts and processing; it produces dark green plants with a very upright habit and straight ribs; its narrow base and dense, blanched center make an attractive romaine heart; the leaves have a strong texture and are moderately savoyed; Kessler has good uniformity and weight and performs best under cool growing conditions; Corky Root resistant. |
| Corky root. | Leaf: | |||
 Romaine Lettuce: Sparx |
0-0 days | , | Sparx, a sister variety to Stryker, produces large, heavy plants that cup and blanch early. Sparx is ideal for production in the mid-season slot and is specifically targeted to the Coastal production areas of Blanco, Castroville and Watsonville. Sparx is extremely burn resistant and unbeatable for fog/inversion burn and internal tipburn in the difficult summer slot in these Coastal areas (even behind Strawberries). DMR I-VI and CRR. (Utility Patent pending) | |
| Leaf: | ||||
 Romaine Lettuce: Stryker |
0-0 days | , | A solid-ribbed, heavy romaine lettuce that is suitable for processing, hearts and cartons. Stryker has remarkable tolerance to fog/inversion burn as well as internal tipburn. It produces large plants that cup and blanch early allowing for harvest flexibility. Stryker is ideal for production in the early and mid-season slots throughout the Salinas Valley; DMR I-VI and CRR. (Utility Patent pending) | |
| Downy Mildew I-VI and Corky Root | Leaf: |
Disclaimer Regarding Disease Resistance: The term "resistance" is defined as a plant's ability to resist, not necessarily prevent disease. Resistance may be conferred by general plant health or by resistance genes. The use of resistance genes is a well documented method of conferring mildew and Bremia resistance in lettuce. The use of resistant varieties, in conjunction with proper pesticide, fertilizer, cultivation and irrigation practices, will go a long way to reducing or eliminating infection. However, various factors, such as stress and pathogen populations, often lead to a resistant plant becoming infected.
Disclaimer Regarding Variety Descriptions and Illustrations: Descriptions and illustrations represent Shamrock Seed Company's products as grown in our trial fields in various locations. Performance and appearance may vary under different growing conditions and in other geographical locations. It is advised to investigate whether differences may be expected in your growing regions.
Plant Variety Protection: Plant Variety Protection has been granted to many of our varieties. The Plant Variety Protection Office of the USDA has certified that Shamrock Seed Co., Inc.'s varieties for which protection has been granted, applied, or contemplated under the Plant Variety Protection Act are the exclusive property of Shamrock Seed Co., Inc. This Act excludes parties from unauthorized seed propagation. Please contact Shamrock Seed Co., Inc.'s main office (Salinas, CA) for details regarding PVP registration.
Utility Patent: Many of Shamrock genetic lines are protected under U. S. Utility Patents. This Patent type allows for "specific use only" and does not provide use for research or "grower exclusions". Utility Patented varieties exclude all unauthorized seed usage and propagation. For more information please contact Shamrock Seed Co., Inc.'s main office (Salinas, CA).
Plant Breeder's Rights have been granted or applied for through the Community Plant Variety Office; unauthorized seed propagation is prohibited.