Crisphead (Summer Crisp)
Muir Lettuce stands out as Johnny's Selected Seeds' most heat-tolerant lettuce variety, a significant achievement in breeding for warm-season gardening. This open-pollinated cultivar reaches harvest in just 50 days from transplants, making it one of the quickest lettuces to mature. With its bush growth habit and proven ability to thrive where other lettuces bolt or struggle in temperature fluctuations, Muir offers reliable production across a wider range of growing conditions than conventional varieties. The organic seed comes with NOP-compliant pelleting for easier handling and more precise sowing.
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What makes Muir exceptional is its heat tolerance in a crop that typically demands cool weather. Most lettuces struggle and bolt quickly when temperatures exceed 70°F, but Muir was specifically selected and developed to perform where heat stress would cause conventional varieties to fail. Combined with its rapid 50-day harvest window and open-pollinated genetics, this variety delivers both speed and adaptability. Gardeners in warmer climates or those extending their season into early summer will find Muir far more reliable than standard heat-sensitive lettuces.
Muir Lettuce is grown primarily for fresh salads and greens, where its quick maturity makes it ideal for succession planting. The open-pollinated nature means gardeners can save seed for future seasons, supporting seed sovereignty and reducing year-to-year input costs. Home and market gardeners use frequent sowings every 2-3 weeks to maintain a continuous harvest of either full heads or mixed salad greens throughout the growing season.
Start seeds indoors 4–6 weeks before your last spring frost, maintaining soil temperatures below 70°F (21°C) for best germination. Use pelleted seed at a rate of approximately 16,000 plants per ounce. Keep seedlings cool and well-lit until transplanting.
Transplant seedlings outdoors as soon as soil can be worked in early spring, or whenever temperatures stabilize between 60–65°F (16–18°C). Muir's heat tolerance makes it suitable for planting earlier in spring and later into early summer than standard varieties. Harden off seedlings gradually over 7–10 days before moving them to the garden.
Direct sow seed as soon as soil is workable in spring, planting shallowly into moist soil. Sow every 2–3 weeks for continuous harvest throughout the season.
Harvest Muir Lettuce 50 days after transplanting when heads reach mature size. Cut full heads at the base using a sharp knife, or pick individual leaves from the outside as the plant grows. For salad mix, harvest by cutting the entire head 1, 2 inches above the soil line. Morning harvest yields the crispest, most hydrated leaves. Harvested heads can be refrigerated at 35, 40°F (1, 4°C) with high humidity for 14, 20 days, though delicate types store slightly shorter; extend storage up to two weeks in cooler weather by holding cut heads in refrigeration before processing into salad mix.
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