Great Lakes

Lettuce

70d to harvest

Crisp as fresh-cut glass, Great Lakes lettuce forms a dense, uniform head with a cool, sweet snap and a clean, refreshing bite. The leaves are thick and sturdy—deep green to blue-green on the outside, pale and buttery within—holding their crunch beautifully in the garden and on the table. Ideal for crisp salads and elegant platters, Great Lakes is a crisphead favorite for gardeners who want dependable, head-forming performance at about 70 days.

Crop Dates

Milestone	Date
Start Indoors	Apr 24th
Last Frost	May 15th
Transplant / Sow Outdoors	May 15th
Harvest Begins	Jul 24th
Harvest Ends	Sep 1st

Crop Details

Trait	Value
Days to Maturity	70
Sun Requirements	Full Sun
Growth Habit	Rosette
Support Needed	None
Planting Depth	Surface
Germination Temp (°F)	45
Min Soil Temp (°F)	40
Min Night Temp (°F)	32
Harden Off (days)	6

Frequently Asked Questions

What pest or disease is most likely on Lactuca sativa (iceberg-type lettuce) and how do I treat it?

Iceberg lettuce (Lactuca sativa) is especially prone to downy mildew (often seen as pale yellow patches on leaf tops with fuzzy gray-purple growth underneath). Improve airflow by spacing plants and water the soil (not the leaves), then remove badly infected leaves immediately to slow spread. If it keeps recurring, treat early with a labeled fungicide for downy mildew on edible greens, following the product’s waiting period before harvest.

How often should I water Lactuca sativa during the main growing phase to avoid problems?

During the 6–8 weeks before harvest, keep the soil consistently evenly moist—aim for about 1 inch (2.5 cm) of water per week, split into 2–3 smaller soakings if it’s hot or windy. Letting lettuce dry out causes bitterness and loose heads, while staying soggy encourages mildew; the goal is moist soil with good drainage. Test by pressing a finger into the soil: it should feel moist 1–2 inches down, not wet or bone-dry.

How can I tell when Great Lakes (Lactuca sativa) is ready to harvest?

Harvest when heads feel firm and reach about full size for your planting spacing; at 70 days from sowing or transplanting, timing typically lines up with head firmness. The outer leaves should be crisp and green, with no significant bolting (flowering stalk) starting in the center. Cut the head at the base with a sharp knife in the morning for best texture.