Idaho · zones 5b–7b
When to plant lettuce in Idaho.
Sow between Apr 3 to May 18 in a typical year, keyed to Idaho's median last frost around May 11. A second, fall sowing fits Jul 15 to Sep 13. Dates below are state medians; your ZIP code shifts them by days to weeks.
The 2026 windows
Lettuce dates for a typical Idaho season.
Direct sow
Apr 3 to May 18
Keyed to the ~May 11 last frost. Sow 0.25" deep, 6" apart.
Fall round
Jul 15 to Sep 13
Counted back from the ~Sep 28 first frost.
Harvest
~45 days later
~0.4 lb per plant over ~1 weeks.
Idaho spans more than one climate: Zone 6 is the most common zone, but the state runs 5b to 7b. That's why the planner works from your ZIP code's frost dates, not your zone: mountain and coastal gardens in the same state can be three weeks apart.
Idaho growing notes
Leaf lettuce turns over fast enough here that a single Idaho garden can run it ten separate times before summer heat and fall cold both have their say.
Ten sowings, not one, and why that math works here
Leaf lettuce goes into the ground directly, a quarter inch deep and thinned to about 6 inches apart, and reaches harvest in around 45 days, one of the fastest turnarounds of anything grown in the state. Set against a season running roughly 140 days frost to frost, that math supports something like ten separate sowings spread through the year instead of one large planting that all comes ready in the same week and turns bitter together. A short season is a real limit on a crop that needs 90 or 100 days to finish; it barely registers against one built to restart itself ten times over.
The trick is treating each sowing as a short row rather than the whole bed, timed roughly two weeks behind the one already growing, so a fresh planting comes into its best week just as the older one is cut hard or pulled. Cutting the outer leaves and leaving the center to keep growing stretches the roughly 0.4 pounds a plant yields here across several pickings instead of one, which matters more on a crop grown in ten short rounds than on something planted once for the whole season.
Reading the plant instead of the calendar
Unlike a root crop or a brassica, which shrug off a warm stretch without much complaint, lettuce is quick to give up once real heat sets in, and the useful signal is what the plant does, not a temperature to watch for. A head that starts standing up tighter and taller instead of staying low and spreading, with the center leaves turning narrow and pointed, has begun bolting, and the leaves still on it turn bitter within days. There is no talking a bolting lettuce plant out of it once that shift starts; the right move is to cut what is usable and clear the row for the next sowing rather than nurse it along.
This is exactly why the spring and fall windows matter so much more for lettuce than for a crop that can simply sit through a hot stretch and wait it out. The Treasure Valley's warmer floor pushes an early planting toward that stall sooner than a high-country garden does, where cooler air buys the same sowing extra weeks before it turns. A grower on the valley floor gets more out of leaning on the back half of the season, while someone gardening at elevation can often ride the spring sowings further into summer than the calendar alone would suggest.
The slug, the cutworm, and two more worth telling apart
Slugs and snails do their worst in damp, mulched beds and irrigated ground, a bigger concern in the northern panhandle's wetter air than the dry valley floor. The tell is a silvery slime trail across a leaf and ragged holes eaten from the edge inward, usually found at dusk or early morning when the slugs themselves are still out and easy to hand-pick. Cutworms work at night too, but lower: a seedling sliced clean through at the soil line overnight, gone by morning, is a cutworm's work, and a simple collar, a paper cup with the bottom cut out pushed into the soil around a young seedling, stops it cold.
Aphids cluster on the undersides of leaves, usually light enough here that a firm rinse before the leaves reach the kitchen handles what a spray of water in the garden didn't already knock loose. Downy mildew shows as pale, angular blotches on top of a leaf with a gray fuzz on the underside directly beneath each one, favoring the same cool, damp stretches that suit a spring or fall sowing better than a summer one. Picking off the affected leaves as they appear, rather than waiting, usually keeps the rest of a planting worth cutting.
In Idaho: watch for
The pests that find lettuce here.
The short season here, about 140 frost-free days, keeps lettuce, leaf in front of aphids only briefly. One early row cover usually carries a planting through the worst of it.
Clusters tucked into the heart of the head.
Organic fix: Rinse well; insecticidal soap on young plants.
Ragged holes and slime trails, worse after rain.
Organic fix: Iron-phosphate bait; a diatomaceous-earth ring; hand-pick at night.
Seedlings clipped off at the soil line overnight.
Organic fix: Collars around the stems; Bt or diatomaceous earth.
Pale yellow patches boxed in by the leaf veins, with white fuzz underneath.
Organic fix: Give plants room, let them dry between waterings, clear old leaves, and pick resistant varieties.
Your season math: Idaho gives lettuce about 140 frost-free days, and it needs roughly 45 days to a first harvest. That fits about 10 re-sown rounds across the season, so you can keep it coming instead of picking once.
Planting lettuce in Idaho: questions
When should I plant lettuce in Idaho?+
In a typical Idaho year, sow lettuce between Apr 3 to May 18, keyed to the state's median last frost around May 11. There's also a fall window: Jul 15 to Sep 13. Your exact dates shift with your ZIP code and microclimate.
What USDA zone is Idaho?+
Idaho spans zones 5b–7b, mostly zone 6. But frost dates, not zones, set planting time. The free planner uses your ZIP code's actual frost dates.
How many lettuce plants do I need?+
Depends who you're feeding. The crop page has exact counts per household size, or the free planner does the math for your family in about 60 seconds.