Concept
Lactuca sativa 'Concept'
A premium loose-leaf lettuce that produces an abundance of deeply lobed, oak-shaped leaves with exceptional heat tolerance and slow bolting characteristics. This variety offers continuous harvest potential throughout the growing season, with leaves that maintain their tender texture and mild flavor even in challenging weather. Concept is perfect for gardeners who want a reliable, productive lettuce that keeps giving all season long.
Harvest
50-60d
Days to harvest
Sun
Full sun to partial shade
Zones
2–11
USDA hardiness
Height
6-12 inches
Planting Timeline
Showing dates for Concept in USDA Zone 7
All Zone 7 lettuce →Zone Map
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Concept · Zones 2–11
Growing Details
Zone-by-Zone Planting Calendar
| Zone | Indoor Start | Transplant | Direct Sow | Harvest |
|---|---|---|---|---|
| Zone 1 | — | — | June – July | July – September |
| Zone 2 | — | — | May – July | July – September |
| Zone 11 | — | — | January – February | February – December |
| Zone 12 | — | — | January – February | February – December |
| Zone 13 | — | — | January – February | February – December |
| Zone 3 | — | — | May – June | June – October |
| Zone 4 | — | — | April – June | June – October |
| Zone 5 | — | — | April – May | June – November |
| Zone 6 | — | — | April – May | May – November |
| Zone 7 | — | — | March – May | May – November |
| Zone 8 | — | — | March – April | April – December |
| Zone 9 | — | — | February – March | March – December |
| Zone 10 | — | — | January – March | March – December |
Succession Planting
Direct sow 'Concept' every 14 days starting around March 1 in zone 7, and keep going through mid-May. Once daytime highs are consistently hitting 80-85°F, germination turns spotty and whatever does come up will bolt before you get a full head — so pause. Pick back up with sowings in late August and run through mid-October for a fall harvest that stretches into November.
The 50-60 day days-to-harvest window is your main planning tool. Count back from your first expected frost date in fall and that gives you the last viable sow date — roughly mid-September in zone 7. Two short rows every two weeks beats one long row all at once; you'll get steady cuts instead of a glut followed by a gap.
Complete Growing Guide
Concept's exceptional heat tolerance makes it ideal for spring and summer growing when other loose-leaf varieties bolt prematurely, though you should still provide afternoon shade in extreme heat above 85°F. Plant seeds every two weeks for continuous harvests rather than relying on a single planting. This cultivar's slow-bolting tendency means you can delay succession plantings slightly longer than typical lettuce without sacrificing quality. Watch for aphids on the deeply lobed leaves where they hide easily—inspect the undersides during your regular harvests. The tender texture that makes Concept desirable also means leaves bruise slightly more than crisphead varieties, so handle gently during picking. Space plants 8–10 inches apart to ensure adequate air circulation and reduce fungal issues during humid weather. Rather than waiting for full maturity, begin harvesting outer leaves at 35–40 days to encourage bushier growth and extend your productive window throughout the season.
Light: Full sun (6 or more hours of direct sunlight a day), Partial Shade (Direct sunlight only part of the day, 2-6 hours). Soil: High Organic Matter. Soil pH: Neutral (6.0-8.0). Drainage: Good Drainage, Moist. Height: 0 ft. 6 in. - 1 ft. 0 in.. Spread: 0 ft. 6 in. - 1 ft. 0 in.. Spacing: Less than 12 inches. Growth rate: Rapid. Maintenance: Medium. Propagation: Seed. Regions: Coastal, Mountains, Piedmont.
Harvesting
Concept reaches peak harvest readiness when the deeply lobed oak-shaped leaves display a vibrant medium to light green color and measure 4-6 inches in length, feeling tender and pliable rather than firm. This variety thrives under a continuous harvest pattern—simply pinch or cut the outer leaves at the base once they reach desired size, encouraging the center crown to produce successive rounds of fresh foliage throughout the season. For optimal results, harvest in the early morning when leaves are fully hydrated and crisp, which enhances their tender texture and mild flavor while minimizing any potential for wilting during the day.
Tiny seeds with a dandelion-like tuft (pappus) to aid in wind dispersal.
Color: Brown/Copper. Type: Achene. Length: < 1 inch. Width: < 1 inch.
Harvest time: Summer
Edibility: Leaves can be used raw or cooked in salads, sandwiches, and other dishes. Head lettuce can be stored for 2-3 weeks while leaf and butterhead store for 1-2 weeks.
Storage & Preservation
Immediately after harvest, rinse Concept leaves in cool water and spin dry gently in a salad spinner. Store unwashed leaves in perforated plastic bags in the refrigerator crisper drawer at 32-36°F with high humidity. Properly stored, fresh leaves maintain quality for 7-10 days.
For longer storage, blanch whole leaves in boiling water for 30 seconds, then plunge into ice water. Drain thoroughly and freeze in freezer bags for up to 8 months. While texture changes, frozen lettuce works well in cooked dishes and smoothies.
Concept's tender leaves also work well for making lettuce wraps that can be briefly dehydrated and stored as chips. The mild flavor makes it excellent for fermenting into lettuce kimchi or adding fresh to lacto-fermented vegetable mixes for a crisp texture contrast.
History & Origin
Concept is a loose-leaf lettuce variety developed and introduced by Johnny's Selected Seeds, a major American seed company based in Maine. Like many modern vegetable cultivars bred for commercial and home garden use, Concept emerged from selective breeding programs focused on heat tolerance and delayed bolting—traits increasingly valued as gardeners sought reliable production across longer seasons and variable climates. While specific breeder attribution and the exact year of introduction are not extensively documented in readily available sources, the variety represents the lineage of improved oak-leaf type lettuces developed through mid-to-late twentieth-century American seed breeding. Its parentage likely traces to European oak-leaf genetics combined with heat-tolerant germplasm selected for the American market.
Origin: Mediterranean to Siberia
Advantages
- +Exceptional heat tolerance allows reliable harvests during hot summer months
- +Deeply lobed oak-shaped leaves provide attractive visual appeal and continuous picking
- +Slow bolting characteristic extends harvest window significantly longer than most varieties
- +Mild, sweet flavor maintains quality even in challenging weather conditions
- +Easy to grow makes Concept suitable for beginner and experienced gardeners
Considerations
- -Susceptible to downy mildew requires preventative fungal disease management strategies
- -Vulnerable to multiple pests including aphids, flea beetles, slugs, and leaf miners
- -Bacterial leaf spot disease can cause significant damage in humid conditions
- -Loose-leaf nature means leaves bruise easily during harvest and handling
Companion Plants
Radishes are probably the most useful thing you can tuck in next to 'Concept.' They mature in 25-30 days and draw flea beetles away from the lettuce — a sacrificial crop that costs you almost nothing. Chives and garlic work through a different mechanism: their sulfur compounds appear to confuse aphids, which are one of the more persistent problems on lettuce. Marigolds (Tagetes spp.) attract predatory insects that feed on aphid populations, and their shallow roots don't compete with lettuce's equally shallow system. Nasturtiums pull double duty as both an aphid trap crop and an edible flower, which is a reasonable trade in a tight bed.
Fennel is the plant to keep on the far side of the garden. It releases allelopathic compounds from its roots that suppress most vegetables, and lettuce is notably sensitive. Broccoli can coexist early in the season, but by the time it's sizing up — usually 40-50 days in — it'll be casting enough shade to stall a low-growing lettuce before that 50-60 day harvest window closes.
Plant Together
Chives
Repels aphids and improves lettuce flavor and growth
Carrots
Deep roots don't compete with shallow lettuce roots, helps loosen soil
Radishes
Quick growth breaks up soil, deters flea beetles and aphids
Marigolds
Repels nematodes and aphids, attracts beneficial insects
Spinach
Similar growing conditions and harvest times, efficient space usage
Garlic
Natural pest deterrent, repels aphids and slugs
Nasturtiums
Acts as trap crop for aphids and cucumber beetles
Dill
Attracts beneficial insects like ladybugs and lacewings
Keep Apart
Broccoli
Heavy feeder that competes for nutrients and may shade lettuce
Fennel
Inhibits growth of most garden plants through allelopathic compounds
Sunflowers
Creates too much shade and competes heavily for water and nutrients
Nutrition Facts
Per 100g serving. % Daily Value based on 2,000 calorie diet. Source: USDA FoodData Central (FDC #2346388)
Pests & Disease Resistance
Resistance
Excellent heat tolerance, slow to bolt, good disease resistance
Common Pests
Aphids, flea beetles, slugs and snails, leaf miners
Diseases
Downy mildew, lettuce drop, bacterial leaf spot
Troubleshooting Concept
What you'll see, why it happens, and what to do about it.
Seedlings collapse at soil level within the first 1-2 weeks after planting — stems look pinched or rotted at the base
Likely Causes
- Damping off (Pythium spp. or Rhizoctonia solani) — a soil-borne fungal complex that hits seedlings hard in cool, wet, poorly-drained soil
- Replanting in the same bed where lettuce has grown for 2-3 consecutive years, allowing pathogen load to build up
What to Do
- 1.Don't reuse seed-starting mix; start fresh each season and make sure trays drain freely
- 2.If this bed has grown lettuce for 3+ years running, move your lettuce to a different spot — NC State's IPM framework flags this kind of accumulated monoculture history as a key risk factor for soil-borne disease
- 3.Let the soil surface dry slightly between waterings once seeds are in the ground; standing moisture at the crown is what kills them
Gray-white fuzzy coating on the underside of leaves, with yellow patches on the upper surface — showing up during cool, wet stretches of spring or fall
Likely Causes
- Downy mildew (Bremia lactucae) — an oomycete that spreads fast in humid conditions, particularly below 65°F
- Crowded spacing that traps moisture between plants
What to Do
- 1.Space plants at least 6-8 inches apart so air moves through the canopy
- 2.Water at the base, not overhead, and water in the morning so foliage dries before nightfall
- 3.Pull and trash (not compost) infected leaves as soon as you spot them — Bremia lactucae spores move fast once conditions are right
Outer leaves develop water-soaked, then brown, irregular spots — sometimes with a slimy margin; plant may collapse at the crown as temperatures climb
Likely Causes
- Lettuce drop (Sclerotinia sclerotiorum) — thrives when soil stays moist and temps push above 70°F
- Bacterial leaf spot (Xanthomonas campestris pv. vitians) — produces similar spotting but without the cottony white fungal growth at the stem base
What to Do
- 1.Check the crown: white cottony mycelium at soil level points to Sclerotinia; angular spots with no mycelium suggest bacterial leaf spot — the distinction changes your next move
- 2.For Sclerotinia, remove the whole plant plus the top inch of surrounding soil and dispose of it away from the garden entirely
- 3.Rotate out of lettuce (and other Sclerotinia hosts like beans) for at least 2 seasons in affected beds
Frequently Asked Questions
How long does Concept lettuce take to grow from seed to harvest?▼
Can you grow Concept lettuce in containers?▼
Is Concept lettuce good for beginners?▼
What does Concept lettuce taste like compared to other varieties?▼
When should I plant Concept lettuce for best results?▼
How do you prevent Concept lettuce from bolting in hot weather?▼
Growing Guides from Wind River Greens
Where to Buy Seeds
Sources & References
External authority sources used in compiling this guide.
See the Methodology page for how this data is sourced, what's AI-assisted, and known limitations.