Vegetable
Lettuce (Loose-leaf / Romaine)
Lactuca sativa · Asteraceae
Also called: Leaf lettuce, Cos lettuce (romaine), Garden lettuce
Lettuce (Loose-leaf / Romaine) (Lactuca sativa) is a moderate-water vegetable well suited to Tucson and the low desert. It's a fast-growing vegetable.
Lettuce (Loose-leaf / Romaine) at a glance
- Water use
- Moderate (established)
- Sun
- Full sun in the cool season; provide afternoon/filtered shade for late plantings to slow bolting as temperatures climb.
- Mature size
- Loose-leaf 6-10 in tall/wide; romaine forms upright heads 8-12 in tall.
- Growth rate
- Fast
- Bloom
- Pale yellow (flowers only after bolting; not desirable), Bolts and flowers in spring as Tucson heats up - harvest before this.
- Cold hardiness
- Cool-season annual; tolerates light frost (especially romaine) but tender seedlings benefit from frost cloth in hard freezes. Bolts and gets bitter once daytime temps consistently exceed ~80 F.
- Soil
- Loose, fertile, well-drained soil high in organic matter; pH 6.0-7.0.
- Native range
- Mediterranean / Western Asia (domesticated from wild Lactuca)
- Best used as
- Salad greens (leaf and romaine), Cool-season raised-bed and container crop, Succession/cut-and-come-again harvesting, Quick fall and winter garden filler
- Wildlife
- Minimal; flowers (if bolted) attract some pollinators.
- Toxicity
- Non-toxic, edible. Safe for pets and people.
How to grow Lettuce (Loose-leaf / Romaine) in Tucson & the low desert
Watering
Cool-season crop in Tucson: sow seed or set transplants from September through February (fall and late-winter plantings are most reliable; it can also be grown through mild winters under frost cloth). Keep soil consistently and evenly moist with frequent shallow-to-medium watering - lettuce has shallow roots and turns bitter or bolts under drought or heat stress.
Fertilizer & nutrients
Light, steady feeder. Amend bed with compost and side-dress with a nitrogen-forward fertilizer (or fish emulsion) every 2-3 weeks for fast, tender leaf growth. Nitrogen drives leaf quality.
Pruning & care
No pruning. Harvest loose-leaf types as cut-and-come-again, taking outer leaves; harvest romaine whole or by outer leaves before it bolts in spring warmth.
Notes
A staple of Tucson's fall/winter/early-spring garden. Avoid summer - heat causes bolting and bitterness. Stagger sowings every 2-3 weeks Sept-Feb for continuous harvest; use shade cloth to push plantings later into spring.
Sources: University of Arizona Cooperative Extension / Pima County Master Gardeners cool-season vegetable calendar; Tucson Organic Gardeners Planting Guide; Green Things Nursery (Tucson) planting guide