Rosemary
Salvia rosmarinus
Also known as: Garden rosemary, Romarin, Romero
Quick facts
- Category
- herbs woody
- Difficulty
- intermediate
- Days to harvest
- 120 to 365 days
- Harvest type
- continuous production over weeks or months
- Spacing
- 45 cm between plants
Environment
- Temperature
- 7–30°C
- pH
- 6 to 7.5
- EC (hydroponic)
- 1 to 1.6 mS/cm
- Daily light
- 18 to 30 mol/m²/day
Climate and zones
- USDA zones
- 7 to 10 (winter low around -18°C or warmer)
- Frost tolerance
- tolerates light frost
- Season
- warm (summer crops, frost-sensitive)
Viable growing environments:
- outdoor year-round (in zone)
- outdoor in growing season (annual)
- unheated greenhouse / hoop house
- heated greenhouse
- indoor (heated home)
- indoor hydroponics under grow lights
USDA zone bounds reflect outdoor year-round survival. Anywhere outside the bounded zone range, this crop still grows as an annual in the warm months (outdoor_seasonal), under cover (greenhouse), or indoors under lights.
Growing systems
Rosemary works in:
- drip / Dutch buckets
- media bed (ebb and flow)
- soil bed
Root mass is heavy - thin-channel systems (NFT, vertical towers) can't hold this crop mechanically, hence the system list above.
Growing media
The substrate the roots sit in. Choice depends on the system (clay pebbles don't fit NFT channels; rockwool isn't used in media beds) and the crop (rosemary works in the media listed below).
| Medium | pH effect | Water retention | Bacterial surface |
|---|---|---|---|
| Expanded clay pebbles (LECA) | neutral / inert | low | high |
| Coco coir (Coconut coir) | slightly acidic | high | moderate |
| Soil-based mix (Potting soil) | varies by source | high | high |
Bacterial surface area matters for aquaponics: clay pebbles, lava rock, and pumice double as biofilter substrate. Low-surface media (rockwool, perlite, pea gravel) work in hydroponics but need a separate biofilter in aquaponics.
Nutrient demand by stage
NPK ratios are relative weights at each growth stage; the nutrient mix calculator scales them to absolute grams or ml. EC targets shift through the plant's life: seedlings need a much lighter solution than fruiting adults.
| Stage | N | P | K | EC target (mS/cm) |
|---|---|---|---|---|
| seedling | 1 | 1 | 1 | 0.6 |
| vegetative | 2 | 1 | 2 | 1.2 |
Aquaponics suitability
Not recommended for pure aquaponics. Fish waste alone doesn't provide enough of the nutrients this crop demands (typically potassium, calcium, or boron). It can be grown in a hybrid system where the reservoir is supplemented with hydroponic-style nutrients, but expect to dose actively.
Care notes
A long-lived perennial herb for container or hydroponic growing. Container (15 L) with very well-drained media (perlite, pumice, or expanded clay; rosemary dies in waterlogged conditions). EC 1.0-1.8 mS/cm (light feeder). pH 6.0-7.5 (tolerates slightly alkaline). Temperature: 10–30°C (Mediterranean; cold-hardy to zone 7-8 depending on variety). Full sun (DLI 18-28 mol/m2/day). Growth is slow to moderate. Harvest by cutting stem tips (10–15 cm); the plant branches freely when pruned. The woody habit means rosemary doesn't grow back from bare, leafless wood; always cut above green growth. For drying: strip leaves from stems, dry at 35–40°C or hang in bundles. Dried rosemary retains excellent flavor for 12+ months. Propagation by semi-hardwood cuttings (taken in summer, root in 3-6 weeks in moist perlite). From seed is possible but very slow and germination is poor. Overwatering and poor drainage are the primary causes of failure. In a hydroponic herb setup, rosemary needs drier conditions than basil or mint.
Verified against: rhs-uk. Last reviewed 2026-05-15.