Spike lavender (Broad-leaved lavender) care

Light

Most houseplants will scorch where spike lavender thrives. Give it the windowsill you'd otherwise leave empty because everything else burned there. Requires at least 6–8 hours of direct sun daily. Poor light causes lax, floppy stems, sparse flowering, and increased vulnerability to rot. A south- or west-facing aspect is ideal in both US and UK gardens. A plant moved abruptly from low light to direct sun bleaches in 48 hours — always acclimatise over a week.

Watering

Aim for every 2–3 weeks once established; more frequent only during planting establishment for spike lavender, but treat that as a starting point rather than a rule. A south-facing summer windowsill will dry the pot twice as fast as a north-facing winter room. Lift the pot; if it feels noticeably lighter than it did wet, water it. Extremely drought-tolerant once established. Overwatering or waterlogged soil is the primary killer — allow the root zone to dry completely between waterings. In rainy UK summers, additional irrigation is rarely needed.

Soil and pot

Spike lavender grows best in lean, sharply drained alkaline to neutral loam or sandy soil; ph 6.5–7.5. Thrives in poor, gritty or sandy soils that larger perennials struggle in. Avoid clay and rich, moisture-retentive mixes. Incorporate horticultural grit liberally when planting in heavier UK soils. Never mulch directly against the crown. A pot with a working drainage hole is non-negotiable for this species — even free-draining mix will turn soggy in a closed planter. If you love the look of a decorative pot without a hole, use it as a cachepot around an inner nursery pot you can lift out to water.

Humidity and temperature

Spike lavender sits happiest at around Low to moderate (30–50% RH) humidity and -15 to 35°C (5 to 95°F). Prefers dry air; high humidity encourages root and crown rots. Good air circulation around plants is essential, especially in sheltered UK garden spots. If you keep the room above year-round and avoid placing the plant near a cold draught, a hot radiator, or an air-conditioning vent, you have already handled the two biggest indoor stressors.

Fertilising

Feed spike lavender sparingly. Apply a low-nitrogen, high-potassium fertiliser (tomato feed) once in early spring, if at all. Rich feeding produces lush, soft growth prone to disease and reduces flowering and essential oil concentration. Established plants in well-chosen sites need no feeding. Skip fertiliser entirely on a stressed, recently-repotted, or actively wilting plant — fertiliser salts make damage worse, not better. Wait for a round of healthy new growth before resuming a feeding rhythm.

Common problems

Below are the issues we see most often on spike lavender in the Growli community. Each is annotated with the most common cause so you know where to start.

• Root and crown rot — The most common cause of plant death — caused by waterlogged soil or heavy clay. Ensure drainage is sharp; raised beds or gravel mulch can help in wet UK gardens.
• Woody, declining plants — Lavandula latifolia becomes unproductively woody after 5–7 years. Cut back by up to one-third in early spring (never into old, leafless wood) to extend lifespan; replace overgrown specimens.
• Shab (Phytophthora ramorum / Botrytis) — Grey mould and dieback are favoured by still, humid air. Improve spacing and airflow, remove dead wood promptly, and avoid overhead irrigation.

Propagation

Take 8–10 cm softwood or semi-ripe heel cuttings in late spring to early summer; root in gritty compost at 18–20°C without mist. Division is not practical for this woody species. Can be grown from seed but germination is slow and seedlings variable — vegetative propagation is preferred for uniform plants. Propagation is the cheapest, most satisfying way to expand a collection — and it doubles as insurance against losing a mature plant to an accident. Take a backup cutting once the parent is established and healthy.

Toxicity to pets

Spike lavender is mildly toxic to pets. ASPCA lists Lavandula species as mildly toxic to dogs and cats due to linalool and linalyl acetate (essential oil components). Ingestion may cause nausea, vomiting, and inappetence. Topical essential oil exposure can be more serious for cats than nibbling the foliage. If you keep cats, dogs, or curious children in the house, weigh placement carefully — a high shelf or a hanging planter is enough for casual safety. For severe ingestion incidents, call your local vet and the ASPCA Animal Poison Control Center (in the US, 888-426-4435).

Pet-safety status is sourced from the ASPCA Toxic and Non-Toxic Plant List, which catalogues the most-asked-about plants for cats, dogs, and horses.

Spike lavender deep-dive guides

Every aspect of spike lavender care, each with its own calibrated guide:

• Spike lavender watering schedule
• Spike lavender light requirements
• Best soil mix for spike lavender
• Spike lavender fertilizing guide
• When to repot spike lavender
• How to propagate spike lavender
• Spike lavender growth rate & size
• Spike lavender cold hardiness
• Spike lavender temperature & humidity
• Is spike lavender toxic to cats & dogs?
• Is spike lavender toxic to cats?
• Is spike lavender toxic to dogs?

Related guides

Spike lavender is also known as Spike lavender, Broad-leaved lavender, and Portuguese lavender.

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