Long-Leaved Phlomis (Long-leaved Jerusalem sage) care

Light

Aim for at least 4-6 hours of direct sun on the leaves. Full sun is required; position against a south- or west-facing wall in the UK to provide the reflected warmth that helps this eastern Mediterranean plant overwinter successfully. If your only bright window faces south, that's perfect for long-leaved phlomis — same window any aroid would fry on.

Watering

Watering long-leaved phlomis: low — water every 2–3 weeks during the growing season; minimal to none in winter. The number that matters isn't the day of the week — it's how dry the top 2-3 cm of the pot feels. A finger in the soil tells you more than a watering app. After every watering, tip the saucer. Naturally drought-tolerant; supplement only during prolonged summer dry spells and cease watering entirely in autumn to harden growth before winter.

Soil and pot

Long-Leaved Phlomis grows best in sharply drained, nutrient-poor sandy, gravelly, or chalky soil. Best in thin, poor, alkaline soils; on heavier ground, dig in a generous quantity of horticultural grit and plant slightly proud of the surrounding soil to aid drainage. 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

Long-Leaved Phlomis sits happiest at around Low (below 50%) humidity and -5 to 38°C (23 to 100°F). Prefers dry, open conditions; the long, densely felted leaves are an adaptation to low humidity and high transpiration — damp, still air promotes mildew on the foliage. 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 long-leaved phlomis sparingly. Apply a single low-nitrogen feed in spring; this species is adapted to infertile soils and over-feeding results in weak, floppy stems that are prone to wind and frost damage. 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 long-leaved phlomis in the Growli community. Each is annotated with the most common cause so you know where to start.

• Root rot from winter wet — The leading cause of plant loss in UK gardens; waterlogged, cold soils in winter rapidly cause fatal root and crown rot — sharp drainage, a grit mulch, and a sheltered site are the principal preventive measures.
• Powdery mildew on foliage — The dense felt of leaf hairs can mask early mildew infections; inspect regularly in humid spells and improve air circulation around the plant, or apply a sulphur-based fungicide as a preventive in susceptible gardens.

Propagation

Semi-ripe cuttings taken in midsummer root readily in a 1:1 perlite/sand mix under a cold frame; alternatively sow seed at 15–18°C in spring, which typically germinates in 2–4 weeks. 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

Long-Leaved Phlomis is mildly toxic to pets. Phlomis longifolia is not individually listed in the ASPCA Toxic and Non-Toxic Plant Database. Due to the lack of confirmed pet-safety data for this species, a mildly-toxic classification is applied as a precaution; seek veterinary advice promptly if a cat or dog ingests any part of this plant. 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.

Long-Leaved Phlomis deep-dive guides

Every aspect of long-leaved phlomis care, each with its own calibrated guide:

• Common long-leaved phlomis problems & fixes
• Long-Leaved Phlomis watering schedule
• Long-Leaved Phlomis light requirements
• Best soil mix for long-leaved phlomis
• Long-Leaved Phlomis fertilizing guide
• When to repot long-leaved phlomis
• How to propagate long-leaved phlomis
• How to prune long-leaved phlomis
• What's eating my long-leaved phlomis?
• Long-Leaved Phlomis growth rate & size
• Long-Leaved Phlomis cold hardiness
• Long-Leaved Phlomis temperature & humidity
• Is long-leaved phlomis toxic to cats & dogs?
• Is long-leaved phlomis toxic to cats?
• Is long-leaved phlomis toxic to dogs?
• All 10 Phlomis varieties
• Getting long-leaved phlomis to bloom

Featured in these plant shortlists

Long-Leaved Phlomis qualifies for 5 curated Growli shortlists — each one filtered objectively from our structured plant-care library, so the selection is consistent and checkable:

• Best drought-tolerant houseplants — Houseplants that prefer to dry out — forgiving of forgotten watering and ideal for travel or busy weeks.
• Best humidity-loving houseplants — Houseplants that thrive in a bathroom, kitchen, or by a humidifier — selected by documented humidity preference.
• Best flowering houseplants — Indoor plants grown for their blooms — selected from the flowering species in Growli’s plant-care library.
• Best houseplants for full sun — Houseplants that want direct sun — the species for a hot south or west-facing windowsill where shade-lovers scorch.
• Best houseplants for a cool room — Houseplants that tolerate cool conditions down to about 10°C — for an unheated spare room, hallway, porch or a home kept cool.
• Browse all 29 plant shortlists — pet-safe, low-light, drought-tolerant and more

Related guides

Long-Leaved Phlomis is also commonly called Long-leaved phlomis or Long-leaved Jerusalem sage.

• Tall Mix pincushion flower care — light, water and common problems
• Black Knight scabiosa care — light, water and common problems
• Salmon Queen scabiosa care — light, water and common problems
• All 10153 plant care guides in the Growli library