Repotting guide

When & how to repot Long-Leaved Phlomis (Phlomis longifolia)

Also called Long-leaved phlomis, Long-leaved Jerusalem sage.

More about long-leaved phlomis

About Long-Leaved Phlomis

Phlomis longifolia · also called Long-leaved phlomis, Long-leaved Jerusalem sage · flowering

Phlomis longifolia is an upright, grey-woolly shrub native to Turkey, Lebanon, and the eastern Mediterranean, recognisable by its unusually elongated, softly felted leaves and tall stems bearing whorls of bright yellow flowers in early summer. It is well suited to dry, sunny borders and gravel gardens where its bold, textural foliage provides year-round interest. Like all Mediterranean phlomis, it is intolerant of waterlogged soil and must have free drainage to thrive in wetter climates. Phlomis longifolia is not listed in the ASPCA database and is classified as mildly-toxic due to the absence of confirmed pet-safety information.

Mature size: 100–150 cm tall and 75–100 cm wide (approximately 3.5–5 ft × 2.5–3.5 ft).

Watch for — 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.

How to tell long-leaved phlomis needs repotting

Repotting on a calendar is less reliable than reading the plant. For long-leaved phlomis, watch for these signs:

Roots spiralling thickly out of the drainage holes or pushing the whole plant up out of the pot.
The pot is so packed that water runs straight through in seconds and barely wets the soil.
It has split a plastic pot, or the rootball is a solid mass with almost no soil left when you slide it out.
Growth and (for long-leaved phlomis) flowering have clearly stalled despite good light and feeding — but remember this plant likes being snug, so a little crowding alone is not a reason to repot.

For the underlying biology of a pot-bound root system and why it stalls a plant, see our guide to spotting and fixing a root-bound plant.

How often to repot long-leaved phlomis

Only every 2–4 years, when genuinely crowded. Long-Leaved Phlomis is one of the plants that genuinely prefers a snug pot — it grows and flowers better with its roots a little restricted, so resist the urge to repot it on schedule. Upright, loosely branched evergreen shrub with notably long, strap-shaped, densely felted grey-green leaves..

What size pot to step long-leaved phlomis up to

Go up only one pot size — roughly 2–3 cm (about an inch) wider in diameter, no more. Long-Leaved Phlomis positively prefers a snug pot: it flowers and grows better when the roots are a little restricted. The single biggest repotting mistake here is over-potting — dropping long-leaved phlomis into a pot two or three sizes up. All that surplus soil holds water the small root system cannot use, stays cold and wet, and rots the roots within weeks. When in doubt, choose the smaller pot.

Not sure of the exact diameter? Our pot size calculator takes the current pot and root spread and tells you the right next size — it deliberately recommends a single step up, never a big jump.

The best time of year to repot long-leaved phlomis

Early spring, just as new growth restarts, is the ideal window for long-leaved phlomis. The plant is moving into its strongest growth phase and re-roots into fresh soil quickly. Avoid repotting in winter dormancy or, for flowering plants, while it is in bud or bloom — recovery is slowest then and you risk dropping the flowers.

Step-by-step: repotting long-leaved phlomis

Confirm it actually needs it. Slide long-leaved phlomis out and check the roots. Only continue if it is genuinely packed — this plant prefers a snug pot, so if there is still soil and room, put it straight back.
Pick a pot only one size up. Choose a pot just 2–3 cm wider with good drainage. Resist anything bigger; over-potting is the main killer here.
Ease it out gently. Water lightly the day before, then tip long-leaved phlomis out, supporting the base. Tease the outer roots free only enough to stop them circling.
Repot at the same depth. Add a layer of fresh sharply drained, nutrient-poor sandy, gravelly, or chalky soil, set the plant so the soil line sits exactly where it did before, and backfill around the sides, firming lightly.
Settle it in. Water once to settle the soil, then let it sit. Hold off on more water until the top of the soil dries — fresh soil around a small root system stays wet for a while.

Aftercare

Because the new soil holds more water than the old crammed rootball did, ease right back on watering — let the top of the soil dry before you water long-leaved phlomis again, or you will rot the roots in the very pot you just moved it to. Keep it out of harsh direct sun for a fortnight. Do not fertilise for about 4 weeks — fresh mix already carries nutrients and feeding freshly disturbed roots scorches them.

The right soil mix for long-leaved phlomis

Long-Leaved Phlomis wants 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. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting long-leaved phlomis — frequently asked questions

How often should you repot long-leaved phlomis?

Only every 2–4 years, when genuinely crowded for long-leaved phlomis. Only repot long-leaved phlomis every 2–4 years, and only when it is genuinely root-bound — it flowers and grows best slightly crowded. Step up just one pot size in spring using sharply drained, nutrient-poor sandy, gravelly, or chalky soil. The key mistake is over-potting: a too-big pot stays wet and rots the roots.

What size pot does long-leaved phlomis need?

When is the best time of year to repot long-leaved phlomis?

Does long-leaved phlomis like to be root-bound?

Yes — long-leaved phlomis genuinely flowers and grows best when slightly pot-bound, so do not rush to repot it. The mistake to avoid is over-potting into a much larger pot: the excess soil stays wet, the roots cannot use it, and the plant rots. Only repot every few years and only one snug size up.

Should you fertilise long-leaved phlomis after repotting?

Not immediately. Wait about 4 weeks after repotting long-leaved phlomis. Fresh mix already contains nutrients, and feeding freshly cut or disturbed roots burns them. Resume your normal feeding routine once you see new growth.