Repotting guide

When & how to repot Sticky Jerusalem Sage (Phlomis viscosa)

Also called Sticky Jerusalem sage, Viscous phlomis.

More about sticky jerusalem sage

About Sticky Jerusalem Sage

Phlomis viscosa · also called Sticky Jerusalem sage, Viscous phlomis · flowering

Phlomis viscosa is a robust, glandular-sticky perennial or short-lived sub-shrub native to the eastern Mediterranean, from Israel and Lebanon through Turkey and Cyprus, growing on rocky, dry slopes and garrigue. It produces bold whorls of golden-yellow hooded flowers above large, sticky, rugose leaves that trap dust and insects. The key care rule is excellent drainage — soggy winter soil quickly kills the rootstock. Pet-toxicity status is not confirmed by the ASPCA; treat as mildly toxic out of caution.

Mature size: 90–120 cm tall and 80–100 cm wide.

Watch for — Root and crown rot in wet winters: The most serious threat in UK gardens and wet-winter climates; plant in full sun on free-draining soil or raised beds, and do not mulch over the crown.

How to tell sticky jerusalem sage needs repotting

Repotting on a calendar is less reliable than reading the plant. For sticky jerusalem sage, 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 sticky jerusalem sage) 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 sticky jerusalem sage

Only every 2–4 years, when genuinely crowded. Sticky Jerusalem Sage 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, bushy sub-shrub or perennial with stiff, sticky branching stems and tiered flower whorls..

What size pot to step sticky jerusalem sage up to

Go up only one pot size — roughly 2–3 cm (about an inch) wider in diameter, no more. Sticky Jerusalem Sage 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 sticky jerusalem sage 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 sticky jerusalem sage

Early spring, just as new growth restarts, is the ideal window for sticky jerusalem sage. 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 sticky jerusalem sage

Confirm it actually needs it. Slide sticky jerusalem sage 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 sticky jerusalem sage 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 free-draining, poor to moderately fertile, alkaline or neutral, 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 sticky jerusalem sage 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 sticky jerusalem sage

Sticky Jerusalem Sage wants free-draining, poor to moderately fertile, alkaline or neutral. Thrives in rocky or gravelly soil similar to its native limestone slopes; amend clay soils heavily with grit before planting and never allow the crown to sit in standing water. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting sticky jerusalem sage — frequently asked questions

How often should you repot sticky jerusalem sage?

Only every 2–4 years, when genuinely crowded for sticky jerusalem sage. Only repot sticky jerusalem sage 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 free-draining, poor to moderately fertile, alkaline or neutral. The key mistake is over-potting: a too-big pot stays wet and rots the roots.

What size pot does sticky jerusalem sage need?

When is the best time of year to repot sticky jerusalem sage?

Does sticky jerusalem sage like to be root-bound?

Yes — sticky jerusalem sage 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 sticky jerusalem sage after repotting?

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