Fertilising guide

How to fertilise Sticky Jerusalem Sage (Phlomis viscosa)— schedule & NPK

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.

Growth habit: Upright, bushy sub-shrub or perennial with stiff, sticky branching stems and tiered flower whorls.

What fertiliser sticky jerusalem sage actually wants — and why

Sticky Jerusalem Sage flowers best on poor soil — feed it and you get a lush leafy plant with very few blooms, the exact opposite of what you want.

Little or nothing. Rich, especially nitrogen-rich, soil pushes foliage at the expense of flowers in this plant — lean ground is the technique, not a deficiency.

For the language behind the three numbers on the bottle — what nitrogen, phosphorus and potassium each do — see the NPK ratio explained entry. The short version for sticky jerusalem sage: match the feed to the job the plant is doing right now, not to a generic “plant food” on the shelf.

How often to feed sticky jerusalem sage, and which months

Feeding only earns its keep while the plant is in active growth and can use the nutrients — pour feed into a dormant or low-light plant and it simply builds up as root-burning salt. For sticky jerusalem sage:

A single balanced slow-release granular feed applied in early spring is sufficient; excessive nitrogen encourages rank leafy growth at the expense of flowers. In practice: no routine feeding at all for sticky jerusalem sage — at most a thin compost mulch for soil structure, never a flowering or nitrogen feed.

The dormant-season rule matters more than the exact interval: skip feeding entirely when sticky jerusalem sage is resting. For the wider context on indoor feeding rhythms across the seasons, the houseplant fertiliser schedule walks through the year month by month.

What strength to mix for sticky jerusalem sage

None is the correct answer for sticky jerusalem sage. The flower-versus-foliage trade-off is the whole point: hold back and you get the display.

Feeding always goes onto already-damp soil, never dry roots — water sticky jerusalem sage first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the sticky jerusalem sage watering schedule.

Signs you are over-feeding sticky jerusalem sage

Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for sticky jerusalem sage:

Abundant leafy growth and very few flowers (the classic over-rich symptom).
Soft, floppy stems and a sprawling, leafy habit.
Scorched edges and salt crust if it has been fed in a container.

Signs you are under-feeding sticky jerusalem sage

Effectively never an issue — these plants flower on poverty.
Only on genuinely dead soil: weak, thin growth and few blooms.
A short-lived plant in completely spent container compost.

If the symptoms point at watering, light or roots rather than nutrition, the full sticky jerusalem sage care brief covers soil, humidity and the common problems for this species.

Flushing and leaching the salts

If sticky jerusalem sage has accidentally been fed and is all leaf, a plain-water flush plus a move to leaner soil resets it; otherwise no flushing is needed because you are not feeding it.

Organic vs synthetic feeds for sticky jerusalem sage

Organic options

A thin compost mulch for soil structure is the absolute most; mostly, give it nothing. UK/US: leave it lean — no manure, no liquid feed. Poor soil is the active ingredient here.

Synthetic / liquid feeds

None. Synthetic feeds, particularly anything with appreciable nitrogen, directly suppress flowering in sticky jerusalem sage.

Brand names are examples, not endorsements, and UK and US ranges differ — check the label’s own NPK and dilution rate, since formulations change.

Fertilising sticky jerusalem sage — frequently asked questions

What fertiliser does sticky jerusalem sage need?

Little or nothing. Rich, especially nitrogen-rich, soil pushes foliage at the expense of flowers in this plant — lean ground is the technique, not a deficiency. Sticky Jerusalem Sage flowers best on poor soil — feed it and you get a lush leafy plant with very few blooms, the exact opposite of what you want.

How often should I feed sticky jerusalem sage?

A single balanced slow-release granular feed applied in early spring is sufficient; excessive nitrogen encourages rank leafy growth at the expense of flowers. A single balanced slow-release granular feed applied in early spring is sufficient; excessive nitrogen encourages rank leafy growth at the expense of flowers. In practice: no routine feeding at all for sticky jerusalem sage — at most a thin compost mulch for soil structure, never a flowering or nitrogen feed.

What strength of feed for sticky jerusalem sage?