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Repotting guide

When & how to repot Sea Heath (Frankenia laevis)

Also called Sea Heath, Common Sea Heath.

More about sea heath

About Sea Heath

Frankenia laevis · also called Sea Heath, Common Sea Heath · flowering

Frankenia laevis is a low, mat-forming evergreen sub-shrub in the family Frankeniaceae, native to the upper saltmarsh margins, sandy cliffs, and coastal shingle of southern and eastern England, France, and the Mediterranean coast. It produces mats of tiny, heath-like leaves (often with salt-encrusted surfaces) that turn reddish-purple in winter, and bears small pink flowers from June to August. The critical care requirement is perfect drainage in a sunny position; it is rare in the UK and specially protected in some coastal habitats. This species has no ASPCA toxicity listing and is classified as mildly-toxic as a precaution.

Mature size: 3–8 cm tall, spreading 20–60 cm wide over several years in suitable conditions.

Watch for — Winter wet rot: The most common cause of death in cultivation is root and crown rot during wet winters; plant on a slight slope or in a raised bed with grit mulch around the crown to keep moisture away from the woody base.

How to tell sea heath needs repotting

Repotting on a calendar is less reliable than reading the plant. For sea heath, watch for these signs:

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 sea heath

Every 2–3 years; top-dress in the in-between years. Sea Heath's growth habit — prostrate, mat-forming evergreen sub-shrub, 3–8 cm tall, spreading widely; stems woody at the base with pairs of tiny, rolled, heath-like leaves. — sets the pace. Frankenia laevis is a low, mat-forming evergreen sub-shrub in the family Frankeniaceae, native to the upper saltmarsh margins, sandy cliffs, and coastal shingle of southern and eastern England, France, and the Mediterranean coast. It produces mats of tiny, heath-like leaves (often with salt-encrusted surfaces) that turn reddish-purple in winter, and bears small pink flowers from June to August. The critical care requirement is perfect drainage in a sunny position; it is rare in the UK and specially protected in some coastal habitats. This species has no ASPCA toxicity listing and is classified as mildly-toxic as a precaution.

What size pot to step sea heath up to

Move up exactly one pot size. A heavy sea heath dropped into a vastly bigger pot sits in a reservoir of wet soil its roots cannot reach, which rots them and destabilises the plant. In the years between repots, lift off and replace the top 3–5 cm of soil (top-dressing) instead — it refreshes nutrients without the shock of a full repot.

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 sea heath

Early spring, just as new growth restarts, is the ideal window for sea heath. 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 sea heath

  1. Consider top-dressing first. If sea heath is not badly root-bound, scrape off and replace the top 3–5 cm of soil instead — far less shock for a big plant that hates moving.
  2. Get help and one size up. For a full repot, choose a pot just one size larger. A heavy plant needs two people and a stable, free-draining pot.
  3. Ease it out on its side. Lay the plant down, slide the pot off, and gently loosen the outer roots. Do not bare-root a mature specimen.
  4. Repot at the same depth. Add fresh dry, sandy, or gravelly, saline, infertile soil beneath and around the rootball, keeping the original soil line. Firm it so the trunk is stable and upright.
  5. Water and leave it put. Water thoroughly, then leave sea heath in the same spot and light — moving and repotting at once is what makes it drop leaves.

Aftercare

Leave sea heath in exactly the same spot and light it was in before — moving and repotting at the same time is what makes a big specimen drop leaves. Water it in well, then let the top of the soil dry before watering again so the larger volume of fresh soil does not stay sodden. Do not fertilise for about 4 weeks — fresh mix already carries nutrients and feeding freshly disturbed roots scorches them.

The right soil mix for sea heath

Sea Heath wants dry, sandy, or gravelly, saline, infertile soil. Requires the sharpest possible drainage; a 50:50 mix of horticultural grit and loam in a raised bed or trough best replicates its natural cliff-edge and shingle habitat. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting sea heath — frequently asked questions

How often should you repot sea heath?

Every 2–3 years; top-dress in the in-between years for sea heath. Fully repot sea heath only every 2–3 years; in the in-between years just top-dress the top 3–5 cm of soil. Step up one pot size in spring with dry, sandy, or gravelly, saline, infertile soil. It is heavy and hates being moved, and a vastly oversized pot holds water against the roots and rots them.

What size pot does sea heath need?

Move up exactly one pot size. A heavy sea heath dropped into a vastly bigger pot sits in a reservoir of wet soil its roots cannot reach, which rots them and destabilises the plant. In the years between repots, lift off and replace the top 3–5 cm of soil (top-dressing) instead — it refreshes nutrients without the shock of a full repot. Use our pot size calculator to size it from the plant's current pot and root spread.

When is the best time of year to repot sea heath?

Early spring, just as new growth restarts, is the ideal window for sea heath. 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.

Should you top-dress or fully repot sea heath?

For a big, heavy sea heath, top-dressing — replacing the top 3–5 cm of soil — is the gentler option most years, with a full repot only every 2–3 years. A mature specimen sulks and drops leaves when fully repotted, so do it as rarely as the roots allow.

Should you fertilise sea heath after repotting?

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

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