Mertensia maritima, the oyster plant

The evergreen leaves of the oyster plant (Mertensia maritima) taste uncannily of the shellfish they are named for, raw or cooked, which is why chefs prize them alongside fish. It is a fragile thing that loathes heat, damp and being moved: give it well-drained soil in part sun, keep slugs off, and pick from spring to autumn.

Oyster plant at a glance

Name	Mertensia maritima
Family	Boraginaceae
Foliage	evergreen
Type	herbs and spices, perennial
Height	1 ½ feet (15 cm)
Exposure	part sun
Soil	well-drained
Flowering	summer

The oyster plant has a quite uncanny taste for a member of the plant kingdom.

How to sow Mertensia maritima

Sowing the plant from seed is certainly the best way to grow mertensia.

That way, you’ll encourage the oyster plant to settle into its growing environment, and will ensure it develops well.

This plant, which is quite fragile, doesn’t much like being moved around or transplanted.

• Mertensia is preferably sown in spring or fall, but you’ve got to ascertain that it won’t freeze.
• Mertensia really hates places that are too hot and too sunny.
• It appreciates well drained soil and detests moisture.

It’s also possible to prepare seedlings in a sheltered spot a bit earlier, and then carefully transplant to the ground in spring.

Planting Mertensia maritima

If you were able to prepare seedlings in a covered spot, or if you’ve purchased your plants in a store, it’s best to wait for spring to transplant your mertensia.

You’ll be able to plant your mertensia directly in the ground or, better still, in pots: growing mertensia in pots is highly recommended to protect it from snails.

• Avoid soils that are too compact and too heavy.
• Favor part sun instead of spots that would get too hot.
• Water when the soil is dry, but don’t overdo it because mertensia hates moisture just as much as it does dry spells.

Growing it in pots has 2 key advantages

• If you elevate your pots by an inch (a couple centimeters) or so, snails won’t be able to climb on it – and if they could, they would, since they really love the plant!
• Mertensia is self-sowing, and growing it in containers will help mark out its growing space: when it pleases itself somewhere, it tends to get quite invasive.

Caring for Mertensia maritima

The oyster plant is rather fragile, and you’ll have to pay attention to its needs if you hope to see it grow to the point of harvesting its delicious herb leaves.

Care it needs is:

• Cut the stems back to half their length regularly, this gives the plant vigor and will fortify it.
• Eliminate flowers as you see them opening up, they’re not really appealing and they absorb a lot of the plant’s energy, diverting it from the leaves which are the highlight of this special plant.
• Water in case of prolonged dry spells and heat waves.

It’s also a good idea to mulch the base of the plant in summer, this helps keep the ground cool.

Harvesting mertensia maritima leaves

The leaves can be harvested when needed from spring to fall.

• A morning harvest will taste more fragrant than harvests that are picked later during the day.
• Never collect more than half the leaves, because the plant needs them to keep growing.

Sowing, planting and harvesting at a glance

Mertensia maritima dislikes being disturbed, so the moment you choose for each operation matters more than with most herbs. Here is how the four key jobs compare.

Respect these timings and a single plant will keep producing leaves for months.

Mertensia, snails and slugs

These 2 parasites, snails and slugs, are the 2 most devastating pests for Mertensia maritima.

Indeed, they simply crave its leaves when they can access them, and will mow down an entire plant in days.

It’s preferable to protect your Mertensia maritima from snails and slugs with a protective net or mulch prepared from sharp, dry needle-like material.

• Because the raw leaves of oyster plant (Mertensia maritima, the sea bluebell) go straight onto the plate, use only slug pellets approved for edible crops, or rely on barriers and hand-picking instead.
• Go out after dark with a torch on damp evenings, when slugs climb the stems, and pick them off by hand.
• Lift the pots and check the rims and saucers, where slugs hide by day.
• Keep the summer mulch a little away from the crown, because damp material pressed against the stems shelters the very slugs you are fighting.

Good to know about Mertensia maritima

This plant is often used in gastronomy by connoisseurs, especially rated chefs that love pairing it with fish.

It’s delicious both raw and cooked.

A few synonyms to impress your audience…

Mertensia maritima was and is known under different names. The most common name is “oyster plant”, but it’s also called “oyster leaf”, sea mertensia, and sea bluebells.

Virginia lungwort is a cousin variety, Mertensia virginica.

• Never dig the coastal Mertensia maritima, also called oyster plant, from the wild, as it is declining in parts of its range; note that “oyster plant” can also mean salsify (Tragopogon porrifolius).
• Oysterleaf (Mertensia maritima) has fleshy blue-grey leaves with an oyster-like flavour; the young, small leaves are the most tender and are usually recommended for raw dishes, while older leaves grow tougher.
• If you cook shellfish such as shrimp, scallops, or oysters, keep it brief, because prolonged heat tightens their proteins and drives out moisture, leaving them rubbery and muting their delicate flavour.
• Plants that grow wild on coastal shingle above the tide line are generally adapted to salt spray and wind, which is why such species often do well in seaside gardens.

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