Kermes oak

How to recognise it

Growth habit

Dense, much-branched evergreen shrub of 0.5–2 m, which after many years sometimes becomes a small tree of 5 m or more. In the wild it forms impenetrable thickets.

Leaf

Alternate, small (1.5–4 cm), stiff and leathery, wavy with spiny teeth, glossy green and hairless on both sides.

Flower

Yellow, hanging male catkins and inconspicuous female flowers on the same plant, in April–May. The wind takes care of pollination.

Fruit

Acorn of 1.5–3 cm that usually only ripens in its second year, in a cup covered with stiff, spreading, prickly scales.

Roots

Deep and vigorous, with a woody root crown that resprouts after pruning or fire.

Confusion with

Holly has larger, thicker leaves, small white four-petalled flowers and red berries, and never acorns. Holm oak (Quercus ilex) becomes a large tree and has leaves with a grey, felted underside.

Flowering: April–May · Pruning: April

Why grow it?

• An evergreen oak of barely 1–2 m: ideal if you want an oak but have little space.
• The dense, prickly thicket gives small birds a safe place to shelter and nest.
• Very tolerant of drought and heat: a climate-resilient shrub for a gravel garden or a sunny slope.
• Grows slowly and regrows from the base after hard pruning, and in the wild even after a fire.
• A plant with a rich history: the red dye kermes gave its name to the word crimson.
• A fine collector’s plant for lovers of oaks or Mediterranean plants.

Kermes oak: where does it grow best?

• In the wild: garrigue, dry, stony slopes, limestone rocks and open oak woodland around the Mediterranean.
• In the garden: full sun in a warm, sheltered spot.
• Dry, free-draining soil, chalky or neutral, including poor, stony ground. No wet, heavy soil.
• Lovely in a gravel garden, on a dry bank, as a low prickly hedge or in a large pot.

Goes well with

• Rosemary: Another garrigue shrub, with early blue flowers for bees.
• Common thyme: Low, fragrant cushions at its feet, in the same dry soil.
• Lavender: Grey leaves and purple summer flowers beside the glossy dark green.
• Rock rose: Large, papery Cistus flowers in June and the same love of poor soil.
• Phoenician juniper: Another evergreen garrigue shrub, with fine scale-like leaves for contrast.

Kermes oak: when and how to plant it?

1. Buy it in a pot from a nursery specialising in oaks or Mediterranean plants. Never bring plants, acorns or cuttings back from the wild on holiday.
2. Plant in April–May, so it is well established before winter.
3. Dig a generous planting hole and mix heavy soil with gravel or coarse sand; add no compost or fertiliser.
4. Set the root ball at the same depth as in its pot and do not damage the long taproot: oaks do not like being moved.
5. Allow 1.5 m of space per plant; for a hedge, plant 60–80 cm apart.
6. In the first year, water every one to two weeks in dry weather; after that it is no longer needed.

Care

Water

Only in the first year and in a pot. An established plant copes in dry summers.

Feeding

Not needed: poor soil keeps it compact and better able to cope with winter.

Mulch

Gravel around the base keeps the base of the stem dry and warm.

Gloves

Wear sturdy gloves when weeding and pruning: the leaves prick like holly.

Pots

In winter, stand a pot against a south-facing wall under an overhang: hard frost combined with wet compost is the most dangerous.

Tip: If you want an oak in a small garden, this is your chance: plant it in gravel in the sunniest spot and be patient, as it grows slowly but lives for a very long time.

Pruning and mowing

Pruning months: April.

When: Rarely needed. Light shaping in April, once the hardest frosts are over.

How:

• Cut out dead and frozen twigs back to healthy wood.
• Shorten over-long shoots to keep the shrub dense and compact.
• As a low hedge: trim lightly once a year, in April.
• A neglected shrub can be cut back hard: it regrows from the base, although this takes a few years.

Caution: Do not prune in late summer or autumn: the new, soft shoots would then freeze in winter.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Seed

Sow ripe acorns straight away in autumn in a deep pot, as they dry out quickly and then lose their ability to germinate. Stand the pot outdoors, protected from mice and jays.

Cuttings

Rarely successful: oaks are almost always grown from seed.

Kermes oak: how does it get through the winter?

Hardy to −15 °C: protect young plants.

• Evergreen: the glossy leaves stay on the shrub all winter.
• Hardy to about −15 °C on dry, free-draining soil. In harder frost the leaves may turn brown, but the plant usually regrows.
• Gives small birds a prickly, safe shelter.
• Wet winters on heavy soil are more dangerous than frost.

Diseases and pests

• Root rot: On wet, heavy soil the roots rot. Plant it in gravel or on a bank.
• Frost damage: Brown leaves and dead twig tips after a harsh winter. Wait until May, then cut out the dead wood.
• Galls: Small balls or distortions on leaves and twigs, caused by gall wasps. They do the plant no harm: just leave them.
• Prickly leaf litter: Old leaves fall and stay prickly for a long time. Use gravel or ground cover under the shrub instead of grass.

Through the year

• March: Do not cut out frost damage yet; wait until new growth starts.
• April: Light shaping. Plant. The first catkins appear.
• May: In flower with yellow, hanging catkins. Plant.
• June: New, light green shoots. Water young plants in dry weather.
• July: Water only pots and newly planted shrubs.
• August: Resting in the heat; no more pruning.
• September: Second-year acorns turn brown.
• October: Gather ripe acorns and sow them in a pot straight away.
• November: Move pots against a south-facing wall and under an overhang.
• December: Resting. Evergreen foliage in the winter garden.

Did you know?

• The species name coccifera means ‘kermes-bearing’: the plump females of the kermes scale insect sit on the twigs like little berries. Dried and ground, they gave a deep red dye, which is where the words crimson and the Dutch karmozijn come from.
• The acorns usually need two years to ripen, so you often see acorns of two generations on the shrub at the same time.
• In the garrigue it quickly resprouts from its root crown after a fire: this is how it survives fires that kill many other shrubs.