Japanese hop

Humulus japonicus

In other languages: Japanse hop (Nederlands) · Houblon du Japon (Français)

Comes from outside Europe, but is often planted here in gardens and parks.

Japanese hop is a fast-growing annual climber from East Asia, with palmately lobed leaves and stems covered in small, downward-pointing hooks. It was planted in gardens as an ornamental and as a quick green screen, including in a variegated form. Elsewhere in Europe, for example along rivers in northern Italy and central Europe, it has escaped and smothers riverbanks and rough ground under a dense carpet beneath which native plants disappear. That is why it is on the EU list of invasive alien species, under the name Humulus scandens. You recognise it by its rough leaves with five to seven lobes, its rasping stems and its small green hop cones in late summer.

Caution: Invasive alien species on the EU list (as Humulus scandens): never plant, sow or spread it, and do not pass on seeds or plants. The hooks on the stems and leaves scratch the skin and the pollen can cause hay fever: work with gloves and long sleeves. Dispose of plants with flowers or seeds in a sealed bag with the general waste, never on the compost heap.

Updated on 9 October 2026

Light
Sun or partial shade
preferably some sun
Moisture
Normal to wet
must not dry out
Hardiness
down to 0 °C
protect in harsh winters
Size
4 m
tall, 2 m wide
Flowering
July–September

Key facts
Pruning months	May–August
Height	4 m
Native to Belgium	No, planted
Flowering	July–September

Identify

How to recognise it

Growth form: Annual twining climber that grows 3–5 m long in one season, or forms a dense carpet over the ground and over other plants.
Leaf: Opposite, palmate with 5–7 deep lobes, 5–12 cm, toothed and rough on both sides, on a long, prickly stalk.
Stem: Tough, with rows of small, downward-pointing hooks that catch on clothes and skin and cause scratches.
Flower: Dioecious. Male plants with loose panicles of small yellowish-green flowers; female plants with small green cones of 1–2 cm; in July–September.
Fruit/seed: Small, flattened nutlets inside the cones, ripe in September–October. They drop beside the plant or float away on water.
Confusion with: Common hop is a perennial with 3–5-lobed leaves and larger, pale, papery cones with a strong scent. Japanese hop has 5–7 lobes, smaller green cones and dies back completely every autumn.

Flowering: July–September · Pruning: May–August

In your garden

Why grow it?

Knowing it lets you stop it escaping early on: a good example of a garden plant that got out of hand.
It is annual: every plant you remove before it sets seed adds no new seeds to the soil.
Our native hop is an excellent and safe alternative for a green screen.
In East Asia its pollen is a well-known cause of hay fever.
It is on the EU list of invasive alien species: do not plant, sow or spread it.

Japanese hop: where does it grow best?

Native range: riverbanks, rough ground and woodland edges in China, Japan, Korea and neighbouring countries.
Where it escapes: river and stream banks, wet tall-herb vegetation, waste ground, verges and woodland edges.
It grows best in sun to partial shade on moist, fertile soil.
Seeds travel with floodwater, imported soil and garden waste: that is how it turns up far from the garden it started in.

Goes well with

Hop: Native alternative: a perennial climber with pale cones, food plant for the caterpillars of the comma butterfly.
Honeysuckle: Native climber with scented flowers for moths.
Traveller’s joy: Fast native climber for a green screen on chalky soil, with fluffy seed heads in winter.
Ivy: Evergreen screen with late flowers for bees and black berries for birds.

Maintenance

Japanese hop: when and how to plant it?

Never plant or sow Japanese hop and do not pass on seeds or plants: it is on the EU list of invasive alien species.
From April, look out for seedlings and young plants with small, palmate, rough leaves, especially where it grew the year before.
Wear sturdy gloves, long sleeves and long trousers: the hooks scratch the skin.
Pull young plants up roots and all, as early as possible and certainly before they flower in July. The roots are shallow, so this is easy.
Mow large carpets low before flowering, and again when they regrow, until the first frost.
Put plants with flowers or seeds in a sealed bag with the general waste, never on the compost heap or with green waste. Check the spot for new seedlings for several years.

Care

Pulling: The best method for gardens and small patches: in May–June, pull young plants up roots and all, wearing gloves.
Mowing: Mow larger patches before flowering, in June–July, as low as possible, and repeat until September: the plant then cannot set seed.
Disposal: Plants without flowers or seed may be left to dry on the spot; plants with flowers or seed always go in a sealed bag with the general waste.
Aftercare: Sow or plant native species on the bare ground so seedlings have less chance, and check again every spring.
Reporting: If you see it along a stream or in the countryside, report it to your local council or on a wildlife recording platform.

Tip: Pull seedlings in May, while they are still small and the hooks are still soft: it takes a few minutes and prevents a new batch of seeds in late summer.

Pruning and mowing

Pruning months: May–August.

When: Pull in May–June; mow in June–August, always before flowering and seed set.

How:

Pull or mow all plants before the first flowers appear.
Come back every 3–4 weeks: new seedlings keep appearing into the summer.
Also remove plants climbing up into hedges and shrubs: cut the stems at the base and pull them loose carefully.
Clean gloves, clothes and tools before you leave so that no seeds travel with you.

Caution: Never put plants with seed on the compost heap: the seeds survive and germinate again the following spring.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Seed: Its only means: each female plant produces many seeds, which drop beside the plant and germinate there the following spring.
Water: Seeds float and wash up downstream on banks during high water, where new dense carpets form.
Soil and garden waste: Seeds travel with moved soil, garden waste and mowing machines. Never dump garden waste in the countryside.

Japanese hop: how does it get through the winter?

Hardy to 0 °C: protect in harsh winters.

Annual: the plant dies completely at the first frost.
The seeds overwinter in the soil and germinate in spring.
The dead stems remain as a brown, tangled mat; clear it away if it still carries seed cones.

Diseases and pests

Smothering: Dense carpets smother native plants and young shrubs. Pull or mow early and repeatedly.
Scratches: The hooks on the stems and leaf stalks graze the skin. Wear gloves and long sleeves.
Hay fever: Pollen from the male plants can cause hay fever. Remove the plants before they flower.
Seed bank: Even after successful control, seedlings keep appearing for years. Check every spring.

Through the year

March: Check the spot; sow or plant native species.
April: The first seedlings appear. Find them and pull them up.
May: Pull up young plants, wearing gloves.
June: Keep pulling; mow large patches before flowering.
July: Flowering begins. Mow or pull everything by now at the latest.
August: Remove new plants before they set seed.
September: The seeds ripen. Plants with seed go in a sealed bag with the general waste.
October: The plant dies at the first frost. Clear dead mats that carry seed.

You and this species

Did you know?

It is also called Humulus scandens: ‘scandens’ means ‘climbing’.
Unlike common hop, Japanese hop is not used for brewing beer.
The hooks on its stems point downwards: it hauls itself up other plants as if with barbs.

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