It is often considered a weed in manicured lawns, but it provides good nitrogen fixation for soil.

Does it need much water?

It prefers consistent moisture but can tolerate short dry spells once established.

Plant guide

Lesser trefoil.

Trifolium dubium

Pronounced try-FOH-lee-um DOO-bee-um

Also known as Cowhop Clover, Irish Shamrock, Irish Shamrock, Small Hop Clover, Cow Hop Clover, Yellow Hop Clover, Shamrock, Least Hop Clover, Lesser Trefoil, Lesser Yellow Trefoil, Lesser hop trefoil, Low Hop Clover

Trifolium dubium — Photo by Anna Kellagher (CC BY) via gbif

Lesser trefoil is a charming, low growing annual often found in lawns and meadows. It produces tiny, bright yellow flower heads that add a splash of color to grassy areas. You will find it is quite resilient and spreads easily through seed.

At a glance

Care level: Easy
Plant type: Annual herb
Light: Full sun to partial shade
Indoor light: Direct sun
Water: Every 3 to 7 days
Mature size: 6 to 12 inches
Growth rate: Fast
Hardiness: USDA 4 to 9
Bloom time: Late spring to early autumn

Care

This plant thrives in sunny spots with well draining soil. Keep an eye out for yellowing leaves, which often signal that the soil is staying too wet. It is a hardy grower that rarely needs much fussing.

Watering: Water when the top inch of soil feels dry to the touch.
Feeding: Apply a balanced liquid fertilizer sparingly during the active growing season.
Pruning: Trim back leggy growth to encourage a bushier appearance.
Repotting: Repot if the plant becomes root bound or if the soil loses its structure.
Soil: Well draining, sandy or loamy soil
Soil pH: 6.0 to 7.5
Temperature: -10 to 30°C
Humidity: 40 to 80%
Drought tolerance: Moderate
Lifespan: Annual, typically 1 year
Deer and rabbits: Moderate

Safety

People: It is generally considered non toxic to humans.
Children: There are no specific safety concerns for children, though standard caution regarding plant ingestion applies.
Contact allergens: There are no known significant skin irritants associated with this plant.
Airborne allergens: The pollen may cause mild seasonal allergies in sensitive individuals.
Edibility: While not toxic, it is rarely consumed and may cause digestive upset if eaten in large quantities.

How to identify it

Three small, heart shaped leaflets
Tiny clusters of yellow flowers
Slender, trailing stems
Small, oval shaped stipules

Height: 0.05 to 0.3m
Spread: 0.1 to 0.4m
Leaves: green, deciduous
Flowers: yellow, 0.3 to 0.6cm
Fruit: brown, Late summer

Problems to watch for

Clover Root CurculioCommon
Powdery MildewCommon
AphidsUncommon
Root RotUncommon
RustUncommon
Slugs and SnailsUncommon

By symptom

Plant problems by symptom

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Growing it

Propagation: seed
When to plant: spring, autumn
Overwintering: As an annual, it completes its life cycle and dies back in winter, leaving seeds in the soil to germinate the following spring.
In containers: It is not typically grown in containers as it is a low growing ground cover that prefers open ground.

Seed

Collect dried flower heads in late summer.
Rub the heads to release the tiny seeds.
Scatter seeds over prepared soil in autumn or early spring.
Lightly rake the soil to cover seeds.
Keep the area moist until germination occurs.

Allow it to grow among grasses to naturally boost soil nitrogen levels without synthetic fertilizers.

Grows well with

Kentucky Bluegrass · They grow well together in lawns and the clover provides nitrogen for the grass.
Dandelion · Both species thrive in similar disturbed soil conditions.

Similar species

White Clover · It is a larger, perennial relative with white flowers.
Hop Clover · It looks very similar but has larger flower heads.

Science

Family: Fabaceae
Genus: Trifolium
Order: Fabales
Class: Magnoliopsida
Native range: Europe and western Asia.
Conservation: It is a common, widespread species and is not of conservation concern.

It acts as a pioneer species in disturbed habitats, enriching the soil through symbiotic nitrogen fixation.

Value to wildlife: nectar source, nitrogen fixation
Pollinators: bees, butterflies
Uses: ground cover, soil improvement, forage

Through the year

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Flowering

Fruiting

Foliage

Ecological indicators

Salinity: 2/9
Soil reaction: 6/9
Light: 7/9
Temperature: 5/9
Moisture: 5/9
Nutrients: 4/9

Taxonomy resolved against GBIF.

Questions people ask

Is this a weed?: It is often considered a weed in manicured lawns, but it provides good nitrogen fixation for soil.
Does it need much water?: It prefers consistent moisture but can tolerate short dry spells once established.

Where the name comes from

The genus name Trifolium refers to the three leaflets, while the species name dubium means doubtful, likely referring to its similarity to other clover species.

Good to know

It is commonly known as suckling clover.
It is an annual plant that spreads readily by seed.
It thrives in disturbed soils and lawns.
It is native to Europe and western Asia but has naturalized globally.

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This guide was generated with AI on September 26, 2026 and checked against GBIF taxonomy. It is general information, not horticultural or veterinary advice. Read about how we build these guides.