Field Buttercup

The field buttercup (scientifically known as Ranunculus arvensis and commonly called the corn buttercup) is a rare arable weed. Unlike common meadow or lawn buttercups, its standout features are its pale lemon-yellow petals and its large, heavily spined seeds that look like miniature horse chestnut husks.

Here is how the field buttercup contrasts with other common buttercup varieties:

The Seeds (Achenes)

• Field Buttercup: Produces up to 8 large seeds per flower, each up to 8 mm in length and covered in thick, wicked spines.

• Other Buttercups: Most common buttercups (like meadow or creeping buttercups) have small, smooth, and hairless seeds.

The Flowers

• Field Buttercup: The flowers are quite small 6 mm to 12 mm across) and are a noticeably paler, almost lemon-yellow.

• Other Buttercups: Common buttercups generally have larger flowers (2 to 3 cm) across) with a vibrant, glossy, deep butter-yellow hue.

Lifecycle & Growth Habit

• Field Buttercup: It is a strict annual that germinates over autumn/winter and flowers in the spring.

• Other Buttercups: Most others (like meadow and creeping buttercups) are hardy perennials that spread via underground corms or creeping above-ground runners. 

Habitat and Rarity

• Field Buttercup: Strictly an arable specialist, found mostly in cultivated fields and on heavy clay or chalky soils. Due to modern agricultural practices, it is a highly threatened conservation priority across regions like the UK.

• Other Buttercups: Highly widespread and abundant; you will easily find them in parks, lawns, marshes, and unimproved pastures. 

Toxicity

• Field Buttercup: Like all members of the Ranunculus family, it is highly toxic to livestock when fresh, causing blistering and gastrointestinal upset. However, it loses its toxicity when dried in hay.

• Other Buttercups: Creeping buttercup and meadow buttercup share this toxicity, though creeping buttercup generally contains slightly lower levels of the toxic oil (protoanemonin). 

Ranunculus arvensis (commonly known as the corn buttercup) is very rare. Once a common weed in European grain fields, it has suffered catastrophic population declines and is classified as Critically Endangered in Great Britain.

Why is it rare?

• Agricultural Intensification: Modern farming techniques, particularly the widespread use of broad-spectrum herbicides and improved seed-cleaning methods, caused a massive drop in their numbers.

• Habitat Loss: They rely heavily on traditional winter-sown arable crops on heavy clay or chalky soils.

• Conservation Status: Because of this dramatic reduction, it is a UK Biodiversity Action Plan (UKBAP) priority species and legally protected under the Natural Environment and Rural Communities Act.

Where can it still be found?

Today, if it is spotted, it is mostly restricted to a few isolated arable field margins, particularly in East Anglia (such as Suffolk) and a few scattered locations in England and Scotland. In some areas, it only survives through specialized conservation agri-environment schemes or deliberate reintroduction projects.