Datura stramonium (thorn apple)

Thorn apple is a weed that prefers a warmer climate than Britain, but in hot summers they are quite commonly found. Another common name, devil's snare, sounds alarming, but a few simple precautions will enable gardeners to handle this weed without great risk.

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The prickly seed pod that gives the weed the common name, thorn apple.

Quick facts

Latin name Datura stramonium
Common name Thorn apple
Life cycle Annual
Areas affected Uncultivated ground, beds, borders

What is Datura stramomium

Datura stramonium (or thorn apple as it is commonly known) is an annual weed of gardens, roadsides and other waste or cultivated land. It is widely naturalised in warmer countries throughout the world, and is quite common in the British Isles, often appearing in waste and cultivated ground.

Although quite a striking plant, it is as well to be aware that all parts, particularly the seeds, are highly poisonous. It belongs to Solanaceae, a family which includes the potato and tobacco, and many members of this family contain toxic substances. This page looks at options for gardeners when Datura stramonium is becoming a problem.

Appearance

This weed can grow to heights of 1m (3¼ft). It flowers from July to October with wide, funnel-shaped flowers. These are usually white but plants with purple or lilac flowers and purplish stems are referred to as Datura stramonium var. chalybaea (syn. D. stramonium var. tatula).

It produces seedpods which are large and spiny (hence the common name thorn apple) though plants with spineless seedpods are known and these are referred to as D. stramonium var. inermis.

The leaves very broad and coarsely toothed.

The problem

The potentially harmful poisonous and hallucinogenic properties of this plant can sound alarming especially when made much of in the media. The leaves and seed pods also look exotic and alien. In fact this is quite a small plant and not very invasive in Britain. Common sense precautions limit risk factors so that gardeners need not be too alarmed by this weed.

The seed appears to retain its viability for many years when buried and germinates when the soil is disturbed. Spread is facilitated by human activities – in gardens it appears to be a contaminant of birdseed.

Control

The RHS believes that avoiding pests, diseases and weeds by good practice in cultivation methods, cultivar selection, garden hygiene and encouraging or introducing natural enemies, should be the first line of control. If chemical controls are used, they should be used only in a minimal and highly targeted manner. 

Cultural control

There are a number of non-chemical control options.

Dig, pull or hoe out plants before seed is set. Seedlings and plants that have not set seed can be added to the compost heap where the toxins will naturally break down. However, plants that have set seed should be consigned to the green waste collection, buried deeply (60cm/2ft or more) or burnt in order that the seed does not disperse in the garden or persist in the compost heap. Always wear gloves or thoroughly wash hands after handling this plant.

Use a mulch of organic matter, at least 5cm (2in) thick or opaque sheeting, such as woven polypropylene, to smother this weed.

Weedkiller control

Contact herbicides such as acetic acid (eg. Weedol Gun! Fast Acting, Roundup Speed Ultra, Spot On Fast Acting Weedkiller or Resolva Fast Weedkiller), fatty acids (eg. Job Done Garden Ultrafast Weedkiller) and pelargonic acid (eg. Doff 24/7 Fast Acting Weedkiller, Roundup NL Weed Control or Resolva Xpress Weedkiller) are good at knocking back young annual weeds such as thorn apple. Systemic herbicides such as glyphosate (e.g. Roundup Fast Action, SBM Job done General Purpose Weedkiller or Doff Advanced Concentrated Weedkiller) will also be effective and can be used when mature plants need to be eliminated.

These herbicides are non-selective and so care should be taken while spraying near other plants. Plants to be avoided can be covered with a bucket/flowerpot or screened with plastic when spraying. 

Inclusion of a weedkiller product does not indicate a recommendation or endorsement by the RHS. It is a list of products currently available to the home gardener.

Download

Weedkillers for gardeners (Adobe Acrobat pdf document outlining weedkillers available to gardeners; see sections 3a and 4)

Links

Chemicals: using a sprayer
Chemicals: using safely and effectively
Chemicals: using spot and broadscale weedkillers
Weeds: non-chemical control

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