Eastern Poison Oak
Rhus toxicodendron

Family: Anacardiaceae

What it is like

Rhus toxicodendron is a deciduous Shrub growing to 0.6 m (2ft) by 1 m (3ft 3in). See above for USDA hardiness. It is hardy to UK zone 7 and is not frost tender. It is in flower from May to June, and the seeds ripen from September to November. The species is dioecious (individual flowers are either male or female, but only one sex is to be found on any one plant so both male and female plants must be grown if seed is required). and is pollinated by Bees. The plant is not self-fertile. Suitable for: light (sandy), medium (loamy) and heavy (clay) soils, prefers well-drained soil and can grow in nutritionally poor soil. Suitable pH: mildly acid, neutral and basic (mildly alkaline) soils. It cannot grow in the shade. It prefers dry or moist soil.

Height (m): 0.6

Where it is found

Dry barrens, pinelands and sands.

South-eastern N. America - New Jersey to Delaware, south to Georgia, Alabama and Texas.

Conservation Status:

Countries/locations it is found in

How it is used

Food

Rating: 0

Oil: Oil

Medicine

Rating: 2

Poison oak has occasionally been used medicinally, though it is an extremely poisonous plant and great caution should be exercised. Any herbal use should only be undertaken under the supervision of a qualified practitioner. See also the notes above on toxicity. A fluid extract of the fresh leaves is irritant, narcotic, rubefacient and stimulant. It has been used with some success in the treatment of paralysis, obstinate herpatic eruptions, palsy and in various forms of chronic and obstinate eruptive diseases. A mash of the leaves has been used to treat ringworm. An external application has also been used in the treatment of herpes sores. A poultice of the plant has been used to treat infectious sores on the lips. The root has been used to make a poultice and salve in the treatment of chronic sores and swollen glands. A homeopathic remedy is made from the fresh leaves. These should be harvested of a night-time, during damp weather and before the plant flowers. This remedy has a wide range of applications and is one of the main treatments for mumps, it is also used in a wide range of skin disorders.

Antirheumatic: Treats rheumatism.

Homeopathy: A plant used in homeopathic treatments.

Irritant: Causes irritation or abnormal sensitivity in living tissue.

Narcotic: Relieves pain, induces drowsiness and gives a sense of well-being.

Parasiticide: Treats external parasites such as ringworm This should perhaps be joined with Parasiticide in

Rubefacient: A counter-irritant and external stimulant, it produces inflammation and redness of the skin.

Salve: Soothes and heals damaged skin.

Stimulant: Excites or quickens activity of the physiological processes. Faster acting than a tonic but differing from a narcotic in that it does not give a false sense of well-being.

Other

Rating:

The leaves are rich in tannin. They can be collected as they fall in the autumn and used as a brown dye or as a mordant. An oil is extracted from the seeds. It attains a tallow-like consistency on standing and is used to make candles. These burn brilliantly, though they emit a pungent smoke. The milky juice makes an excellent indelible marking ink for linen etc. It is also used as a varnish for boots and shoes.

Dye: Plants that provide dyes.

Ink: Plants that can be used as an ink.

Mordant: Used for making a dye more permanent, it also affects the colour of the dye.

Oil: Vegetable oils have many uses, as lubricants, lighting, soap and paint making, waterproofing etc. This does not include the edible oils unless they are also mentioned as having other uses.

Parasiticide: Kills external body parasites such as hair lice.

Tannin: An astringent substance obtaied from plants, it is used medicinally, as a dye and mordant, stabilizer in pesticide etc.

Varnish: Plants that can be used as a varnish without any special treatment. Does not include varnishes made from oils etc.

How it is grown

Succeeds in a well-drained fertile soil in full sun. Judging by the plants natural habitat, it should also succeed in poor acid soils and dry soils. The young growth in spring can be damaged by late frosts. Plants have brittle branches and these can be broken off in strong winds. Plants are also susceptible to coral spot fungus. Plants in this genus are notably resistant to honey fungus. This species is a small suckering shrub, it can spread freely in suitable conditions. There is some confusion over the correct name of this species. It is united with R. radicans (under that name) by some botanists whilst others split this species off into another genus, Toxicodendron, and unite it with R. radicans as Toxicodendron radicans. Many of the species in this genus, including this one, are highly toxic and can also cause severe irritation to the skin of some people, whilst other species are not poisonous. It is relatively simple to distinguish which is which, the poisonous species have axillary panicles and smooth fruits whilst non-poisonous species have compound terminal panicles and fruits covered with acid crimson hairs. The toxic species are sometimes separated into their own genus, Toxicodendron, by some botanists. Dioecious. Male and female plants must be grown if seed is required.

Propagating it: Seed - best sown in a cold frame as soon as it is ripe. Pre-soak the seed for 24 hours in hot water (starting at a temperature of 80 - 90c and allowing it to cool) prior to sowing in order to leach out any germination inhibitors. The stored seed also needs hot water treatment and can be sown in early spring in a cold frame. When they are large enough to handle, prick the seedlings out into individual pots and grow them on in the greenhouse for their first winter. Plant them out into their permanent positions in late spring or early summer, after the last expected frosts. Cuttings of half-ripe wood, 10cm with a heel, July/August in a frame. Root cuttings 4cm long taken in December and potted up vertically in a greenhouse. Good percentage. Suckers in late autumn to winter.

Best place to grow: Woodland Garden Sunny Edge; Dappled Shade; Cultivated Beds;

Habit: Shrub

Hardiness: 6-9

Growth:

Soil: Light (sandy), medium, heavy (clay)

Shade: No shade

Moisture: Dry, moist

Things to keep in mind

This plant contains toxic substances and skin contact with it can cause severe irritation to some people. The sap is extremely poisonous. The sap contains 3-N pentadecycatechnol. Many people are exceedingly sensitive to this, it causes a severe spreading dermatitis. The toxins only reach the skin if the plant tissues have been damaged, but even indirect contact can cause severe problems.

Its other names

Local names

Synonyms

R. quercifolia. Toxicodendron radicans. T. pubescens. P.Mill.