Photo: Ian Brooker and David Kleinig, CC BY 3.0 au, Wikimedia Commons

Eucalyptus

Eucalyptus globulus

The blue gum that covers much of Portugal, whose leaves give the sharp camphor steam of every winter kitchen and whose oil must never be swallowed.

Educational content, not medical or professional advice. In an emergency call your local emergency number (112 in Europe) first. Never eat a wild plant or mushroom because of a website or photo.

⚠️ Never swallow eucalyptus oil. It is toxic by mouth, and small amounts have caused seizures, unconsciousness and death, especially in children. Swallowing it is a poisoning emergency: call your poison centre or emergency services immediately and do not try to make the person vomit.

⚠️ Never apply eucalyptus oil, or any product containing it, to the face, nose or chest of a baby or child under about six years old. It can cause sudden spasm of the airway and stop them breathing. This includes vapour rubs on the chest of small children.

⚠️ Keep bottles of eucalyptus oil locked away from children. They are one of the most common causes of essential oil poisoning in young children.

⚠️ Undiluted oil irritates and burns skin. Dilute properly and test a small patch first.

⚠️ People with asthma can find eucalyptus steam or vapour triggers wheezing rather than relieving it. Stop at once if breathing gets tighter.

⚠️ Scalding from the inhalation bowl is a genuine and common injury. Keep it away from the edge of the table and away from children entirely.

⚠️ Eucalyptus may affect how the liver handles some medicines and may affect blood sugar. Ask a pharmacist if you take any regular medication, and be careful if you have diabetes.

⚠️ Avoid medicinal amounts in pregnancy and breastfeeding.

⚠️ A cough lasting more than three weeks, coughing blood, breathlessness, chest pain or high fever needs a doctor promptly.

⚠️ Persistent or serious symptoms need a doctor, not a plant. In an emergency call your local emergency services, 112 in Portugal and across the EU.

Confused with

Other Eucalyptus species, of which hundreds are planted

Danger: Their oil composition differs, and some species are much higher in irritant compounds than blue gum.

How to tell: E. globulus has the large warty four-ribbed bud cap, the big top-shaped ridged fruit and strongly blue-waxy juvenile leaves. Other species have smaller fruits and different bark. All share the camphor smell, so identifying the genus is easy and the species is not.

Bay laurel and other leathery-leaved trees (Laurus nobilis)

Danger: Bay is a kitchen herb, not dangerous, but cherry laurel, which looks similar, is toxic and releases cyanide compounds when its leaves are crushed.

How to tell: Smell decides it. Eucalyptus smells sharply of camphor and medicine. Bay smells warm and savoury; cherry laurel smells of bitter almonds or marzipan, which is a warning sign, not an invitation.

Leaves

Two completely different forms on the same tree, which is the identifying feature. Juvenile leaves, on young shoots and stump regrowth, are opposite, stalkless, heart-shaped to oval, 6 to 15 cm, and coated in a waxy blue-white bloom. Adult leaves are alternate, hanging vertically on a twisted stalk, narrow and sickle-shaped, 10 to 30 cm long and 2 to 3 cm wide, thick, leathery and glossy dark green on both sides.

Flowers

Creamy white, 3 to 4 cm across, made almost entirely of a brush of stamens with no visible petals. The bud is capped by a warty, blue-white, four-ribbed lid that is pushed off when the flowers open. The woody fruit is a hard, top-shaped, blue-grey capsule 1.5 to 3 cm wide with four ridges. Mostly flowers in the Portuguese winter.

Stem

Trunk with smooth bark in patches of grey, cream, blue and orange-brown that peels off in long ribbons and hangs in strips, leaving the rough fibrous bark only at the base. Young twigs are four-angled and often blue-waxy.

Smell or taste

A crushed leaf releases an unmistakable sharp, cold, camphor-and-medicine smell that clears the nose. It is the smell of the whole Portuguese interior on a hot day. Do not taste any part, and never swallow the oil.

Habitat

Vast plantations for pulp, plus roadsides, riverbanks and abandoned land throughout Portugal. Native to Tasmania and southeastern Australia; in Iberia it is an introduced and heavily debated tree.

Preparation

Adult leaves are picked at any time of year, from a low branch or from fallen fresh material, and dried flat in a warm airy shaded place for one to two weeks; they go stiff and leathery rather than crumbly. Store in a sealed dark jar. Steam inhalation is the traditional household use: a small handful of fresh or dried leaves in a bowl of very hot water, the face held well above the bowl with a towel over the head and eyes closed, breathing for a few minutes. Keep a safe distance from the surface, put the bowl where it cannot be knocked over, and never let a child lean over a bowl of scalding water. Leaves are also hung in the shower, added to a hot bath, or burned outdoors as a fragrant smoke. Eucalyptus essential oil is a separate, concentrated product. Do not attempt to distil it at home, do not add it to a child's inhalation bowl, and do not take it internally in any amount.

Traditional use

Eucalipto is stitched into Portuguese winters. Leaves have traditionally been boiled on the stove so the steam filled the room during a cold, added to hot water for an inhalation over a blocked head, and hung in the bathroom. The wood, the honey and the pulp industry built on it are part of the modern Portuguese landscape, for better and worse, and it is worth saying that these plantations are also a major factor in the country's wildfire problem. This is household custom. It is not a treatment for any respiratory illness, and steam does not cure a cold.

Harvest rule

Eucalyptus is superabundant in Portugal and nobody needs to damage a tree for a handful of leaves: take fresh fallen branches after wind, or clip low regrowth. Plantations are private commercial property, so ask before entering or cutting, and stay out of areas closed for fire risk. Never break branches off roadside or municipal trees. Check local rules, which vary by country, and remember that in Portugal eucalyptus planting itself is legally restricted in places because of fire and water concerns.

Eucalipto (PT); eucalipto (ES)