Tea tree oil is a strong essential oil derived from the Australian melaleuca tree. It is commonly used for a variety of household applications, but its best garden use is as an insect repellent.
For most uses of tea tree oil, it needs to be diluted. It is quite powerful and can irritate the skin or even blister it. For uses where oil is best, add a few drops of tea tree oil to a vegetable oil. When spraying or washing, dilute it with a good amount of water.
Tea tree oil repels insects of many types, but works especially well on small crawling insects like mites. It is often used in combination with other natural oils, like citronella, pennyroyal and eucalyptus, as oil that can be burnt on candles to repel insects. You also can put a few drops on cloth or paper strips and hang them about to discourage flying insects. Do not apply pure oil directly to plants as it might injure them.
Add four or five drops of tea tree oil to a spray bottle of water and use as a cleaning spray outdoors or indoors. Take care as you would any cleaner; it is not safe for ingestion or use by young children. It will disinfect and clean most surfaces, soft or hard.
The oil has antibacterial and antifungal properties, and is often used as a medicinal remedy to treat external fungal infections like athlete’s foot. It can do the same for plants, diluted well in water and sprayed on a fungal infection.
Tea tree oil’s antifungal benefits also make it a great mold-control tool in the garden. If you live in a humid, warm climate prone to mold and fungus, spray outdoor furniture, patio stones and other objects that show mold, and scrub afterward.