The introduction, growth and persistence of orchid mycorrhizal fungi in situ were studied by using a seed-baiting method. A mycorrhizal fungus from the carousel spider orchid, Caladenia arenicola (Hopper & A.P.Br.), was introduced to sites within an area from which the orchid and fungus were absent, adjacent to a natural population of C. arenicola. In the first growing season, the fungus grew up to 50 cm from its introduction point, usually persisted over the summer drought into the second season and even into the third season, stimulating germination and growth to tuber formation of the seeds in the baits. Watering the inoculated areas significantly increased seed germination. This suggests that it is possible to reintroduce the mycorrhizal fungi either before or together with seeds of orchid species needing re-establishment in an area.