Young orchids depend entirely on symbiotic fungi to provide energy for growth, and new research shows that those fungi are finicky, preferring older forests. Scientists had previously speculated that fungal distributions influenced orchid distributions. But separating out the effects of soil condition, such as moisture and acidity, has been difficult. So researchers from the Smithsonian Environmental Research Center in Edgewater, Maryland, planted seeds from three endangered orchid species in plots on six sites in Maryland: three in younger forests aged 50 to 70 years old and three in more mature forests aged 120 to150 years old. The scientists added the symbiotic fungi for each orchid to half of the plots. Over 4 years, they found that fungal abundance was highest in mature forests and that orchid germination and growth depended on an abundance of their partner fungi, not merely their presence.