Red Maple (IMAGE) Penn State Caption The researchers found that trees, like maples, oaks and willows, were the most important spring pollen sources for honey bees. Credit Douglas Sponsler, Penn State Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.