Trees, grasses, and weeds that usually don’t bear fruit or flowers are the ones to avoid. They make lots of small, light, dry pollen granules that can be carried through the air for miles.
Common plant allergens include:
Weeds, such as ragweed, sagebrush, redroot pigweed, lamb's quarters, goosefoot, tumbleweed (Russian thistle), and English plantain.
Grasses, such as timothy grass, Kentucky blue grass, Johnson grass, Bermuda grass, redtop grass, orchard grass, sweet vernal grass, perennial rye, salt grass, velvet grass, and fescue.
Hardwood deciduous trees, like oak, ash, elm, birch, maple, alder, and hazel, as well as hickory, pecan, box, and mountain cedar. Juniper, cedar, cypress, and sequoia trees are also likely culprits.