Tree Pollen: Allergy, Types & Season

Tree pollen opens the allergy year, and the tree index on every Pollen Atlas city page is built from it. This page explains what tree pollen is, which trees produce the counts, and how the season runs from a handful of winter specialists into the great spring wave.

What is tree pollen?

What is tree pollen? It is the pollen of wind-pollinated trees — the catkin-bearing species that release their pollen into the air in late winter and spring rather than relying on insects. Tree pollen opens the year: a few winter specialists, then the great spring wave from February to May. Pollen Atlas reports eleven plants individually in its city data; the trees below are the ones that drive the tree index.

The trees in the count

• Mountain cedar (Juniperus ashei) — winter, December to February; central Texas above all. Juniper pollen guide
• Alder (Alnus) — late winter to early spring, January to March; the Pacific Northwest and Alaska above all. Alder pollen guide
• Maple (Acer) — early spring, February to April; eastern and central United States. Maple pollen guide
• Elm (Ulmus) — early spring for American elm, some species again in fall; across the United States. Elm pollen guide
• Birch (Betula) — spring, March to May; the Northeast, Great Lakes and Pacific Northwest. Birch pollen guide
• Oak (Quercus) — spring, March to May, peaking in April; heaviest across the Southeast, Mid-Atlantic and Texas. Oak pollen guide
• Pine (Pinus) — spring, March to May; the Southeast's pine belt above all. Pine pollen guide
• Mulberry (Morus) — spring, March to May; the desert Southwest and warm cities across the South. Mulberry pollen guide
• Cottonwood (Populus) — spring, April to May; river corridors of the Midwest, Plains and West. Cottonwood pollen guide
• Ash (Fraxinus) — spring, April to May; Midwest and Northeast street and forest ash. Ash pollen guide
• Pecan (Carya illinoinensis) — spring, April to May; Texas, the Gulf states and the Southeast. Pecan pollen guide
• Hickory (Carya) — spring, April to May; eastern US forests — the Ohio Valley, the Appalachians and the Southeast. Hickory pollen guide
• Olive (Olea europaea) — spring, April to June; California and the Southwest in the US, and around the Mediterranean. Olive pollen guide

Tree pollen allergy

A tree pollen allergy is the classic spring hay fever: most tree pollens produce the same core pattern in people who are sensitive to them — sneezing, a runny or blocked nose, and itchy, watery eyes — and any pollen can aggravate asthma. Tree allergies layer on top of each other because the types of tree pollen overlap: the spring tree pollen wave runs for months, and a person sensitive to an early opener like alder or maple may also react to the April peak of oak and pecan. Knowing which trees drive your city's spring is the first step to knowing which weeks are yours — and if the pattern is severe, it is worth a specialist's testing; you can find an allergist in the Pollen Atlas directory.

When tree pollen runs

Tree pollen season starts with the winter specialists — mountain cedar pollinates from December to February, when almost nothing else is in the air — then alder and maple open the early-spring wave, and the full spring cast peaks from March to May. The complete calendar is in the tree pollen season guide. Follow today's tree index on the Houston pollen count and Charlotte pollen count pages — both are oak cities — and compare the spring wave across cities in the city rankings and on the pollen heatmap. The other family reference pages are grass pollen and ragweed.