Elm Pollen Season: Spring's Opener and Fall's Encore

Elm pollen has the most unusual calendar of any tree in this series: it opens the season, and then, in parts of the country, it comes back and closes it. Elm pollen from the classic spring elms is among the very first tree pollens of the year — out before most people have started thinking about allergies — while a separate cast of fall-flowering elms produces a second, genuinely surprising season in late summer and autumn. If you have ever had "spring allergies" in September, an elm may be why.

Key takeaways

• Elm pollen is the only tree pollen in this series with two seasons: spring elms open the year, and fall-flowering elms return in late summer and autumn.
• The Annals of Allergy, Asthma & Immunology's elm review records that fall-pollinating elms tend to be more allergenic in studies than the spring-pollinating elms, though both are significant.
• In central Oklahoma, a second elm season runs from late August into October, with cedar elm and lacebark elm reaching very high levels even as ragweed and mold run high alongside.
• Spring flowering slides with latitude, beginning in January or February in southern latitudes and as late as April in northern regions.

Act one: the spring elms

The American elm (Ulmus americana) was the defining street tree of eastern and midwestern America — a tall tree whose branches arch out and inward like a vase, shading whole avenues. Elms are wind-pollinated and flower before the leaves appear, which puts their pollen at the front of the spring queue. Standard genus references describe the majority of elms beginning to flower in January or February in southern latitudes and as late as April in northern regions. University researchers in Oklahoma describe the same handoff locals experience: the early pollinators, cedar and elm, running really high in February, before everything else joins in March. LSU AgCenter's spring pollen overview tells the same story from Louisiana: deciduous trees begin releasing pollen as early as January, with elms and maples among the first, followed by the rest of the spring cast.

The two elm seasons at a glance:

In Chicago, Illinois, Denver, Colorado, and Dallas, Texas, elm is an opening-act pollen — significant for a few early weeks, then folded into the general tree mix as maple pollen, oak, and the rest arrive. Its earliness is its identity: elm symptoms arriving in late winter, when the calendar says nothing should be pollinating, are a classic pattern.

The Dutch elm disease backdrop

Behind the spring season is a famous ecological story. Dutch elm disease — a fungal blight carried by elm bark beetles — decimated American elms across the twentieth century; the Annals of Allergy, Asthma & Immunology's elm review describes the fungus (Ophiostoma ulmi), its beetle vectors, and how susceptibility varies by species, with American elm among the highly susceptible and Chinese and Siberian elms more resistant. Surviving mature elms, resistant species like lacebark elm, and newer disease-resistant American elm plantings now carry the spring season — in lower numbers than the elm-canopied past, but far from gone.

Act two: the fall elms

Here is the part most pollen calendars miss. Several elm species flower in late summer and fall instead of spring: cedar elm, lacebark (Chinese) elm, and September elm. The Annals review records pollination for lacebark elm as most intense in August and September, with lower counts in July and October, and notes that September elm and cedar elm also pollinate in late summer or early fall. It adds a finding worth knowing: fall-pollinating elms tend to be more allergenic in studies than the spring-pollinating elms, though both are significant.

The southern plains' second season

The fall season is no footnote in the southern plains. The Oklahoma Allergy & Asthma Clinic, reporting National Allergy Bureau data in October 2026, described a second elm season in central Oklahoma from late August into October, driven by cedar elm and lacebark elm, with elm tree pollen reaching very high levels even as ragweed and mold ran high alongside it. In Oklahoma City, Oklahoma and Tulsa, Oklahoma, fall elm overlaps the ragweed season so completely that the two are routinely confused — a genuine tree season hiding inside weed season.

How elm pollen behaves

Elms are prolific, wind-pollinated pollen producers, and the Annals review describes pollination that can be intense over a short period, with counts varying through the day. Grains are in the small-to-mid range typical of wind-pollinated trees in standard genus descriptions — light enough that Oklahoma reporting describes elm grains carried hundreds of miles on windy conditions. The Asthma and Allergy Foundation of America includes elm in its list of the trees that cause the most symptoms, and genus references rate elm pollen's allergenicity as moderate overall — with the fall species, per the studies above, punching higher.

Mostly its own problem: cross-reactivity

Cross-reactivity is a quieter story for elm than for birch or olive: the Annals review notes that immunological studies have suggested little cross-reactivity between elms and other trees. Elm, in other words, is mostly its own problem — which makes its two-season trick easier to identify from a symptom diary matched against daily data.

Recognising the elm seasons in the field

Elms announce themselves modestly. In spring the flowers are small, greenish, and easy to miss on bare branches; the giveaway comes weeks later, when the wafer-like winged fruits — samaras — spin down and litter pavements. In fall, the flowering of cedar elm and lacebark elm is even quieter, which is one reason the second season goes unrecognised: there is no spring spectacle to notice, just symptoms in September and a tree most people walked past all summer. Lacebark elm is easy to spot once you know it, though — its bark sheds in irregular flakes, exposing mottled orange-brown patches beneath, a detail the Annals review uses to describe the species.

Tracking elm pollen on Pollen Atlas

Elm rides the daily Tree Index on Pollen Atlas city pages (0 to 100 — Low 0–33, Moderate 34–66, High 67–100), and its per-plant detail is what separates the story: a Tree Index spike in February with elm on top is act one; a spike in September with elm on top, while everyone assumes ragweed, is act two. Watch both windows on the national city rankings, and place elm in the full sequence with the tree pollen season guide.

If a late-winter or early-autumn pattern repeats for you every year, an allergist can confirm whether elm is behind it — search the Pollen Atlas Find an Allergist directory. This article is general information, not medical advice.

Frequently Asked Questions

When is elm pollen season?

Elm pollen season happens twice: in spring and, in parts of the country, again in fall. Spring elms flower from January or February in southern latitudes to as late as April in northern regions, while fall elms pollinate in late summer and autumn.

Why are my symptoms bad in September — could it be elm?

Yes — several elm species, including cedar elm, lacebark elm, and September elm, flower in late summer and fall instead of spring. In central Oklahoma that second season runs from late August into October and overlaps ragweed season, so the two are routinely confused.

What happened to the American elms?

Dutch elm disease, a fungal blight carried by elm bark beetles, decimated American elms across the twentieth century. Surviving mature elms, resistant species such as lacebark elm, and newer disease-resistant American elm plantings now carry the spring season.

Is fall elm pollen worse than spring elm pollen?

In studies, yes — the Annals of Allergy, Asthma & Immunology's elm review notes that fall-pollinating elms tend to be more allergenic than the spring-pollinating elms. Both seasons are described as significant.

Two seasons, one tree, and the second one fools almost everybody. Track elm at both ends of the year and neither act has to be a surprise.

Early spring or early fall, elm gives fair warning if you check: see today's Tree Index and 5-day forecast for your city, free, on PollenAtlas.com.

Sources cited in this post: Annals of Allergy, Asthma & Immunology, "Allergen of the Month — Chinese Elm" (Dutch elm disease fungus and beetle vectors, species susceptibility; lacebark elm pollination most intense August–September; fall elms more allergenic in studies; little cross-reactivity with other trees); Oklahoma Allergy & Asthma Clinic, NAB-data alert, October 2026 (central Oklahoma's second elm season, late August–October, cedar elm and lacebark elm at very high levels); AAFA, "Tree Pollen: Spring's First Allergy Offender" (elm among the trees causing the most symptoms); standard genus references for spring flowering (January/February south to April north).