When does Jack-in-the-Pulpit bloom in New York?

Most often in April. Across 385 dated, research-grade observations of Arisaema triphyllum in New York, the flowering season runs roughly April to May.

Peak April In flower 385 Examined 622 State New York

Flowering 385 in flower of 622 examined

95%

93%

51%

18%

Proportion of examined Arisaema triphyllum in New York in flower, by month
Month	In flower	Examined	Share	95% interval
Jan	0	0	too few examined
Feb	0	0	too few examined
Mar	0	0	too few examined
Apr	55	58	95%	86% to 98%
May	279	299	93%	90% to 96%
Jun	40	79	51%	40% to 61%
Jul	4	64	6%	2% to 15%
Aug	1	29	3%	1% to 17%
Sep	0	67	0%	0% to 5%
Oct	4	22	18%	7% to 39%
Nov	2	4	too few examined
Dec	0	0	too few examined

Peak flowering in Apr. Each bar is the share of Arisaema triphyllum in New York observations in which someone actually recorded the reproductive state and found the plant in flower, not the raw number of flowering records. That distinction matters: people observe plants far more in spring than in winter, so a bare count of flowering records partly measures when people go outside. Dividing by the number examined removes that. 385 of 622 examined observations were in flower, every one of them research grade. The whisker on each bar is a 95% Wilson interval. 5 months have fewer than 5 examined observations, so no proportion is drawn for them. This is still a global aggregate and not a forecast for your garden: the same species flowers on different dates in different hemispheres. Where a species has fewer than 30 flowering records we do not draw this chart at all. Computed from 10.15468/dl.wt38fd.

What this is, and what it is not

This is a record of when people in New York found Arisaema triphyllum in flower, not a forecast. It is computed only from observations made in New York, so it is not the species’ global average dragged onto a map: the same plant flowers on different dates in different places, and that is the entire point of the page.

It will not tell you what your particular plant will do this year. Bloom time moves with the season, with altitude, and with the weather, and a warm February pulls everything forward. We publish the distribution and the sample size, and we refuse to draw a month that too few people examined.

The plant

Arisaema triphyllum

Jack-in-the-Pulpit

Sourcesevery claim on this page

GBIF (iNaturalist Research-grade Observations). Dated flowering annotations in New York. Every record achieved iNaturalist quality grade Research, which is applied upstream at export. 10.15468/dl.wt38fd. Retrieved 2026-07-14.
World Flora Online Plant List. The accepted name. CC0. Retrieved 2026-07-12.