En EspaŅol
Share

Ask Mr. Smarty Plants

Mr. Smarty Plants - Difference between Erigeron strigosus and E. annuus

Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.

Search Smarty Plants
    
 
See a list of all Smarty Plants questions
Can't find the answer in our existing FAQs, submit a question to Mr. Smarty Plants.

Need help with plant identification, visit the plant identification page.
 
rate this answer
Not Yet Rated

Thursday - July 07, 2011

From: Grinnell, IA
Region: Midwest
Topic: General Botany, Plant Identification
Title: Difference between Erigeron strigosus and E. annuus
Answered by: Nan Hampton

QUESTION:

How can you tell the difference between Erigeron strigosus or Erigeron annuus. Does one have more flowers on it than the other? Thanks.

ANSWER:

As you have already discovered, I'm sure, the differences are not obvious.  In fact, they are VERY subtle.  Erigeron strigosus (Prairie fleabane) was once considered a subspecies of Erigeron annuus (Daisy fleabane).  (Erigeron annuus ssp. strigosus is the synonym for the accepted name Erigeron strigosus var. strigosus.  See the entry from ITIS–Integrated Taxonomic Information System.)

You can read a description of E. strigosus and a description of E. annuus from eFlora.org, the online version of Flora of North America.  There are many technical botanical terms used in the description.  If you have James Harris' excellent book, Plant Identification Terminology, you shouldn't have any problem working your way through the terms.  If you don't have Harris' book, here are a few sites that should help you.  For leaf shape, try the Berkeley Echo Lake Camp Leaf Shape Terms and Leaf Shapes and Arrangements from The Seed Site.  You can find a very good list of Botanical Terms on the Calflora.net site.  Reading through and comparing the descriptions, you can see there are small differences in the types of hairs on the stems and leaves, the leaf shapes and whether the leaves persist during flowering.  You will also note there is considerable overlap in sizes and numbers of structures.  E. annuus is listed as having 5–50+ flower heads and E. strigosus is shown as having 10–200+, but still there is some overlap.  Just to complicate things more, please note the statement at the end of the description of E. annuus:

"Apparent intermediates between E. annuus and E. strigosus are encountered."

If you go to the 'parent' page for Genus Erigeron on eFloras, you will see that the the genus is divided into 23 Groups.  E. annuus and E. strigosus are part of Group 4.   The key to Group 4 of Erigeron spp. summarizes the differences in the two species and is a bit easier to get through; but, as you will see, there is still overlap in the descriptions and you are going to need a magnifying glass to see some of the differences.

Good luck in distinguishing between the two!

 

From the Image Gallery


Daisy fleabane
Erigeron annuus

Prairie fleabane
Erigeron strigosus

More General Botany Questions

What caused purple heartwood in my Tuliptree?
June 15, 2009 - My Tulip tree was hit by lightning and all bark from the base of the tree up to 50 feet was blown off. The tree also sustained a significant crack through the trunk. When the tree was cut down, we...
view the full question and answer

Percentage of worlds flowers of each color
July 14, 2007 - What percentage of the world's flowers are blue? red? white? yellow?
view the full question and answer

Comments on article in Austin paper
January 22, 2012 - Why can't we comment on your piece in the Statesman? It says no comments possible at the bottom.
view the full question and answer

Strange form of Dasylirion sp. (sotol)
December 27, 2008 - Mr. Smarty: I have a client with a huge (2 ft. diameter trunk), multi-headed dasylirion. On one or more of the heads, the leaves arch inward instead of outward. Someone said this is because of an inju...
view the full question and answer

Are Prunus minutiflora male and female flowers on different plants?
March 12, 2014 - I have a Prunus minutiflora and have recently learned the male and female flowers are on separate plants. How can I determine if I have a male or female plant?
view the full question and answer

Smarty Plants's Facebook profile Support the Wildflower Center by Donating Online or Becoming a Member today.

Mr. Smarty Plants wants you to be his Facebook friend. Click the Facebook icon to add yourself to Mr. Smarty Plants list of friends.
E-NEWSLETTER | BECOME A MEMBER | DONATE NOW | MEDIA | SITEMAP
© 2014 Lady Bird Johnson Wildflower Center