Native Wood Poppy vs Invasive Greater Celandine Identification

Greater celandine, Chelidonium majus, is a yellow-flowering plant in the poppy family.  I first noticed this plant on my travels in Europe, where it is widespread.  It is one of many plants that has been introduced to North America, where it has become invasive, harming local ecosystems because it out-competes native plants, but few insects eat it.

The Wood Poppy, also called Celandine Poppy or Poppywort, Stylophorum diphyllum, is native to North America, and fills a similar ecological niche to the invasive greater celandine.  Although it is still common in some areas, and has even expanded its range due to being planted as a garden plant, it has become endangered in parts of its range, such as in Ontario.

By learning to distinguish between these two species, you will be able to help with removing greater celandine when it occurs in North America, as well as by encouraging the native wood poppy.

Although at first glance they look similar, I find that with some practice, the plants can be easy to identify at any time of year.  The easiest way to distinguish them, which can be done without looking closely, is their seed pods.

• Flowers - Both plants have yellow flowers with four petals, and bloom at about the same time, but the flowers are easily identifiable upon closer look, especially if you see them side-by-side or take a photograph to compare.  The North American wood poppy has bigger, more showy flowers.  The petals are much wider, and nearly always overlap each other.  The petals also look floppy.  Greater Celandine, on the other hand, has narrower petals (much longer than they are wide) which are sometimes so narrow that they have a visible space between petals.  There are other differences in the flowers, such as a denser concentration of stamens on the wood poppy, and a green color of the pistil on Greater Celandine.
• Leaves - The leaves of both plants are similar, with deeply lobed leaves growing about the same height, but if you look closely, you will easily be able to distinguish them.  Greater Celandine has leaves with a very rounded look, but many small cuts into the lobes.  The wood poppy native to North America has more pointy looking leaves, with large lobes but no fine cuts.
• Seed Pods - Greater Celandine (from Europe) has tall and narrow seed pods that look a lot more like the pods of a mustard plant than typical poppy pods.  The North American wood poppy has short, stout, blue-green seed pods, covered in bristles, that look more like other poppy seed pods.

Below you will see these species side-by-side.

Below I have included un-labelled pictures.  Try ID-ing each one using the tips above, and then scroll down to check your answers below.

1. Greater Celandine

2. Wood Poppy

3. Greater Celandine

4. Greater Celandine

5. Wood Poppy

6. Wood Poppy