How do I tell these apart?

ms_minnamouse(7a)June 10, 2008

How do I tell the difference between Trees of Heaven and Black Walnuts? I'm almost positive that I have them growing side by side b/c I find seedlings that smell gross and look like Tree of Heaven (a.k.a. Stink Tree) but I also get black walnuts crop in the same spot too, in the fall.

I'm having a really hard time telling them apart and I'd like to cut the stink trees down already to plant something native.

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kman04(z6 KS)

Black Walnuts(Juglans nigra) typically drop their end leaflet, while Tree of Heaven(Ailanthus altissima) doesn't do this nearly as much so the Black Walnut leaf will look like it ends with a pair of leaflets, while the Tree of Heaven leaf appears to end with 1 single leaflet. Also, Black Walnut leaflets have teeth(serrated edges) while the leaflets on Tree of Heaven are smooth and entire, with the exception of a characteristic notch (single tooth, rarely two) on each side of the leaflet near the base.

It's amazing how there are no good photos of Black Walnut leaves and lots of unrepresentative line drawings there are on the internet!

    Bookmark   June 10, 2008 at 3:28AM
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hairmetal4ever(Z7 MD)

Black Walnut leaves are a brighter green as well - both at emergence and maturity. Tree of heaven leaves emerge reddish and are a darker green at maturity.

The bark is different too - Black Walnut bark has ridges and Tree of Heaven tends to be smoother, except on large specimens.

    Bookmark   June 10, 2008 at 10:04AM
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It's confusing in that mature specimens resemble each other so much. I noticed the red thing, which is what I've been going by for weeding, also the smell.

    Bookmark   June 10, 2008 at 4:47PM
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Black walnuts have a somewhat rank odor too, in my experience. (Pulled a few out of perennial beds today!?


    Bookmark   June 10, 2008 at 9:48PM
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newbiehavinfun(7a - Southern NJ)

I am also frustrated by this. We recently cut down a large black walnut tree (toxic to plants and dogs) but I swear what I'm pulling up are tree of heaven. The stems are a reddish brown, as are the top leaves. The leaves stink when touched and the roots typically bend out to the side. The leaves are not entirely smooth--they aren't serrated but have a ripple towards the stem. Am I right--are these tree of heaven?

    Bookmark   July 15, 2008 at 5:18PM
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alexander3_gw(6 Pennsylvania)

If these are first year seedlings, you can dig down a couple inches and find the walnut shell pretty easily...the squirrels don't bury them very deep. If you have a lot to go through, you could at least use this method to help you learn to distinguish between the two.


    Bookmark   July 15, 2008 at 11:11PM
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pinetree30(Sierra Westside)

When there are no leaves or fruit to look at, cut a small twig lengthwise and check out the pith -- the pulpy tissue in the center. In walnuts it's dark brown and broken up into crosswalls ("chambered"), in ailanthus it's continuous.

    Bookmark   July 17, 2008 at 12:29PM
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livingfossil(6a Dayton OH)

The easiest way to tell them apart is that the leaves of Tree of Heaven are smooth while Black Walnut leaves are serrated. Also, Tree of Heaven leaves have that peanut butter-like smell when crushed.

    Bookmark   July 18, 2008 at 11:56AM
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