The plant in the photograph above is Parthenocissus quinquefolia, while that in the photograph below is P. inserta (which is treated as a synonym of P. vitacea by some authors, though the nomenclature of these two is quite confusing).
One thing to notice is that the leaflets of P. inserta are more shiny above than those of P. quinquefolia, which often appear dull on the upper surface.
Looking at the undersides of the leaflets, those of P. quinquefolia (above) are almost always pubescent, while those of P. inserta (below) are more often glabrous. There is, however, a rare hirtellous form of P. inserta known as P. inserta f. dubia.
Another part of the plant to check is the junction of the petiolules with the petiole.
In P. quinquefolia (above), this junction is also pubescent; in P. inserta (below), the junction is glabrous.
Growth habit is yet another way to distinguish between these two similar species.
Parthenocissus quinquefolia (above) is often high climbing, but it can also be found growing at ground level. Parthenocissus inserta (below), however, sprawls over the ground, structures, or other vegetation.
The reason for this difference in habit is all in the tendrils...
The tendrils of P. quinquefolia (above) have several branches that end in dilated adhesive discs, which are used to attach to vegetation or structures, allowing the plant to climb. Those of P. inserta (below), however, have few branches and no adhesive discs, and it therefore does not have the ability to climb the way that P. quinquefolia does.
Finally, if you are lucky enough to have flowers or fruit, the distinction between these two species is simple. However, as Swink and Wilhelm point out in Plants of the Chicago Region, P. quinquefolia rarely produces fruit, while P. inserta produces fruit routinely.
As you can see in the photograph above, the inflorescence of P. quinquefolia has a distinct central axis, with 25-200 flowers/fruit in panicled groups of cymes. The inflorescence of P. inserta (below), however, is dichotomously branched and therefore does not have a central axis. It most often has 10-60 flowers/fruit per inflorescence. The fruit of P. quinquefolia are a bit smaller in diameter than those of P. inserta, as well.
It's as easy as that. There is no longer an excuse for lumping all members of the Vitaceae with five palmate leaflets into P. quinquefolia. Now that you can distinguish between mature plants of Parthenocissus, be sure to check The Vasculum to see how to determine the difference between Parthenocissus and Vitis in the cotyledon stage.
Looking at the undersides of the leaflets, those of P. quinquefolia (above) are almost always pubescent, while those of P. inserta (below) are more often glabrous. There is, however, a rare hirtellous form of P. inserta known as P. inserta f. dubia.
Another part of the plant to check is the junction of the petiolules with the petiole.
In P. quinquefolia (above), this junction is also pubescent; in P. inserta (below), the junction is glabrous.
Growth habit is yet another way to distinguish between these two similar species.
Parthenocissus quinquefolia (above) is often high climbing, but it can also be found growing at ground level. Parthenocissus inserta (below), however, sprawls over the ground, structures, or other vegetation.
The reason for this difference in habit is all in the tendrils...
The tendrils of P. quinquefolia (above) have several branches that end in dilated adhesive discs, which are used to attach to vegetation or structures, allowing the plant to climb. Those of P. inserta (below), however, have few branches and no adhesive discs, and it therefore does not have the ability to climb the way that P. quinquefolia does.
Finally, if you are lucky enough to have flowers or fruit, the distinction between these two species is simple. However, as Swink and Wilhelm point out in Plants of the Chicago Region, P. quinquefolia rarely produces fruit, while P. inserta produces fruit routinely.
As you can see in the photograph above, the inflorescence of P. quinquefolia has a distinct central axis, with 25-200 flowers/fruit in panicled groups of cymes. The inflorescence of P. inserta (below), however, is dichotomously branched and therefore does not have a central axis. It most often has 10-60 flowers/fruit per inflorescence. The fruit of P. quinquefolia are a bit smaller in diameter than those of P. inserta, as well.
It's as easy as that. There is no longer an excuse for lumping all members of the Vitaceae with five palmate leaflets into P. quinquefolia. Now that you can distinguish between mature plants of Parthenocissus, be sure to check The Vasculum to see how to determine the difference between Parthenocissus and Vitis in the cotyledon stage.
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