Käyttäjän aenglandbiol päiväkirja

An excellent resource for telling Arundo from Phragmites is at http://desertfishes.org/cuatroc/organisms/non-native/arundo/Arundo_Phrag_id/Arundo_Phrag_id.html

Arundo is taller, with broader leaves and stouter stems (canes) than Phragmites.

The infloresecence for Arundo typically has a stiff, upright plume, whereas Phragmites is looser and more droopy. These are fresh in the autumn.

In Arundo, the base of the leaf blade clasps the stem over halfway around, and has a larger, pale auricle. Phragmites' leaf blades clasp less far around the stem, and have a much smaller auricle.

In Texas, about 90% of the wild iNaturalist observations of Araceae are Colocasia esculenta, and about 8% are Xanthosoma sagittifolium.

Colocasia leaves reach a height of about 3', and are generally heart shaped with the petiole (leaf stem) attaching to the back side of the leaf. There is often (but not always) a light purple colored dot on the front of the leaf where the petiole attaches. The far edge of the leaf (tip of the heart shape) hangs downward (except in very young leaves).

There are multiple Colocasia species sold ornamentally, but only Colocasia esculenta seems to thrive when it escapes into the wild in Texas.

Xanthosoma leaves can reach a height of about 9' tall, and are generally arrowhead shaped with the leaf stem attaching at the edge of the leaf in the notch of the arrow. The tip of the arrowhead shape hangs downward (except in young leaves).

Xanthosoma sagittifolium is the only species documented to thrive when it escapes into Texas. This species seems best confirmed from photos that show the notch where the petiole attaches - this species has leaf margins that extend almost completely to the edge of the notch.

Xanthosoma robustum has been documented from a few sites in Texas, mostly ornamental gardens. It has leaf margins that end about 1.5-2.0 cm from the posterior rib at the base (the V shaped ribs are "naked" for about one inch).

Alocasia has large leaves like Xanthosoma but the leaves typically point upward even when mature. Observations of this species from Texas seem to mostly be non-wild, potted plants.

A quick visual of the differences between elephant ear genera can be found at
https://durablegardening.blogspot.com/2011/01/whats-difference-alocasia-colocasia-and.html

The best reference for distribution and identification of Colocasia, Xanthosoma, and Alocasia in the southeastern US is Serviss et al., 2000, which can be found online at
https://www.jstor.org/stable/41967766

For details of Xanthosoma ID, see Croat et al., 2017, at
https://adoptabosque.org/wp-content/uploads/2020/09/XanthosomaAraceae.pdf

An excellent photo-based resource for telling Arundo from Phragmites is at http://desertfishes.org/cuatroc/organisms/non-native/arundo/Arundo_Phrag_id/Arundo_Phrag_id.html

Arundo is much larger, hence the "Giant Reed" name. Stalks can reach 20 or more feet in height. The leaves are broader, and the canes are thicker. The base of the leaf blade wraps over halfway around the stem, and has large white/beige/yellow auricles that are prominent. In the autumn, it produces a stiff, upright plume of an inflorescence.

Phragmites can reach about 12 feet tall. The leaves and canes are more slender. The base of the leaf blade wraps less than halfway around the stem, and the auricles are smaller. The inflorescence is looser, and droopy.

Tucker, 1990, has an excellent detailed key for those interested in formal descriptions. https://www.jstor.org/stable/43782240

In Texas, these differences will allow ID to the genus level.

The only Arundo that has been documented in Texas is Arundo donax.

The only Phragmites documented in Texas is Phragmites australis.

There are several subspecies of Phragmites in the New World:
Phragmites australis ssp. americanus "American Common Reed"
Phragmites australis ssp. australis "European Reed"
Phragmites australis ssp. berlandieri "Subtropical Common Reed".
The distribution of these subspecies apparently overlaps in Texas, and they are very difficult to tell apart from photos.