Tick-Trefoils in New Jersey

I am not an expert; this is what I've learned so far:

Tick trefoils are pink flowers in loose clusters in mid to late summer with three parted leaves and fruit that are chains of flat semi-circles which are clingy.

In New Jersey there are two genera of tick trefoils: Hylodesmum and Desmodium.

Hylodesmum is easy to separate. The three parted leaves are in a whorl at the base of the plant. In naked flowered tick trefoil (H. nudiflorum) the flowers are on a separate stem from the leaves, in pointed leaved tick trefoil (H. glutinosum) the flower stalk arises from the center of the whorl of leaves. The leaves are also more long-pointed.

Desmodium is more complicated. The important points are leaflet shape and size, hairyness, length of stem on leaves, and number and shape of fruit (loments) in the chain.

Tall plants (more than 10 inches), Narrow leaves, 1 inch stem:

Probably the most common species is panicled tick trefoil, (D. paniculatum), the leaflets are very narrow, about three inches long by half an inch wide (though that can vary). They have stems about one inch long, they are not particularly hairy (though the leaf underside has appressed hairs). Their veins are not very obviously netted. There are 2-6 fruits in a chain.

Tall plants, sessile leaves, more than 20 flowers in a cluster which tapers at the end:

Showy tick trefoil (D. canadense) is similar to panicled, but with leaves not so linear, with extremely short stems, and massively more flowers. The tapered tip to the flower cluster is distinctive. They have 2-5 fairly round fruits in a chain.

The following species I'm not as familiar with:

Tall plants, leaves not narrow, leaf stems about 1 inch, leaflets very pointed at tip.

Toothed tick trefoil, D. cuspidatum is not very common in NJ but present, has triangular fruit, and stipules at the base of the leaf stalk that don't fall off. It's most distinctive feature is the long tips on the leaflets.

Tall plants, the fruit semicircular, long stems on leaves, the leaflet stems all the same length, not hairy

Maryland tick trefoil, (D. marilandicum) is pretty smooth all over. the fruit are semicircular rather than rounded and there are about 2-3 in a chain.

Tall plants, leaves not narrow, not extremely hairy, leaf underside has hooked hairs

Hoary tick trefoil, (D. canescens) has larger leaflets and broader. The stem is about an inch. The stipules at the base of the leaflets are oval and tend to stay all season. The fruit are triangular and 4-6 in a chain.

Tall plants, leaves not narrow, stem quite hairy, triangle fruit

Perplexed tick trefoil (D. perplexum) has long, straight hairs all over all the stems and leaf stems but otherwise looks like other tick trefoils. Fruits are triangular. Stipules at base of leaves tend to fall off. leaflet tips often pointed but not extremely so.

Tall plants, leaves not huge, leaflets very oval, end leaflet much larger with longer stalk than side ones

Stiff tick trefoil (D. obtusum) has oval leaflets which are thick and dark green. The side leaflets are sessile, the whole leaf does not have a long stem. The end leaflet is nearly twice as big as the side ones and tends to bend over backward or be off at a different angle than the rest of the leaf on a very distinct stem of at least a cm. Fruit are semicircles with 2 or 3 in a chain.

Tall plants, leaflets under 1.5 inches.

Little leaf tick trefoil (D. ciliare) has leaflets all about the same size, the side ones sessile, the end with a bit of a stem, leaflets thick and often folded along the center vein. whole leaf is generally under 2 inches long. Fruit semi-circular, 2-3 in a chain.

Trailing plants, round leaflets

Roundleaf tick trefoil (D. rotundifolium) trails along the ground and looks most like a clover of all the tick trefoils. It has round leaflets about an inch or a bit more long, the side ones sessile and sometimes almost heart shaped at the base, the end one on a bit of a stem and slightly larger.

When looking at tick trefoils also rule out bush clovers (clustered flowers), sweet clovers (smaller, narrow leaves, flowers not pink), and hog peanut (vine).

Publicado por srall srall, 22 de noviembre de 2020

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