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Friday - July 08, 2005

From: Austin, TX
Region: Southwest
Topic: Vines
Title: Differentiating between Cow-itch vine and Balsam-gourd vine
Answered by: Joe Marcus and Nan Hampton

QUESTION:

How can I tell the difference between Cow-itch vine and Balsam-gourd vine?

ANSWER:

Cow-itch vine (Cissus trifoliata), a member of the Family Vitaceae (Grape Family) and Balsam-gourd vine (Ibervillea lindheimeri), a member of the Family Cucurbitaceae (Cucumber Family) are easily confused since they have foliage that looks very similar. Here are some tips on telling them apart.

1. Cow-itch leaves are typically, but not always, fleshier than Balsam-gourd leaves.

2. The stem of Cow-itch vine is also usually fleshy, soft and brownish in color; while a Balsam-gourd vine stem is normally thinner, stringier, and green. This may be the easiest recognition feature to use if the plants are not in flower or fruit.

3. The crushed foliage and stems of Cow-itch exudes a foul, burnt rubber odor, while Balsam-gourd does not. However, since handling Cow-itch vine causes contact dermatitis on some people, caution should be exercised if you're not sure about your own sensitivity to it.

4. The tendrils on Cow-itch emerge from the stem opposite the leaf axil, while on Balsam-gourd the tendrils emerge in or next to the leaf axil. Distinguishing the species by this feature is not always certain because of variability within individuals. The tendrils have another characteristic that is often useful but not always sure. The tendrils of Cow-itch tend to have more of a meandering appearance than those on Balsam-gourd. Balsam-gourd tendrils usually exhibit a more regular spiral, resembling the wire spring of an ink pen.

5. Cow-itch flowers are small, greenish and occur in large clusters. Balsam-gourd flowers are larger and showier, yellow to greenish-yellow and typically have one to few flowers per inflorescence.

6. The fruits of Cow-itch are small, black berries occurring in large clusters; while Balsam-gourd fruits are large, red and showy when ripe and typically occur singly at any leaf axil.

7. Finally, if you have access to a magnifying glass, you can see small pores on the surface of the underside of Balsam-gourd leaves. There are no pores on the underside of the leaves of Cow-itch.

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Friday - July 08, 2005

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