Invader into the garden or wildscape

The first time I encountered dodder was in a giant greenhouse in Akron, Ohio. They were growing chrysanthemum cuttings by the hundreds of thousands and somehow this plant had gotten a start on one side of one bench. We were on a horticultural field trip with one of my classes from Ohio State, and I quickly found out that I was the last plant guy to learn about this unusual parasite.

Later I saw a quarter-mile of Texas roadside blanketed by dodder near Independence, Washington County (near Brenham).

You wouldn’t expect dodder to be growing in arid Alpine, but there it was before my eyes a few Aprils back. Click image for larger view.

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The details of this plant are simple…
It is an annual.
Seeds germinate in the soil in spring.
The seedlings have just enough chlorophyll to support themselves for 5 or 10 days, until they’re 10 or 12 inches tall.
Plants that are growing near suitable host plants will force their adventitious roots (called “haustoria”) into the tender stem tissues of the hosts.
Eventually the roots of the dodder plant will wither away and all sustenance will come from the host.

Dodder is growing here with the support of what appears to be sensitive briar, Mimosa pudica.

Small, bell-shaped flowers develop in late summer and numerous seeds are produced.
The dodder plants are killed by the first freeze and the cycle begins again.

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Dealing with dodder…
Pull all young seedlings before they attach to the host plants.
Trim out stems that have dodder attached.
Remove infested plantings before dodder blooms and goes to seed.
If you feel the need to use a herbicide, glyphosate-only weedkillers will eliminate both the dodder and the host plants without leaving residues in the soil.

Posted by Neil Sperry
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