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Dodder Alert! Another Aggressive Invasive Plant Appears in Harpswell

By Priscilla Seimer

Dodder (Priscilla Seimer photo)

Volunteering for the Harpswell Invasive Plant Partnership means getting to know a variety of invasive plants up close and personal. At times, however, it also means encountering native plants we may not have seen before. Usually that is good; maybe it means a native is trying to re-establish itself where only invasives had grown before.

Unfortunately, finding a new plant in the neighborhood is not always positive. Meet the Dodder, Cuscuta spp. (In New England about 95 percent of all dodder found is C. gronovii, Common Dodder). From a botanical perspective this is a fascinating plant. It does not maintain roots or leaves so cannot make its own food. It is a total parasite. My favorite description is from the Kittery Land Trust — they have had to cope with dodder for years — describing it as “Silly String though not so funny.” This is a perfect description. Dodder does look like someone sprayed, draped or wound often-orange Silly String around plants, lots of string. Because dodder gets all its food from the plants it is parasitizes it doesn’t need to manufacture its own and can use its energy to grow; and grow it does. According to weedalert.com dodder can grow up to three inches per day. Based on what I have seen, I have no doubt this is true.

Dodder produces small pink or white flowers in early summer. It spreads primarily through its seeds and those seeds can last in the soil for decades. Successful germination of any seed requires host plants be growing within one to three inches of the dodder’s seedling. A new seedling produces one small root, capable of supporting the seedling for only one or two days. The seedling sways around looking for a host to attach itself to. If it cannot find one, the seedling dies.

Kittery Land Trust (KLT) Board Member Rob Nichols unfortunately has a lot of experience with dodder. Below is the protocol KLT currently practices to try and eliminate dodder:

When a new infestation is found:

  1. Carefully determine the outer boundary of the dodder infestation.
  2. Cut a wide “dodder-free” buffer zone around the entire area.
  3. For small areas carefully cut everything inside the buffer area to the ground, trying not to spread the dodder outside the buffer area since it may start growing again. Ideally, it is best to bag the debris and remove it since the remains can live for sometime and may still go to seed.
  4. For larger areas an herbicide can be used to kill off the entire area. However, if the dodder already has little white flowers then it is likely that some of the dodder will live long enough to form seed. In this case see next step.
  5. If the dodder has little golden or brown seed pods then the best course of action is to very carefully cut and bag as many of those seed stalks as possible. Once complete, the rest of the dodder should be cut down to prevent any more seed creation. It is highly likely that dodder will germinate in this area in subsequent years. See protocol for managing previous dodder sites.
    After removing dodder, it is always wise to monitor the site well into August to make sure no new growth is occurring.

KLT adds that dodder should never be composted as the seeds can live such a long time. The ideal disposal is to leave the bags in the sun for a few weeks before transporting them to a landfill. (This is a process recommended for the disposal of mechanically-removed invasives as well.)

There have been several reports of dodder in the Harpswell area in the last few weeks. It is worth getting to know this aggressive plant, and how to best remove it.

Thanks to Rob Nichols and the Kittery Land Trust for the information they provided, and their offer of help if anyone has questions.

Here are some resources:

weedalert.com

plants.usda.gov

GoBotany (New England Wildflower Society)

2017