Doublefile viburnums

(Question)

Thank you for reading my question. I am wondering what you might advise when it comes to doublefile viburnums. I do not think they have been noted as invasive in Ontario but there are some places in the U.S. where they have been. I have Marieseii/SummerSnowflake/Shasta and am wondering whether to continue letting them grow. Maybe I am getting ahead of myself but would appreciate hearing what you think. Thank you.

(Answer)

I agree, non-native doublefile viburnums like yours don’t seem to be on any lists of “invasive plants”.  I checked the US Invasive plant atlas  as well as Canadian/Ontario sites and although none of the 3 viburnums you have  – all are Viburnum plicatum f. tomentosum  – are on their list of invasives, that’s not the end of the story.  For example, if these plants spread to wooded areas, they can crowd out the understory by forming dense shrubs.

Credit Valley Conservation’s Invasive Plant List categorizes invasive plants by their ecological rank, from 1 to 5, with those in rank “1” being a threat to natural areas wherever they are found.  Rank “5” includes species with the potential to become invasive, but which have not yet been identified as a serious threat to Ontario’s natural areas.  The list includes Viburnum plicatum as a rank “5” plant.

Some areas do consider these shrubs as species of local ecological concern, for example the US National Park Service’s Six Invasive Viburnums in the Greater Washington Area includes your viburnums.

I suggest that you continue to enjoy your shrubs, but cut off their old flowers and also the fruits prior to maturity, in order to prevent the seeds from being spread widely by birds.  This should minimize the plants’ escaping from your garden.

For additional information, see

  • Brandywine Conservancy. Invasive species spotlight: Japanese snowball.  This article provides a good overview of viburnum – I had no idea there are 150 species or so!! They suggest planting native viburnums.
  • Maryland Invasive Species Council. Choose your viburnums with care.
  • The Maryland article refers to Cornell University’s Guide to identifying viburnums.  This is a helpful site as you can identify the shrubs by Latin name. (i.e., Viburnum plicatum tomentosum ‘Marieseii’, Viburnum plicatum f. tomentosum ‘Summer Snowflake’, and Viburnum plicatum f. tomentosum ‘Shasta’)

Thank you for your concern about the impacts of your shrubs on natural habitats!