The Secret Lives of Dioecious Plants

My mother called the other day to chat, and my husband answered the phone.  ‘No, Emily can’t come to the phone right, she’s out back sexing the pussy willows,” he said. “What?!” my mother said into the phone. She’s not a plant person like I am. Sometimes you forget that something that makes perfect sense to you might sound a bit strange to others…

Many gardeners are already familiar with dioecious shrubs such as Ilex.  There are many cultivars available at garden centers of the popular Winterberry (Ilex verticillata) that are either male or female – so you don’t have to figure it out on your own.  When you grow straight species Winterberry, like we do at our nursery, you have to sex the plants yourselves.  It takes a few years for them to mature, but once they do, the flowers are easy to tell apart once you know what you are looking for (Click here to see photos of male and female winterberry flowers from a past blog).  But Winterberry doesn’t flower until June, so it is still a while from now until you can head out to sex them if you haven’t already.

Right now, there are some other dioecious shrubs that it is the perfect time to look at.  At our nursery I am working on our pussy willows (Salix discolor) and Spicebush (Lindera benzoin), as well as the fragrant sumac (Rhus aromatica) and sweetfern (Comptonia peregrina).  For a great list of many of our native dioecious plants, check out Carolyn Summers’ book, Designing Gardens with Flora of the American East.

The pussy willow (Salix discolor) catkins are still pretty small right now (we are in zone 5a in upstate NY), but once they open up, I am going to be ready.   The male catkins are covered in staminate flowers, and the females in pistillate.  Here are some photos of what they will look like.  I hadn’t paid much attention to the pussy willows at the nursery in the past, but I had a beekeeper call me up that was interested in some to put around her hives for her bees, and she wanted both male and female plants. So I figured I had better figure it out!

Male Pussy Willow Catkins. Photo Credit: BRUNO PETRIGLIA/SCIENCE PHOTO LIBRARY

Female Pussy Willow Catkins. Photo Credit: BRUNO PETRIGLIA/SCIENCE PHOTO LIBRARY

The other dioecious shrub that I am working on right now is Spicebush.  Sometimes called the ‘forsythia of the woods’, this native shrub blooms in early spring, right around the time that the non-native forsythias are blooming in yards and along the street everywhere.  There is a post about Spicebush here.  It took a little more digging to figure out how to tell the flowers apart, but the male flowers have 9 fertile stamens,  and the female,or pistillate, have a fertile ovary and 12-18 rudimentary, infertile stamens. Both male and female have 6 short, yellowish sepals. I wasn’t able to find a great photo, but I am hoping I will be able to sex our shrubs based on the descriptions and then take some good photos myself from our own shrubs.

As native plants grow in popularity and are available at more nurseries and garden centers, unfortunately that fact that some of the plants are dioecious is often overlooked. Gardeners read about Spicebush and its great red berries as an alternative to invasive shrubs such as Burning Bush.  But unless they get a male and a female, they aren’t going to get those berries.  And I have not found a nursery besides my own that sells Spicebush that can tell you if it is a male or female. (maybe you know of one? if so, please share!)  This post by team member Vincent Vizachero talks about issues with native cultivars, and how only female inkberry are sold in nurseries.  Without males, you won’t get those nice berries that the shrub is named for.  We don’t want people to be disappointed and frustrated with their native plants.  If people are buying them for the berries, and then don’t get berries and don’t understand why, I think it could be easy to have a bad taste left in your mouth.  If we can work to have plants that are dioecious sexed before they are sold at nurseries and garden centers, or at least labeled with some sort of a disclaimer like ‘You need males and females of this shrub’ – I think it would be very helpful for gardeners trying to do the right thing!




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    About Emily DeBolt

    Emily has a Bachelors degree from Cornell University and a Master's of Environmental Interpretation from the State University of New York College of Environmental Science and Forestry. She lives with her husband Chris and Greater Swiss Mountain Dog McKinley in northeastern New York where they run Fiddlehead Creek, a 100% New York native plant nursery that specializes in growing plants for water quality and conservation projects.


    1. Sue Reed says:

      Nice post Emily. Great reminder. Thank you.
      One minor note: If you stick in a link to Carolyn Summers’ book, I’m sure she’d appreciate it! :o }

      • Emily DeBolt says:

        Sue. thanks for the reminder – I added a link in.

    2. Donna@Gardens Eye View says:

      Emily this has been my frustration. You need a male and female but they are not marked and so you take your chances…thx for all the info to help us with this.
      Donna@Gardens Eye View recently posted..Beauty

    3. UrsulaV says:

      I would have been very happy to get this info about inkberries before I planted them, let me tell you!

      Mind you, I’m still a little irked by the fact that nobody tells you that Viburnum cultivars are almost universally self-sterile, so all those gorgeous “Blue Muffin” with the big glossy photos of the berries are completely useless unless you can find another version that happens to bloom around the same time. (Thank goodness for Viburnum specialist nurseries…)
      UrsulaV recently posted..Grumpy Toad

      • Emily DeBolt says:

        good to know. I didn’t know that about ‘Blue Muffin’. We just grow the straight species Arrowood at our nursery – and I am phasing it out – which is such a shame bc I really like it – but with the viburnum leaf beetle in our area it just doesn’t make sense to plant shrubs that are going to have problems. I have seen some viburnums pretty much totally defoliated by the little buggers!
        Emily DeBolt recently posted..Comment on January’s Plant of the Month by The Secret Lives of Dioecious Plants

    4. Carol Duke says:

      Great post Emily! Important lesson and one that I hope will soon be more widespread. Would love to have seen your mom’s expression!
      Carol Duke recently posted..Flower Hill Farm BUTTERFLIES OF 2011 ~ GRAND FINALE


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