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!




© 2012, Emily DeBolt. All rights reserved. This article is the property of Native Plants and Wildlife Gardens. We have received many requests to reprint our work. Our policy is that you are free to use a short excerpt which must give proper credit to the author, and must include a link back to the original post on our site. Please use the contact form above if you have any questions.

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  1. 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}

  2. 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

  3. Bridget Looney says

    Speaking of dioecious disappointments, fully knowing rhus aromatica was dioecious I ordered ten plants and all turned out to be male. At my local garden center, they also have only male plants, with nursery salespeople mistaking the male catkins for fall berries.

    If anyone has female cuttings, I would be happy to trade!


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