Dioecious Plants: Dioecious species have the male and female reproductive structures on separate plants.

The Annual Rose Viewing was a success, but it was the hardy kiwi vine on our shed that also got a lot of attention.

Of course, it is the unusual green, white and pink foliage that makes the hardy kiwi so notable. I first saw this vine at the LakewoldGarden in Washington state many years ago. It was growing on a long trellis, so I did not realize how rampantly it could grow. I did not know the artful pruning it was receiving every summer – and winter.

Our hardy kiwi (Actinidia arguta) was planted on a trellis attached to our shed. I thought the colorful foliage would be very pretty when the roses in the Shed Bed were not in bloom. This has certainly worked very well. I have been happy that it has grown so vigorously and covers the better part of the shed wall. I have only done the most basic pruning, but this year I have come to realize that I need to take a firmer hand – and get out the ladder.

Since visitors to the garden are familiar with fuzzy kiwis that can be found on supermarket shelves they ask if my kiwi bears fruit. It does not, because kiwis are dioecious plants. This means that you must have a male and a female to get fruit. I was only interested in the unusual foliage so I was happy with one vine. I don’t know its sex.

I do have a friend who wanted the fruit which is different from the supermarket variety. Hardy kiwis are as big as a large grape and have a smooth skin that can be eaten. He bought a male and a female vine from a nursery. One of the vines died over the winter, but he couldn’t remember which was which, so he planted another male and female. Again, one vine died, and his list and map were lost, so again he was not sure which vine had survived.  I don’t actually know whether he finally got a male and female, and a fruit crop, but this is a problem with other dioecious plants as well.

I should add a caveat. Without pruning the hardy kiwi can reach a height of 40 feet, and if unattended or abandoned can overwhelm other plants and areas.

Perhaps the most commonly known dioecious shrubs are the hollies, the Ilex family. This includes the kinds of evergreen hollies with the beautiful red berries that are such a part of our Christmas traditions.  I have a single ‘Blue Prince’ and a ‘Blue Princess’ holly, Ilex x meserveae. The male produces the pollen that is needed to fertilize the female’s flowers and so create the beautiful red berries. It only takes one male to fertilize nine females. You do not need to have as many males as females.

These hollies produce tiny white flowers in April and May. They are easy to miss, but not the red berries.  My ‘Blue Prince’ took a beating this past winter, and the ‘Blue Princess’ also showed winter damage, but both are recovering nicely. There were lots of flowers, and even though the ‘Blue Prince’ is much smaller, I am expecting a good showing of berries later this season.

There is also the native deciduous holly, Ilex verticillata, which is more commonly called the winterberry. It also needs male and female plants in order to produce the orange-red berries that appear in the fall and persist through the winter. They tolerate wet soils which makes them an attractive shrub to plant in damp spots in the garden.

In addition to the hardy kiwi vine and the evergreen hollies, I have four ginkgo trees in my garden. We planted these about 16 years ago when our grandsons were hardly more than toddlers. We planted them partly as a memorial to our two years in Beijing. I was afraid they might be slightly too tender, but they are thriving and are even big enough now to throw welcome shade on hot summer afternoons.

Ginkgo biloba trees are used in cities because they are hardy, but the fruit of the female is said to be unpleasantly smelly. I cannot attest to this from my own experience because during our New York city years, and our Beijing years, I never came across ginkgo fruit. It takes at least 30 years for the tree to mature and produce fruit, which means that when my trees drop their fruit smelling of rotten eggs or vomit, I will not be around to suffer.

However, it seems to me that 30 years or more of a beautiful, hardy, disease resistant tree is better than those years without the tree even if it ultimately has got be cut down. Or at least the females have to be cut down.

The ginkgo is an ancient tree, sometimes called a living fossil, and is known for its unusual fan shaped leaves. They turn a beautiful gold in the fall which tend to fall all at once. We have often gone to bed on an October night, and awakened to find every golden leaf on the ground.

These are the three types of dioecious plants in my garden, but I recently checked a long list of dioecious plants online and found that the stinging nettles among my weeds, Urtica diocia, and the hop vine, Humulus, that is growing in a tangle of grapes and multiflora roses, are also dioecious plants, but they are subjects for another time.

Between the Rows   July 5, 2014