Finding a Mate for My Plants

Berries of Winterberry Holly persist into well into winter
 when they provide late season food for birds.

Shortly after we moved into to our new place I identified a nice looking Winterberry Holly (Ilex verticillata) growing near the front door.  It was mid fall and I didn't see any berries on the shrub.  This meant that either it was a male plant or that there were no compatible males within 100 feet to provide pollen.  The bright red berries of Winterberry are its main ornamental and ecological feature. 

Female flowers have a large central ovary surrounded by undeveloped
stamen-like structures (lacking anthers).  This plant was blooming in early June.

I had to wait until the following June to get a good look at the flowers.  After careful examination it turned out that this plant was in fact a female.  The solution was to find a suitable mate, that is one with a similar bloom time.  I found a male cultivar at a nearby nursery called ‘Jim Dandy’.  I sat him next to the established female for a few days while I located a nearby spot to plant him.  

Male flowers have well developed stamen and a very small ovary-like center.
The male plant seemed to attract smaller sized insects.

By September I noticed a few of red berries on the plant.  Success!  I hope to see more berries next year as there will be a much longer time for pollination to occur. 

These red berries were formed by mid-August.  

One of my goals in designing a landscape is its habitat value.  That is, what does the landscape gives back to wildlife in the form of food and shelter.  So when I select plants I look for ones that produce flowers, fruits and/or seeds that wildlife can use.  When selecting plants from a commercial nursery many of them are cultivars, which are genetically identical.  This becomes an issue in the habitat garden if the plants are single sexed (dioecious).  It is also a problem for plants that have both male and female flowers on the same plant (monoecious) or have perfect flowers (both male and female parts in the same flower) if the plants are not self fertile. 

All this plant fertility can have a down side.  In a formal garden production of viable fruits and seeds may lead to increased weeding and spreading of plants out of their designed boundaries.  Also, some consider that the mess that falling fruits create outweighs providing food for birds and other wildlife.  Personally I think of the landscape as a dynamic thing that changes over time.  In the designed landscape plants need to be kept under some degree of control, but I really enjoy seeing native species spreading to new areas where they are happier than in my initial design.

Here are the flowers of a female persimmon.  They have large ovary structures.
Male flowers are narrow at the base.

My experience with the Winterberry Holly has heightened my awareness of dioecious plants.  I want to generate as much natural food for wildlife as possible.  Also I would like to grow some ‘wild’ fruits and berries.  Persimmons (Diospyros virginiana) are dioecious.  My established persimmon is a female, but I have not seen any fruit on it.  I have brought in four more new wild-type plants, at least one of these should be male.  I don’t know of any named male cultivars of persimmon; however there is one called ‘Meader’ that is self-fertile. 

In general female plants need at least one pollen source (male) close enough that pollen can be transferred.  This transfer can be by wind (grasses and many trees) or by insects (vectors) most flowering plants.  For native hollies, like Winterberry, a male should be located with in 50 ft for effective pollination, though pollination over greater distances (100-200 ft) may be possible. 

Female Box Elders are covered with seed pods (samara) in the fall.
I noticed some squirrels eating them right off the tree.

Some other dioecious plants that I have are Box Elders (Acer negundo), Junipers, Tupelos (Nyssa sylvatica), Yews and Goatsbeard (Aruncus diocus). 

Some plants with perfect flowers are not self-fertile.  This may not be convenient for a habitat gardener with limited space for lots of plants. However, it works out on the larger scale to provide the greater genetic diversity adaptation to change and continuation of the species.  I have posted a number of times about the difficulty of getting Viburnums to bear fruit when only a single cultivar was planted.

There are some practical situations where limiting plant fertility and reproduction is called for.  In urban landscapes Ginkgos are very successful street trees.  The fruits, however, are loaded with butyric acid and smell of dog poo when stepped on.  For this reason most cultivars in the trade are males.  In my last post about Jerusalem Artichokes I noted that these are not self-fertile.  By only using only a single cultivar one limits the risk that this somewhat aggressive native will spread by seed. 

Another issue for some in urban and suburban landscapes is pollen allergies.  In many cases these are due to the (over) use of male cultivars.  Males don’t produce messy fruits, but they still send out their pollen.  This results in a type of air pollution that effects sensitive individuals.  While searching for information about dioecious plants I came across an excellent resource book by Thomas Ogren titled Allergy-Free Gardening.  This book contains a lengthy list of dioecous plants and the sex of individual cultivars.  There is also an allergy rating for a wide variety plants including monoecious plants and those with perfect flowers.  I did not realize that many maples, such as Red and Silver Maples, came as separate male and female plants.  Since I am more interested in facilitating plant fertility for enhancing habitat value I see using this book differently than the author intended.  But, if I had a client with particular allergy problems this book would be an excellent resource for plant selection to design a low-allergen garden.

Fall's First Fruits

We are finally getting some frosty weather here in Knoxville, MD.  That was a signal to take in our first harvest of Jerusalem artichokes.  The flavor of the tubers is supposed to be improved by a little cold weather.  I wasn't sure how many to expect.  From what I've read, yields are high and it is important to dig out all of the tubers; otherwise the plants will spread throughout the garden.

View to South Mountain from the southern end of Pleasant Valley in Maryland in early November.
Foliage is about a week past peak.

A mass of 4 Helianthus tuberosus
'Stampede' in mid-September.  

I selected the cultivar called 'Stampede' (from Oikos) because the tubers stay close to the base of the plant making them easier to harvest.  This was generally the case, however there were a few longer runners with large tubers at the far end.  While this cultivar was supposed to be early maturing, it did not begin to bloom until late summer, a bit later than I expected.  The plants grew to about 12 feet in height.  They were holding themselves up OK until a big storm hit in early October.

As you can see in the photo the yield of tubers from the four plants gave me a wheelbarrow full, well over 20 pounds.  Now we need to find some recipes for how to prepare them.  One caution about these tubers is that the form of starch in them is inulin.  This is not easily digestible by most people, resulting in some gastro-intestinal discomfort (to be discreet).  One article suggested eating small amounts of them at first to help your digestive system adjust.  This is a warning not to serve heaping portion at a dinner party to uninitiated guests.

These tubers will keep for about 3 months if stored in a cool dry location.
We need to find some ways to prepare them soon,
or at least some folks will to take them off our hands.

I've eaten a few slices raw and am surviving.  The taste is slightly sweet and refreshing.  They are crispy like jicama, but much more flavorful.  Soaking them in vinegar keeps them from turning brown like a potato.

As I mentioned above, keeping these plants under control is a concern for the gardener.  They are large and prolific plants that can take over if they escape.  There are a number of things that can be done to control there spread in and around the garden.

First, as already mentioned, harvest all the tubers each year to reduce the number of plants in the ground. Don't allow bits of the tubers to be spread while tilling the soil. Second, Helianthus species are generally not self-fertile.  So if you only have one cultivar (clone) and there are no wild plants growing nearby, you will not get any fertile seeds.  If you do have potential mates, cutting off the flowers before they set seed is the way to go.  Lastly, the deer around here really like to eat the stems and leaves of Jerusalem Artichoke.  I planted a few tubers outside of the garden enclosure and these never got taller than about 8 inches due to deer browsing on the young shoots.  After the deer broke into the garden, they ate all the leaves up as far as they could reach.  So I would expect any plants that escaped the garden to fall to a similar fate.

These seeds from 'Stampede' are really  hollow husks.
If they were viable, the entire seed would be full and firm.

Some other fall vegetables that I hope to harvest soon are from my Collards and Swiss Chard.  These are plants that I started in the spring.  They have survived the beetles and a deer attack and are now putting out some fresh leaves.