Tuesday, December 11, 2018

Inkberry berries



This past spring I replaced some non-native Leatherleaf Mahonia, Mahonia bealei, with inkberries, Ilex glabra.  While moderately invasive, the mahonia did produce a decent crop of berries over the winter which was available to the resident bird population.  I wanted to make sure that these inkberries would also produce berries that the bird could use through the winter. Inkberries, like most other hollies, tend to be dioecious, that is have male and female flowers on separate plants.  Most inkberries commercially available are listed as being female.  The only male cultivar I could find listed is 'Nordic', which was selected for is cold hardiness.  Here in the relatively warm Mid-Atlantic, I couldn't find any for sale.  I did find a mention that you could use another species of male holly as long as it blooms at the same time as the inkberry.  Jim Dandy winterberry holly, Ilex verticillata 'Jim Dandy' (blooming in late May-early June), seemed to be a good fit for inkberries which bloom from about mid-May to mid-June.

The selection of native hollies that I put in to replace the leatherleaf mahonia.  Left to right:
Jim Dnady winterberry (male), Nigra inkberry and Shamrock inkberry (both female)

The selection of inkberries I settled on were two Shamrocks and one each of Densa and Nigra.  The Shamrock cultivars a supposed to top out at around 4' while the other two should grow larger to about 6'.  By having a mix of cultivars I hope to add a little extra texture and variation in height to this planting.  Right next to these I put in the Jim Dandy winterberry, to help with fertilization.

Here's the Shamrock inkberry at the end of May.  Looking closely
you can see some of the flowers have anthers with pale yellow pollen. 
Other flowers are lacking stamen, but have a large central ovary.

This Nigra inkberry has only female flowers.  The flowers are
not in dense clusters like many of the male flowers on the Shamrock cultivar.

At the end of May the flowers on this male winterberry are just opening up. 
This timing overlaps with the flowers on the inkberries.

As the inkberries were blooming I paid attention to when the flowers were opening up on each plant.  To my surprise I noted that the Shamrock inkberry seemed to have both male and female flowers on it.  The Nigra and Densa cultivars appeared to have only female flowers.  I would have thought that if the Shamrock cultivar is typically monoecious (have both flower genders on one plant) then that should be called out in the description of the plant as this would be a great benefit to wildlife gardeners. 

Fast forward to mid-fall and there are reasonable numbers of black berries on both the Shamrock and Nigra cultivars.  I can not say unequivocally that the Shamrock did all the pollination work since the male winterberry was right there in the mix, but at least I have been successful in replacing the leatherleaf Mahonia with a native evergreen shrub that provide berries for the resident bird population in the winter.

Got a few berries on this Shamrock inkberry.  It's missing
 quite a few leaves, my guess would be deer browse.
 Unfortunately the Densa cultivar died back by the end of summer.  Two possibilities are that it was in the shadiest spot of all the newly planted hollies, and/or that it is planted at the edge of the drip line of an English walnut, Juglans regia.  While not as potent as the native black walnut, Juglans nigra, the English walnut does produce juglone, a compound the inhibits the growth of a number of plants, including inkberries.  We'll see how the other inkberries overwinter before I find something to replace the Densa cultivar.



This Nigra inkberry also has a few berries, as expected.  It too
has taken some deer damage.  I've since sprayed them with some deer repellent.  


5 comments:

Curtis said...

I replaced the 'Densa' cultivar with another 'Nigra' in nearly the same spot. After nearly 2 years the 'Nigra' is doing quite well.

Evelyn said...

Hi Curtis, I’m thinking about adding a row of Shamrock Inkberry along the side of my house (part shade, soil stays moist), but I haven’t been able to find information on how popular the berries are for feeding wild birds. Have you noticed much activity, or are the berries being ignored?

Curtis said...

Inkberries are listed as being of high value to wildlife, both songbirds and small mammals. My planting is just getting established; however the few berries I've had are gone by spring. For a new planting it may take a season or two for them to be 'discovered' by wildlife.

Schneider2211 said...

So here we are almost 5 years later and I am looking for a male plant to polinate 3 Ilex Glabra Shamrock which I bought last spring not knowing that none of them are males. I hadn't read this column yet and they certainly weren't labeled at the nursery. From what I am reading online now, Shamrock is female and I can't find a male inkberry available. Do you still feel the winterberry polinated the inkberry?

Curtis said...

Unfortunately I don't have any unambiguous results on Ilex verticilata cross pollination. I have gotten some berries on my 'Nigra' inkberry, so that would say that cross pollination works. However, on close examination, I believe I have also found some male flowers on the Shamrock cultivar planted nearby. Then there is also the question of whether these male flowers on 'Shamrock' can self pollinate another 'Shamrock' or if they are only able to cross pollinate with a different female inkberry. I will keep watch on mine and report what I find. The only male cultivar that I know of is 'Nordic' and that is available in the colder climate areas. Good Luck.