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) |
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. |
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. |