Dick Bir
NC State University
UNDER OUR CONDITIONS is intentionally written in capital letters. Every report from a plant evaluation study should have these words prominently displayed at the beginning of the report and this is no exception. In magazines that have nationwide distribution, everyone should pay attention to the fact that all gardening is local and all garden writing should be considered local. Regardless of what we think we are doing, ultimately these plant evaluations end up in a public or private landscape garden. Plants with roots in Dallas or Atlanta or Connecticut landscape soils and tops in the local climate are likely to respond quite differently than they did wherever the original test was done.
The test: This test involved deciduous hollies. We have spent years evaluating cultivars of our native Ilex decidua, Ilex verticillata and hybrids of Ilex verticillata crossed with Ilex serrata from the orient. We originally set up the test to evaluate cultivars for cut stem production . . . winterberries for the florist trade. We thought it was straightforward stuff. In another article I will discuss the cut stem research.
Early in the test we discovered that possum haw or Ilex decidua was not well suited for cut stems under our conditions. In our acidic red clay loam soils (pH at the start of the test was 5.5 but 4.9 at the end of the test) it grew and recovered from being cut back too slowly. Therefore, early in the test we decided not to continue with cultivars of possum haw in the cut stem trials. Instead, we decided to enjoy them as landscape specimens mixed in with the rest of the plants in our experimental design.
We enjoy cooler temperatures and more regular rainfall than much of the rest of the south with average summer highs in the low to mid 80’s and rainfall averaging 4.5 to 5 ft annually in our research station fields. Only during periods of extended drought did we irrigate. Plants received low (0.5 to 1 ou N per plan) rates of 10-10-10 fertilizer top dress applied in late winter. One other thing we did was to prune the possum haws to one to three stems so that they could achieve the small tree form that I find so attractive in this plant.
Results: Our experience when cutting stems for holiday decorating was to cut just a few. Berries held well on stems but we did not get enough stems under our conditions to make Ilex decidua an economically viable crop for cut stems. However, possum haw can be a good source of berries for home decorating if not for commercial use. Migrating birds were not drawn to these plants as they are to certain other plants like viburnums so the berries remained attractive well into winter.
From the beginning, the question we got from visitors, whether professionals or not, was “Which one is best?” I’d respond by talking about the need to be patient and be sure you have an appropriate male (Our only Ilex decidua male was ‘Red Escort’ which came to us labelled as ‘Escort’ so maybe both names should be considered acceptable. We had one male possum haw for every four females.) I’d ask folks to come back at Thanksgiving or in early December and make their own judgement but few ever did. Rarely did I offer an opion on which cultivar was best.
So, for all of you who visited and pressed me for an answer, here it is: Every one of them is good. Every one of them is different. I like them all.
You deserve a better answer so I offer these comparisons. All of the pictures were taken on the same day so you can see differences in leaf drop during the extended warm fall of 1998. “Warm” means that we had regular frosts for over a month but temperatures never got below 24 F. before pictures were taken.
‘Council Fire’ was slow to drop leaves under our conditions. Perhaps equally important is a fruit surface growth that we did not find attractive on the smaller but abundant berries. We called it ‘scab” in the field but when we sent specimens to plant pathologists for identification the report we got back indicated that it was not a parasitic fungus and could be wiped off. I guess if you had soap and a pressure washer in your landscape this substance might not be a problem if the washer did not knock the berries off the tree when you washed it off. For those of you who visited and heard us call this gunk scab, please note that it is not the organism that causes apple scab.
‘Red Cascade’ drops its leaves early but not quite as early as ‘Sentry.’ The berries are abundant, large and bright scarlet-red. The name ‘Cascade’ is apt. Branch tips tend to droop but this plant was in no way pendulous under our conditions, just slightly cascading. This was the most popular possum haw among those who visited plots in late fall.
‘Sentry’ also had abundant large red berries very much like ‘Red Cascade’ but it was a much more upright grower. In fact, without regular pruning this cultivar could quickly resemble a large pile of brush under our conditions. Leaves dropped even earlier than ‘Cascade’ so the berries were impossible to miss.
‘Warren’s Red’ had been my favorite possum haw cultivar until we ran this test. I still like the tree form of ‘Warren’s Red’ as well as or better than most of the others but the persistent leaves and smaller, dull red fruit at a time when the fruit of other cultivars was large and brightly colored make it less desirable under our conditions. The leaves on ‘Warren’s Red’ were the most persistent of all in the test, still present in good numbers approaching Christmas when night temperatures were consistently in the low 20’s.
Our thanks to the Simpson Nursery Company, Vincennes, IN, for providing the possum haw plants in this test.
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North Carolina State University