I enjoy making and consuming sloe gin using the fruits of the blackthorn (Prunus spinosa).
I have noticed that fruit only appear on bushes in particular localities. In the spring there are large areas that are white with blossom but, at this time of year, I find sloes only on certain bushes. Large expanses of bushes are totally devoid of even a single sloe. The same areas are fruitful from year to year, although the crop can be heavier or lighter.
Are there male plants which cannot fruit (Wikipedia seems to indicate that the flowers are hermaphrodite)? What other reason can there be for such a marked difference in the fertility of this plant?
Also try the Brogdale Horticultural Trust, and more specifically, their collections web site
...which will point you to:
Contact: Tracey Gurney – Education Officer
Telephone: 00 44 (0)1795 536250
We'd be interested to hear the answer; please post it here if you can.
I have been giving some more thought to this question and I may have the answer, which will result in a couple more questions.
Prunus Spinosa is a hermaphrodite plant and reproduces sexually via sloes and vegetatively by suckering. Apparently there is a mechanism in such plants to prevent self-fertilisation. I have found references to this on the web, but do not have the technical background to understand the finer points.
It is well known that certain varieties of e.g. apple need a 'pollinator' if fruit is to be produced.
I suspect that the large banks of blackthorn that flower in early spring but yield absolutely no fruit are large clones that have grown over the years by making suckers. The places where I find sloes in abundance are, perhaps, places where blackthorn has been planted as hedging and shelter. There would thus be genetic diversity to enable fertile pollination.
Is this a reasonable answer?
Would it be environmentally ethical to ask the landowner to allow the planting of blackthorn from another location in Jersey in the hope that there will be more sloes for me to pick (and the wildlife to eat)?
I think this is more likely to be a result of the weather conditions at the time of flowering. Because March and early April in 2013 were rather cold and wet the activity of bees was probably lower than normal for this time of year. This would have resulted in fewer flowers being pollinated and hence less fruit. In contrast by the time Apples can into flower the weather was much better leading to a good apple crop last Autumn.
I would still try to talk with the Brogdale HT, if you can.
I would not see significant ethical issues with asking the landowner to use different stock for further plantings.