Blackberries - whose fruit is it anyway?

15 September 2020 | Posted in Charlotte Owen , Plants
Blackberries - whose fruit is it anyway?
Nuthatch with blackberries © Alan Price

By Charlotte Owen, WildCall Officer

It’s blackberry season and there’s a bumper crop this year. Perfect for making jams and crumbles, blackberries also provide a veritable feast for a huge range of wildlife. From water voles to dormice, wasps, moths, birds and badgers, few can resist the bramble’s free buffet and a good patch of blackberries can be a real wildlife hotspot.

These sweet, pulpy fruits are deliberately delicious to lure in potential seed-dispersers. Blackberries are known botanically as an aggregation of drupes, with each shiny black sphere (or drupelet) housing a single seed at the centre. These are the perfect size for small birds to swallow whole and these are the bramble’s intended dinner guests. Their gentle digestive systems make short work of the fruity flesh but pass out the seeds unharmed and intact, usually a good distance away from the original bramble. The process of digestion can even improve germination rates by thinning the seed’s protective outer layer, allowing moisture and air to reach the seed more easily and kick-starting the growth process. And of course the seed is ultimately deposited in a healthy dose of fertiliser.

Since the bramble wants its fruits to be eaten, it seems unhelpful to guard them with such ferocious thorns. They present a significant hazard to larger mammals, as any keen blackberry forager will know, and efficiently protect the plant’s leaves and stems from browsing deer and rabbits. The thorns also make it harder for them to gorge on the berries: their more powerful mammalian digestive systems are efficient enough to destroy the seeds on their way through, and any that survive are deposited together in one big heap, making mammals a poor option for seed dispersal. They may still manage to eat one or two berries, but the bulk of the fruit is protected for the bramble’s desired diners, who are small enough to hop nimbly between the thorns and avoid being prickled. The thorns also function as effective climbing hooks for the long, whippy bramble stems to grow towards the light and tangle together into an impenetrable briar. Perhaps coincidentally, this also favours small birds by providing them with a safe place to roost and nest.  

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