He is regarded as the symbol of the deterioration of nature, but he himself can do nothing about it. The blackberry is advancing, but not (only) thanks to nitrogen. Ecologists are calling for rehabilitation of this thorny forest and roadside inhabitant that bears an exceptional amount of fruit this summer.
The tastiest are the most difficult to pick. They hang high above the ground, shiny dark purple, almost black and almost bursting with sweet juice. Right there for the taking, were it not for the fact that they are ‘guarded’ by an impressive web of thorny branches. Every enthusiast knows: if you want to enjoy freshly picked blackberries, you shouldn’t look at a scratch.
Two hundred species
Get to know the Rubus . At least, that’s the family name. And the unsuspecting picker will not stop to think about it, but that family is as widespread as the plant itself. There are more than six hundred blackberry varieties worldwide, of which more than two hundred in the Netherlands alone. With glorious names such as the fine mouseberry, the snake forest bramble or the hedgehog scallop.
With the nettle, the blackberry is considered the proverbial canary in the coal mine, but for nature. A warning that the disruption of nature due to rising nitrogen concentrations and acidification of the soil is going in the wrong direction. Where these two flourish, the soil is out of balance and action must therefore be taken, is the general view in the environmental debate.
And that they flourish, northern forest rangers see around them every day. Jaap Kloosterhuis, who watches over an immense working area from Lauwersmeer to the Groninger Hogeland for Staatsbosbeheer, sees the blackberry advancing. “We were at Ten Boer a few weeks ago. We have now designated a place in the Ten Boersterbos for a dog field for the village. Originally it was an open field with grass, but the blackberries there now turned out to be up to four meters high. Completely overgrown. We really need to win that back on the bramble.”
Clear hiking trails
“The ‘burring’ of nature has been going on for decades,” says Kloosterhuis. “We also get that from the volunteers who help keep the hiking trails clear in many of our areas. That was always a matter of running the electric hedge trimmer along the overhanging vegetation, and done. But now we often hear from volunteers that pruning is becoming increasingly difficult, because ‘we can’t get through the blackberries’.”
Kloosterhuis’ colleague Lysander van Oossanen in Southwest Drenthe recognizes that image. The blackberry is also proliferating there, says the public forest ranger for the Drents-Friese Wold. “That is very welcome in many places, but it will be different if they colonize small heaths, for example. We are seeing that increasingly. If you are not careful, the heath will be completely replaced in a few years. Blackberries grow shoots of up to two metres. When they hit the ground, they take root. Then it goes fast. It’s very difficult to keep it under control.”
Still, both forest rangers are reluctant to use the pruning shears. “Many people see the blackberry as an indicator of the increasing acidification due to the much-discussed nitrogen problem,” realizes Kloosterhuis. “But I am not in the anti-blackberry camp. To put it in Cruyffian style: every disadvantage has its advantage. Bramble bushes are also great hiding and resting places for birds and small mammals. And they’re a rich source of food, from the berries to the insects that flock to them during bloom.”
Many animal species
Van Oossanen also sees more advantages than disadvantages. “Brambles have a very important role for many animals. So as long as it is not at the expense of other species, there is no reason to actively combat them.” Kloosterhuis fully endorses this. Also around the Lauwersmeer and on the Hogeland, the scissors do not just go into the bramble, as happened with the Japanese knotweed and giant hogweed.
“But these are invasive exotics that can displace native plants if you give them free rein,” explains Kloosterhuis. “Many people get a red haze in front of their eyes when it comes to exotics. But the blackberry just naturally occurs here, you know. You have to take it seriously and ensure that they are not at the expense of other species. But as long as it remains more or less in balance, I don’t see a big problem.”
It is also the other way around to make the blackberry as a bearer of bad nitrogen news a head smaller, says ecologist Rienk Jan Bijlsma. Together with his colleague Rense Haveman, the Wageningen researcher is regarded as the authority on blackberries in the Netherlands. Haveman even graduated on it, together they wrote one in-depth study and they provide ‘field workshops’ for wildlife managers on causes and consequences of ‘bramble dominance’ and what to do about it if it becomes a real problem.
Rehabilitation
It is time for rehabilitation, says Bijlsma. “The blackberry has always had a bad reputation. In our study we came across publications from the eighteenth century in which forest managers reported that they were abandoning a reforestation plan because it would not be possible due to the proliferating brambles. But you rarely read about the enormous value for nature. Not then, and not now. That is our main message: we advocate for the rehabilitation of the blackberry.”
The shrub may apparently flourish in nitrogen-rich soil, but that does not mean that it itself contributes to acidification, says the Wageningen bramble expert. In fact, there is still something to be said about the whole alleged connection with nitrogen. ,,There is hardly any connection,” says Bijlsma. ,,Of those more than two hundred subspecies, there are only two of which we know that they respond positively to high nitrogen values, especially . Whether that is necessarily such a problem, I doubt.”
Focusing on blackberry and nettle also distracts from the real nitrogen problem and measures that can help to slow down acidification and the harmful effects on nature. It is only treating the symptoms, Bijlsma believes. ,, Nature managers have the impulse to intervene immediately, but we are against the removal of brambles. You do more harm than good to nature.”
desiccation
Where does this unmistakable advance come from if it does not have to do with nitrogen? “This ‘burring’ is primarily the result of the drying out of the soil,” says Bijlsma. “Wherever the blackberry is now advancing, whether it is Drenthe, Twente or the Achterhoek, it was originally mainly peaty soil or stream valleys. That has dried up further and further due to land consolidation and lowering of the groundwater level.
And when it comes to that relationship with nitrogen, the situation is exactly the opposite of the general view, says the researcher. “Where many blackberries grow, the soil is much less nitrogen-rich. While you encounter less blackberries on the light sandy soils where the nitrogen concentrations are much higher because it leaches more easily to the soil there.”
Bijlsma and his colleagues see this in the Veluwe and in Drenthe, for example on the Dwingelderveld. “It is dead quiet on the moors now. You no longer hear an insect or bird. The oak leaves and heather on which the caterpillars live are so full of nitrogen that they hardly contain any other essential nutrients. We now enjoy that beautiful purple heather, but actually the biodiversity has become a desert. That is where the real nitrogen problem lies.”
Top harvest
Meanwhile, this summer there will be a top blackberry harvest in the bushes for enthusiasts. ,,If you want to make jam, it’s a good year”, says Van Oossanen. Last year was really bad. That is a matter of the right temperature and the right precipitation at the right time. Not too cold in the flowering period from May onwards, enough rain for the fruits to grow and enough summer sun for them to ripen.
Pickers are welcome in the forestries of Staatsbosbeer. ,,Now you have to be there”, says Van Oossanen encouragingly. Although: it should be kept within limits. “Do it with an eye for the environment. Also leave something hanging for the ‘others’, not only the people but also the animals. And check well in advance whether there are no nests in the bush. People always think that the breeding season is over after spring. But many species still start a second or third laying in the summer.”
Another tip from fellow forest ranger Kloosterhuis: ,,Only pick from waist height. With anything hanging lower, you run the risk that a fox or a cat has urinated on it and you could become infected with the fox tapeworm. A fox has to try very hard to get higher than hip height. So if you maintain that safety margin, there is nothing to worry about.”
Buckets full is poaching
As long as it remains with a few trays or a bucket, the ranger will not be difficult. ,,Provided it is for our own use, we will not say anything about it”, says Kloosterhuis. ,, Although people should of course not look for three hundred meters from the paths, because then they can disturb resting animals. And we are not applauding when they go home with buckets full at the same time. In fact, that counts as light poaching and is therefore punishable.
‘They taste best right off the bush, still warm from the sun’
He looks forward to it every summer. Chef Benjamin Vandenberg can be inspired by the blackberry. “They taste best when they come right off the bush after a beautiful summer day. ‘ Sunkissed ‘, still warm from the sun so to speak. That sweet, warm juice when you bite into it. Delicious!”
In his restaurant The Black Tie in Assen, the 36-year-old chef does not (yet) have blackberry on the menu this summer. But that could change, because Vandenberg is an enthusiastic wild picker who likes to work with ingredients from nature. ,,Whether I am a fan of the blackberry? I am a fan of everything nature has to offer.
Last summer he was very pleased with the dessert he composed of blackberries with basil and passion fruit. ,,That sour and sweet of the fruit and the spicy of the basil. Fresh but also aromatic, as if you are back on holiday in Italy.”
,,But you can not only use blackberries in desserts, they are also delicious in savory combinations. For example in sauces with game or poultry. For that I often make a puree of blackberries, which you can freeze well to use later in the kitchen.
“I would prefer to go into the woods every day to look for ingredients,” says Vandenberg. He grew up in Assen, so it was an early start. He can still be found regularly in the woods around the capital of Drenthe. He finds mushrooms, herbs and fruits.
,, Unfortunately, it doesn’t happen that often anymore because since the corona time I’ve been alone in the kitchen. Then there is not much time left. But luckily I have a dog that I can walk. That’s a good excuse to poke around every now and then. If you know where and what to look for, and especially how – without disturbing nature – there is so much beautiful to be found.”