The Dutch elm (Ulmus) should easily survive two hundred years. This ornamental tree with a narrow crown and sturdy wood is known as a powerhouse under difficult conditions. No wonder you see him everywhere in Dutch cities. Such as one of 34 meters high in Amsterdam’s Oudemanhuispoort and the thickest of almost five meters in circumference in Alkmaar. And the trees in Haarlem’s Molijnstraat were also Dutch elms.
The image of the row of trees in this street blown down on Wednesday, four of them almost synchronously landing on pre-war homes, has now become iconic. It marks summer storm Poly that raged across the country on Wednesday with wind gusts of up to 140 kilometers per hour. The storm not only resulted in one death and, according to an estimate of insurers, up to 100 million euros in material damage, but also many trees fell victim. They have snapped, branches have fallen off, or, as in Haarlem, blown over with the root ball and all.
The Dutch elms in the Molijnstraat have reached the age of 73, according to data from the Haarlemse Bomenridders Foundation. Almost the monument status of eighty years. And that is actually still old, if you consider that the average age of its more than 4,100 congeners in Haarlem is 35 years old, and most trees in the Netherlands do not even live older than forty.
60,000 trees
Two hundred? Hardly any tree will make it in the Netherlands. While those monumental whoppers are so beautiful, says Tom van Duuren, tree specialist in Eindhoven. “So mighty big. Picture an oak tree. It first needs hundreds of years to grow up, then hundreds of years to stay big, and then hundreds of years in the veteran phase. Crown on the ground, hollow inside, children playing inside, but the outer shell still very much alive…”
The strength of the storm was exceptional – and most of it is still standing. But the fact that so many trees, root ball and all, were blown down also says something about the layout of the public space. Because even though trees look beautiful above ground, they are “often the Sjaak” underground, according to Tom van Duuren. The competition is cutthroat: sewage pipes, electricity cables, fiber optics. There is not always enough space to take root properly, and roots are often removed during work. “And that may be just one that gave the tree a lot of stability.”
Also read this article: The roots were already sticking out above the ground
In Haarlem, the municipality is still investigating why five trees in Molijnstraat fell over as a result of the storm. According to the spokesman, all more than sixty thousand trees are checked at least once every three years. The municipality employs tree experts and tensile tests are carried out on high-risk trees.
The row of trees in question was last checked in 2021 and then four of the five – now fallen – trees were found to be in good condition, the last one in moderate condition – but no immediate action was deemed necessary. In recent years, a number of reports had been made about upright tiles in the street. According to the spokesman, only the hair roots were removed during the repair work, “certainly no stability roots”.
‘Bloodletting’
According to Harry Hobo, chairman of the Haarlemse Bomenridders, the underground “cable terror” is a concern and the municipality should also pay more attention to the soil care of old trees. “Are these trees getting enough nutrition?”
Especially front gardens with tiles are a “huge loss” for street trees, Tom van Duuren knows. Under those tiles, trees can no longer get nutrition from the ground and it gets very hot. “Heat means stress and stress will not make a tree grow, not even underground.” And rooting is already difficult in the Randstad. “Ideally, such a tree would have roots eight meters deep, but because of the peat they can’t get further than five feet, so they have to go wide.”
Also view this In pictures: The power of summer storm Poly in the picture
Storm Poly largely passed Tom van Duuren – even though one poplar fell in his garden. But when there was a heavy storm in Eindhoven a few years ago, he attempted to explain, while walking through the city, why one tree fell and the other did not. Most of the cases were explicable: “A tree produces supporting tissue based on the resistance it experiences over the years. But if suddenly a neighboring tree is felled, or a new building is built next to it, then a tree has to deal with a new situation.” Suddenly the wind comes from a different direction, or he misses a few branches because a garbage container has been placed next to him. “Sudden interventions, trees are not set up for that.” A tree’s response is often only a few years later.
When Tom van Duuren saw the images in Haarlem, he could only conclude: not well rooted. Trees are particularly vulnerable during a summer storm. They are heavier because they are full of leaves, and tall trees catch a lot of wind. And maybe 45 days of drought also play a role: then a tree roots less well. But the explanation is not always simple. Just as he does not know about his own fallen poplar in the garden. “I’ve been worrying. Set up four years ago, it was the largest of the whole club.”
Also read this article: Damage from storm Poly estimated at 50 to 100 million euros