An annual survey of damages and growth was conducted two and three years after selective mechanical cleaning in two Norway spruce plantations‐7 and 11–16 years old—and one 11‐year‐old lodgepole pine plantation. The base machine was a modified Bruunett Mini with a rotating disc with two short steel flails, mounted at the tip of the crane. The results show that very few damages were caused by the cleaning device. 5–8% of the seedlings were driven over or otherwise damaged by the wheels and these seedlings show high mortality and great growth reduction. In stands with 1.5–4 m high trees, the trees are often damaged when they are straddled by the machine, which causes growth and quality losses. 14–25% of the undamaged seedlings in Norway spruce stands showed a 25 % annual height growth reduction the first two years after cleaning due to soil compaction and to possible root damage.