Norwegian science journalist Gunnar Tjomlid published an article [Norwegian language] in the online newspaper Nettavisen.
Blogger Pepijn van Erp summarised it in English.
In brief, the experiment was not properly controlled, not blinded, had publication bias, was misreported, had faulty statistical analysis, had bias in the methodology and relied on a cherry-picked hypothesis.
> The WiFi and control group were not just different because of the presence of the routers. On the pictures in the report it can be seen that also the laptops in the WiFi group were placed quite near to the plates. It’s very likely that this had an effect on airflow and temperature around the plates and that could have an effect on germination, which has nothing to do with the presence of EM-fields.
[...]
> A second experiment in which the laptops had been ‘pinging’ each other constantly did not show the dramatic difference in germination. Only the first experiment was used in the report