Winter wheat early April. Short enough to land.
Winter wheat June. No safe landing.
Winter wheat August, ready to harvest. Do not land if
you want to fly the next day
(with the same glider!).
Maize in June. Suitable to land.
Maize in August. Not suitable to land.
Potatoe field in May. Not suitable to land.
Potatoe field in June. Not suitable to land.
the website from Adrian Hatton