Vehoniemi is part of the esker chain running from Kauhajoki to Hollola. Vehoniemenharju - Keisarinharju (created in between the two lobes of the ice sheet) forms a 4.5 km-long isthmus between Lakes Längelmävesi and Roine. The highest spot on the esker is 51 metres above the surface of the surrounding lakes. Due to the height of the esker and the narrowness of the isthmus, the slopes are very steep in places.
The growing conditions greatly vary on the slopes of the isthmus that runs from northwest to southeast. The dryish pine-dominated heaths are prevalent on the sunny esker slopes on the side of Lake Roine, whereas the vegetation on the shady slopes on the side of Lake Längelmävesi is spruce-dominated and resembles herb-rich forests in places.
As to the plant cover, the kettle holes and their paludified bottoms are different from each other and their surroundings. The most impressive of the kettle holes is Uhkainlampi Pond – the only water area in the esker isthmus. The shoreline is softened by the vegetation belt of alder, birch and bird cherry. The specialities of Vehoniemenharju are the curly birches, some of which are natural, the others planted in the 1930s.