The protected area is on a wam hill that inclines steeply westward, on the eastern border of an open field. The grove area is divided by the deep groove of a brook valley. In spring and summer, the brook only has water running through it after heavy rain. The eastern part of the area has small rocky fields, but most of the protected area is covered by boreal forest and groves with dense tree crops. There are large quantities of decomposing wood. The northern part of the protected area also has s…ome old forest pastures, but the marks of grazing are slowly disappearing underneath new growth.
Pyymosa belongs to a national grove protection programme. Some individual small-leaved lindens grow around the grove. Extensive dog's mercury growths cover the area's northeast corner. The west-facing hillside features common hazel bushes, liverworts, wood anemones, common dog-violets, unspotted lungwort, and Kashubian buttercups. Rarer but eye-catching plants in the area include lesser butterfly-orchid and bristly bellflower, a nationally endangered species that grow towards the southern side of the protected area.
White-tailed deer enjoy the sheltered grove forest of Pyymosa. The path they use twists through the grove's steep west hillside. Pyymosa has many birds, such as woodpeckers, Eurasian treecreepers and thrushes. Birds of prey can also be spotted in the area, most commonly common buzzards, European honey buzzards, northern goshawks or Eurasian sparrowhawks. The grove's molluscs species were studied in 2011. Twenty different species were quickly discovered, among them the snail species perforatella bidentata, carychium tridentatum and malacolimax tenellus which all prefer lush groves.