Yttröskogen, Naturreservat

• Swamp forests and coniferous forests with calcareous soil are typical of northern Uppland. They are important to preserve because there are many rare plants that require just such an environment to survive.

Several different orchids thrive here, including one of Sweden's rarest, the small and delicate knotweed, which can almost be confused with another rarity: the mosquito flower. Knotweed is difficult to spot, but a keen observer can certainly spot it in June and July. This is when it blooms with small yellow-green flowers in a long, spike-like cluster. The name knotweed probably comes from the fact that the flowers are very small and resemble a small insect, or perhaps the explanation is that it thrives in the same places as knots?

Many birds, such as the three-toed woodpecker and the robin, also thrive among the old trees. The traffic on the E4 highway, which is close by, and the woodpeckers' drumming can make the birds' calls difficult to hear.

If you are lucky enough to spot the rare orchid, remember not to damage it. Digging up plants is not allowed in the reserve.