[2] The nature reserve was created to protect a very rare for Latvia plant - cross-leaved heath (Erica tetralix), as well as it inherent special biotope locally called grīnis.

Locals burned grass to increase fertility, but after several years of use, such fields ceased to yield, and villagers again set fire to the forest to capture new land.

Until the 1930s, the core of the modern Grīņu Reserve (about 750 hectares) was a small, but not very productive forest, bordered by unforested swamps.

However, due to the infertility of local lands, they were bought by only 60 poor Latgalian families, who lived by cutting down trees for sale.

Documents from the Latvian Forest Department for 1936 contain information that large thickets of cross-leaved heath (Erica tetralix) were found in the Strautini forestry.

[5] Scientists University of Latvia opposed the economic use of Grīņu's forests, and all land reclamation work and tree felling were immediately stopped.

In 1979, the Grīņu Reserve, while remaining a separate conservation institution, was administratively subordinated to the Slītere National Park.

Lielā Kārpa has a valley 4–6 m wide and high shores, but its drainage capacity is insignificant and already at a distance of tens of meters from riverbed you can see wetlands.

[6] At the end of the 20th century, it included Lake Grīņu with an area of 2 ha, but due to eutrophic processes its water surface is constantly decreasing.

However, there are no conditions for the formation of a thick layer of peat in the reserve because all the low-lying areas receive excess moisture in the cold season, and in summer completely dry up.

Most of the territory is occupied by low and sparse forests, only on the elevated banks of the river Lielā Kārpa tall slender pines with elegant spruces grow to a limited extent.

In the sedge-molin grīnis, the arboreal layer is also formed by pines, but with a significant admixture of birch, in some places willow undergrowth is developed, interspersed with buckthorn and juniper.

But these wet forests differ from real swamps in that they receive a large amount of moisture mainly in autumn and dry up almost completely in summer.

Alder buckthorn (Frangula alnus) and juniper (Juniperus) have been observed in the undergrowth of such forests, European blueberry (Vaccinium myrtillus), blueberry (Cyanococcus), wavy hair-grass (Deschampsia flexuosa), stiff clubmoss (Spinulum annotinum) predominate in the grass cover, May lily (Maianthemum bifolium), purple moor-grass (Molinia caerulea), heath wood-rush (Luzula multiflora), common heather (Calluna vulgaris), pill sedge (Carex pilulifera), arctic starflower (Lysimachia europaea), common cow-wheat (Melampyrum pratense) There are also many oppressed bushes lingonberry (Vaccinium vitis-idaea).

Several species of fescue (Festuca) and meadow grass (Poa), broadleaf plantain (Plantago major), common mugwort (Artemisia vulgaris), field thistle (Cirsium arvense) were found around the abandoned buildings, along the railway and on both sides of the forest roads silverweed (Argentina anserina), yellow toadflax (Linaria vulgaris).

[4] Crossleaf heath (Erica tetralix) is widespread throughout the Grīņu Preserve and its surroundings, but this plant prefers open sunny places.

During flowering, crossleaf heath looks attractive due to the pink flowers-glasses, but often goes unnoticed by outsiders, because it looks like common heather (Calluna vulgaris) and blooms at the same time.

[4] Among other rare plants, ornamental species such as martagon lily (Lilium martagon), harsh downy-rose (Rosa tomentosa), lesser butterfly-orchid (Platanthera bifolia), European columbine (Aquilegia vulgaris), common spotted-orchid (Dactylorhiza fuchsii) and heath spotted-orchid (Orchis maculata).

Less showy, but also subject to protection curved sicklegrass (Parapholis incurva), allseed flax (Radiola linoides), club sedge (Carex buxbaumii) and tawny sedge (Carex hostiana), marsh pea (Lathyrus palustris), northern firmoss (Huperzia selago), downy willow (Salix lapponum) and close to it creeping willow (Salix repens).

The reason for this is both the botanical focus of conservation activities and the small size of the protected area, which does not allow to maintain large animal populations within its boundaries.

[7] As already mentioned in the "History" section, people have been trying to manage the lands of the reserve for a long time, but practically no branch of either agriculture or forestry here had any prospects for development.

Only deforestation was profitable, but attempts to plant groves of black alder and birch in place of low-grade pines were also unsuccessful.

Already in the year of the founding of the Grīņu Nature Reserve, it was forbidden to cut down trees, graze cattle and drain wetlands.

Currently, the reserve has a strict protection regime, the free crossing of borders by outsiders is prohibited, and for scientific purposes it can be visited only with the permission of the staff of the Slytherin National Park.

In the buffer zone of the reserve it is allowed to change the vegetation in the framework of scientific experiments (for example, to conduct test piles).

Also in the Grīņu Reserve are partially preserved objects of historical heritage of Latgalians: the cemetery, the buildings of the village "Ceriņi" [7] The first research of this territory was carried out by Karl Reinhold Kupffer [ru] (1872—1935).