Juniperus virginiana

 ( Virginiana ) 

Eastern red cedar grows in a wide range of climatic and soil conditions. The tree is extremely tolerant of drought due to its extensive, fibrous root system and reduced leaf area. It can be found from droughty, rocky soils with few nutrients to rich alluvial soils with abundant moisture. However, eastern red cedar is almost never dominant on such rich mesic sites due to intense competition with faster growing, more shade tolerant hardwood trees.

Outside of its native range it is considered an invasive species, and it can be aggressive even within its range. It is fire-intolerant, and was previously controlled by periodic . Low branches near the ground burn and provide a ladder that allows fire to engulf the whole tree. Grasses recover quickly from low severity fires that are characteristic of prairies that kept the trees at bay. With the urbanization of prairies, the fires have been stopped with roads, plowed fields, and other fire breaks, allowing J. virginiana and other trees to invade. Trees are destructive to if left unchecked, and are actively being eliminated by cutting and prescribed burning. The trees also burn very readily, and dense populations were blamed for the rapid spread of wildfires in drought stricken Oklahoma and Texas in 2005 and 2006. On the Great Plains, expanding red cedar populations are altering the plains ecosystem: a majority of the region's bird species are not present in areas where the tree's land cover exceeds 10 percent, and most small mammal species are not present where land cover exceeds 30 percent.

Eastern juniper benefits from increased Carbon dioxide levels, unlike the grasses with which it competes. Many grasses are C4 plants that concentrate CO₂ levels in their bundle sheaths to increase the efficiency of RuBisCO, the enzyme responsible for photosynthesis, while junipers are C3 plants that rely on (and may benefit from) the natural CO₂ concentrations of the environment, although they are less efficient at fixing CO₂ in general.

Alterations of prairie ecosystems by J. virginiana include outcompeting forage species in pastureland. The low branches and wide base occupy a significant portion of land area. The thick foliage blocks out most light, so few plants can live under the canopy. The needles that fall raise the Soil pH, making it , which holds nutrients such as phosphorus, making it harder for plants to absorb them. However, studies have found that Juniperus virginiana forests that replace grasslands have a statistically insignificant decrease to a significant increase in levels of soil nitrogen. J. virginiana forests have higher overall nitrogen use efficiency (NUE), despite the common grassland species Andropogon gerardi having a far higher NUE during photosynthesis (PNUE). The forests store much greater amounts of carbon in both biomass and soil, with most of the additional carbon stored aboveground. There is no significant difference in soil microbial activity.

are fond of juniper berries. It takes about 12 minutes for their seeds to pass through the birds' guts, and seeds that have been consumed by this bird have levels of germination roughly three times higher than those of seeds the birds did not eat. Many other birds such as turkeys and bluebirds, along with many mammals such as rabbits, foxes, raccoons, and coyotes also consume them.

Virginia juniper's compact, evergreen foliage makes it favorable for bird nests and as a winter shelter location for birds and mammals.

The oil derived from foliage and twigs has two main constituents: safrole and limonene. One minor compound is the podophyllotoxin, a non-alkaloid toxin lignan.

Native American tribes have historically used poles of juniper wood to demarcate agreed tribal hunting territories. French traders named Baton Rouge, Louisiana, which denotes "red stick", from the reddish color of these poles. Some nations continue to use it ceremonially.

The Cahokia Woodhenge series of that the pre-Columbian Mississippian culture in western Illinois erected were constructed of massive logs of eastern juniper. One iteration of such a circle, Woodhenge III, which is thought to have been constructed circa 1000 AD, had 48 posts in the circle of in diameter and a 49th pole in the center.

Among many Native American cultures, the smoke of burning eastern juniper is believed to expel evil spirits prior to conducting a ceremony, such as a healing ceremony.