Contrasting natural regeneration and tree planting in fourteen North American cities

There is little information available on the percentage of trees in cities that are the result of natural regeneration vs those planted intentionally. In this article, data collected for earlier studies in 14 U.S. and southern Canadian cities were used to estimate the proportion of naturally regenerated trees. The initial data were collected using standard i-Tree Eco methodology (random 0.04-ha plots across each city where a number of data points are collected, including an estimate of whether each tree on the plot was planted or was naturally seeded). The average percentage of planted trees in the studied cities was 32.7%, but ranged from 7.3% in Baltimore to 89.0% in Los Angeles. It should be noted, however, that the cities studied were overwhelming located in naturally forested areas. In Los Angeles, most of the naturally regenerating trees were found on land classified as “other” or “vacant.” The most common L.A. species naturally regenerating were Juglans californica, Quercus berberidifolia, and Malosma laurina.