BBG hosts numerous educational programs, plant-science and conservation, and community horticulture initiatives, in addition to a herbarium collection.

BBG began operating three additional sites in the New York metropolitan area in the 1950s and 1960s, while its main garden in Brooklyn fell into decline.

[11] In February 1860, a group of fifteen commissioners submitted suggestions for park locations in Brooklyn, including a 320-acre (130 ha) plot centered on present-day Mount Prospect Park and bounded by Warren Street to the north; Vanderbilt, Ninth, and Tenth Avenues to the west; Third and Ninth Streets to the south; and Washington Avenue to the east.

[26][27] New York City government and the Brooklyn Institute signed the maintenance agreement on December 28,[29][30] and an endowment fund for BBG was created three days later.

[33] Gager wanted to create "an animated textbook in botany", with a Palm House and laboratories facing Washington Avenue, as well as a landscape with valleys, hills, a pond, and rocks.

[37] McKim, Mead & White had completed plans for two wings of the Palm House and the first part of the Laboratory Administration Building that March.

[53] Dirt from the Brooklyn Botanical Garden was used to flatten land in Prospect Park,[54][55] and workers also landscaped BBG's watercourses and laid out paths.

[60][61] At that time, BBG started admitting visitors every day of the week; the grounds had been closed during the previous year because workers were regrading the paths.

[61] McKim, Mead & White filed plans for expansions of the Palm House and the Laboratory Administration Building in August 1915 at a projected cost of $150,000.

[62] The Board of Estimate approved the rock garden in March 1916,[63][64] and the Laboratory Administration Building's cornerstone was laid at a groundbreaking ceremony that April.

[92] Gager announced in June 1929 that an ornamental gate designed by McKim, Mead & White would be installed at BBG's Flatbush Avenue entrance, following a donation from Richard Young.

[83] Civil Works Administration (CWA) workers began landscaping the 2.5-acre (1.0 ha) north addition next to the Brooklyn Museum the same year.

[119] By the early 1950s, Avery planned to expand BBG's children's garden by 1 acre (0.40 ha) by covering the open-cut Franklin Avenue subway line.

[126] Elizabeth Van Brunt sold 223 acres (90 ha) of forest at Kitchawan in Westchester County, New York, to BBG in 1956 for use as a research center.

[139] Furthermore, an increase in crime had caused BBG officials to close off most of the botanical garden's exits by the end of the decade,[140] and litter was beginning to accumulate in the surrounding area.

[147] Under Scholtz's leadership, BBG shifted its focus to its three "outreach stations" in Westchester County and on Long Island, as there was very little space to expand the original garden in Brooklyn.

[157] BBG began allowing events, such as parties and weddings, on its grounds in 1982;[158] it also started hosting an annual cherry blossom festival that year.

[186] The project included repainting the torii, restoring the viewing pavilion and Turtle Island, making the lower level accessible, and planting extra trees.

[208][209] The Water Garden, which was named for Shelby White and Leon Levy after they donated $7.5 million to BBG,[210] reopened in September 2016 following a restoration.

[238] The structure is accessed by a set of stairs, which lead to a concrete plaza with a rock garden on its northern border (abutting the Brooklyn Museum's parking lot).

[242] It is named after Walter V. Cranford, a construction engineer whose firm built many of Brooklyn's subway tunnels, and who had donated $15,000 to BBG for a rose garden.

[282] Located in the south-central section of BBG,[242] the Shelby White and Leon Levy Water Garden is a 1.5-acre (0.61 ha) wetland and riparian environment with numerous sustainability features.

[211][292] Designed by landscape architecture firm Michael Van Valkenburgh Associates, the renovated Water Garden contains plants such as black tupelo, sedges and rushes.

[300] The Rock Garden, on the western boundary of BBG, contains alpine plants[163][236] around 18 boulders left behind by glaciers during the Ice Age.

From north to south, the collection contains primitive plants (ferns and conifers), ginkgos, beeches and birches, elm and pawpaw trees, laurels and roses, legumes and citruses, heath and olive families, and monocots.

[259][305] A Celebrity Path honors famous Brooklynites such as Barbra Streisand, Woody Allen, and Walt Whitman with a trail of engraved paving stones.

[306][307] The Celebrity Path consists of 18-by-24-inch (460 by 610 mm) concrete blocks and leads from a hill south of the Japanese Garden to the Alfred T. White Amphitheater.

[346][347] These specimens, some from as early as 1818, aid scientists in tracking species, analyzing the spread of invasive plants, and modeling changes in the New York metropolitan area's vegetation.

The first to open was a 223-acre (90 ha) research facility at Kitchawan Preserve in Westchester County,[372] on land that it purchased from Elizabeth Van Brunt in 1956.

[391] Other events include the Chile Pepper Festival, which has been held annually since the 1990s,[394] and Lightscape, a light art show that is hosted at the end of each year.