With the exception of the giant fern trees that grow in several South Pacific regions, all trees produce seeds. Some trees protect their seeds inside berries or fruits, while other create hard cones or winged samaras. Some trees produce sticky or viscous seed pods. Seed-pod-producing trees grow in a variety of sizes, shapes and forms. They can be deciduous, or lose their leaves in winter, or evergreen, keeping their leaves year-round. Some sticky seed pods have culinary or medicinal value, while others just create a mess on the ground.
Native trees have grown in North American since before European settlement began.
The thornless honeylocust (Gleditsia triacanthos "Inermis") grows to 70 feet tall with a 40-foot spread. This deciduous tree has a relatively short trunk and a spreading canopy of long, bright-green binately compound leaves that turn yellow in autumn. It produces yellow blossoms in summer, followed by red-brown, 7- to 8-inch-long seed pods that split to reveal a sticky interior. Honeylocusts grow rapidly and are native to the central U.S. The Kentucky coffee tree (Gymnocladus dioica) grows from 60 to 100 feet tall. This deciduous tree has compound, oval leaflets and blooms with white-to-green flowers in late spring. Kentucky coffee trees produce 8-inch-long, flat, thick, purple-brown pods full of sticky pulp and four to seven wide, flat seeds. The seeds, pulp and foliage of the Kentucky coffee tree are toxic to livestock. Its natural range encompasses the flood plains, creek and river banks and moist woodlands of the Midwestern and southeastern U.S.
Some members of the Liquidambar genus produce sticky seed pods. The sweetgum (L. styraciflua) grows from 60 to 100 feet tall and has five- to seven-lobed, star-shaped leaves that turn yellow, red, orange and purple in autumn. This deciduous tree produces spiny, round seed pods filled with sticky pulp. The seeds attract birds. The Formosan sweetgum (L. formosana) also produces spherical, spiny and sticky pods, but they are softer than those produced by L. styraciflua. The Formosan sweetgum grows to 50 feet tall with a 25-foot spread. It has three- to five-lobed leaves that turn red to yellow in autumn.
The tamarind (Tamarindus indica) grows to 65 feet tall with a 50-foot spread. This evergreen has pale, compound leaflets and a spreading, round or vase-shaped canopy. It grows well as a shade tree in urban settings. Tamarind trees flowers with red and yellow blossoms in spring, followed by sticky, brown, hard, 3- to 6-inch-long seed pods filled with edible paste and two or three seeds. Tamarind pods present a mild litter issue. They require warm, frost-free climates. The cacao or chocolate tree (Theobroma cacao) grows from 13 to 65 feet tall. Native to South America, this tropical, deciduous tree is cultivated around the world. It produces small flowers along its trunk, each of which produces a 4- to 12-inch-long white, green, yellow, red or purple pod that contains sticky pulp and 20 to 60 bitter-tasting seeds. The cacao tree has long been a source of both food and medicine in South America. Today, this tree is cultivated on a large scale to produce chocolate for the world market.
Some sticky-pod-producing trees have fragrant bark or flowers. The Jamaican caper (Capparis cynophallophora) is native to Central America, the Caribbean and South Florida. This evergreen tree grows from 10 to 20 feet tall and has thick, shiny-green and copper foliage. Its grey-to-black bark has a spicy aroma and taste. This tree blooms year-round with fragrant white flowers that mature to purple. Fuzzy, brown seed pods follow the flowers. These pods are filled with bright-orange, sticky flesh embedded with seeds.
The tobira (Pittosporum tobira) grows from 6 to 15 feet tall with a similar spread. This small, moderately slow-growing tree has 2- to 4-inch-long, grey-green foliage and produces fragrant, white-to-yellow flowers in late spring. Tobiras produce dark seed pods that split open to reveal a sticky interior filled with brown seeds. They create sticky seed litter when planted in urban areas. The monkeypod or o'hai (Pithecellobium saman) grows from 50 to 75 feet tall but only has a 2-to 4-foot-tall trunk. This low-canopied tree has almost-horizontal branches that spread to 100 feet wide. Monkeypods are evergreen except for a brief period of leaf-drop in early spring. They bloom through spring and summer with tubular, pink flowers followed by sticky, 8-inch-long, brown or black, flat pods filled with red-brown seeds. Livestock can eat the pods. When planted in urban areas, Monkeypods can create a litter problem when they shed their sticky flowers and pods.