Bitterbark is a native of Australia and hardy in USDA zones 9 through 11. The dried fruits explode and send seeds three feet into the air. The sandbox tree sends its seeds hurling nearly 150 feet, and the exploding seed pods create a loud noise comparable to a rifle discharge. The sandbox tree is hardy only in USDA zones 10 through 11. The rubber tree , the source of natural rubber, can shoot its seeds 50 feet from the tree. It’s hardy in USDA zone 10 through 11.
One of the largest groups of plants that uses ballistichory is the pea family, or Fabaceae. This is just one type of plant that shoots seeds when touched and the pod is cracked open. Lupins (Lupinus spp.), a garden favorite that’s hardy in U.S. Department of Agriculture plant hardiness zones 3 through 9, form columns of pea-like fruits that burst open when dry. Orchid trees (Bauhinia spp.), hardy in USDA zones 9 through 11, bear large pods that can fling seeds nearly 50 feet. Gorse (Ulex spp.), an aggressive broom-type plant that is considered a noxious weed in some states, makes a popping noise when the seed pods burst open.
Another plant that shoots seeds when touched is Euphorbiaceae. The Euphorbia family produces segmented seed capsules that somewhat resemble a peeled orange in shape. Examples of plants in this family include bitterbark (Petalostigma spp.), the sandbox tree (Hura crepitans), and the rubber tree (Hevea spp.)
Most Plants in Euphorbiaceae Family
Some plants disperse their seeds forcefully by ejecting them. Sometimes the tension is so great, seeds may be ejected up to 200 feet away from the mother plant. This method of seed dispersal is called “ballistichory,” a label that hints at the projectile-like emergence of seeds from their pods or capsules. This type of seed dispersal occurs because the fibers in the dried fruit pull against each other to create tension, and when the tension is great enough, the fruit splits open and the walls of the fruit spring back, flinging the seeds out with force.
The Acanthus family (Acanthaceae) produces a number of shrubs that distribute seeds through explosive action. Most produce highly ornamental flowers. The Mexican petunia (Ruellia spp.) has small petunia-shaped flowers and produces pods that disperse seeds up to 10 feet away. Mexican petunias are hardy in USDA zones 8 through 10, and may be an invasive plant in some states. Justicia produces colorful flower spikes and is hardy in USDA zones 9 through 11. The seed capsules explode when mature. Firecracker plants (Crossandra spp.) are aptly named because of their pretty orange flowers and exploding seed pods. These capsules dry out first then pop open once they become moist again.
Some plants in the mallow family (Malvaceae) disperse seeds via ballistichory. The common garden vegetable okra (Abelmoschus spp.) is a plant that shoots seeds when touched, projecting its seeds several feet. Okras are annuals that are hardy in USDA zones 4 through 11. The kapok tree (Ceiba pentandra, also known as cotton tree) is native to South America and produces cream-colored flowers with an unpleasant smell. The pods burst open, sending both seeds and the exploding seed pod’s cottony insulation into the wind. Kapok trees are hardy in USDA zones 10 through 11.
Nuts like cashew and almonds are made tasty, nutritious and irresistible to animals. Gray squirrels in cold countries collect a lot of nuts and hide them during summer, planning to snack on them during winter; but the squirrels usually forget where they hide the nuts, which makes new trees!
Gliders, parachutes and helicopters. You may think I am talking about fun ways for us to sail through the air, but no. I am talking of smart ways plants have devised to send their seeds far and wide.
The coconut has an outer covering of husk — that’s what the tender coconut vendor peels away before giving it to you — which is so light, it can float for miles on water.
Plants adopt ingenious techniques to disperse seeds over long distances. Find out how…
Agents of dispersal
The copper pod tree, found on the roadside in many of our cities, is a stunning example: bright yellow flower bunches get replaced by copper coloured pods, which rattle with seeds. Some seeds drop right next to the parent plant and start growing. This is common in annual plants, which live for only a year; parents die out and the next generation grow to take the parents’ place in the ecosystem.
More than wind and water, animals and birds can make valuable allies who can help disperse seeds. Some fruits have spines and hooks, which get stuck on the fur of animals as they pass by the plant. Biting into a juicy mango probably drives other thoughts out of your minds — but, the mango tree has put in a lot of effort to make the fruit delicious to animals like us.
The Indian birthwort, Aristolochia india, has brownish purple flowers that form green, cylindrical fruits. When the fruit matures, it breaks to form an inverted umbrella or parachute; winged seeds are blown out from inside the parachute when the wind blows. Silk cotton trees also have pods stuffed with cottony seeds.