Gravity dispersal limited range comes from the simple fact that heavy seeds just fall straight down. Scientists call this barochory. Without wings, parachutes, or other flight aids, these seeds land right under the parent plant where they face tough competition.
I first noticed this pattern when I looked under the oak tree in my backyard one fall. Acorns covered the ground in a thick layer right beneath the branches. Almost none had rolled more than a few feet away. You can see the same thing under any fruit tree in your area.
Heavy seed dispersal works through gravity alone with maybe some help from slopes. Your seed drops from the branch and hits the ground below. On flat land, it stays where it falls. On a hill, it might roll a short way down. Either way, the seed ends up close to where it started.
This method creates a tradeoff that plants must accept. Large seeds pack lots of food for the baby plant inside. This gives seedlings a strong start in life with plenty of stored energy. But all that food makes seeds heavy and unable to travel far from home.
The crowding under parent trees creates real problems for your young plants. Seedlings compete with each other for light, water, and nutrients. They also fight with the parent tree that takes most of the good stuff. Many seeds in that pile will never grow into adult trees.
In my experience, this is why so few oak seedlings survive under mature trees. You might find hundreds of acorns on the ground but only one or two sprouts the next spring. The rest get eaten by animals, rot in the wet leaves, or die from shade and root competition.
Plants that use barochory often need a backup plan to succeed. Squirrels bury acorns in your yard and forget where they hid some of them. Birds carry cherries to perches far from the parent tree. These animals become partners that move heavy seeds to better spots for you.
Your garden shows you gravity dispersal every time fruit falls from trees. Apples pile up under apple trees and walnuts form rings around their parents. Peaches drop and rot right where they land. Each fruit that falls adds to the crowding problem you see below.
This limit helps you plan your own plantings better if you know about it. Space fruit trees far apart so their drop zones do not overlap. Pick up fallen fruit before it rots and attracts pests. Watch for volunteers sprouting from seeds that animals carried to new spots.
Read the full article: 6 Key Seed Dispersal Methods Explained
