The ovary is the part of a flower that produces seeds and becomes the fruit. It sits at the base of the pistil (the flower’s female reproductive structure) and contains tiny structures called ovules, each holding an egg cell. After pollination and fertilization, the ovules develop into seeds while the ovary wall thickens and ripens into the surrounding fruit tissue. Every fruit you’ve ever eaten, from apples to tomatoes to grains of wheat, started as a flower’s ovary.
Where the Ovary Sits in the Flower
The ovary is the bulging base of the pistil, which also includes the style (a narrow stalk) and the stigma (the sticky tip that catches pollen). Inside the ovary are one or more chambers called locules, and attached to the walls of these chambers are the ovules. Some flowers have a single chamber with just one ovule, like a cherry blossom. Others have multiple chambers packed with dozens or even hundreds of ovules, like a tomato flower.
The ovary’s position relative to the rest of the flower varies by species. In some flowers, like lilies, the ovary sits above where the petals and sepals attach, which botanists call a superior ovary. In others, like apples and bananas, the ovary sits below the other flower parts, called an inferior ovary. This positioning affects the shape and structure of the fruit that eventually forms.
Guiding Pollen to the Egg
The ovary does more than passively wait for fertilization. It actively recruits pollen tubes and guides them to the right destination. When a pollen grain lands on the stigma, it grows a long tube down through the style and into the ovary. Getting from the ovary entrance to the correct ovule is a precisely guided journey that happens in stages.
First, the ovule’s outer layers emit long-distance chemical signals that help the pollen tube find its way out of the central channel and into the ovary chamber. Once inside, the pollen tube attaches to the chamber wall and follows short-range chemical signals, including small guiding proteins, that direct it along a stalk called the funiculus toward the ovule’s opening. Finally, the tube enters through a tiny pore in the ovule called the micropyle and delivers two sperm cells. One sperm fuses with the egg to create the embryo. The other fuses with a second cell to form the endosperm, a nutrient-rich tissue that will feed the developing seed. This “double fertilization” is unique to flowering plants.
Protecting the Developing Embryo
One of the ovary’s most important roles is shielding the embryo from the outside world. In more ancient plant groups like mosses and ferns, the egg cell sits inside a structure only one cell layer thick, leaving it exposed to bacteria, fungi, and environmental stress. Flowering plants evolved a dramatically different approach. The embryo develops deep inside the ovary, wrapped in multiple layers of maternal tissue: the inner lining of the ovule, one or two protective coats called integuments, and the ovary wall itself.
These layers aren’t just physical barriers. The surrounding maternal tissue actively controls which molecules can pass through to the embryo. In some species, the plant produces defensive compounds in the tissue connecting the ovule to the ovary wall and transports them into the maturing seed. This layered defense system is considered a key evolutionary innovation that helped flowering plants become the dominant plant group on Earth.
Transforming Into Fruit
After fertilization, the ovary undergoes a dramatic transformation. The ovary wall, now called the pericarp, develops into the flesh, rind, shell, or husk of the fruit, depending on the species. Plant hormones drive this process. In the earliest stages, the developing seeds produce growth-promoting hormones that trigger rapid cell division and enlargement in the surrounding ovary tissue. A second class of growth hormones works alongside the first to keep the fruit expanding. Meanwhile, a ripening hormone is actively suppressed during these early growth phases so the fruit doesn’t mature too soon.
In strawberries, this hormonal relationship is especially clear. The tiny seed-like structures dotting the surface (called achenes) are the actual fruits, and they produce the growth hormones that cause the fleshy red part underneath to swell. If you remove the achenes from a developing strawberry, the flesh stops growing. Grapes follow a slightly different pattern, developing in three stages: an initial burst of rapid growth, a pause, and then a final phase of ripening where the berries soften, change color, and accumulate sugars.
The Three Layers of a Ripe Fruit
The mature ovary wall typically develops into three distinct layers, each with a different texture and function depending on the species. In a peach, these layers are easy to see. The exocarp is the thin, fuzzy skin. The mesocarp is the thick, juicy flesh. The endocarp is the hard pit surrounding the seed. In a coconut, the exocarp is the smooth outer shell, the mesocarp is the fibrous husk (usually removed before you see it in a store), and the endocarp is the hard brown shell you crack open.
These layers can take on wildly different forms. The exocarp of an orange is leathery and packed with oil glands. The exocarp of a kiwi is covered in fine hairs. Some fruits have a fleshy mesocarp and a papery endocarp. Others are entirely dry and hard at maturity, splitting open along seams to release their seeds, like a pea pod. Whether a fruit is soft or hard, whether it splits open or stays sealed, and how many chambers it contains all trace back to the structure of the original ovary.
Why Ovary Size Affects Seed Count
The number of seeds a plant can produce is directly linked to the size of its ovary and how many ovules it contains. A larger ovary with more internal chambers and more ovules has the potential to produce more seeds per fruit. This matters enormously for crop plants. Seed yield in species like canola and other grain crops depends in part on how many ovules the ovary develops before fertilization. Not every ovule necessarily gets fertilized or matures into a viable seed, but the ovary sets the upper limit.
Some ovaries contain a single ovule and produce a single seed, like a sunflower’s individual floret. Others contain hundreds, like a poppy capsule that can scatter thousands of tiny seeds. The internal architecture of the ovary, including how many chambers it has and where the ovules attach to the walls, determines the arrangement and number of seeds in the mature fruit.