An apple can hold up to about ten seeds, but the number in any one apple is rarely fixed. The core has a set number of seed spaces, and each seed forms only if the flower was pollinated well enough to fill it. The seeds also do more than sit in the core: they quietly steer how the fruit around them grows.
The Typical Seed Count Inside an Apple
Cut an apple crosswise and the core shows a five-pointed star. Each point is a seed chamber. Most apples have five of these chambers, though some have as few as three.1Wikipedia. Apple Each chamber holds one or two seeds.2Wikipedia. Apple That puts the ceiling at about ten seeds for a five-chamber apple and about six for a three-chamber one. The number of chambers is set when the flower forms, before any pollination happens, so an apple with three or four chambers is just normal variation, not a defect.
Real counts usually come in lower than the ceiling. Many apples have empty chambers or small, flat, shriveled seeds that never developed. Varieties also differ clearly in how many seeds they produce and how heavy those seeds are,3Europe PMC / Springer Link. Comparison of fatty acid profiles and contents of seed oils recovered from dessert and cider apples and further Rosaceous plants so two apples from different varieties in the same bowl can have very different counts.
To count seeds yourself, slice the apple across its middle rather than top to bottom, which shows every chamber at once. Count the star’s points first so you know the maximum. Then look at the seeds: plump brown ones are developed, pale flat ones are not. Two seeds sharing a chamber can sit side by side and be easy to miss until you pull them apart with a fingertip.
It helps to write down plump seeds and flat seeds as separate numbers, because only the plump ones tell you how well that fruit was pollinated. To compare varieties, cut several apples of each and look at the average, since any single apple can be unusual.
Why Some Apples Have More Seeds Than Others
Each seed forms only when pollen reaches its part of the flower, so poorly pollinated blossoms make apples with fewer seeds. Most apple varieties also need pollen from a different variety to set fruit at all.4Growing Fruit. What Causes an Apple to Be True to Seed? A lone tree with no apple or crabapple nearby may set little fruit, and what it sets will have few seeds. The partner has to bloom at the same time as your tree, or its pollen arrives too early or too late to be useful.
In orchards, apples had more seeds where more kinds of wild bees visited and where wild bees were more plentiful.5Agriculture, Ecosystems and Environment. Pollination services for apple are dependent on diverse wild bee communities The number of honeybees made no difference to seed count in those orchards.6Agriculture, Ecosystems and Environment. Pollination services for apple are dependent on diverse wild bee communities Having bees of different types, such as ground-nesting and bumble-type bees, raised seed numbers most of all.7Agriculture, Ecosystems and Environment. Pollination services for apple are dependent on diverse wild bee communities A backyard tree near varied wildflowers and wild bees may therefore make seedier apples. To help, plant a second compatible apple or crabapple variety nearby, grow early-flowering plants that feed wild bees, avoid spraying insecticides while the tree is in bloom, and prune so light reaches the inner branches.
Apples on a single tree differ for the same reasons. Each flower is pollinated separately, so some get more bee visits than others, and flowers on the shaded inside of the tree get fewer seeds.
Weather changes counts from year to year. A hard late-spring frost can damage blossoms and cut pollination, and in some regions frosts are getting harsher as springs warm.8European Journal of Agronomy. Climate warming may accelerate apple phenology but lead to divergent dynamics in late-spring frost and poor pollination risks in main apple production regions of China A cold, wet bloom keeps bees from flying, so the same tree can make seedier apples in a warm spring than in a cold one. If a tree flowers before the bees are active, fewer flowers get visited.
Growing practices matter too. Heavy shading cut the number of healthy seeds roughly in half in one popular variety.9HortTechnology. Effect of Chemical Thinning Sprays on Apple Fruit Set Growers sometimes spray young fruit to thin the crop, and one thinning spray reduces the number of fully developed seeds.10HortScience. Blossom and Fruitlet Thinners Affect Crop Load, Fruit Weight, Seed Number, and Return Bloom of `Northern Spy’ Apple11Scientia Horticulturae. ‘McIntosh’ apple fruit thinning by benzyladenine in relation to seed number and endogenous cytokinin levels in fruit and leaves Other common thinning sprays left seed numbers unchanged.12HortTechnology. Effect of Chemical Thinning Sprays on Apple Fruit Set
How Seeds Shape the Apple Around Them
Developing seeds release plant hormones that make the flesh around them grow.13HortScience. The Role of Hormones in Fruit Set and Development Each seed acts like a small growth switch for the flesh nearest to it. When seeds form all around the core, the apple usually grows evenly.14apples.extension.org. What causes mis-shaped apple fruit? When seeds form on only one side, that side outgrows the other and the apple turns lopsided.15apples.extension.org. What causes mis-shaped apple fruit?16The Journal of Horticultural Science and Biotechnology. Modelling the influence of seed set on fruit shape in apple17Department of Agriculture and Water Resources, Fruit Growers Tasmania, Tasmanian Institute of Agriculture and University of Tasmania. Factors affecting post-harvest management of apples: a guide to optimising quality
You can check this at home. Slice a lopsided apple and compare the seeds on the fat side and the flat side. The flat side usually has empty or shriveled chambers, while the fuller, rounder side is where seeds developed. Lopsidedness usually points to uneven pollination, and such an apple is still good to eat.
Seeds also help keep fruit on the branch. Young apples naturally tend to drop from the tree, and signals from the seeds hold them on.18Journal of Horticultural Science. Studies of Fruit Development in Relation to Plant Hormones: I. Hormone Production by the Developing Apple Seed in Relation to Fruit Drop The seeds send these holding signals in two bursts, about 3 to 4 weeks and 7 to 10 weeks after petals fall.19Journal of Horticultural Science. Studies of Fruit Development in Relation to Plant Hormones: I. Hormone Production by the Developing Apple Seed in Relation to Fruit Drop So the early-summer drop gardeners often notice is a test of whether fruitlets have enough seeds to stay, and poorly seeded ones are more likely to fall. Many small apples on the ground in early summer is normal: the tree is shedding fruit it cannot support and keeping the better-seeded ones. Within a variety, more seeds mean more of a growth hormone leaving the fruit, which can affect whether the tree flowers well next year.20ishs. THE ROLE OF SEED DERIVED HORMONES IN THE CONTROL OF FLOWERING IN APPLE
Are Apple Seeds Poisonous
Apple seeds contain amygdalin, a natural compound that releases cyanide when the seed is crushed or chewed.21PubMed. Determination of amygdalin in apple seeds, fresh apples and processed apple juices22PubMed. Dynamics of cyanogenic glycosides in apple and plum fruits, products, and byproducts: A concise review Seeds from different varieties hold about 1 to 4 milligrams of amygdalin per gram of seed.23PubMed. Determination of amygdalin in apple seeds, fresh apples and processed apple juices Since each seed is small, a few eaten by accident carry very little.
A whole swallowed seed passes through mostly intact because its hard coat isn’t broken, which gives the body little chance to release anything. Chewing or grinding breaks that barrier, which is why how a seed is eaten matters more than whether it was eaten. The concern grows with quantity: a handful of chewed seeds is a very different matter from one or two.
Blending or juicing breaks seeds open and frees cyanide as they mix with water.24PubMed Central. Cyanide Toxicity of Freshly Prepared Smoothies and Juices Frequently Consumed Even so, smoothies made with whole apples, seeds included, had only low cyanide levels.25PubMed Central. Cyanide Toxicity of Freshly Prepared Smoothies and Juices Frequently Consumed Drinks that also contained flaxseed had clearly higher levels.26PubMed Central. Cyanide Toxicity of Freshly Prepared Smoothies and Juices Frequently Consumed Occasionally swallowing a few seeds is not a worry, but there is no reason to blend cores in large amounts. If you make smoothies daily, core the apples first, and take the most care when combining apple cores with flaxseed.
If a child swallows a few seeds, there is usually no need to do anything. If a child has deliberately chewed a large number, call a local poison control line and say how many seeds and how old the child is.
Why Some Apples Have No Seeds
Seedless apples are rare in nature. Growers can make them by treating apple flowers with plant growth hormones, which produce fruit without pollination or seeds.27Horticulture Research. Gibberellic acid induced parthenocarpic ‘Honeycrisp’ apples (Malus domestica) exhibit reduced ovary width and lower acidity The hormones work because they mimic the growth signals seeds normally send to the flesh.28HortScience. The Role of Hormones in Fruit Set and Development The flesh gets its cue even though no seeds form.
The signal is only a substitute, though, and the fruit may not turn out like a normal one. Hormone-made seedless Honeycrisp apples grew narrower and less tart than normal ones.29Horticulture Research. Gibberellic acid induced parthenocarpic ‘Honeycrisp’ apples (Malus domestica) exhibit reduced ovary width and lower acidity This is a growers’ technique, not something a home gardener does by accident.
An apple with empty chambers at home likely came from a flower that was poorly pollinated but still kept its fruit. It is safe to eat, though it may be smaller or misshapen because seeds didn’t drive its growth.
Can You Grow an Apple Tree From a Seed
Fresh apple seeds are dormant and won’t sprout right away.30PubMed. Dormancy removal of apple seeds by cold stratification is associated with fluctuation in H2O2, NO production and protein carbonylation level About 70 to 90 days of cold, moist chilling lets them sprout.31PubMed. Dormancy removal of apple seeds by cold stratification is associated with fluctuation in H2O2, NO production and protein carbonylation level Dormancy keeps a seed from germinating in autumn, when a seedling would be killed by the coming winter.
To do it at home, choose plump, dark brown seeds, since pale flat ones were never fully developed and are unlikely to sprout. Rinse them, wrap them in a damp paper towel, seal them in a bag, and keep them in the fridge for about three months. Check about once a month that the towel is damp but not wet, and throw out any seeds with mould. When roots appear, plant the seeds in pots of soil near a sunny window.
The new tree will be different from the parent. Each apple seed carries a mix of genes from two parent trees, so a seedling’s apples usually differ from the apple it came from.32Growing Fruit. What Causes an Apple to Be True to Seed? That’s why named varieties are grown by grafting branches onto rootstock, not from seed.
Expect to wait several years for a seedling to flower. The fruit may be small or sour, or occasionally excellent. Either way, the tree can still be a pollen partner for other apple trees nearby.
Why Apples Evolved Small Seeds Inside Sweet Fruit
Apples and their relatives began evolving large fruit about nine million years ago, mainly in Europe and Asia.33PubMed Central. Bearing Fruit: Miocene Apes and Rosaceous Fruit Evolution Big, sweet, colourful fruit attracted large animals that ate it and spread the seeds.34PubMed Central. Origins of the Apple: The Role of Megafaunal Mutualism in the Domestication of Malus and Rosaceous Trees35PubMed Central. Bearing Fruit: Miocene Apes and Rosaceous Fruit Evolution
Apple seeds’ small size lets bears and mid-sized animals swallow and spread them today.36PubMed Central. Origins of the Apple: The Role of Megafaunal Mutualism in the Domestication of Malus and Rosaceous Trees The hard seed coat lets the seed pass through the gut without being broken down. The animal then deposits the seed in droppings far from the parent tree, giving the seedling space and light.