Watching seeds germinate is fascinating. It is particularly interesting watching as the seedlings first emerge with cotyledon leaves (sometimes referred to as seed leaves) and then grow true leaves. I can remember sitting in one of my Master Gardener classes and not understanding the discussion about cotyledon vs true leaves. In case you find yourself in a similar situation, I hope you find it interesting to learn about the differences between cotyledon and true leaves. As I grow new vegetables, herbs and flowers I will continue to add new examples as I grow new vegetables, herbs and flowers.
SEED ANATOMY
First, to appreciate the cotyledon leaves, it is important to understand some basic information about the anatomy of a seed. The embryo (e.g. seed) has everything it needs to form a plant. It is protected by its seed coat (the outside of the seed). Inside the embryo, there will be either one or two leaves. If the embryo has only one leaf, it is called a monocotyledon (monocot). The leaf of a monocot will appear as a vertical growth such as in an onion or grass. Embryo’s with two leaves are called dicotyledons (dicot) and the two leaves will appear as the first growth above the ground on a seedling. These leaves provide the initial nourishment to the seedling.
Gradually, as the seedling grows, the “true” leaves will appear. True leaves resemble the leaves of a fully mature plant. Cotyledon leaves may last only a few days after germination or may persist up to a year. What fascinates me is the fact that cotyledon leaves are present inside the seed. As water is absorbed into the seed, the germination process begins, and the cotyledon leaves appear.
What are some clues to identifying the cotyledon from the true leaf? For dicots, the seed leaves are the lowest leaves on a stem, are opposite each other and are rather plain looking. Let’s look at some examples:
“The love of gardening is a seed once sown that never dies.”
Gertrude Jekyll
Here are a few resources to help you understand and start seeds:
BRASSICA'S
BROCCOLI
This variety of broccoli is called De Cicco. De Cicco is good for extended harvests because side shoots continue to develop even after the main head is harvested. The first cotyledon leaves appeared 3 days after the seed was planted. In the image above, the cotyledon leafs are the kidney bean shaped leaves that are opposite each other at the lowest level on the stem. The true leaf is the leaf to the right with the beautiful ridges all the way around.
Family: Brassicaceae
Genus: Brassica
Species: oleracea
KALE
This variety of kale is called Westlander. Westlander has very curly, broad leaves with a tender texture. The first cotyledon leaves appeared 5 days after the seed was planted. In the image above, the cotyledon leaves are the kidney bean shaped leaves that are opposite each other. The true leaf is the leaf in the center with the ridges all the way around. Notice the similarity of the leaves to the broccoli. Kale and broccoli are both in the brassica family.
Family: Brassicaceae
Genus: Brassica
Species: oleracea
RED RUSSIAN KALE
As the title indicates, this variety is Red Russian Kale which is cold tolerant and sweet. You may find this variety in mixes of baby greens. Notice the similar kidney shaped cotyledon leaves and then the lobed shaped true leaves.
Family: Brassicaceae
Genus: Brassica
Species: napus
CABBAGE
This variety of cabbage is called All Seasons. All Seasons is a heat resistant variety with heads that grow 10 inches in diameter. The first cotyledon leaves appeared 3 days after the seed was planted. In the image above, the cotyledon leafs are the kidney bean shaped leaves that are opposite each other on the bottom. The true leaves are the leaves above with the ridges all the way around. Hard to tell the difference between the broccoli and cabbage at this stage.
Family: Brassicaceae
Genus: Brassica
Species: oleracea
HERBS
DILL
This variety of dill is Banquet and it is full of aroma. Banquet is an early maturing variety. I grow dill for use in canning dill pickles (I also grow the pickling cucumbers). Dill is one of my favorite seedlings because the true leaves look so much different than the cotyledon leaves. In the photo above, the cotyledon leaves are the long narrow leaves. The true leaves are the lobed bunch of leaves standing up straight. These lobed leaves are beginning to look like the dill you purchase in a supermarket.
Family: Apiaceae
Genus: Anethum
Species: A. graveolens
PARSLEY
This variety of parsley is Single Italian. It’s a flat-leaf variety with a strong flavor. Growing up, my mother always had a bunch of fresh parsley ready for adding to her cooking. In the picture above, there are actually three parsley seedlings. You can see the three sets of cotyledon which are the long narrow leaves. Then you can see the three true leaves which are the beautiful leaves with the ridges all around.
Family: Apiaceae
Genus: Petroselinum
Species: crispum
CILANTRO
This variety of cilantro is Caribe and has good bolt tolerance. Cilantro is my favorite herb, I love the smell and taste. In the image above, the cotyledon leaves are at the bottom of the stem and are the oval shaped leaves (there are two seedlings in this picture). The true leaves are at the top of the stem and have the deeper ridges around the perimeter of the leaf. The only way I can tell the difference between a cilantro plant and a parsley plant is to smell the leaf.
Family: Apiaceae
Genus: Coriandrum
Species: sativum
BASIL
This variety of basil is Genovese and is one of the best varieties for pesto. Who doesn’t love the smell of basil. In this photo you can see the cotyledon leaves under the larger true leaves. The true leaves are what you would see when purchasing this herb at a supermarket.
Family: Lamiaceae
Genus: Ocimum
Species: basilicum
FRUITING VEGETABLES
EGGPLANT
This variety is called Eggplant Long. I obtained the seeds from a local public library where a seed lending program is maintained. In the photo above, you can see the narrow leaves on the bottom which are the cotyledon leaves. The ovate shape leaves on the top are the true leaves.
Family: Solanaceae
Genus: Solanum
Species: melongena
TOMATO
This variety of tomato is Stupica and it is a heirloom. It is semi-determinate and known as a very early tomato. The cotyledon leaves are the leaves in which you don’t see the veins coming out from the center of the leaf. The true leaves are the prettier leaves that are fuzzy.
Family: Solanaceae
Genus: Solanum
Species: lycopersicum
CUCUMBER
This variety of cucumber is National Pickling. It is a short thick cucumber, growing approximately 5″ long. The cotyledon leaves are the two leaves on either side of the true leaf that is in the middle. Notice how the true leaf has more jagged edges.
Family: Cucurbitaceae
Genus: Cucumis
Species: sativus
PEPPER
This variety of pepper is called California Wonder Sweet. These are green peppers that are quick to mature to red. The cotyledon leaves are the two darker leaves on the right and left. The true leaves are the bright green leaves in the center.
Family: Solanaceae
Genus: Capsicum
Species: annuum
LEAF VEGETABLES
GREEN LETTUCE
This variety is a looseleaf lettuce called Bergams Pelleted. Bergams is slow to bolt and retains crispness and flavor throughout the season. The cotyledon leaves are the smaller leaves at the bottom of the plant. The true leaves are the larger ridged leaves on the sides and coming up from the middle. Lettuce is a cool weather crop and grows best at temperatures of 60–65°F (16-18°C).
Family: Asteraceae
Genus: Lactuca
Species: sativa
MAGENTA LETTUCE
This variety is looseleaf lettuce called Magenta. Magenta has crunchy bronze leaves and a bright green center at maturity. It is heat tolerant, disease resistant and has a long shelf life.
Family: Asteraceae
Genus: Lactuca
Species: sativa
SPINACH
This variety is Matador spinach. Hardy spinach for spring, fall and overwintering. The cotyledon leaves are the long slender leaves and the true leaves are the oval leaves.
Family: Amaranthaceae
Genus: Spinacia
Species: oleracea
FLOWERS
COSMOS
This variety is called Sensation Mixed Colors and will result in a blend of white, pink, magenta and lavender blooms. The flowers are 3-4″ wide and the plant grows 3-4′ tall. Cotyledon leaves are the two slender single leaves on the right and left. True leaves are the multi-lobed bunch of leaves. These lobes leaves remind me so much of dill but in fact, Cosmos is in the same family as lettuce: Asteraceae.
Family: Asteraceae
Genus: Cosmos
Species: multiple
MARIGOLD
This is a Dwarf variety of marigold. Cotyledon leaves are the two slender single leaves on the top and bottom. True leaves are the leaves on the right and left with the jagged edges and the ‘dots’ of the edge of each lobe.
Family: Asteraceae
Genus: Tagetes
Species: patula nanaC
SUNFLOWER
This variety is called Jerusalem Gold Hybrid. These will produce golden orange flowers that are 5″ in diameter and grow 34-48″ tall. The cotyledon leaves are the two smaller leaves just beneath the larger sets of true leaves that have emerged on top.
Family: Asteraceae
Genus: Helianthus
SWEET PEA
This variety of the Sweet Pea flower is called Galaxy Mix and will produce flowers of various pastel colors. Cotyledon leaves of the sweet pea are different from other plants in that the leaves appear together on one side of the stem. In addition, cotyledon leaves look similar to the true leaves. Cotyledon leaves are distinguished by being the lowest leaves on the stem.
Family: Fabaceae
Genus: Lathyrus
Species: odoratus
REFERENCES
Better Homes & Gardens: https://www.bhg.com/gardening/garden-quotes/?slide=slide_85256#slide_85256
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