October 19 :: Cotyledons? True Leaves? What the what?

Welcome Back!

After recently witnessing spinach, lettuce, basil, radishes, and volunteer sunflowers emerge from their seeds in the ground I started wondering about the first set of leaves that appear when the seeds germinate. These initial leaves (two for vegetables and herbs) rarely look like the adult leaves of the plant and can make seedling identification tricky if you forgot to label your planting trays or soil blocks carefully.

It turns out that the first leaves are called cotyledons (pronounce COT-a-LEE-dens) and are present in the seed while it awaits germination. Without getting too scary technical, here's the scoop:

When the seed is exposed to the correct combination of heat and moisture, these babies absorb the water and inflate. The seed has nutritious reserves with which to extend the stem and push the leaves up through the soil's surface where they can reach the light. They are fully equipped to carry out photosynthesis and therefore pave the way for the rest of the plant to develop by generating food. For more information on the subject, go here.

Here are photos of a newly emerged cilantro plant. The cotyledons are the straight leaves, the serrated leaf is the plant's first true leaf (more on that later). Sometimes the husk of the seed stays attached as the seedling develops, but it will fall off after a few days (see below).

Often you'll read instructions about thinning or transplanting seedlings, or applying fertilizer that refer to doing a task when the plant has its first set of 'true leaves'. These are the first adult leaves and their appearance indicates that the seedling has passed the most stressful time of germination and development and is a little more hardy.


Let's play a game! Ok? Ok. Here are four photos (A-D) of baby plants and their cotyledons. Following those are four photos of teenage and adult plants with true leaves (1-4). Match the cotyledon plants with their adult versions. Answers will be available next week!


For bonus points: Name these plants! (hint: they are all veggies and herbs but are not all mentioned in the first paragraph of this post)

[A]

[B]

[C]

[D]

And those with true leaves:

[1]

[2]

[3]

[4]

Grow on!

Tyler

[edited on 11/5/2010] I decided to include the answers on this post, instead of making a new post for them. Answers: A - 3 Cucumber, B - 1 Basil, C - 4 Radish, D - 2 Rainbow Chard