Gardening Word of the Day: Cotyledons

Tomato Seedlings after 1 week

After only one week, we have Tomato sprouts that are nearly to the top of the Jiffy Seed Starting Kit clear plastic cover.  Each has a pair of leaves that are nothing like the rest of the leaves it will produce.  They are called Cotyledons or "seed leaves", and they are the solar power panels to allow the roots to start to dig deeper, and to help generate the first real pair of leaves.

From Wikipedia:

"A cotyledon (pron.: /kɒtɨˈliːdən/; "seed leaf" from Greek: κοτυληδών kotylēdōn, gen.: κοτυληδόνος kotylēdonos, from κοτύλη kotýlē "cup, bowl") is a significant part of the embryo within the seed of a plant. Upongermination, the cotyledon may become the embryonic first leaves of a seedling. The number of cotyledons present is one characteristic used by botanists to classify the flowering plants (angiosperms). Species with one cotyledon are called monocotyledonous ("monocots"). Plants with two embryonic leaves are termed dicotyledonous ("dicots") and placed in the class Magnoliopsida.

In the case of dicot seedlings whose cotyledons are photosynthetic, the cotyledons are functionally similar to leaves. However, true leaves and cotyledons are developmentally distinct. Cotyledons are formed during embryogenesis, along with the root and shoot meristems, and are therefore present in the seed prior to germination. True leaves, however, are formed post-embryonically (i.e. after germination) from the shoot apical meristem, which is responsible for generating subsequent aerial portions of the plant."

In the next few days, we will be removing the cover, and allowing these sprouts to start spreading their leaf pairs.  We will keep them under the gentle LED light for at least another 2 weeks, before starting to put them under stronger Metal Halide lights.  This is an indoor version of hardening off the plants.

Once they have several leaf pairs, and maybe even some true branches, we will then transplant them into 2"x2" plastic starter pots, which fit neatly into trays.  They will remain in these until we transfer them to #1 pots (aka 1-gallon pots, although they aren't really 1-gallon) which is where they will remain until they are strong enough to be hardened off outside, then eventually planted under Wallowaters outdoors.