Garden & Greenhouse


Propagating Plants from Seeds

Posted February 13th, 2015 by Eric Hopper in

A plant started from seed receives its genetics in a manner similar to the way humans receive genetics. Just as we are made up of a combination of our father and mother, a plant started from seed is made from the genetics of its father and mother. As with humans, some traits can skip generations and there is no guarantee that a plant started from seed will inherit specific traits from its mother or father. This is the main reason the majority of commercial plant propagation is done by clone or tissue culture. Starting from seed is unpredictable but it is also a chance to start a completely unique plant that will add more biodiversity to our wonderful planet.

Temperature and Humidity for Starting Seeds

Germination is the process in which the plant emerges from the seed to start its life. For most plants germination is best done in a very moist (high humidity) environment at a reasonably warm temperature, usually around 75-85 degrees F (the exception to this would be seeds that are generally planted in early spring when the ground temperature is much cooler). Propagation trays with humidity domes are great for starting seeds because they create a microclimate that is more easily controlled. Seeds can be placed directly into a moist medium in the tray and covered with the humidity dome. If the environment is not at least 75 degrees F consistently, it is advised to place a seedling heat mat under the tray to keep a constant temperature. Plants, in general, respond better to consistency and this is especially true with seeds or clones. Keep the top portion of the medium moist until all of the seeds have sprouted. Once the seedlings have broken the surface, lift the dome off periodically to bring in fresh air and also acclimate the seedlings to the lower humidity of the environment. Slowly increase the amount of time each day the dome is removed until it is removed entirely. Most varieties of plants can be acclimated in a matter of a few days. Follow the seed packet’s instructions for thinning, spacing, and transplanting.

Another popular germination method is the wet paper towel technique. Place your seeds in a damp paper towel and fold the paper towel over the seeds. Put the paper towel in a ziplock bag and place it on top of your refrigerator (toward the back; this keeps the seeds at a consistent temperature). Check daily by gently unfolding the paper towel to examine the seeds. Keep the paper towel moist; adding water if necessary. In a few days you should see the first root coming out of the seed (radicle root). Gently, using a tweezers if necessary, place the seed into the soil with the radicle root facing downward. Cover the seed and keep the top layer of soil moist until the plant breaks the soil’s surface. The paper towel technique is a fun way to teach children how plants start from seeds. This technique works best with larger seeds (melons, cucumbers, squash, corn, sunflower, etc.). Most smaller seeds, such as lettuce, are best planted directly into the soil.

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