We are getting close to the typical average last frost date at March 3rd. So now is the time to start some cucumber, squash or melon seeds indoors.
Starting Mix
First, you need some seed starting mix. You can use ready-made mixes, or you can make your own by using potting soil mix you have on hand. Since I always have some potting soil mix on hand for use in containers or up potting starts, I use that. I suggest screening it through a ¼ inch hardware cloth sieve to take out any larger pieces which might block the seeds from poking through the mix.
Once the soil is hydrated, add it to the seed trays. Since cucumber, squash, and melon seeds are larger seeds, they are planted at about twice their size or roughly ½ inch depth.
Next, place your starter tray on a rack or designated place, covering it with a humidity dome. If you have plant-start heating mats, they can be very helpful by warming the soil, but are not absolutely necessary. It is customary to “bottom” water seeds, so add water to the tray your seeds are in. The soil should be moist enough from the initial wetting process described above, thus only a little water should be needed in the tray. Add water only when soil dries out slightly. After about 15 minutes, if any water remains in the tray, drain it. The humidity dome should stay on until the seedlings begin to show.
Seedlings
The Armenian cucumber seeds in these photos germinated over five days from February 17th through the 22nd with the humidity dome being removed on February 22nd.
At this point the seedlings should be placed under grow lights slightly above their height. Adjust the height of the light as the seedlings grow. If the grow lights are too high, the seedlings will likely become “leggy,” because they are stretching to reach more light. This will cause them to be weaker due to the main stem being too long and thin, and likely top heavy. The first set of leaves on the seedlings are the cotyledon leaves. The next set of leaves you will see are the first true leaves and the cotyledon leaves will likely drop off.
Preparing Plants for the Garden
Hardening off is the process of acclimating the new seedling to the outdoors. This starts by moving them outdoors the first day for perhaps 2 hours. This continues daily, increasing amount of time of outdoor exposure each day for about 1 week. By then your new starts should be able to handle being transplanted into your outdoor garden.
If you prefer not to jump start your growing season by starting seeds indoors, cucumbers, squash, and melon seeds can be started in the ground in late March. Just be sure to check the long-range weather forecast to see if any possible freezing temperatures might happen.
Tim Long has been a UC Master Gardener in Stanislaus County since 2020. All photos are by the author.
