I want to share one of the techniques that a lot of farmers use to save space in the greenhouse. When you are seeding trays by the dozen, you can quickly fill up your tables and run out of precious real estate.
We call this technique "potting up" which refers to taking a young seedling and transplant it into a larger block of soil from a densely seeded tray. This method not only saves space, but it allows you to choose the healthiest , strongest looking sprouts. Healthy transplants have an advantage over disease and pests and can better withstand less than ideal conditions.
At our farm, we use this method for tomatoes, eggplant, peppers, celeriac, parsley, basil, celosia, zinnias, statice, and more. We would not recommend this for anything in the cucumber family, plants with sensitive root systems, or plants that have deep taproots.
Start with a 20 row tray or any shallow tray with drainage holes. Mix a high quality organic potting soil with enough water to make it moist, but no water should drip out when you squeeze it. We use Vermont Compost Company's Fort Light. Fill the tray 2/3 - 3/4 of the way with your lightly damp soil. Sprinkle your seeds across the surface and cover with more damp soil (depending on whether or not the seeds need light to germinate). We use popsicle sticks as labels to mark the variety and the date that the seeds were sown.
Water your trays often enough to keep the soil moist as they will dry out quickly. Once your seeds sprout, wait a few days until they seem hardy enough to be disturbed without damaging the roots. The zinnias on the right of the tray pictured above look ready but the flowers to the left are too small.
Fill your tray (or small containers) with lightly damp potting mix all the way to the top but don't pack it in too hard. Use a pen or a wooden dowel similar in size to poke a hole in each cell about half to three quarters of the way down. The longer the roots of the sprouts, the deeper you should make the hole.
Using a popsicle stick, gently dig out the sprouts from your tray. I usually put a popsicle stick under the row and pop out a chunk of sprouts then tease them apart very gently in my hand.
Use your popsicle stick to guide the roots down into the holes you created in the soil. Drop the sprout down as deep as it will go, burying most of the stem. All that stem buried under the soil will create new roots! Pinch the soil at the surface around the stem and gently push down to secure the roots.
That's it! We have found that with limited space, using the potting up method ensures that 100% of each tray has a usable transplant. Often times if you are seeding directly into a tray you could experience poor germination and waste time, labor, and materials. We always pot up how many plants we need and keep the extra sprouts in the 20 row tray for a few weeks in case a few of them don't make it.
That's it for now, we hope you find this post informative for a farm or garden of any size!