Caring for Seedlings in the Greenhouse

March 20, 2018

Today is the first official day of spring, but here in the Northeast, we’re preparing for another big storm that’s expected to drop at least eight to 10 inches of snow in the area tomorrow. At my Bedford, New York farm, that means more work continues indoors to nurture and maintain the growing seedlings in my greenhouse.

My gardeners, Ryan and Wilmer, have planted thousands of seeds into flats since January, and until they are planted in the gardens, these seeds are kept inside where temperature, humidity and light can be properly controlled. During these early stages of growth, the seedlings also need some regular maintenance - thinning out those that are weak, pricking out those that are growing too big for their seed starting trays, and transplanting them into larger pots.

Yesterday, I shared photos of how we start our plants from seeds. Here are photos of how we care for our young sprouts - enjoy.

: These seedlings are in different stages of growth. They were planted from seed over the last few weeks. As they germinate and begin to mature, it’s important to check their development, so they continue to thrive.

: Regardless of how perfect seeds may appear, germination is never guaranteed, so multiple seeds are always planted in each seed starting tray cell. This provides a better chance at least one in each cell will take root.

: When the seedlings are a couple inches tall, and have reached their “true leaf” stage, which is when each seedling has sprouted a second set of leaves, it’s time for a process called selective thinning.

: Selective thinning prevents overcrowding, so seedlings don’t have competition for soil nutrients or room to grow.

: When thinning, carefully inspect the seedlings and determine the strongest ones. Look for fleshy leaves, upright stems, and center positioning in the space. The smaller, weaker, more spindly looking seedlings are removed, leaving only the stronger ones to mature.

: Once selective thinning is complete, there should only be one seedling in each cell of the seed starting tray or container.

: The stronger plants now have more room to grow before getting transplanted into larger pots or into the ground.

: The span of windows in my greenhouse helps to concentrate heat and sunshine to maximize plant growth.

: This is a heat mat specifically designed for seedlings. It warms the area and helps to improve root growth and increase germination rate.

: Here is Wilmer preparing to transplant a seedling that’s outgrown its tray. He uses his finger to create a hole in the pot – the end of a thick marker pen can also be used.

: This tool is great for transplanting seedlings – it’s from Johnny’s Selected Seeds. It’s called a widger. It has a convex stainless steel blade that delicately separates the tiny plants. http://www.johnnyseeds.com/tools-supplies/seed-starting-supplies/widger-7340.html

: A good quality organic mix designed for seedlings will be fast draining, and light. It will usually contain sphagnum moss and perlite or vermiculite. These mixes are formulated to encourage strong, healthy growth in new plants.

: Wilmer carefully loosens the soil around the seedling with the widger and lifts the seedling. The widger also helps to avoid damage to the plant’s leaves, or roots.

: He places the seedling in the hole and gently firms up the surrounding soil. Avoid handling the seedling by its tender stems, which can bruise easily.

: The growing seedling will remain in the new larger pot or cell tray until it is ready to plant into the ground.

: The purpose of transplanting is to provide enough room – overcrowding can stress the sprouts.

: These look so much better in the pots.

: There are also many different kinds of pots and trays available in different sizes and materials. These are Fertil pots from Johnny’s that are made from 80-percent wood fiber and 20-percent peat moss. http://www.johnnyseeds.com/p-7606-fertil-pots-round-3-18-dia-x-3-18-h-90-pots.aspx

: Smaller seedlings can go in slightly larger cell trays.

: Experiment with pots made from different materials to see which ones work best for what plants. And, always choose containers or trays that have proper drainage holes at the bottom.