Q. I was asked to look at a greenhouse full of seedlings that were not growing, and in various stages of dying, in the hopes that I could save the crop. Here’s what I found was wrong – for starters.
A. The trays or flats were built with no drainage. Number one No-No! Plants must have oxygen, and will drown without proper drainage, or at the very least there will be a build-up of salinity, which will totally stop them from growing.
The soil medium was more like clay soil than the soft and fluffy sawdust, peatmoss, and perlite that we recommend. Even though sawdust and sand were being used, the sawdust was truly DUST and the sand was finer even than masonry sand. In addition, they were pressed down firmly before planting. We recommend coarser materials than that – again for the oxygen and drainage.
Pre-Plant and Weekly Feed fertilizers were not applied properly. They needed 1/2 again the amount they had been given. For a flat 18″ square (1/2 meter) 1 1/2 ounces Pre-Plant and 3/4 ounce of Weekly Feed should be applied and worked into the soil before transplanting.
The plants were planted too close together. This means more plants are sharing the same amount of air, light, water, and fertilizer. Most plants should not be planted closer than 64 in a 1/2-meter square flat. The ones I saw were all planted 81 per tray.
The flats were also very shallow, which would become a problem soon, if the plants happen to live. Plant roots need room, and a flat should be 2 3/4″–3″ deep.
Almost all plants were exhibiting deficiency symptoms of at least one nutrient, and I believe several were needed. Purple leaves indicate a phosphorus deficiency, and these needed that plus magnesium, and probably calcium (the major nutrient in the Pre-Plant Mix).
I began by drilling 32 1 cm holes in each flat, and applied Pre-Plant and Weekly Feed sufficient to correct the original deficiency. I next aerated 200+ flats 1″ deep by dragging a dibble beside every row in both directions. I then applied the other two nutrients I felt were needed immediately by including them in the first watering.
It would be very time-consuming, costly, and stressful to the plants to transplant them into better soil medium. And I could not tell if the holes were sufficient to solve the drainage problem – I suspect they were not, mostly because of the soil medium being much too dense. Sadly I had to leave more than 15,000 vegetable plants to their fate, in the hands of people who know next to nothing about their proper care.
I recommend anyone who is interested in growing their own seedlings, which is very rewarding on several levels, should get the Mittleider Gardening Library CD, which is available at www.foodforeveryone.org in the Store section, and study Let’s Grow Tomatoes and Gardening ByThey Foot for starters.