The past few years, I have preferred to buy transplants from local garden centers. I figured, they are the pros, let them decide when to start seeds. I will just select the healthiest, best-grown transplants for my garden. Unfortunately, the garden centers also get to choose which varieties to plant or purchase. Last year, there were a number of varieties I wanted to plant but I could not find the transplants.
So this year I chose to buy seeds and start some seedlings myself. I am not new to this. I have started seeds in the past. I have the heat mat, the domed trays, and the grow lamp on a timer with a fresh full-spectrum bulb. I purchased seeds and made a planting schedule, So how did things work out?
Actually, not so good. Usually the two problems I have with seed starting is plants becoming leggy from inadequate light and plants becoming overgrown before I can transplant them. This year, the problem was a general unhealthiness and failure to thrive, true across all seedlings I planted. So what is different this year?
In the past, I have used traditional soil-less mixes based on peat moss and perlite. This year I used a starter mix based on coconut coir placed in peat strips, and some coir pellets for the cool weather items like lettuce, chard and escarole/endive placed in a small cell tray. The cool weather items would quickly go into the garden while the tomatoes, peppers and eggplants would grow on under the lamp.
Most seeds germinated fairly fast on the heat mat with a dome covering the tray. I had problems with a few of them. The Striped Roman tomatoes all damped off and were reseeded. I only got one cilantro to germinate even after re-seeding the strip twice. The major problem was that after germinating, all of the plants seemed to struggle, showing very little growth. Initially green, they started to lose color. Fertilizing with fish emulsion and then with an inorganic soluble fertilizer did not help. The seedlings were stunted and failed to add new sets of leaves. I wondered about the coir in the planting mix, the only change from past practice. Then I came across this research paper which pretty much describes what was happening to my seedlings.
I do not have a lot of documentation of what happened because I did not set out to fail, nor was I interested in running an experiment. I was just trying to start transplants for my garden. I can show you a few examples of what happened.
Here is a Matt’s Wild Cherry tomato. The plant on the left was transplanted into my SFG on Saturday, May 26. The plant on the right is a sibling still sitting in its coir-infested peat pot. This picture was taken on May 31, five days after transplant. You can see the transplanted tomato is greener and is stretching out, actually starting to grow. Both looked similar on transplant day, I simply picked the best of the sorry lot. If you look at my planting schedule, you will see that seeds were planted March 24 and they germinated on March 31. The transplant in the peat pot you see below has been growing for TWO MONTHS and looks like this. It has been watered, fertilized and given adequate light.
The sickly looking transplants below are Escarole Natacha. The plants just above them looked similar when they were transplanted on April 21, a month before, but are now green and growing lushly in Mel’s Mix. I started a second set of transplants for succession planting, which are the sickly transplants below. I am hoping they will now recover and start growing as well.
Below are transplants of Endive Dubuisson, and above them the same transplanted on April 21 along with the escarole.
Finally, in the middle row here are transplants of Broccoli Di Ciccio, germinated on March 22. They still are tiny plants but show less discoloration than other seedlings. The study I cited seemed to indicate that broccoli was more tolerant of coir than other species.But still, they are stunted in growth so much that I went out and bought replacement transplants, I did plant two of these several weeks ago but they are essentially not growing. I think I would do better now just direct seeding these. Come on, these plants germinated on March 22 and this picture was taken June 1.
I can tell you now I will never buy a coir-based planting mix again. The stuff I have is going into the compost bin where its negative properties will hopefully be diluted..I do use coir as bedding material in my worm bin and that has worked OK. But as a planting medium, based on my involuntary experience, coir is detrimental to plant growth and should not be used