Now for the fun part! To seed, or to plant your seeds, you want to fill your seed tray with your potting soil. If you have a size 50 through 128-tray size, you are going to want to fill your tray all the way to the rim with soil. If you are just planting one plant in a pot, like a tomato, then leave an inch or two of space below the rim of the seed container. This will allow for the water to sink in slowly, as all you will need to do is fill the pot with water and let it drain.
Next scrape all the excess soil off the top of the tray by flattening your hand and sliding it across the tray. Put the excess soil back in your potting soil bag for later.
TIP: Make sure you press the soil firmly into the seed tray, paying special attention to the edges and corners, although no one cell should be compacted in the slightest.
I promise this too will be one of your favorite words and activities of all time. Sophia’s dibbling definition: the act of making impressions in soil so as to make a ‘seed nest’ for your seeds before you drop your seeds in and cover them. I use my pointer, middle, and ring fingers to press lightly into the soil. If your fingers do not make a ¼ inch impression on your first try, you have compacted your soil too much. The soil should feel springy, but not cave when you press on it. Make one uniform dibble mark in the middle of each cell.
TIP: The size of the seed you are planting is going to determine the depth of your dibble mark. A good rule of thumb is that a seed should be planted 2-4 times its diameter. For instance when I planted my onion seeds, I made my dibble marks ¼” deep. If this is your first time planting I recommend you hold a ruler in the soil so you get a feel for how shallow ¼, or ½ of an inch actually is! The most common mistake to inhibit germination with new seeders is to seed plants too deep.
(the picture to the left is of actual 'dibbles' that I found on americangardenhistory.blogspot.com. Really cool, but I do just fine without buying additional tools. You can dibble your whole tray at once if you like. Just Google 'dibble'. That sounds ridiculous...)
First, carefully DROP one to four seeds into each cell. The number of seeds you drop into each cell is going to depend on the germination rate, and the date of the seeds. (This information should be printed on the outside of your seed packet). The end result is to have one plant in each cell, but the germination rate is rarely going to be 100%. In general two to three seeds per cell should be plenty. You will ‘thin’ the extra seeds that germinate later. (The one exception to the 2-3 seeds per cell rule is scallions and bunching onions. I seed at least 5 seeds per cell for those two crops because they are so small and you want them growing close together in maturity).
Second, COVER your seeds up with a little bit of extra potting soil you saved. Make sure the surface level of the soil is level with the top rim of your seed tray, and that the individual plastic cell walls are cleanly visible from a birds eye view. This will keep a disease from spreading between cells if one cell comes down with a plant disease.
4.) Label and Record
Before you forget where you planted what when, take a popsicle stick, or buy a labeling stick at your local nursery and write down the crop variety, and date you planted you seeds. Place them in the dirt in your seed tray. I also find it useful to record what you have done in a spreadsheet. This is essential for farmers who have 40 different crops that need to be started in the green house, transplanted, or direct seeded at different times.
This may be the simplest, yet most important part of this entire process in terms of guaranteeing the successful growth of your future plants. Water with a gentle, even watering can, or gentle setting on a hose sprayer attachment so that you do not expose the seeds when you water, or wash the seeds away. If you do not have access to a hose with a gentle setting, or a suitable watering can, I recommend you water from the bottom with small seeds such as onions and brassica seeds. To do this, fill up a brownie tray, utility sink, or bath tub with enough water to come just below the top of your seed tray. (For my 2” deep 128-tray I fill a sink just under 2 inches with water). Then carefully lay your seed tray in the water and wait until the top of your soil saturates with water from the bottom. Remove from water and let drain over a screen or rack. After about an hour when most of the water has drained, transfer to the your green house or sunny window.
Water once a day, or once every other day during the first few weeks. It is important in the first week, during the time of seed germination, that the soil remain damp at all times. If your seed starts to sprout, and then the soil dries out, that fragile seed sprout may die instantly without any root system yet to keep it alive.
WARNING: Do not overwater. Over-watering is caused not by saturating the soil during one watering session, but from watering too frequently. If I water my seed tray twice a day it will most likely develop mold, and the seeds will rot.
TIP: Keep seed tray on screen or rack at all times so that air can enter through the bottom of the tray, and so that excess water can drain. Root growth is greater when trays sit on a something that allows air and water to flow freely.
TIP: Try to water in the morning when the temperature and light are greater, making the transpiration rate greater, thereby decreasing your chance of mold, rot, disease or fungi growth.
Depending on the type of seeds you planted, how deep you planted your seeds, and the temperature of the soil, your seeds should emerge within 4 to 14 days. Technically the soil doesn’t need to be in a sunny place until plants emerge, but because they do soak up some sunlight when they are just below the soil surface, I like to keep them in sun at all times in anticipation of sprouting.
I will keep you updated as to what I plant when! There is a couple week range on either end of the suggested planting times, so don’t worry if you can’t plant on the recommended days. And remember, as one of my teachers always said, “Plants are professional plants. They WANT to live. So don’t worry about them too much.”