Concentrated Planting

(or, how to produce up to 2000 healthy tomato (or pepper, or eggplant...) seedlings in a 1' X 2' space)

Several years ago, when I decided to try my hand at selling heirloom tomato seedlings at a local farmer's market, the issue of finding enough room to produce sufficient plants surfaced.  Most people use seed starting methods that involve planting of only a few seeds of a particular variety per space - be it Jiffy pot, cell or pot.  I noticed in previous years how tough tomato, pepper and seedlings seemed to be, taking all sorts of apparent punishment - overcrowding, manhandling of the seedlings, root damage - yet there always seemed to be a way to end up with healthy seedlings.  I decided to undertake a new concentrated planting technique that has made the production of thousands of transplants a reality.  I've been using this method for 8 years, and it still amazes me that you can produce literally thousands of seedlings in the space of a small table top.  Here is how I do it.

The key ingredients to this are a good soilless mix, an appropriate seed starting container, very warm water, some stick on dots and a waterproof pen, some Saran wrap, a table in front of a sunny, south facing window, and a couple of heat mats (probably not essential because I start this in a room in my house, therefore warm temperatures in the late winter is not an issue) - and whatever seeds you want to plant.  I typically use one of the MetroMix products - 360 is my favorite, but there are lots of similar products that can be purchased.  The seed starting containers I use are rigid plastic 50 cell flats purchased on line from Johnny's Selected Seeds.  They are called Plug Flats - and cost around $10.00 for a case of 5 - it is item number 9498.  The cells are 2 inches square, so the entire flat is a bit less than one foot by a bit less than two feet. 

I put dots on the four corner cells - numbering them 1, 10, 41 and 50 - reference points for the varieties I plant.  Careful record keeping is necessary to ensure you know which varieties are in which cells.  The dry soilless mix is scooped into the flat; I fill the cells to within about 1/4 inch of the top, ensuring that there are no sticks or big lumps on the surface and that the levels of mix are uniform.  I then water each cell with warm water (I use a small watering can with a small diameter spout), until just a bit of water leaks out the bottom of the cells.  Prior to seeding, this is what the prepared flat looks like. Here is another view. The surface of the cells is then gently firmed with my index finger to give a smooth surface for the seed.  I then sprinkle up to 40 seeds onto the surface of each cell, being careful not to let seeds of a particular variety jump in to another cell.  Here is an example of planting pepper seeds – and a close up of one cell is here. Once all cells are planted, I mist the surface of the seed lightly with water from a spray bottle.  I then lightly cover each cell with dry mix - covering the seeds no more than 1/16 to 1/8 inch.  After all seeds are covered, I again mist the surface with water to moisten.  A strip of Saran Wrap, enough to cover the entire flat, is placed loosely on the top of the flat - the flat is then put on a table, on a heat mat, in front of a south facing window.  Here are some flats in the process of germinating.

After about 4-5 days, seedlings start to emerge - once the cotyledon leaves open on about half of the cells, I remove the Saran Wrap - the flat stays in front of the window on the heat mats until the majority of seeds have germinated.  If the cells even begin to dry out, I mist the surface with the spray bottle.  Once the seedlings are a bit taller, I gently water the cells with the watering can.  When the seedlings really start to stretch for the sun, and are about 1.5-2 inches tall, they go into my cool garage under fluorescent shop lights, lowered by chains to ensure that the light is within an inch of the growing point of the plants.  When it starts to get reasonably warm outside, I ease the seedling flats into the sun, increasing from an hour or so on the first day to half day sun after a week or so.  Here are some flats under grow lights in my garage – and a close up of a few cells is here.

Once true leaves form and the seedlings are about 2-3 inches tall, it is easy to pop out the cell of seedlings (gently squeeze the bottom plastic part as you tug on the bunch of seedlings from above, pulling them up and out).  It is easiest to separate the seedlings if the growing medium is a bit dry.  Grab the root mass and gently pull it apart - the seedlings can be pulled apart, and though there is always some root loss, the seedlings will recover quickly.  Once all seedlings are separated, transplant them into individual containers - I use 4 inch square plastic pots filled with dry soilless mix.  I poke a deep hole into each pot, then ease the seedling in with my thumb as deep as it will go - shake the pot a bit to move the mix around the base of the plant, then water deeply with warm water until it comes out the bottom a bit.  Typically, each cell of seedlings will have some that are larger, and some that are quite small - those that germinated last.  I like to use one 4 inch pot and poke several holes and cluster the very small ones in that single pot - in a week or so they will have caught up and will be ready for their own pot.  The newly transplanted and labeled seedlings should have a day in the shade to recover a bit, then can be eased back into the sun.

That's all there is to it - using 4 flats this year and lots of Soilless mix, along with many hours of transplanting, I now have about 4000 seedlings happily growing in my driveway.  In general, peppers have firmer stems and it just feels a bit safer separating and transplanting them.  Eggplant are intermediate between peppers and tomatoes.  Using the above method, I typically get a greater than 95% survival rate from the crowded seedlings to the single 4 inch pot stage.