Here in Manitoba, we’re 6-weeks away from our last frost risk, which means it is time to start up the greenhouse if we want some of those frost-tender favorites like tomatoes and peppers in our garden this year.

For the past 6 years, I’ve been experimenting with various approaches to starting seedlings. Seed-starting trays from a garden center are invariably cheaply made plastic which is both relatively expensive and unlikely to last more than a couple of seasons. Nurseries have slightly more robust trays which can be found used, but while I liked having the large, sturdier trays—especially when moving/hardening off plants—these trays, too, were cracked and on their way to the local recycler after several seasons.

I began making my own ‘single-use pots’ out of recycled cardboard, which was nice in a way, since I could size them however I liked—however the cardboard tended to promote mold growth, and the pots themselves required more effort to construct than I would have liked. There had to be a better solution!

Last year, I hit upon the idea of re-using 4-litre plastic milk-jugs as pots.  I simply cut the jug in half and punched a few holes in the bottom.  One milk-jug pot could hold 9 decent-sized tomato or pepper plants.  I planted all one variety per pot and used permanent marker to write right onto the milk-jug material, which precluded me having to use separate labels.

Another ‘innovation’ was skipping over the re-potting step that I had undertaken for so many years.  Instead, I only filled my milk-jug pots HALF FULL when planting seeds—then when seedlings were tall enough, I simply ‘topped up’ the pots—removing any leaves that would end up below the soil surface. This worked like a charm, and turned what HAD been a 2-night transplanting project into something I could easily accomplish in 20 minutes! (this approach works especially well with tomatoes, whose stems readily root when buried more deeply)

By this time, my ‘recycling radar’ was fully engaged in the search for pot-candidates.  I realized one day that all of the food-grade BAGS—coffee, frozen berries, etc.—would make excellent bags if they were hole-punched for drainage.  Advantages:

• They are free
• They are DEEP for tap-rooted plants like Goji Berry
• They store flat, taking up almost no room
• They can be easily ‘cut off’ the transplant for minimal disturbance of the root mass

I made a few wooden trays which could hold my homemade pots—lining them with construction poly to make them waterproof.  This enabled “bottom-watering”—which I find is a huge time-saver.  Rather than daintily misting my baby plants every day, I just glug a healthy amount of water into the waterproof trays and let the capillary action of the planting medium draw the moisture up into the root zone.  This approach not only DRAMATICALLY speeds up the process of watering, but also mitigates fungal problems which can be caused by top-watering, when the leaves and soil-surface is kept too wet. (On a related note, a dusting of cinnamon works like MAGIC if you do end up with ‘damping off’ or other molds/fungal problems)

I sized my trays so they would ALSO fit on my living room window-sill, which enables me to start plants which take a little longer (like my sweet potato slips, for example) in the living room, well before ‘starting up’ the greenhouse.  Once I begin heating the greenhouse in mid-April, I simply relocate these plants onto my grow-shelves.

I would conservatively estimate that I am now spending 25% of the time I USED to starting plants in the greenhouse, while spending less money, recycling some of my own household plastic waste, and getting a better result.

If you’ve discovered some of your OWN greenhouse ‘shortcuts’—please post them in the comments, below!

-Tim