Square vs Circular Plugs Trays

Hi all,
New market gardener here looking for some sound product advice to cut through the marketing gimmicks.
Anybody have experience with both square and circular cells? For example, comparing these (I'm in Canada, so unlikely to order specifically these)
http://www.johnnyseeds.com/p-8133-plug-flats-72-cellsflat-pack-of-5.aspx
http://www.johnnyseeds.com/p-8092-pro-tray-cell-flats-72-cellsflat-pack-of-5.aspx

My two main concerns are:
1) Is one more or less likely to cause root bound?
2) Is getting the plugs out for transplanting harder in one or the other?

Any other suggestions and info is greatly appreciated.

Edit: there are also deep dish and octagonal and all sorts of other trays too which I am curious about.

Round vs. square:

A round pot will only hold about 78% as much soil as a square one the same size.
This gives roots a little less room to grow in, but if they do reach the edge, it is easier on them to make a gentle curve than the hard right angle they would encounter on a square pot.

For most seedlings in small pots, such as these, the standard nursery practice is to up-pot them at the same time that they develop their first set of true leaves. That practice should eliminate the root-bound situation.

Small square pots may be a little easier to get the plants out - a putty knife makes a handy tool for sliding the seedlings out of the container.

Octagonal pots, I guess would be about half way between round and square. I've never used them. Sounds more like a marketing ploy to me. I would assume that they are more fragile than the square ones.

Because of the gentle turns of a round pot, they will suffer less cracking than the square ones, which means that you can probably reuse them a few more times than the square ones.

Whatever size you use, just try to up-pot them before the plants get root bound. Stress on the roots at this stage of infancy will greatly effect the overall health/vigor of the mature plant. Pests attack the least healthy plants first. That is Mother Nature's way of culling. Survival of the fittest.

Per the cited literature, the round tray says "use with seedling trays". The square one says "use without a tray". I haven't priced them lately, but I bet the price of trays is similar to the price of the pots.

Are you intending to sell plants? If yes, you might consider less expensive "disposable" flats in 6 packs or 4 packs instead of reusable ones. I'd really like to train the people that I grow for to accept bare-root transplants. But I'm not there yet. Some are great about recycling pots.

For transplanting, I really really like cells that have a singe round hole in the bottom of the plug. Then I can stick a pencil into the hole and easily dislodge the rootball.

My view towards roots in pots is that everything grown in a pot is going to end up root-bound, so I don't worry about it.

The round trays suggested bottom watering. As a market farmer, those sorts of fiddly watering schemes don't work for me. I want to water once or twice a day, and walk away. I want the excess water to take care of itself and drain away. I don't want to have to monitor whether or not the water in a tray is drowning the plants. As far as I can tell, excess water kills more potted plants than too little watering.

Plants grown in square-ish pots with rounded corners.

I'm a bit biased (see below for the reason), but I prefer to just avoid plastic pots all together.
For my own personal use I prefer to make soil blocks. I have never taken the time to use the small ones and absolutely swear by the 2inch soil blocks.
There is something satisfying in making my own soil block blend too. I also feel like when I do use flats I make a mess and feel like I am wasting good seed starting mix.

When I am planting seeds that I intend to sell as seedlings or transplants, I prefer peat pots. I have since completely gotten away from peat and now use CowPots. I say I am a bit biased because I also sell these on my website listed below. I think the idea of limited transplant shock, and roots being bound is ideal. I also like telling my customers, "just rip off the bottom and plant!" It also negates the argument (if there is one) of square vs round.


Just my thoughts,
Jeremy Elwell
Elwell's Supplies-A Farmers' Market Supply Store
http://elwellsupplies.com/

I experimented with lots of different types of potting methods before settling on plastic pots. In my super arid climate, slowing down how quickly the pots dehydrate was the most important selection criteria for me.