Didn’t think I’d ever be doing sums in the greenhouse but it turns out there are some important ones to be done.

What is the optimum staging/bench configuration? floor space to move around in vs usable bench space.

What size pots/trays should be used for what purpose, and how many of them can said staging support?

If I have a heated bench, what is the optimum use of that resource? how many pots of germinating seeds vs pricked out seedling vs cuttings etc etc. This boils down to how much propagation activity do I have the capacity to undertake – how much can I start and still have the space to finish? This is a proper operational research problem.

The above will take some working out, but I already know that pot size and shape has a surprisingly large impact on propagation efficiency. I have typically reached for a full size seed tray for seed sowing, maybe a half tray or a large ish pot if I was feeling stingey or didn’t have one around. I was surprised to read recently* that a full size seed tray or flat is enough to handle upwards of 1000 seedlings up to the point of pricking out, more if they are teeny tiny ones.. That’s a huge amount! Way more than the typical garden user needs for a typical seed sowing. The large trays also use a large amount of compost, relatively speaking.  At the other end of scale are 7cm pots. These are big enough to handle 50-200 seedlings till pricking out, which covers a typical seed packet nicely, majority of them anyway. Much more of these fit on a bench than full-size seed trays, and they use way, way less compost.

Even better to use square pots. Square 7cm pots can be packed in more closely than 7cm diameter round pots. I knew this but was surprised to read that about 30% more square pots can be fitted in a given space than round ones. That’s a lot more seeds! Square pots also use less compost than round ones the same size. 15 square pots of this size fit into the space occupied by a single full-size seed tray. 15! I’ll be swapping out my circular pots. It’s hip to be square…

I’ll be back.
*my reference for the pot size info was Creative Propagation – A Grower’s Guide.