When i buy a seed package at the local gardening store it usually has the following information on the back (this is an example):
- Can sow from march-may
- Flowers from may-june
- Harvest starts in june-august
- Days until maturity 85-90 days
- Sun exposure full sun
I assume that for each different region they make a different sow plan. The above may work for buyers living in the netherlands, but i take it that the sow instructions have completely different months and perhaps even a different maturity day indication when the same seeds are sold in australia for example.
My question is: On what data do the vendors base their instructions on the back of the package? Is it the USDA zone of a specific region? Or do they base it on the average monthly temperatures of a region? Also, I don't understand how they come up with the 'days until maturity' estimate. Some months have allot lower temperature averages then others so it cant be the same number or the same range like 85-90 days for every month. For instance, i grew some field lettuce once, and on the package it said it would take 2 months or so to grow, but i decided to grow it from autumn through winter. The lettuce grew fine but it took an extra month i believe for it to reach maturity.
So i'm really curious how the vendors determine when a certain region can start growing a certain crop.