I grew spearmint from seeds that came in a amazon hydroponic kit (i.e. who knows how authoritative the labeling was). It grew well, I transplanted it outside, it is a mint flavor but very weak.
I was at a nursery (well known and reputable) today and bought a pot of Spearmint. It is MUCH stronger, and looks very different. Almost so strong I wonder if it is Spearmint since my understanding it is not overly strong (e.g. compared to Peppermint).
And looking at the images compared to those online I remain even less sure. Would anyone care to opine?
Here are leaves of the seed origin plant:
Here are the same for the nursery plant:
Update 7/6 by request a clean cut on the stem vs what I originally posted. The seed plant is on the right top, the nursery plant on the bottom left. Both were taken from larger steps in the middle of the growth.
As to the growing conditions: the from-seed was germinated in October 2020, transplaned late in 2020, and so has been growing in a pot outside (S Florida) since. It grows in very long somewhat fragile stems, which wilt quickly with just brief dryness. A light touch yields no menthol, you have to crush it pretty hard to get a good odor. It has never flowered. It does best in bright sun (I had it in about 4 hours a day and it grew slowly, moved to 7 hours or so and it had a growth spurt).
The nursery plant is small, in a pot of about a pint and with stems up to about 5" in length. A light touch yields a strong mint odor immediately.
My mention of menthol levels was based on numerous postings listing Spearmint as 0.15% vs 40% for peppermint ([Example link no idea of accuracy])6
Additional update 7/6 whole plant view, from-seed on left, nursery on right. Note the dark (dying) sections of the from-seed are new, the landscaper cut off all irrigation in prep for the tropical storm and I didn't water for a couple days. It faded VERY quickly with much of the core (not tips) turning brown/black. The tips wilted but came back quickly with water.