I am unable to grow fresh herbs living in an apartment in a city. So I order my herbs through wholesale retailers. It's now May after a long/cold winter. Other than imported herbs from warm climates, does that mean that the stock of herbs being sold by wholesale retailers is whatever is left over from last years crops and thus the herbs I will receive are old? Or would this be true of only wildcrafted herbs? How can I guarantee freshness and potency of herbs from online wholesalers?
I also noticed certain herbs are out of stock by wholesale resellers. Could it be because the plant was over harvested or it's just a popular herb and they can't keep it in stock? Pleursy root. I recall it was out of stock last year. Parsley root and others.
Honestly, the best thing to do is to ask your supplier. What you're asking could absolutely be true but there are other variables as well. Some suppliers get their herbs from places with longer growing seasons or they might have several growers in different areas. It's also important to note that if an herb is dried, cured and stored properly, it's not an issue being carried over through the winter months. I personally harvest/forage some of the herbs that I use in my skin care business but obviously, I can't harvest all year; so I cure my herbs instead of drying them (there's a bit of a difference) and I store them in a light tight closet. Doing this, they retain a great deal of their potency so I imagine that a reputable herb seller is going to go to great lengths to make sure their herbs are high quality.
The first thing I would do is to ask the supplier. Most are pretty forthcoming with their information. If they're not, go somewhere else. Then you can order small quantities from a few suppliers and see which ones you prefer. You're still looking for a bit of a scent in most herbs. Green herbs should still be pretty green. If you get stinging nettle and it's brown, it's old. The less broken down a plant is, the longer it will stay potent; so look for suppliers who don't pulverize the herbs.
As far as the supplier being out of stock - it doesn't mean that they're over harvested. It could be exactly what you're asking; perhaps they've run out and they're not into their growing/harvesting season. If they're getting the herbs from an herb farm, they only plant so much. If the herb is wildcrafted, there are sustainability practices in place that keep us from harvesting too much of the plant (we need to leave enough in place so that the plants come back the next season).
So there are a lot of variables, even for each individual plant. Hope that helps