Why do you think you have to discard the plants?

Why do you think they are unsafe for use?

Good question. I wish I knew. Because they were sprayed with pesticides by the growers and chemical fertilizers were used would be my guess. I would ask the horticultural agent at your local agricultural center. Let us know what they think. I am trying to go all natural myself. I don't spray, but I don't know how to garden using organic fertilizers.

This is a tough question to answer, because systemic pesticides take longer to be metabolized, and also because systemic pesticides are taken up from the soil, and it could take several months for this process to be completed. If you knew that the pesticide of concern was sprayed onto the surface of the leaves, then you could put the plants out in the weather for several months, and be reasonably certain that the residuals had been rinsed off by rainfall. However, if a pesticide was applied to the soil, and it is being slowly absorbed by the roots, and then moving up into the leaves, the time frame is longer. In that case, you would have to know exactly what was applied to the soil, when it was applied, and how much.

There is reason to be concerned (see below), but the pesticides will break down over time. The effective 'half-life' of many pesticides are measured in days, rather than weeks or months. Though this will depend on factors such as temperature, humidity, sunlight exposure, etc. There are some pesticides that will last longer, but everything breaks down eventually. If it were me, plant them, leave 'em alone for 3 months and then forget any worries.

Quote from link below:

"As bee populations plummet in the US and Europe, people have been urged to plant bee-friendly gardens to create safe havens for the endangered little pollinators. But a first-of-its-kind study released today found that flowers and vegetables bought from American nurseries are contaminated with the same agricultural pesticides linked to the mass die-off of honey bees that pollinate a third of the food on your dinner plate.
+ An analysis of supposedly bee-safe backyard plants like daisies, tomatoes and salvia purchased from Home Depot, LoweâÂÂs and other big-box US retailers discovered they were contaminated with neonicotinoids. That class of pesticide has been implicated in Colony Collapse Disorder, an affliction that has wiped out 10 million beehives over the past six years in the US. In April, European regulators banned the pesticide manufactured by Bayer CropScience and Syngenta for two years in response to crashing bee populations in France and elsewhere.
+ âÂÂGardeners may be unwittingly purchasing toxic seedlings and plants attractive to pollinators for bee-friendly gardens, only to poison them in the process,â states the report from the Pesticide Research Institute and the environmental group Friends of the Earth. âÂÂUnfortunately, pollinator friendly nursery plants sold to unsuspecting consumers carry neither a list of pesticides used, nor do they carry a warning that these pesticides could harm pollinators.âÂÂ

Here is a link that might be useful: http://qz.com/115135/your-garden-may-be-a-pesticide-tainted-death-trap-for-bees/

Thanks so much for all of your responses! Ericwi: I hadn't even considered changing out the soil, but it seems entirely logical that it's contaminated with pesticides and should be changed out immediately - especially in light of the post by yukkuri_kame. I appreciate the enlightening link. The thought that I've been inadvertently killing off the bees I've been working all summer to save (by having turned my lawn into clover, etc.) makes me sad - and angry. When one considers just how vast this problem is across the nation and the world AND how much there is to learn about ways to combat it, one wonders how much one little old lady can really do to make a difference - even in her own back yard. :( That said, I will do my best. I've spent the summer turning my home into a green zone (cleaning products, etc.) and learning about homeopathic remedies. I haven't used pesticides on my own property for several years, so the tinctures and infusions I've made thus far should be relatively safe. Hopefully, by next summer, the bee balm and rosemary will be safe, too. I've learned a valuable lesson here. Thanks, everyone!

Plant material treated with chlorpyralid type herbicide is known to require 24 months of composting before it breaks down and becomes harmless. However, I don't think that your plants have been treated with this herbicide, because it would have killed them. I mention this only because it is the most persistent pesticide that I know of, so it gives an idea of how long it can take natural processes to decompose toxic chemicals.