My garden produces a lot of herbs, like mint, sage, rosemary, lavender, etc. I use to wash them, after gathering, and dry them in the shadow to preserve (as much as possible) their scent, color and beneficial qualities.

Once dried, sometimes it happens that tiny spiders appear in my (sealed) jar. I suspect they were present among the dried leaves, maybe in form of eggs when I filled the jars. I don't want it to happen again, either with spiders, or insect, fungus, bacteria, etc.

So, is there a way to ensure that any kind of unwanted life is destroyed, before storing dried herbs? The only idea that came to my mind is to put dried herbs in the microwave oven for a while. Could it be a good idea?


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    I would be concerned about using the microwave, and how it might impact the scent of the leaves. But I am not sure.
    – ychirea1
    Sep 7, 2015 at 23:40
  • Just for information, I applied the microwave treatment to my lavender: I put a glass (about 20 cl) of dried flowers in the oven at 850 W for 20 seconds, just before putting the flowers in small bags (1 glass = 2 bags). Of course, some scent went away (the whole house, the courtyard and the countryside all around were smelling of lavender!), but still the bags preserved a still very intense flavor. Don't know if this treatment was effective against insects or fungus. Sep 16, 2015 at 6:14
  • Again about the micro-wave: before drying them, I chopped some chilly peppers and put them in two cups. I put one cup in the micro-wave oven for about 20 seconds at 850W. Then I left both cups on the same table. After 3 days, the micro-wave untreated cup started to show development of fungus that I cannot notice in the other cup. So, it looks like the micro-wave treatment helped to prevent fungus development. Again I cannot say if it effectively killed the mycelium or dried the chilly just enough to delay the fungus development. Sep 17, 2015 at 6:10
  • I don't believe that heat is applied uniformly from a microwave. So, there might be spots it misses and spots it over-cooks. Mar 12, 2016 at 7:49
  • If you are horrified about eating spiders DON'T TRY TO KILL THEM in a microwave. Allow them to live and LEAVE! Drying in a microwave oven is not good...drying takes time to prevent damage to the organics, serious ventilation and darkness. If there were any spiders or insects that were alive they would all be able to go about their duties elsewhere. Spiders are so cool, and to kill baby spiders is like killing kittens...moisture WILL cause favorable conditions for fungus...if one doesn't use enough ventilation to blow off the moisture as it comes out of the dying plant material = fungus.
    – stormy
    Mar 13, 2016 at 22:53

6 Answers 6


Carbon dioxide is heavier than air, and displaces oxygen. You can make carbon dioxide by adding vinegar to baking soda. 84 grams of baking soda plus 1.2 liters of (5%) vinegar will produce 22.4 liters of CO2 which you can pipe into your bottles before sealing. Insects and spiders can go a long time without air, but not forever. The CO2 atmosphere will eventually kill them, without harming your herbs.

  • Inventive but assumes bottles with air tight seals and plumbing to go with.
    – kevinskio
    Sep 8, 2015 at 9:51
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    Seals don't need to be hermetic or anything. The gas is heavy enough that it'll stick arouns a week or more with just a peanut butter jar style plastic lid. Plumbing is a bit tricky, but if you have access to dry ice. it'll turn in to gas too, and you can just drop it in the bottom of your jar on a non-humid day. It takes about 2 grams dry ice to produce a liter of gas. An excess is always nice when doing stuff like this so 4 gram per quart/liter is about right. Oh yes, Do Not seal the jars until the dry ice has sublimed. That can cause explosions. Sep 8, 2015 at 11:07

One possible solution is to soak your herbs in salt water for 10 minutes before drying. Any instects or eggs on the herbs will be washed off/drowned and you will not have the problem of having little stowaways in your herb bottles. You may lose a little of the aroma from the herbs, but this should not be a significant difference.


I dry my basil in the fridge. First I wash it after cutting the stems, dab dry it as much as I can, and then remove the leaves. I then loosely wrap the leaves up in tissues, and put it in one of the closed small compartments in the fridge. The fridge is actually designed to remove any moist air inside.

Over a few weeks the basil dehydrates without loss of the oils, and turns quite brittle, and brown. I would expect any eggs to dehydrate as well over this period. I then take the dehydrated leaves and store them in an air tight glass container. I guess in the unlikely event there were any eggs that survived the dehydration process they would now hatch at room temperature but you would see them in the jar.

You could add a food grade desiccant bag to keep the moisture levels down. They normally change color if the moisture rises.

This method can be used with most herbs.


After washing my herbs, I add a small amount to vinegar to a fresh bowl of water and let my herbs sit in the water for a few minutes. Often, I have seen little spiders scurrying out of the bowl, even though I had washed several times.

As for the fungus, I stored some of my oregano in a plastic bag, after drying, and several weeks later, it had fungus growing in the bag. I had thought about putting a small piece of a paper towel in the bag initially to absorb any moisture that my have been in the dried leaves.

  • The best thing I know is similar to using the vinegar; that is hydrogen peroxide 1 cup in 5 gallons of water. Otherwise, we eat insects all of the time whether organic or commercial. I try not to think about it. After all, Lobsters and shrimp are insects and we pay big bucks to eat them, grins.
    – stormy
    Mar 27, 2017 at 15:57

I'm not sure about spiders and insects on herbs, but if there are just eggs that might hatch later, you could always pickle your herbs or something (they shouldn't hatch after that). That should also help against pathogens. However, that doesn't answer the question (but just in case you didn't think about pickling them, I thought I'd say that).

Alternatively, as far as fungus goes, you could dry your herbs in brown paper bags. They wick moisture away very well from wet seeds, anyway, and this prevents them from molding where they otherwise would mold in a dark or dim area. I imagine the same thing could work with herbs. Keeping the moisture away should help to keep fungus away. I've never tried it, though.

You could try adding a substance to the herbs that keeps bugs away, although it may affect the taste or appearance of your herbs. Cinnamon and/or diatomaceous earth might work, but that doesn't sound ideal at all for herbs.


Really!? The best way to preserve herbs is to dry them like you said out of the sun and in a warm ceiling/attic? How long did you dry them, what time of year, the regular temperatures, how thick your bundles? To find spiders tells me that something was wrong or that you had a lot of other kinds of insects that needed to be taken care of by spiders...or that you had an egg laid by a spider and you've got baby spiders accidentally in those jars.

SPIDERS are GOOD guys. Make no mistake! You do not want to kill insects especially if you are a gardner!! If you kill everything then you have nothing with which to govern non-beneficial insects. And you won't be eating any herbs for sure. And you'll have to rely on pesticides forever. Not good.

This has never happened with my dried stuff...I am sure this is a total anomaly...but I'd let the little guys out and be glad my herbs were...'Organic' and not 'GMO'...if I ever get to come back in this life I want to be an entomologist. Insects are so very COOL. Period.

When you are drying stuff, there are ways to ensure you are not canning or putting away food that has a bit of moisture left or that you've got a spider egg entrenched. Please don't worry about insects, just moisture content. Never use any pesticide for edibles. Not necessary!! Trust me! And remember, SPIDERS you WANT!!

  • 6
    stormy. read the question again. Consider that the primary concern here seems to be "How do I dry my herbs without getting spiders in them?" not "How do I kill all spiders?" You yourself say "When you are drying stuff, there are ways to ensure you are not canning or putting away food that has a bit of moisture left or that you've got a spider egg entrenched." what are these ways? THAT is the question that needs to be answered here. Spiders are good and all, but I'd rather not have them in my food, and I'd wager THEY'D rather not be in my food.
    – GardenerJ
    Sep 7, 2015 at 1:20
  • @GardenerJ: yes, you got the point. I like to have insects and spiders in my garden, but not in my food (well... if it was only for me, I wouldn't care about some little, almost invisible spiders among the leaves of mint, but you know...). Sep 7, 2015 at 6:56
  • @stormy: my question is not bout destroying insects IN THE GARDEN, but IN THE KITCHEN/HOUSE after vegetables have been gathered and dried! Sep 7, 2015 at 6:58
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    Dang, you guys just make me work so hard...sigh. Ok, I have dried more flowers and herbs and vegetables than you will be able to in the rest of your lifetime. Sigh again. I HAVE NEVER EVER had a problem with spiders/insects in my dried crops. NEVER. Sweetie, you just got a healthy dose of baby spiders, TOTALLY RARE!! The only way you could prevent this unlikely event again would be to KILL ALL INSECTS and keep in a climate controlled and separate universe. How are you storing your...product? In jars? Vacuum packed? I guess I expect others to read between the lines, sorry!! Grins.
    – stormy
    Sep 8, 2015 at 19:50
  • (Baby spiders go away...) What about the mold, fungus? THAT is a moisture problem, primarily! Putting them in storage without being dried enough/correctly is the main culprit here...
    – stormy
    Sep 8, 2015 at 19:59

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