logo logo

Tomato tar – yellow on the skin, green on your towels

Tomato tar is a tacky yellow powder that gets onto your skin when you handle tomato plants, and causes yellowish green stains on fabric afterwards. You can solve the problem by washing your hands with a little vinegar before you go near the soap – but where’s the fun in that?

yellow green stain on towel, imageIt’s bound to happen at least once every year: a cry goes up ‘who’s got these green stains all over this clean towel?’ Everyone denies it, and you keep a very low profile because you were handling tomatoes. You don’t remember your hands being that dirty when you pinched out the sideshoots – a quick spot of water and they looked fine. Could they really have been that dirty?

The culprit is a substance that commercial growers call ‘tomato tar’. It’s a powdery deposit that is all over the plant – leaves, stem, and fruit. On your skin (which is slightly acid) it is a faint yellow, inoffensive enough to be all but invisible on the skin of most gardeners unless you get really covered in the stuff. If you realise it’s on you and try to wash it off with soap (which is usually strongly alkaline) it turns a really intense green, so you scrub… and scrub… and scrub. You can wash and rinse three or four times and still see it in the rinse water.

The real¬†trouble is when there’s just a little on your skin, and you don’t realise it’s there at all. You get back to the house and give your hands a quick rinse under the tap. So far, so good – water’s pH neutral, so you don’t see the stain. Then you wipe your hands on a towel and head off to another task, leaving the tomato tar you just left on the towel to react slowly with the alkaline detergent residues on the cloth. Half an hour later, your negligence is revealed.

The culprits here are trichomes, tiny appendages on the surface of the plant that look like miniature water towers (you can see a charming microscopy photograph at the Solanum Trichome Project website). These contain a bunch of chemicals including essential oils that give your skin that lovely fresh tomato smell, but also compounds called acylsugars which form the basis of a fast-drying glue. This helps defend the plant from microscopic predators, stopping them wandering too far by giving them the microscopic equivalent of concrete boots. Acylsugars aren’t soluble in water, which is why they’re so hard to wash off.

The solution to tomato tar is to get some acid onto your hands before you go anywhere near the towel, which dissolves the acylsugars. Commercial tomato growers squish an unsaleable green tomato in their hands and rub the gunk well in, but if you’re already inside (or don’t wish to sacrifice a precious tomato) then a couple of tablespoons of vinegar will do the job just as well. Wash your hands with the vinegar first, then rinse it off before using soap. Hey presto, no green colour – and no towel-based guilt later.

If you enjoyed this post, please leave a comment or subscribe to the RSS feed to have future articles delivered to your feed reader.

16 Responses to “Tomato tar – yellow on the skin, green on your towels”

  1. Alien One says:

    Thanks for the info, this is the only place I’ve found so far that deals with stains from tomato leaves. I didn’t even know the substance was called tar. From now on it’ll be vinegar wash but meanwhile I have towels with stains! I’ll try soaking them in vinegar before laundering but it might be too late. Any tips on removing existing stains?

    • Andy McKee says:

      That’s what I was looking for when I started out with this article, but sadly there doesn’t seem to be a good way of getting the stains out once they’ve “developed” – the key is getting the stuff off your hands before they hit the towel, and not wearing nice new clothes while gardening.

      Answers suggested in various tomes include pre-soaking stained items with baking soda, pre-soaking with vinegar, and pre-treating with an enzymatic cleaner like Vanish. The dedicated FIMP team tried all of them, and weren’t impressed with any. It looks like burning the evidence before your partner sees it is the best option.

  2. Catherine says:

    Wondered why when I washed my hands that the towel turned green, Thanks….vinegar wash from now on :)

  3. Gary Park says:

    Thanks been looking for the answer to this for a while. Posted the question on Yahoo Answers and the only response I got (obviously from a very knowlegable botanist) was “…that I must have got some chlorophyll on my hands…”

    I particularly notice this when you lather you hands up with hard soapsuch as Imperial Leather or Dove. Lather goes very green after snipping off side-shoots. Must be a pH thing again as hard soaps will probably be a little alkali.

    Now I know to look for”tomato tar”.

    Cheers – Gary

  4. Julian swift says:

    My wife has just told me that her dad said the tomato growers trick was to wash their hands with pee (urine) . It would save all that business of going home to find the vinegar!

  5. Jack McNeary says:

    I came in this morning from working at the homeless shelter garden where I messed with tomatoes all morning long… not the first time.

    I decided to see what google had to say about this and got to your site. My wife prides herself on knowing and dealing with stains. I told her I had and idea that I thought she would really like. She did.

    My hands were almost black with tomato tar. Vinegar worked great.



  6. Don says:

    Had the same problem with towels as everyone else, my wife soaked the towel in hand hot Ariel diabolical (biological) left overnight the water was green next morning and the towel dried OK. Hope that helps.

  7. Norma says:

    I squirt Dawn dish detergent into one hand and then spray hands w/Clorox Cleaner. That stuff turns the color of iodine. Sometimes it is so thick I have to repeat the process three or four times to get a clear rinse. This is how I clean all the garden tools too. Also, I have been fighting w/blight for most of the season. I have been very tempted to spray my tomato plants w/a diluted bleach/Dawn solution.

  8. George Mansell says:

    With regard to staining towels after handling tomatoes, I discovered that whilst using the “modern” anti bacterial hand wash pump soap dispensers, the end result was useless and my wife would berate me no matter how thoroughly I washed my hands that appeared to be clean. I discovered to my amazement that if I used the old fashioned hard green bar soap such as “Fairy” the yellow stain would just fall off in the lather. Modern advances? I think not. The problem has dissapearred!

  9. KaylaWildflower says:

    I came in today looking so yellow it looks like I had jaundice! But I didn’t have any time to clean up before going out! Glad I read this. I just did one arm. One arm clean, one-arm yellow. Wish I could send you a pic!

  10. Val H says:

    Hi there need a bit of help, I was at a garden centre yesterday and I rubbed against tomatoe plants and got the yellow tar on me . I sat in my car and got it on the panel of my door , any ideas on how to remove that

Leave a Reply

Your email address will not be published. Required fields are marked *