Cross Pollination Of Heirloom Tomatoes

I’ve done a little homework since Warren ask me if I worried about my heirlooms cross pollinating. I feel a whole lot better about the situation too.

First off-if you’re not planning on saving your seeds to replant-you don’t even need to read the rest of this post. Just continue to buy heirloom plants each year-and feel totally safe planting them as close to each other as you want too.

If you do plan on saving your seeds from year to year-these are the questions you need to ask yourself:

  • is the heirloom a treasured family variety passed down for the last 100 years?
  • do you think the variety is very rare and only exists in a handful of gardeners?
  • do you plan to sell the seeds?
  • would you only be satisfied with an exact carbon copy of the heirloom tomato?
  • how devastated would you be if cross pollination did occur?

I asked Keith Wood, my County Extension Officer, for his advice on the matter-this is what he said:

“If you let the seeds ferment in water a few days it will protect against bacterial canker.  It also dissolves the gelatinous coat which contain germination-inhibiting substances.  Tomatoes are self pollinating. The probability of tomatoes cross pollinating is about 2%.  If you want to be sure of them not cross pollinating, plant them at least 10 feet apart.”

Next I asked the nice folks at Appalachian Seeds what they thought about the issue-this is what they said:

“So the news is that tomatoes are self pollinating with a minimum of cross pollination occurring…usually the wandering bumble bee. They definitely can cross pollinate though. To be sure that this doesn’t happen, folks usually isolate different varieties from one another. The isolation distance varies from 10′ to 1/4 mile depending on who you listen to. We isolate by 15′ and have virtually no crossing. To be absolutely sure you could bag the blossoms (making sure that they pollinate themselves by tapping, jiggling or whatever…to make sure the pollen falls from the anther to the stigma of the flower) Try the seeds you saved next year and see what you get. You know even if they cross you might get something wonderful!”

I also checked out links a few of you sent me (thank you!!). Most of the informational sites stated cross pollination can happen-most agreed it happened between 2 and 5% of the time. Some sites suggested you should plant different varieties at least 1/4 a mile apart-others said 10 feet would be sufficient. While other sites seemed to think the only way to get pure seed was to bag blossoms to ensure cross pollination couldn’t happen. At least one site said-the large heirlooms are more likely to cross-than smaller tomatoes.


How I feel about the issue as it relates to me:

  • I’m certainly not growing heirlooms that are rare-and while I do want the same tomatoes I grew this year-as long as my future tomatoes tasted good and produced good-I don’t think I’d be too sad if they were a little different.
  • I might be able to plant a few varieties 10 feet apart-but no farther-and even that would take some extra planning.
  • I could narrow my varieties to just 2 but I don’t want to do that-yet I’m not willing to give up starting my own seeds either. Since I saved seed before I knew about the cross pollination issue-I’m just going to go for it and see what happens. I will attempt to separate my plants next year to the extent that I can-and I do hope they all stay true to the variety I saved them from.

JD left me an encouraging comment about the issue on Facebook-he said I should look at it like this-in a few years I may be growing Tippers Toms- a brand new heirloom variety of my very own.

Hope you found the information I gathered helpful.



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  • Reply
    Brenda Kay Ledford
    September 17, 2010 at 2:29 pm

    Thanks for doing research on heirloom tomatoes. I’m so glad to learn this information. We sure would be sad to lose our family seeds. Thanks for the work and time you spent providing this information to us. This makes me feel much better about our garden.

  • Reply
    September 17, 2010 at 10:57 am

    Thank you for doing this research, Tipper! Now I won’t worry about the cross-pollination–which was something I hadn’t thought of until you posted about it, LOL! I agree that as long as the tomatoes produce and taste good, it’s nothing to worry about. And at a 5% rate, most should stay ‘true’ anyway, I guess.

  • Reply
    September 17, 2010 at 4:04 am

    Thanks for the really informative post!

  • Reply
    September 16, 2010 at 10:02 pm

    I did.
    And thank you!
    I’m glad to see I’m not the only one with homework. tee hee

  • Reply
    Vicki Lane
    September 16, 2010 at 4:57 pm

    Thanks for all the interesting information!

  • Reply
    September 16, 2010 at 2:30 pm

    Always enjoy the Blind Pig and the
    Acorn blogs. And those tomatoes you grow look great. Has the deer
    hunter got foundered on ’em yet? He told me that was his most favorite thing in the whole world
    to eat. Next year I want to be sure to plant the German Pink, and
    yellow pear tomatoes so save some
    seed for me if you can. My Rutger
    tomatoes were plentiful but kinda
    small and they tasted good…Ken

  • Reply
    September 16, 2010 at 10:54 am

    Stacey-I’m just learning too. But I think-if they aren’t heirlooms-the seeds will produce but they will revert back to one of their parents that were put together to form the hybrid. In tomatoes-that usually means tommy toes. Hopefully some other gardners will chime in on the subject.
    Blind Pig The Acorn
    Music, Giveaways, Mountain Folk
    All at

  • Reply
    B. Ruth
    September 16, 2010 at 9:15 am

    Tipper wonderful post and very interesting….
    The only seeds we saved were a few pepper seeds….
    Our garden was the “pits” maybe next year…(illness)
    We grow daylilies and iris and have attemped to cross a few..but this business of helping Mother Nature can get very, very involved!….It makes me admire her work even more…
    Just think what we have to go thru to try to make a different flower, tree, or fruit and she does it without a hitch! LOL
    I have yet to see her soak her little seeds in milk (like I do okra) or nick her morning glories seed with a file..(like I do) or tie little nylon net bags over iris or daylily pods to protect the seed (like I have done)LOL. Law, we’ve had the most beautiful and abundant morning glories, no time to “milk the okra”, they sprouted and I swear there was a different daylily and iris that I didn’t remember buying or planting bloomed in my garden this year…and she did it all by herself without a bit of help from me…LOL
    Thanks for your research Tipper, we love your website…

  • Reply
    Granny Sue
    September 16, 2010 at 8:51 am

    I have wondered about the same issue, Tipper. I’ve only saved seeds a few times so it hasn’t been an issue for me. However, it does make me wonder when I buy tomato seeds, just how care were the growers? I plan to save seeds in the future, so I will need to figure out how to do it and give the 10′ spacing. That will be tricky. Thanks for the information. It’s very helpful.

  • Reply
    September 16, 2010 at 8:43 am

    You are always a wonderful wealth of information, Tipper. Thanks!

  • Reply
    September 16, 2010 at 8:40 am

    Excellent report! Sounds like it’s nearly a non-issue for most people. I remember my grandpa hand pollinating tomatoes when I was a kid…I wonder if he was trying to cross them or keep them uncrossed? Interesting…

  • Reply
    September 16, 2010 at 8:18 am

    All my tomatoes came from the nursery but a few plants produced wonderfuly & I am going to save some seeds from them. I have no idea if they are heirloom or not. I’ve heard that some plants are altered so that they will not reproduce and I’m wondering what the chances are that my seeds will.They don’t have to be heirloom to reproduce, right? Can any gardeners comment on this?

  • Reply
    September 16, 2010 at 7:29 am

    Although I’ve not had a garden in awhile, do like to read about them. It never hurts to learn all you can and I do enjoy reading what you have to say.

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