Heirloom tomatoes cross pollinating?

keeversgirl(9)June 18, 2009

Ok, so I am relatively new to heirloom tomatoes, but not gardening by far. I'm hoping you all can settle a debate for me. Is it possible for all tomatoes to cross pollinate each other? I know potato leafed, and double bloom beefsteaks can, but in my seed saving book it argues most other tomatoes bloom stolens are so far removed, there is virtually no possibility for them to trade pollen.

Anyone have any experience on this? I thank you in advance for your help. :)


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zeedman Zone 5 Wisconsin

"Is it possible for all tomatoes to cross pollinate each other? I know potato leafed, and double bloom beefsteaks can..."

...and currant tomatoes.

Just as with beans (which also self-pollinate effectively), there are those who say they will not cross, and those who say they can. I stand with the second group. While some can grow different varieties side-by-side without crossing, I can personally testify that is not true for everyone. When I began trading tomato seed, I received quite a bit of crossed seed, mostly for large-fruited varieties - so it can & does happen. Never had crosses with paste & smaller varieties received in trade, though. In my own saved seed, using a combination of distance + barrier crops, I have yet to see a cross.

Since some of the larger varieties I received (such as "Goldie") had rates of crossing close to 50%, I recommend at least some distance between larger varieties when saving seed, preferably with other flowering crops between.

IMO, the statement that "tomatoes don't cross" is not a rule, but a myth... one that has been responsible for the distribution of a great deal of polluted seed.

If you want some lively debate (and more information) post this question on the Tomato Forum.

    Bookmark   June 21, 2009 at 3:44AM
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Thank you very much! That might be a good idea :)

Have you ever tried blossom bagging? I am really curious to try this....I'd like to sell a few seeds locally for a little "play" money (even though I know I'll just buy MORE seeds), so I will def be experimenting with blossom bagging this year.

    Bookmark   June 21, 2009 at 12:14PM
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digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

Here is a link to the FAQ on the Tomatoes forum here that explains all about cross-pollination and how to bag flowers if you choose.

While I agree with zeedman and all his good info above, that it isn't a "rule" and that it is more possible on the larger fruited varieties, I have never found my crossing to exceed the usual amount of +/- 5%. In some 40+ years of growing 100's of plants and saving my seeds I have run across maybe 8 or 9 accidental crosses.

I think I am safe in saying that the majority of us who grow large numbers of open-pollinated plants and save our own seeds don't bag any blooms simply because of the work involved, the rate of crossing is so low, and because most blooms will have self-pollinated themselves before they even open.

Clearly there are always exceptions and in a small home garden where plants may be over-crowded, bagging the blooms can be very helpful. Especially so if the variety is a rare or unusual one or if you plan to trade seeds with others and want to insure purity.

Hope this helps.


Here is a link that might be useful: Cross-pollination FAQ

    Bookmark   June 21, 2009 at 1:35PM
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spiced_ham(z5 OH)

in 1965 the first short stigma varieties were developed. These were mostly put into modern hybrid breeding lines, but if you look closely, after several bees have bite-buzzed a tomato blossum to extract pollen the anthercone shrinks back from the damage exposing the stigma even on short stigma varieties.

I do not know where the myth that potato leafed varieties cross pollinate more than regular leaf varieties came from other than that the short stigma varieties are/were RL, but that still leaves a lot of RL varieties out there that are not ancestors of the short stigma breeding lines. It is just easier to tell that your PL plant has been cross pollinated because you can see it as soon as the true leaves develop. When you are growing red RL varieties you usualy can't tell if they have been cross pollinated because the visible traits are all dominant (no matter what you cross with a red RL plant you will get red RL offspring the next year --unless it crossed with a cherry, which is also dominant).

What is the rate of cross pollination? It depends on your area. I have a lot of bees, and in mid season I have about 20% of the seed from any one tomato crossed. This is an average of fruits showing from 0% to over 40% crossed seed, with the probability of crosses with like-leaved plants factored in (PL plants being crossed with other PL plants). My grow outs with a very small sample size indicate that a single blossom can get pollen from multiple other plants/varieties growing several feet away, so crowding/touching plants is not an issue.

Bagging is simple, go to the Walmart party/wedding/fru-fru section and get a 12 pack of 4.5"x6.5" drawstring sachets (I bought some last night for $5/pack), and place them over trusses of unopened buds. You might have to pinch off the first opened flower. I find it easier to turn the sachets inside out so that the protruding cuff doesn't get in the way so much. Once you see fruits form, tie a brightly colored string around the truss to mark it and then sterilize the bag before using again. I drop them in boiling water for a minute or two, some people run a hot steam iron over them. That will kill any remaining pollen from the last plant.

For peppers it is easier just to buy organza/tule netting at the Walmart fabric counter and bag entire branches or small plants.

    Bookmark   June 28, 2009 at 8:57AM
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zeedman Zone 5 Wisconsin

Dave, my own experience thus far has paralleled yours. Utilizing 20-30 feet of separation, with other flowering plants between, I have had very little crossing. However, the seeds I have obtained from several of the larger tomato growers in SSE have exhibited the rates of crossing mentioned by SpicedHam. I don't know the conditions under which the heavily-crossed seed was grown, I'll have to inquire the next time I encounter it.

I did learn that when starting tomato seedlings with seed from an unknown source, not to select for the largest plants. Because of "hybrid vigor", the larger plants are more likely to be crosses.

SpicedHam, nice tip about sterilizing the bags, if they will be re-used. When I blossom bag (which is seldom) I just use a piece of spun-polyester row cover, and dispose of it afterward. For the most part, I prefer the use of cages or tents if I need full isolation for seed saving. Pepper plants respond well to being fully covered. Tomatoes, on the other hand, can be disease-prone if grown under spun polyester. A more breathable cover, such as screen or the previously-mentioned tule, is best for tomatoes.

    Bookmark   June 28, 2009 at 6:43PM
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Might be a bit off-topic, but here are my questions related:

1. My garden is split among several tiny areas wherever I get sun in my wooded lot. I am growing Pink Brandywine tomatoes and have 5 plants behind the garage and 5 plants in front of garage. The closest neighboring tomato plants are about 75 ft away but it's a straight shot across a cul-du-sac. How much do I have to worry about a cross? Should I only collect seed from the plants behind the garage? Is 10 plants even enough to keep a decent gene pool going?

2. We loved the romas we grew last year but starting this year I'm trying to grow all heirloom plants. I thought the Brandywines would be easy to start with. For future years, is there an heirloom variety that's more meaty and less seedy (closer to roma)? Are romas strictly a hybrid tomato?

3. (I know this one's misplaced) Gotta sneak it in the tomato post cuz it's quick and easy :) Do I have to worry about radishes crossing with anything (other tubers, local weeds, radishes from that neighbor's garden)?

I'm really new to seed saving :)

    Bookmark   July 8, 2009 at 12:21AM
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zeedman Zone 5 Wisconsin

For tomatoes, 75 feet is quite a bit of separation. You should be able to save seed, and any crossing that might occur would likely be minimal.

Are you are looking for heirloom tomatoes, or just open-pollinated varieties to save your own seed? There are several OP versions of the Roma tomato.

There are also many heirloom paste tomatoes; my small-fruited favorites are "Quebec 1121", "San Marzano Nano", and "Red Sausage". I also like the "banana" type paste tomatoes, which have very long pointed fruits & few seeds. "Federle" and "Gilbert Italian Plum" are two which I have grown... they are my favorites for making salsa.

For larger tomatoes with few seeds, you might want to look at the oxheart-type tomatoes.

Oh, and regarding saving seed from radishes. Your biggest threat of crossing is from wild radishes which might be growing nearby. A little tricky saving radish seed... you need the plants to bolt to get seed, but if you save seed from the first ones to bolt, you are encouraging that (undesirable) trait in future generations.

    Bookmark   July 9, 2009 at 3:41AM
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