Please click on the FAQ link at the top of this first page and scroll down to the article on how to prevent cross pollination.

In terms of geographic isolation there is no one distance that would ensure complete lack of possible cross pollination unless plants of a given variety were grown many miles apart. OTOH self pollenization is the norm for tomatoes and occurs maybe 95% of the time.

You might want to go to Southern Exposure Seed Exchange and read the excellent article written by Dr. Jeff McCormack, the former owner of SESE, about cross pollination.

Bagging blossoms does ensure seed purity and that's discussed in the FAQ article.

How pure you want your seeds is really a function of how you plan to use them. Using them for home use only is far different from as an SSE member listing them in the SSE Yearbook or wanting to use them to trade for other tomato varieties, etc., if you're a person who likes to trade seeds, which I'm not. ( smile)

Carolyn

Carolyn, thanks for your reply! I read all of the FAQ, and saw the " bagging method" , but was hoping for more info. Thank you so much for helping me. I will read DR. McCormack's article.

EG

EG posted:
I read all of the FAQ, and saw the " bagging method" , but was hoping for more info. Thank you so much for helping me. I will read DR. McCormack's article.

*****
EG what specific info are you looking for? Since I helped write that FAQ I knew that geographic isolation you asked about was included, and have cut and pasted it below.

If you could tell us what more you want to know perhaps I or someone else could give you an answer or refer you to a resource, but since you asked about geographic isolation I assumed that's what you were after. ( smile)

Note also the info about currant tomatoes, S. pimpinellifolium, in the FAQ.

Here's the geographic isolation part of the FAQ:

Using Isolation Distance to Prevent Cross-pollination

A general rule is that the further apart varieties are grown, the lower the probability of cross-pollinating events. Experts disagree on the distances required. For most gardeners with limited area to grow plants, distance is NOT an effective means of obtaining 100% purity. Inadequate isolation, season after season, will result in some natural cross-pollination and may eventually produce undesired changes in the characteristics of a variety.

There are no hard and fast rules to follow with regard to isolation. If you are knowledgeable about the pollinating insects in your locality, you may be able to design a system that reduces natural cross-pollination to a very low level with a small amount of isolation. If you lack specific knowledge about your locality, the following guidelines may be useful.

Generally, tomato varieties should be isolated 20 to 25 feet, and they should have a pollen-producing crop planted between. The objective of the inter planted crop is to divert insects away from the tomatoes. The amount of natural cross-pollination will depend on the factors previously discussed. Generally, organic gardening methods result in many more pollinating insects than would be present in a area where pesticides and tilling have been extensively used.

To obtain 100% seed purity by isolation distance, very large separations are required, possibly a 1/4 mile or more. Obviously, these resources and geography are difficult to achieve. Also, tomato volunteers from previous seasons could remain undetected within the isolation perimeter. Again, if you desire 100% seed purity, look to the physical isolation as provided by bagging or caging.

If you rely on isolation distances, it's best to grow several plants of the same variety and if in a row, harvest fruits from the inner plants and if in a square area, from the interior plants. If only a few plants, it's best to harvest several fruits from each of the two or three plants for seed saving so as to minimize the chance of getting nothing but crossed seed if you chose only one or two fruits.

Many varieties that are potato leaved and have large pink fruits often show very large double and triple blossoms early in the season which are quite attractive to insect pollinators, and some other varieties do the same. And sometimes the result is fused fruits. So it's best to not use fused fruits for seed saving since one or the other of the fused fruits could be cross-pollinated.

Special Concerns regarding the Currant Tomato

Home growers are growing more and more of what are called currant tomatoes, which are in a different species from our garden tomato. All currant tomatoes (L. pimpinellifolium) have exerted stigmas. Some folks highly recommend that you don't plant currant tomatoes near garden tomatoes ( L.lycopersicon) since they might serve as a source of foreign pollen in terms of cross-pollination. Others say that they'd worry more about regular garden tomatoes cross-pollinating currant tomatoes, and a third group might say that not all currant tomato varieties are of concern as regards cross-pollination.

Recognizing a "crossed" tomato

Depending on the varieties involved, it may be quite difficult to realize when one variety has crossed with another. Sometimes its easy to tell that something went wrong because the tomatoes are far from your expectations. Other times, you may not notice any problems until you begin seeing off-types in the F2 generation. Just remember, growing your seed out the first year is not always a 100% verification that your seeds are pure.

Credits:
This FAQ is a collaborative effort of Gardenweb members. Specifically,
Bets, canadiantomato, Carolyn137, Earl, Fusion_Power, gardengalrn, Gardenmama1, JHCaden, Korney19, Paul2101, vaped
Illustration by : Paul2101
Bagging Photo by : Bruce_B

References :
(1) Isolation distances for Tomatoes, Jeff McCormack; Ph.D
(2) Breed Your Own Vegetables, Carol Deppe
(3) Seed to Seed, Suzanne Ashworth

Entered by Paul2101

Carolyn

Carolyn - After reading that again, it's more apparent. :)
20 - 25 ft of distance is what I was looking for. Thanks, sorry for not paying attention.

EG

Thanks for this great information. I'm a new tomato gardener and would like to collect seeds from my crop next year and avoid cross-pollination. I believe the article that was referenced is here.

It was mentioned that a pollen producing crop should be placed between two different varieties. Could you recommend some pollen producers for this? I see that squash was mentioned as a good choice. Are there other fruits/vegetables or annual/perennial flowers that would also fit the bill? My lemon tree as well as lantana and mexican heather attract quite a few bees but I'm not sure if they are heavy pollen producers.

Keep in ind that since the odds of cross-pollination are less than 5% most of us who save seed for our own personal use or for trading with others don't worry about it. ;)

If it is convenient for you to space your plants far apart, great. For most that simply isn't possible so cross-pollination for seed savers - unless commercial - is seldom a concern.

Dave

Thanks, Dave! I was wondering about that. Actually, I do have room to separate them by over 50 feet - so, that's what i'm gonna do.

EG

Does anyone know what the minimum safe distance between different cultivars needs to be to keep cross pollination from occuring? I'm planning on saving my seeds...

On the OP tom seed saving bidness, an obvious but largely unaddressed issue here is one of proper identification. This is important if one wants to reprise the same cult from one's own saved seeds. I am no paragon of virtue on it, but I try to keep track of the tom cults.

Reg

Reg - here are the varieties

1. Cherokee Purple
2. Giant Oxheart
3. Opalka
4. Mortgage Lifter
5. Brandywine

EG

On the OP tom seed saving bidness, an obvious but largely unaddressed issue here is one of proper identification. This is important if one wants to reprise the same cult from one's own saved seeds. I am no paragon of virtue on it, but I try to keep track of the tom cults.

*****

Reg, I'm not following you entirely on this but I think you are saying be sure that you have properly IDed the variety ( not cults, aka cultivars) that you are taking fruits from to save seed.

If so, time after time I have urged folks to NEVER plant a tomato plant unless the person knows the variety traits as to plant habit, indeterminate or determinate, leaf form, RL or PL or other, fruit shape and size and color.

A lot of casually traded seed turns out not to be what the seed recipient expected either b'c of crossed seed or b'c the person who saved the seeds did not properly ID the variety being used for seed saving and the seed traded is pure but not the right variety.

Carolyn

Reg - here are the varieties
1. Cherokee Purple
2. Giant Oxheart
3. Opalka
4. Mortgage Lifter
5. Brandywine

EG

That is a good list. On OP tom seed saving, it is not practical for most townie gardeners to use isolation as a method to attain seed "purity."

And "bagging" the flowers is a skill that most (including myself) do not possess.

Most saved seed from truly OP (homozygous) tom cults will come true. Even if the berry from which the seeds were subsequently saved had some cross pollination, most of the seeds in the berry will still produce the same plant as its OP parent. Of course this is because almost all current tom cults are self-pollinating.

Reg

I live in a rural area, and the closest house is 1/4 mile away. The seeds will only be saved for my own use.

Carolyn - I will know exactly which plant is located where, and always make an autocad drawing of my plants/locations in my sfg. I'm the ultimate neat freak, and everything has got to be perfect. Check out my blog, and you'll understand.LOL. My seeds are being ordered from tomatofest.com, and should be as advertised.Thanks for all your help!

Reg - I've never grown any types except better boy and roma. This is definitely going to be interesting. I chose the opalka because it was the largest paste tom that I found, and the others were for their size and beauty. I'm planning on canning alot next year, especially since the economy is looking bad. Thanks for your help!

EG

My seeds are being ordered from tomatofest.com, and should be as advertised.

****

I do hope so EG but Tomatofest and Baker Creek have had quite a few varieties received that were crossed or otherwise unknown this past season.

So do check out what you get carefully when the plants are grown.

Just trying to be helpful here and I hope that the wrong variety problems at T fest and Baker Creek are soon solved. And Gary at T fest and Jere at Baker Creek know of the problems, at least some of them, b'c not everyone who gets wrong varieties feels confident enough to report same. My info on this is from posts here and at two other places where I post.

Carolyn

Carolyn - I certainly hope I get what I paid for, I didn't know of any problems....I'm gonna be worried now. lol. Thanks for taking the time to help me, I know your time is limited, because of all of the questions that people ask you.

EG

There is no art or skill involved in bagging. You go to WallMart and ask at the fabric desk or arts and crafts aisle where they have their drawstring mesh sachettes, which will be a little display of wedding/party knick-knacks somewhere close by. They cost about $3-$4 per dozen for the large 5"X7" size. You put them over top of a truss of unopened flowers and wait. Once all of the flowers have opened and fruits are developing you tie a marker ribbon around the truss and take the bag off.

I drop the bag in boiling water for a few minutes to kill any stray pollen, dry it and then bag something else.

I bag because I have first fruits (when pollinator populations are low) with cross pollination as high as 13% of the seed. Mid season when pollinators are active each flower gets visited by little halictid bees several times per hour so I expect that rates will be higher.

I bag because I have first fruits (when pollinator populations are low) with cross pollination as high as 13% of the seed. Mid season when pollinators are active each flower gets visited by little halictid bees several times per hour so I expect that rates will be higher.

spiced ham - that's the first I have ever heard of CP rates that high. Can I ask what you are basing this high rate on? I assume since your rate is so specific that you have grown out all these seeds and documented this much CP in them?

Since so much research shows that many blooms pollinate themselves before they even open one would expect the less then 5% to be a more accurate figure.

Dave

Yes I have grown out the seeds (40 seeds per fruit) from my potatoleaf plants, which are either surrounded by or well mixed with RL plants. Anything that comes up RL is obviously crossed. I am about to grow out seeds from fruits collected late in the season (now), and I have halictid bee visitation rates to blossoms at the time those fruits were pollinated in early August (up to 20 times a day per blossom). The bees are so small and the visits so quick that unless you are looking you don't notice them. I don't have many bumble bees around here.

Out of ten 1st truss fruits tested, 4 were cross pollinated, with 1-5 seedlings coming up RL.

Next year I plan on doing a proper study with more fruits and look at catfacing, mega blooms, fruit size etc.