Dean

Somebody needs to ask the author where s/he got that information. I certainly don't know the answer. But elsewhere they make another odd claim: Even though soil contact creates acidity in the fruit, you can imagine that most growers don't go through the trouble of keeping the tomatoes off the ground.

I've never heard that, either. I thought it was genetically determined.

What's been repeated at that website is old information that's been around for years about X pollination.

I've grown over 2000 different varieties and have not seen that PL's cross anymore than do RL's and I know others who would say that same thing.

I looked over some of that site, including the comment about contact with the ground creating acidity inside the fruits, which is not true, and I'm not thrilled with what I read, if you catch my drift.

Carolyn

"I know this is a broad statement, but if I read right, regular leaf tomatoes do not cross as easily as potato leaf tomatoes as long as they are not beef-steak tomatoes?"
It is a broad statement and is not true IMHO. The likelihood of a tomato variety crossing is due to the shape of the flowers (especially the style) not because of the leaf form.

"For home use then, I can plant two medium fruit sized regular leaf tomato varieties side by side and save seed and in general not worry about cross pollination?"
To be absolutely sure you might want to follow the isolation distances recommended by Dr. Jeff McCormack (I've included the hyperlink below). BTW, generally at normal distances (3' rows 4' apart) there is a 5% probablilty of getting an accidental cross. I plant different varieties next to each other at 3 foot intervals, and save seed after the sweat bees are out of the picture. I have had only one accidental cross in more years than I care to mention. :-)

At least the web site referenced above has some things right, but the bottom line is there is a lot of misinformation.

Just my 2 cents worth.

Randy

Here is a link that might be useful: Dr. McCormack's Isolation Distances Paper

"For home use then..."

For home use seed-saving Dean, you can plant any type of plants right next to each other at 3' spacing and only get a minimal chance of crossing at less than 5%. So for most of us the site's info is not only inaccurate but it's irrelevant. ;)

If you want 100% guaranteed accuracy rather than 95% for some reason then just bag a few bloom clusters before the blooms develop.

Dave

Randy, I find Jeff's isolation distances to be very very conservative and we've had quite a bit of talk about it.

But it stems from when he owned Southern Exposure Seed Exchange and was producing a lot of his own seed which was being sold commercially and he thought it was best to use such isolation distances, and for commercial sales I would agree.

But I do think that for a home grower closer distances can be used.

And speaking of your accidental crosses, planting at a 3 ft distance within a row and 5 ft between rows I also had a very low rate of X pollination.

I once sat down and tried to remember how many, and these were seeds I was offering in the SSE Yearbook, and I think I came up with 4 X pollinations from about 1990 to date, at least that I knew of.

The problem is that you can produce seed in the summer of 2008, for example, and the forms for listing have to be filled out and submitted that Fall, so there's not been a chance to test out the seeds except possibly for leaf form as seedlings.

Another problem is a xing rate that's so low that it doesn't show up for sometimes several years down the road.

If I process 15 Chapman's for seed and only one of those fruits has some X pollinated seed the presence of those X pollinated seeds is very low in the whole seed batch and it may take 100's of plants to show up those seeds. Sigh.

Carolyn

I've always compressed my plant density, I'm afraid, so I could grow more varieties each year. Typically 3' between rows and 30 to 36 " between plants in the row: I've even cheated on that down to 26" between plants in a row. All this probably shouldn't work very well but it seems to because I prune back to two leaders on 26" spacing and 3 to 4 depending on type and variety with 30 plus inches between plants in a row. Shame on me, but I even crowded things like the above when I had my orchard and 35 acres and there was plenty of room then!

Over 40 years of growing and at least 35 saving seed I can recall only 6 to 8 crosses, and unfortunately every one of those resulted in something less desirable than whatever was involved in the cross. I surely lost 2 damn good varieties
to accidental crosses and could only get good replacement seed for one.

I surely lost 2 damn good varieties
to accidental crosses and could only get good replacement seed for one.

****

larry, what's the one you couldn't find seed for?

It's an outside chance but perhaps if I know it I could find some seed for you somewhere.

Carolyn

I thought the statement sounded fishy, so that is why I decided to asked the question here.

Personally for seed saving and trading I heard 10 feet was a good distance, so I have separated my tomatoes by 20 feet, it might sound like overkill I know but I only save 3 or 4 varieties a year so I can afford the space.

Thanks everyone.
Dean

Dean,

I found most of the statements made in the article you linked to be unsubstantiated. Same for many of the comments made here about natural cross pollination, which I think is highly dependent upon the species of pollinators native to the area in which you grow (a big problem when discussing this on the worldwide Web), how far those pollinators may end up travelling to subsequently visited blossoms (ever actually followed a bee? I have, and you might be amased at how far and how many tomato blossoms it'll visit), and the physical structure and receptive condition of the blossoms it lands on. Spacing of plants in most hobby gardens is of little consequence, IMO.

In other words, I think any tomato plant in a backyard garden is subject to cross pollination, whether the distance between pollen donor and pollen receptor is 3 feet, 10 feet, 25 feet or a hundred, when the physical conditions of blossoms are right and regardless of the calculated "odds" often repeated here and possibly accurate only as a generalized "rule of thumb."

Ask yourself this ... does the pollen somehow fall off the pollinator's legs or abdomen, and the insect arrive totally clean just because it flew 50 feet rather than five?

Bill

If you don't need more than seed from a few fruits per plant it's easy enough to go to Walmart and get a pack of sachettes to bag the blossoms. I watched a couple of bumble bees the other morning hit most of my plants one after the other. Sometimes they skipped a plant, which meant 10 ft from the previous plant.

In other words, I think any tomato plant in a backyard garden is subject to cross pollination, whether the distance between pollen donor and pollen receptor is 3 feet, 10 feet, 25 feet or a hundred, when the physical conditions of blossoms are right and regardless of the calculated "odds" often repeated here and possibly accurate only as a generalized "rule of thumb."

*****

I agree completely Bill.

Bees have been shown to travel up to 2 miles but I don't know which bee species.

Jeff McCormack and others have said that the primary pollinator of tomato blossoms are Halictid or Sweat bees and they're so tiny it's very difficult to even see them.

Years ago when I started growing lots of OP's the word was that if you wanted to help ensure seed purity and maintain variety diversity that you should plant 4 of a kind in one row and only save seeds from the inner two.

So I'm looking at my then tomato patch where the rows were about 250 ft long and the rows were 5 ft apart and I'm thinking OK fine, 4 of a kind in a row, so what's with all the other nearby rows in terms of X pollination. LOL

Through the years I found out that indeed X pollination is NOT the rule, self pollenizatio is, and I'm perfectly happy with plants about 3 ft apart in the row and the rows about 4-5 ft apart. And I've had darn few X pollinations and didn't bag blossoms which is a method that wasn't even discussed back in the mid-80's when I first started growing OP heirloom types.

Carolyn

Ham, that's exactly what I've observe frequently ... bumble bees buzzing from one plant to the next often skipping ten feet or more.

Halictid bees are smaller, yes, but apparently could still be observed as to their activities, I suppose ...

Halictid Pictures and Videos

Some text quoted from that link includes: "There are more than 3,500 species of bees in North America, about 500 of which form the family Halictidae. All bees are covered with hair, to which pollen sticks when flowers are visited; most female bees have apparatus for gathering this pollen; it is combed into a special basket or brush located on the hind legs. Males do not collect pollen and lack these structures. There are a few species, especially the parasitic bees, that have no pollen baskets."

The points I was trying to make in the post above include that yes, while the tomato flower is structured to self-pollinate ("perfect" flower), that process often is incomplete ("imperfect") due to climatic or other conditions (witness catfacing and other manifestations of incomplete fertilization of an opened blossom).

That means when some pistils push up through the stamens and exhert the stigma out into an exposed position, yes that stigma should be covered with pollen blown out by its own anthers. But each pistil is comprised of numerous tubes each of which is intended to convey one grain of pollen into the ovary to fertilize what becomes a seed. One grain of pollen per tube per seed.

Up at the stigma, if a pollen grain does not adhere to the receptor for one of those tubes, no viable seed will result at the other end of that tube down in the seed locule. However, that particular receptor remains receptive for a brief period of time while the entire structure is operative. So, in in the case of incomplete pollination of an operative and receptive stigma/pistil/ovary, a bee happens along, there is still the opportunity for cross pollination ...

And that's why there is a small percentage of crossed seed (whether it's the oft-repeated 5% or not) popping up in so-called true line saved seeds. It also is the ONLY reason for saving seed from more than one plant when claiming to preserve "diversity" in an inbred, open pollinated population of self-pollinating cultivars. Otherwise, you would be better off saving seeds from the best plant only ... which is what I prefer to do.

But then my opinion is just another opinion and just as subjective as the opinions I find too subjective I suppose.

Up at the stigma, if a pollen grain does not adhere to the receptor for one of those tubes, no viable seed will result at the other end of that tube down in the seed locule. However, that particular receptor remains receptive for a brief period of time while the entire structure is operative. So, in in the case of incomplete pollination of an operative and receptive stigma/pistil/ovary, a bee happens along, there is still the opportunity for cross pollination ...

*****

Bill, I do think you meant to say tomato ovary rather than seed locule.

And there's an opportunity for even more than one X pollination, the second one from another variety as long as the stigma is still receptive and as long as there are still unfertilized ovules in the tomato ovary.

Ain't tomato life just grand. LOL

Carolyn

schemes I have seen (and worked with) for self pollinated plants utilize blocks of several rows rather than just one row

like:

AAAAAA BBBBBB CCCCCC
AAXXAA BBXXBB CCXXCC
AAAAAA BBBBBB CCCCCC
(with gaps between blocks)

instead of

AAXXAA
BBXXBB
CCXXCC

or
AAXXAABBXXBBCCXXCC

"X" denotes the plants for seed

Published studies range from 2%-20% outcrossing.

"I find Jeff's isolation distances to be very very conservative "

this to me explains many of the so claimed "spontaneous mutations"