Pretty close:
2) "...I have grown a sieva type [lima] right beside a large type with zero crossing. The two subspecies have some kind of barrier that reduces or eliminates crossing."
If they are different subspecies yes. If not, no. Sieva and Florida Butterbean ( baby pole limas) will cross with giant pole limas like King of the arden, Calico.

3) "...[cow]pea...are less likely to cross than common beans or Limas.
Cowpeas cross about as readily within the species as limas do. Some cultivars are more prone than others

"All members of the common bean family Phaseolus Vulgaris will cross whether they are pole or bush varieties, however, because of the flower structure, crosses are rare."

For the most part, I agree. Pole beans can cross pollinate with their bush counterparts, although the rate for P. vulgaris is generally low. Over the years I have received several bean samples that were heavily crossed (one well over 50%) so crossing can be severe under the right conditions... but since I have never experienced that in my own seed, I'm not sure what those conditions are. With even modest separation, crossing is generally 1% or less. In a 100 X 100 plot, I can grow 9-10 varieties with 30-50 feet of separation & other flowering crops between, and seldom see a cross.

You would hope that any bean cross would be between a bush & a pole, since the cross would likely appear different from the plants around it, and could be destroyed before it flowered. Habit and flower color are your best early indicators of crossing.

Cowpeas (mostly bush) & yardlongs (mostly pole) are the same species, Vigna unguiculata. With their large, conspicuous flowers, they are said to be more likely to cross, so I give them more distance, at least 50-75 feet. I also plant at least one pole bean, runner bean, or pole lima between varieties, and try to place a squash, melon, or cuke between them as well. This allows me to plant 4-5 varieties in the same plot mentioned above, with no crosses to date. But again, I have received heavily crossed seed in trade, so I know it can happen. Further South, where "peas" are more commonly grown & more pollinators may have adapted to feed on them, the rate might be higher.

Limas have high quality nectar, and bees will fly great distances to feed on them; so where different varieties are grown together, crossing can be fairly common. Quite a few years back (in the 80's) I grew "Christmas" and "King of the Garden" in the same garden, 50 feet apart. When I planted the KOG seed the next year, there were many red-tinted crosses. I didn't record data back then, but I'd estimate the crossing rate to have been about 20%.

"...I have grown a sieva type [lima] right beside a large type with zero crossing. The two subspecies have some kind of barrier that reduces or eliminates crossing."

No experience with that, and I won't tempt fate by trying it. Since I grow several limas in rotation, nearly every year is a seed saving year. I wouldn't put too much faith in "subspecies" isolation, since the USDA considers all limas to be P. lunatus.

For limas & runner beans, you should grow only one if saving seed... and even that is no guarantee of purity, if one of your neighbors is growing another.

Soybeans would be the legume I would rate as least likely to cross. In the same plot above, I can safely plant 15-20 varieties with only 10-15 feet of separation between them. There was once a rogue in the middle of a row that had been included with the original sample, and grew to maturity. The rogue was black seeded, in a row of green seeded edamame. In subsequent years, there has been no sign of crossing. The rogue had to have come from somewhere, though, so crossing is still possible.

I am left wondering, for the bean crosses that I have received, how closely they were grown to different varieties, and under what conditions. It's hard to get good data without offending the source.

It has been often stated that beans "can't cross", because of their flower structure. While this may be true for some, under their conditions, experience in my bean trials over the last 10 years has proven that this rule is anything but absolute. I believe that the promulgation of the "can't cross" myth has led many to plant beans more closely than they might have otherwise, and led to the unnecessary contamination of a great many cultivars.

Chris,

I too am perplexed about how beans can get really crossed. For many years I hardly ever had any crossing, following much the same practices as you describe above. Then, in 2008, I grew a greasy mix, and... bingo! I got crosses between it and several other varieties. I hope this year, to finish eliminating any leftover crosses in my seed stock.

George
Tahlequah, OK

George,

It is not too hard to give an explanation. Pollinators are active on beans depending entirely on what is competing with them in producing nectar and pollen. If for example a large field of squash is blooming next to your beans, there will be little or no activity on the bean flowers because the squash is highly attractive to the bumblebees and mason bees. If your beans happen to bloom early in the spring, there will be lots of competition. If they bloom in the middle of the summer say around July, there is almost nothing else available so the beans will be worked heavily.

Some years we have a mild winter so more of the overwintering bees survive which results in a huge increase in the number of pollinators searching for food.

If you have a beekeeper in the area with lots of honeybees, the competition between the honeybees and the solitary bees will either push the solitary bees to search elsewhere or will force them to work crops the honeybees don't favor. Guess what? Honeybees do NOT favor working bean flowers. They are just not big enough to rip the flower open to get to the nectar and pollen. Mason bees and bumble bees happen to be just the right size to open bean flowers.

There are lots of other interactions. Ain't nature GRAND?

DarJones

Hmmm... I am a bee keeper. Thanks DarJones. I bet, if I go through my records, that it had something to do with, say, not growing squash on that end of the property. Will look into it!

George

Thanks for the responses! That's exactly the kind of feedback I am looking for!

Now, here's a few more. Comments (pretty) please.

4) "Yardlongs (which botanically are climbing cowpeas) do not appear to cross easily."

Do you agree and does this mean just with other yardlongs, or does it include all cowpeas?

5) "Beans rarely cross because they self-pollinate the evening _before_ the flowers open. So the pollen is not readily available to pollinators."

Very interesting statement. Do others agree?

6) "Beans are one of the easiest seeds to save, since their chances of crossing are so low."

As I continue my readings, I've seen some wide ranges regarding chances for a cross; anywhere from less than 1% to as much as 80%. Lots of reasons, explanations, etc. What percentage of crossing have you actually experienced during your bean growing adventure?

Thanks again for sharing your wisdom.

Rick

(Sorry I am no help)......I have never saved pole bean seeds before. I am going to try to save fortex seed. They are planted near rattlesnake beans.Will they cross? Should I try to put space between them next year ?

Well, guess I am overdue for one of my long-winded posts. ;-)

4) "Yardlongs (which botanically are climbing cowpeas) do not appear to cross easily."

This was covered, for the most part, by my post & Fusion's. I grow at least 2 yardlongs & 2 cowpeas each year in a 100 X 100 plot and have never had a cross... but that was with a substantial number of barrier crops between them. I have always assumed that they would cross, and taken measures to prevent it.

Cowpeas are Vigna unguiculata (or V. unguiculata subsp. unguiculata) and yardlongs are V. unguiculata subsp. sesquipedalis. Botanically, crossing is generally easy within a species; sub-species are just type classifications. A good example of this is cabbage, cauliflower, broccoli, kale, kohlrabi, and Brussels sprouts. While they are different sub-species, all of them are B. oleracea, and all will cross with each other if they bloom at the same time. (More on the "time" issue later.)

I noted Fusion's comment that cowpeas tend to cross for him as readily as limas, which are much more prone to crossing than common beans. To put that in perspective, the only bean cross I have had from outside my garden was a lima, which appeared to have crossed with "Henderson". Given that this was in a rural setting & the nearest neighbor was 1000 feet away, this was some accomplishment! Fusion's statement would seem to support the theory that there could be regional differences in the rate of crossing for cowpeas. In my Northern location, I don't think bees know what they are. ;-)

5) "Beans rarely cross because they self-pollinate the evening _before_ the flowers open. So the pollen is not readily available to pollinators."

Well, I don't know about the second part of that statement... it's not as if the pollen just goes away overnight. ;-) Beans are, however, better sources of nectar than they are for pollen. The assumption in the first statement seems to be that since pollen drop has already occured before the flower opens, no further pollination can take place. That may not be the case. While the science is there to support the bud-fertilization statement - and it is generally true - you can't argue with evidence to the contrary. Severe crossing, while rare, can & does happen. Fusion covered the pollinator issue well. There are varieties that appear to be more prone to crossing than most, as illustrated by my experiences with "Jeminez", George's with his greasy mix, and Gardenlad's comments in past threads that "Goose" had been heavily crossed.

I've read of how bees could chew through a bean flower before it opened & cause crosses, but never seen any evidence in my garden that this is a common occurrence. Nor am I fully convinced that such an entry would be an effective method of pollen transfer... which is not to say that it can't happen. But there seems to be a missing part to the puzzle; perhaps a condition (or combination of them) which inhibits self pollination, and/or interferes with the process of fertilization long enough for crossing to occur when the flower opens. Water or temperature stress perhaps, or the side effects of nutrient deficiency or disease. Maybe it takes a "perfect storm" of multiple factors to get heavy crossing, which would explain why it happens so seldom.

6) "Beans are one of the easiest seeds to save, since their chances of crossing are so low."

As a dedicated bean seed saver, I'd have to agree. If you grow only one bean, chances are the seed will be completely pure. Even with multiple varieties, while severe crossing can happen, it seldom does, or happens at a very low rate (5% or less). Even modest precautions can significantly reduce the odds, and improve seed purity.

There are several techniques that can minimize crossing, or make make detection of crosses easier:
- Take notes on the characteristics of the different varieties (stem color, flower color) and avoid planting beans with similar characteristics side-by-side. Any variations in subsequent years could perhaps be detected early (depending upon genetic dominance) and the crosses destroyed before they caused further contamination.
- Try to plant good pollen sources throughout the garden (whether herb, flower, or flowering vegetable). Diversify the garden as much as possible. This has the added benefit of reducing the spread of disease, and attracting beneficial insect predators.
- If diversification & barrier crops are impractical, plant multiple rows of a variety, and save seed from the middle row (or from the center plants in a single row).
- Use time isolation. Plant different varieties at different times. For example, plant bush beans or short DTM pole beans first, then a later variety 15-30 days after that. When the second variety is ready to bloom, snip all remaining flowers & buds from the first variety, which should have already set large numbers of pods. This method requires some vigilance, since the first variety may attempt to grow new flowers, which must be snipped off before they open. When the second variety has bloomed for about 2 weeks, allow both varieties to flower freely - but only harvest the first dry pods from each variety, for about a week or so. This can produce very pure seed where space is limited. More than two varieties can be difficult, though, unless you have a long season.
- Blossom bag a few flower spikes, perhaps one on each plant. The number of blossoms to bag would depend upon the amount of seed desired. For personal use, where only a small amount of each variety is needed, this method is highly effective. This is the safest method of saving seed if growing a large number of varieties side-by-side, especially if one of them is an irreplaceable heirloom.
- If none of these procedures was followed, save the very first pods to dry, which would have been set when the flower concentration was low & less attractive than when the flowers were more widespread.

so once again the natives where right, if they knew it or not, by planting corn with climbing beans around it to fix nitrogen(not if they did it for increased crop or bcause the corn just grew better) then a few hills of squash to shade out weeds and make it harder for deer to get to. if beans self polinate corn wind polinates and the squash draws the bees.

anyone else still plant like this?

Sticky,

There are lots of 3 sisters gardeners here in the U.S. I personally do not use the method because it requires several changes in culture and makes harvest a bit harder. I do however grow watermelons and cowpeas in my corn. This is a very effective way of doubling up on use of my garden space.

Re crossing of beans, I grew a row of Striped Bunch beans in the garden this year. They were from seed produced in 2009 and were from a row that contained 8 different varieties with from 10 to 20 feet of row dedicated to each variety. From the seed I planted this year, about 350 to 400 plants germinated. Of those plants, 4 were identifiable crosses. That is a crossing rate of 1 percent.

The crossed plants were very easy to identify because Striped Bunch is a unique variety in my garden. It is not a bush bean and it is not a pole bean. It produces short runners up to 4 feet long and is perfectly happy being grown with no support similar to bush beans. The crossed beans all produced vigorous runners similar to the pole bean parent. Three of them had purple stems where Striped Bunch has only pale green stems.

From the crosses, I can tell that one was a black bean either Kilgore Black or Alabama #1 or Supermarconi, one was Black Logan Giant, and one can't be identified because all it changed was the color of the stripes on the seed from brown to black. One of the crosses gave clear stems so was possibly a cross with Fortex. Of these, the cross with Black Logan Giant is clearly identifiable because it is a frosted bean similar to Turkey Craw and it makes very large seed at the green shell stage.

I have saved seed from three of the crossed plants but the clear stem plant did not produce beans. Growing out the crossed seed next year should give plants with a range of growth habit with one fourth bunch form and three fourths pole type. The Logan Giant cross is particularly interesting because of the seed size and the possibility of getting them in a small plant form.

DarJones

Thanks again to all who responded, especially Zeedman, George, Dar and FarmerDilla. For me, you guys are like E.F. Hutton when it comes to beans. When y'all speak, I listen lol.

We see it written all the time - "...just use the search feature at the bottom of the page". Well, there were over 160 posts related to "cross" on this forum. I read them all. There is indeed a wealth of information residing in these posts; all you have to do is search and read. And you guys, along with a few others, are well represented in them.

In my readings, someone recommended the book 'Seed to Seed', by Suzanne Ashworth. So, I purchased it and read it. What a WONDERFUL book on seed saving. Thank you for recommending it. I definitely recommend it to others interested in seed saving.

Anyway, enough babble. Now off to the garden to watch the beans grow. *smile*

Thanks again for taking the time to share your experience and expertise with all of us. (And please don't stop)

Rick

This was a very interesting discussion. Someone referred me here after I asked a question about beans hybridizing on another site.

I have grown Fortex pole beans and Pelandron bush beans in adjacent rows for several years and I always save my own seed. This year I noticed that some of my Fortex beans have purple splotches and a configuration more like that of Pelandron, which is a shorter, fatter bean with purple streaks.

It sounds as though they may well have cross-pollinated, so I'll be buying fresh Fortex seed for next spring.

If you grow several varieties of beans, as some of you have said you do, what crops do you use to separate the varieties?

And more specifically, will my plan of planting tall flowers in my garden, specifically Valerian, wormwood, asclepias, and pyrethrum be effective as separators between bean varieties? They're all between 80 inches and 36 inches tall, and I'll plant them at the ends of each 8-foot trellis length. I'm hoping the bees will use the flowers to wipe their pollen footprints before moving on to the next set of beans!

I'm planning to grow 8 feet each of Sieva pole limas, Emerite pole beans, Roma pole beans, and Dixie bush butterpeas, as well as only one variety of cowpeas. The cowpeas will be in a separate bed, but the other beans will be in a long row with the flowers between each variety, probably in this order.

Romas -- Sievas -- Emerites -- Dixie bush butterpeas

Anney, I only grow (1) lima & (1) runner bean in my main plot; but I try to grow 2-3 rows, in different locations. Both of these are tall, free flowering, and more attractive to bees than common beans... so they make great barrier crops. I use pole yardlongs as barriers too, but they are less effective, since the blossoms close early in the day.

Multiple rows can enable a variety to be a barrier for itself. Provided that I have enough seed, I grow a row of limas on the outside of the garden (facing my neighbors), with a second row of the same variety close to the center. If the bees are very active, the center row is more likely to "cross" with the outside row than with anything grown by my neighbors.

As Fusion mentioned, cucurbits (such as squash, melons, & cucumbers) make great barrier crops. I grow a lot of bitter melon, which is a vigorous climber. When grown on a trellis, it forms a dense flowering barrier as tall as the pole beans (fragrant too, when in bloom). Trellised cukes or Tromboncino squash work well too. Instead of placing all cukes & bitter melon in one large planting, I divide them up into 2-3 smaller plantings, scattered throughout the garden.

I do the same thing with okra, dividing it into several rows at different locations.

For flowers, I use cleome, a flowering mallow (Malva sylvestris "Zebrina"), sunflowers, cosmos, and basil. These are also dispersed throughout the garden. I can't speak highly enough of the "Zebrina" mallow; it flowers heavily & continuously, and is a really great pollen source. I've seen 6-7 different species of bees at the same time on a single plant, and large plantings will attract honeybees. It volunteers heavily, but to me that is a good thing... I choose my weeds carefully. ;-) It has now displaced the 2 wild mallows that were native to my area.

When all of these barriers are combined (which takes a bit of planning), the effect is to create a maze that controls and/or restricts the movement of pollinators, and provides numerous places for them to "wipe their feet" as they cross the garden.

I also use tomatoes, grown in 5' cages, and in blocks, as a barrier between my beans. It works well, since the tomatoes are benefited by a barrier crop (beans).

Anney, since you live in GA, you might also consider using time as an isolation factor. You could plant something earlier, and another thing later, so that the first crop produces pods, which will mature into seed, before the second one comes into flower.

George

zeedman

Thanks for the information.

I'd decided to separate my plants in the vegetable garden next year to break the cycle of mini-monoculture -- all the beans together, all the tomatoes together, etc. Partly because the tomatoes are always foliage disease-ridden by the end of July, I've been looking for a way to minimize common tomato foliage diseases. Separating the plants from each other and growing disease-tolerant varieties seems to be a good start, and I may as well make use of the principle to keep my beans from crossing, too. I plant more beans and tomatoes than anything else in the garden and have practiced space-intensive gardening because of my arthritis. I will, however, re-think that, and see if I can relax about spread out a little more.

It requires a lot of re-thinking on my part to realign the garden with flowers and herbs and interrupt them with edible plants, such as beans and tomatoes and okra and cukes and peppers and squash. Hard to teach an old dog new tricks and all that. I see you must be an old hand at it! The cleome and mallow are both gorgeous plants that I will add to my repertoire. I'll also be thinking about the other principles of plant separation.

George, that's a good idea, given the longer growing season here in the south. I'd need to pay attention to the timing of each of the limas and snaps to avoid their cross-pollinating with the other variety. The limas, both of which are given a DTM of 70-75 days, could be separated in time by several weeks and we'd still get plenty of them. The snaps might be trickier, since they'll slow down production considerably when the heat sets in, so I'll want them to be as productive as possible in the time they'll grow. Maybe they'll be all right if separated with enough other plants.

Just an aside -- I set out ONE zucchini plant, a Caserta squash, primarily as a lure for cucumber beetles, and that danged thing has spread to 14 FEET! I've never seen a garden plant get so large. I'm not sure I'll plant them again, though the zucchinis are absolutely delicious.

If that Caserta plant has rooted along the stem, then it could be a real good variety for resisting squash vine borers. So far I've lost every single c. pepo planted this year. The borers and squash bugs have annihilated them!

George
Tahlequah, OK

I LIVE IN BAUCHI IN NORTH EASTERN NIGERIA I HAVE BEEN HAVING PROBLEM WITH COW PEAS IN THE LAST THREE YEARS FLOWERS HARDLY NICK EITHER DUE TO POOR WEATHER OR SOMETHING NOT CLEAR . WHAT DO THINK IS THE PROBLEM ?
UMAR BUBA