Outcrossing/Hybridization

[JPB]

Which measures do you take to prevent outcrossing or hybridization when you aim for collecting seeds of "true species" in your garden/greenhouse/nursery? Especially insect-pollinated flowers do not travel far with their pollen, but in a garden it will be all mixed once they get the opportunity... How can you be sure that no unwanted genes creep in?

For clarity, with hybridization I mean interspecific crosses, of which some genera seem very fond (e.g. Cistus; Aquilegia). Unwanted outcrossing can occur f.i. between two groups within a species from different geographic origin you don't want to mix.

My impression is, that, at least here in the Netherlands, many plants sold as "true" species, have a promiscious background...

Cheers,
Hans

[JPB]

Anyone? or is this a silly question?

[Paddy Tobin]

Hans,

I think you must think of some form of isolation or segregation of these promiscuous plants. It is not something I have previously considered as I have not been over anxious to collect pure specific seeds. I understand your problem  and feel segregation is the only answer. I have seen people enclosing flowers in small bags to prevent access by insects.

Paddy

[Onion]

Hans,

you have every time a hybridization when insects pollinate the flowers. The question is if the pollen is able to pollinate the "seed". You have genera like Cistus who hybridzed very easy, but you have other genera like the cherries with interspecif groups. They are not able to pollinate the other groups.
To get true species you must segregate this species, handpollinate them and prevent access by insects, as Paddy mention by small bags.

[Rodger Whitlock]

In promiscuous genera, you must assume that seedlings are hybrid. The only way to prevent this is to grow no more than one species of known authenticity. Even then, you'd really need to scout around the neighborhood to make sure no one else within bee-flight distance is growing other members of the relevant genus.

It's for this reason that wild-collected seed is so important in the exchanges.

But unless you are a botanist puzzling your way through the thickets of aquilegiology, does it matter if your garden contains hybrids rather than pure species? After all, we are gardeners, not botanists...most of us, that is.

[iann]

Its definitely an issue if you are collecting and disseminating seed from your own plants.  When its important to maintain a pure seed line, or equally when you are deliberately trying for a hybrid, there's no substitute for isolating the flower and pollinating it manually.  This might mean bagging the flower, covering the whole plant, moving it inside, whatever is going to work in your situation.

For cacti and succulents, the majority of available seed is from cultivated plants but hopefully still representative of particular populations.  Habitat seed is still available in many case, but for example all cactus seed from Mexico is now controlled under CITES.  A number of desirable species are CITES I listed (not always a coincidence!) effectively meaning there is no legal source of habitat seed.

[Lesley Cox]

Yes, total and secure isolation and hand pollinating, for pure species. However, from most nurseries' point of view, if selling seed of, say, Aquilegias, the seed would usually be listed as "ex A....." or as the species with the additional note that hybridization has been possible and this should be taken into account when assessing the seedlings. It annoys me that both SRGC and AGS seedlists list hybrids AS the hybrid rather than acknowledging that it is seed FROM the hybrid, by the simple use of the "ex" word.

[JPB]

Lesley, I agree. Of all my plants, I keep the plants from wild-collected seeds (or even wild collected plants/cuttings themselves) and only propagate them vegetatively. So I can always be sure that it is the real species. There are lot of plants, offered as species, which are not true species and have a long history as garden plant and one can only guess if there are some wild genes left...

It gets even worse when they escape to nature. F.i. Digitalis purpurea, Campanula persicifolia and Ornithogalum umbellatum are extremely endangered in the Netherlands. But nobody notices, as escaped garden plants are all over. There are many other examples.
With annuals and biannuals it is even worse. I haven't seen a proper Papaver rhoeas in years. Different colors and even some double-flowered. What a joy to find the real Poppy's in a deserted field in SE-Spain...

Also, maintaining a seedstock generation after generation enhances the chances of inbreeding.

I'm a botanist rather than a gardener (or a gardening botanist for that matter)

Hans

[Lesley Cox]

This raises an interesting question for me Hans, not really related to hybridizing or only quite indirectly. what plants really are native to Holland and might be found in the wild, natural landscape? In fact, what wild or natural landscape is there, at all? When I think of Holland I think bulb fields and highly cultivated areas and I wonder if there is anything at all that is NOT under cultivation. Holland seems to me, to be one huge garden in the middle of the more natural European environment. I don't mean literally in the middle, but a garden whereas other countries are more as nature intended. I'm probably quite wrong about this but would like a lesson in the Dutch/Belgian landscapes.

[JPB]

There is no habitat in Holland that is completely natural. Very acre has been ploughed or at least heavily used. Not only the last, say, hundred years, but also during the 16th century onwards. Even in those days, most forests were cut for timber and replaced by (cheap!) trees imported from eastern Europe.

Holland is small as you know, with lot of people, and every acre is or had been used...We find a pleasure in digging everything straight and canalize every brook or small river we see without knowing why. Just habit, I'm afraid...It is a pleasure to be in France, where they throw old fridges in the woods, but they don't ruin the forest for no reason...

Still there are some gems. And the good thing is that the public opinion has changed the last 15-20 years. Restoration-ecology is now taken seriously and many interesting habitats have developped in an unexpected possitive way... Still no comparison with our neighboring countries

[Lesley Cox]

Thanks for this information Hans. I suppose it's much as I imagined it would be. The pictures that Luit has shown on other threads said much the same message. I hope the Dutch succeed in remaking some of their "natural" places. They are refreshing to the soul in a way cultivated land can never be. I'm sorry to hear the French throw their refrigerators away in the woods though.

[JPB]

It is not that I blame the French for incidentally throwing away an old fridge (it happens everywhere). But once I found a bunch of Cephalanthera's just besides an old fridge. I was quite happy. We would have cleaned it up, that's tue, but together with the orchids, make it straight and paved it for bicycles...and built a pancake-house... That's why I like France so much

[cohan]

It is not that I blame the French for incidentally throwing away an old fridge (it happens everywhere). But once I found a bunch of Cephalanthera's just besides an old fridge. I was quite happy. We would have cleaned it up, that's tue, but together with the orchids, make it straight and paved it for bicycles...and built a pancake-house... That's why I like France so much

i wish i was in cycling distance of a dutch pancake house
i suppose some of the areas with a bit of nature include the dunes? and i remember cycling through a forest park somewhere in the middle of the country--i'm going to guess at the name, its decades since i thought about the name-- 'Hoge Veluwe'? of course it was not a large area, but i remember some very dark forest, and some sandy areas..i do remember some bits of forest/woods near canals by small towns between amsterdam and rotterdam (i'm grasping for memories, this was a long time ago)--of course not big forests, but not just all square fields, either..
of course small natural areas cant be selfsustaining and no doubt need lots of management, but thats true of even of some much larger parks etc in canada when humans intervene in fire cycles, animal populations, etc..