if you mean like this "peach X plum =nectarine" ;the X means crossed with.

Sorry, I should have been clearer. I mean like Aquilegia x hybrida. I think I remember reading that it meant the wild species plant that wasn't hybridized but I am not at all sure.

As I understand it the 'x' denotes that the plant in question is a hybrid between two species as in;

Phygelius x rectus this is a cross between Phygelius aequalis and Phygelius capensis.

OR

Salvia x sylvestris a cross between Salvia nemerosa and Salvia pratensis.

OR to complicate it a bit more;

Salvia x superba a cross between Salvia nemerosa and Salvia x sylvestris.

from THE WET ZONE 8
SG

Doesn't that mean the cultivator of the plant? For example, Rosa x "Peace", or Rosa x "Secret" or Rosa "Sutter's Gold. (More or less, that's how it's written if memory serves right) Doesn't it signify the named type of the certain plant? All of them are roses, but the "X" after to show what is the named vareity of rose a person is purchasing.

No, the cultivar is listed in quotes after donating the genus, species, subspecies, or variety (or after donating the cross of the two species). Such as salvia x superba "Blue Queen".

Hey I found an explination hidden in one of the other posts

Sorbopyrus is an intergeneric hybrid which originated sometime before 1610, probably in Europe, and has since been propagated as a clone. The name Sorbopyrus is derived from the two parents, mountain ash (Sorbus) and pear (Pyrus). In his Manual of Cultivated Trees and Shrubs, Alfred Rehder listed this plant as X Sorbopyrus auricularis (Knoop) Schneider. Plants that are a cross between two different genera begin with an "X". Hybrids between two different species of the same genus have a lower case "x" between the genus name and the species name. Hillier calls this plant the "Bolwyller Pear".

There you go!

Thanks moosedog! I didn't know about the BIG X.

I learned something new today!

from THE WET ZONE 8
SG

Well, I learned more than one thing. First, I was totally wrong about what I remembered (big surprise) and also that different genera can be crossed. Like I said, I am new to this forum and have never attempted hybridization. My husband tells me he read in a botany book that different genera are not closely related enough to cross. Does anyone have any more thoughts on that? Also, not pertaining to hybridization,he wants to know how you can keep your stomach out of the way when you're down on your knees gardening? I told him what I thought.(LOL)

different crosses are being made all the time they are usually shakey at first,take the beafaloe for instance . crosses that were thought to be impossible are now happening.

So, just to review what was already said:
x denotes a cross. When used in front of a genus name it indicates that the genus is a hybrid (or intergeneric) genus derived by crossing plants of two different genuses (actually "genera" is the plural of genus, but most people don't know this). When two genera are crossed, a new genus is created, using parts of the names of both parent genera. In gesneriads we have, for example, "x codonatanthus" for hybrids of codonanthe and nematanthus, or "x achimenantha" for hybrids of achimenes and smithiantha. In orchids intergeneric hybrids are often fertile and have been bred with more than two genera such that hybrid genus names have gotten ridiculous. Rather than combine three, four, five or more genera into one looong name they have a system where such new multi-generic hybrid genus names end in the letters "ara". The first one of these was Potinara (Cattleya x Laelia x Sophronitis x brassivola). Now there are hundreds of such combinations.

By the way, clone names (i.e. "cultivars") are always shown with single quotes and are capitalized--i.e. Cantua 'Hot Pants'. Also, in writing cross names one should put the female parent first (though this is not necessary). So Sinningia leucotricha x canescens would indicate that leucotricha was the seed parent and canescens was the pollen parent.

About capitalizing the "X" in front of genus names--I never knew that. I will have to check with my botanist friend who knows even more silly rules about plant names than I do (by far).

I thought the pollen parent (male) was listed first then the seed parent (female).

SG

Salvia guy, No, it is female first! I used to think of the "x" as meaning "on", which would make the male first. Then I learned that I was wrong.

But, when the parents' roles are not known, it doesn't matter which name is first.

Just my two cents worth on bigeneric hybrids -- botany text books will often say that plants in different genera are not closely related enough to interbreed, and that does tend to be true -- but the fact is, it isn't always so. And scientists don't really know how closely related different plants are -- they are always moving things from one genus to another and then back again! Bigenerics are great fun -- I love trying to make them and think everyone else should too!
Joseph.

HuH?????????????????????? LOL

JCoum, Wide crosses like intergenerics certainly are fun. Some great creations have come about that way. Being a gesneriad grower I take particular interest in such crosses in this family. Some of the most interesting are crosses of nematanthus and codonanthe called x codonatanthus. They combine the color of the first group (aka goldfish plants) with the small cascading foliage and more open flower shape of the second.

But, in general, the most satisfying hybrids come about by working within a genus, with a set of goals in mind. I love to work with genera where there is a large number of available species and fertile hybrids. Especially where relatively little work has been done. In gesneriads we have quite a few such genera, such as sinningia, with over 60 species in cultivation, plus countless hybrids and mutated peloric forms, streptocarpus with even more species in cultivation, and chirita with about 30 (mostly new)species available. In these three, many of the species are newly discovered or new to cultivation, and thus, have never been crossed with.

In succulents, I found a similar situation with aloes--at least 200 species in cultivation plus many hybrids. Also, aloes are self-sterile making hybridizing much easier. Aloe hybrids vary in fertility but most seem to be fertile.

A problem with inter-generics is that hybrids are generally sterile, creating dead ends to breeding. An valuable rule in breeding is "the gold is in the F2" so if the F1 is sterile, the true potenial of such crosses is unrealized.

Certain genus will interbreed. However I think they have to be in the same family. For instance x Heucharella is a cross between Heuchera and Tiarella,but both are of the family Saxifragaceae. I don't have any other info. but presumably only certain Heuchera will cross with certain Tiarella. Perhaps some botanical genius can explain further.

Just came upon this 20-year-old thread!! I have a question for botanists: how does one pronounce the "X" when saying aloud the name of such a cultivar?

I say 'Abelia cross grandiflora' for Abelia X grandiflora.

Hmm... I see it's had a name change. Groan. Apparently it's now Linnaea X grandiflora.

.

An "x" will often be used in the name if the variety is not a true original species, but rather a hybrid.

Example: Quercus robur, Quercus x warburgii

because "Quercus x warburgii" is a variety that is believed to be hybrid (between Quercus robur and Quercus rugosa)

In speech, the "x" in this case would be pronounced as "hybrid". So "Quercus hybrid warburgii".

Although in many contexts a reader would not bother pronouncing the "hybrid" part, since it is a little verbose and redundant, overly technical.

They might either be likely to pronounce the "hybrid" only the first time the name is spoken, or perhaps even not bother pronouncing it if it has already been made clear it is a hybrid.