Careful Gardening

The holly plant, unlike many, is not an asexually reproducing one. Generally speaking, the female plants, which produce berries, are considered more aesthetically pleasing.

For the purposes of propagating these females, growers often pair them off. For example, one will usually plant three blue princes (the males) with one blue stallion (female). By doing so, the male's generative nuclei, or microspores, are almost guaranteed to fertilize the female's egg nuclei, or megaspores. This deliberate pairing ensures that the female will be successful with one of the males, although the heredity of two males will ultimately be lost.

So if we label our blue stallion H and our blue princes T, P and A, the outcome might be, hypothetically, that while P and A have environmental influences on H, T becomes the only plant to pass on its gametes and form zygotes with H. The existence of P and A, while largely superfluous, does serve a purpose as insurance that H will prosper irregardless of whether they do or not.

But P withers and dies, because a dog repeatedly pisses on it.

A is unused, but is able to be transplanted for the insurance of another blue stallion, however the gardener generally opts not to use A's gametes, because they are aesthetically inferior.

T fertilizes H, and H prospers.

The zygotes (berries) of T and H are used to create hybrid plants. The grower becomes careless, and rather than keeping the line of hybrids in tact, allows them to cross-polinate with other hybrids. The result is that by the fourth generation, the grower is lucky if one in sixteen plants resembles the original in any way that can be described other than "vague."

Eventually, none of the plants survives outside of a latent genetic relation, and has no relation outside of genus and species.

H dies.
T dies.
A dies.

But with careful gardening, H has been successful.