On patents read upstream the link Alice posted and in addition:
Here is an excerpt from Patents.com, since I am not a patent lawyer and don't wish to write down erroneous details.
Patent
o Plants propagated asexually, e.g., by rooting, layering, budding, grafting, etc.
o Includes cultivated sports, mutants, hybrids, and newly found seedlings
o Excludes tuber propagated plants or plants found in an uncultivated state
o Inventor(s) must have asexually reproduced the plant to establish reproducibility
o Claimed invention must be a distinct and new variety of plant, not just a flower or a fruit
o Term - 20 years from date of filing
Plant patents are used to protect plants that are propagated asexually. If the plant is capable of sexual propagation, that is fine, but the plant also has to be capable of asexual reproduction. It can include cultivated species, mutants, and newly found seedlings, but it excludes plants found in uncultivated state. That is important. If the plant is found in an uncultivated state, you cannot obtain a plant patent on it. The reason is that products of nature are unpatentable. Man has to have intervened in nature to do it. And the Congress in its wisdom said, if you found it in a cultivated area, man cultivated in the area, so there was some effect on the plant, so it is patentable, but you cannot go to a rainforest some place, pull one out and obtain a plant patent on it. You can get another kind of patent on it; I will talk about that later. The inventor must have asexually reproduced the plant so that there is some proof that the plant is asexually reproducible. The plant must be a distinct, and a new variety of a plant. You cannot obtain a patent on a flower or another piece of a plant. It must be the entire plant. The term is 20 years from the date of filing.
Plant Patent Owner Can Prevent
o Asexual reproduction of the claimed plant in the U.S.
o Using, offering for sale or selling all or part of the claimed plant in the U.S.
o Importing all or part of the claimed plant into the U.S.
This is in addition to the rights that we talked about earlier that all patent owners have. Before 1995, these were the only rights that a plant patent would give you. In 1995, Congress changed the rules of the game. There have not been any court cases to determine what the new law really means. At a minimum, however, you can prevent people from asexually reproducing claimed plants in the U.S. using, offering for sale, selling all or part of the plant in the U.S. and you can stop them at the border from bringing that plant into the U.S. In order to actually enforce a plant patent, you must have evidence that the infringing plant your plant. It cannot just be a similar plant. It cannot just look like your plant, it truly has to be a clone of your plant, and that is the significant limitation of plant patents. What you can protect is limited to clones.
Plant Patent Application Content
o Characteristics that distinguish the plant from related known varieties, including colors of plant structures, if distinctive
o Where and in what manner the plant was asexually reproduced
o Location and character of area in which a newly found plant was found
o A single claim in a specific form
o Two copies of color drawings or photographs
o Declaration by inventor(s)
o Can be filed as a provisional application
A plant patent application is very straightforward. The main problem is coming up with a biological characterization of the plant - the shape of its pieces and the color of its parts. That is what makes it a distinct kind of plant. You have to use color charts like the Royal Horticultural Society color charts. With such charts, under a certain light, you look through the hole in the card that has a certain color, and characterize the color of the flower and other parts of the plant that make it distinct. You have to tell where and the date on which the plant was asexually reproduced. Remember, I said that the inventor has to have accomplished that task. The key point here is to make sure the inventor has supervised, at least one instance of asexual reproduction. If somebody else does it independently, that does not count. Remember, it has to be found in a cultivated area if you found the plant. A plant patent contains a single claim because you are claiming the entire plant. Two copies of color drawings or photographs are needed. I am sending around a declaration form - it is a one or two page form that you fill out depending on how many inventors were involved. You can even file a plant patent application as a provisional application at a lower cost. Obtaining a plant patent application can cost you the U.S. Patent and Trademark Office fees of a low hundreds of dollars to file, and it costs you in the high hundreds of dollars to get it to issue as a patent. You do not have to hire a patent practitioner, but if you do you will probably have to hire one by the hour. If you do the work, i.e., you do all the biological characterization, all the patent practitioner has to do is put it in the right form and in fact, if you type it up using Microsoft Word, it might only cost you $600 to pay the practitioner to do the actual patent application process. There is a prosecution process where the Patent Office, once the patent application goes in, checks their databases to make sure there is not some similar plant out there. If there is, then a battle will go on. But if your plant is distinct, then the application just goes to issue.
If you want to read more, here is the link
http://www.webpatent.com/talks...
Now registering a Cultivar is usually done for Awards purposes. Every plant derived from that will carry that name. Now if someone else comes across another plant like this and likes it very much, that person can register that one under another Cultivar name they wish to give it and propagate it also.
Look here
http://www.users.on.net/~gmcor...
Cultivar
Any named individual and its’ vegetatively produced progeny. It does not include self-pollinated or cross-pollinated plants. ie. a particularly good example of an orchid may be given a cultivar name to uniquely identify that plant from other lesser quality plants of the same species. That plant and all its vegetatively produced progeny, eg. mericlones, and divisions, can use that cultivar name, but not sexually produced progeny, ie. from seed. All plants bearing the same varietal name should be identical and flower identically, excepting the normal seasonal and environmentally caused variations.
Now I hope I am not saying anything wrong here, but it is my understanding that if you patent your plant nobody can meristem/tissue culture -propagate your plant and profit by selling hundreds of idendical clones.
I don't think that restriction applies to your registered cultivar.
Anyone else here add to this?
And of course as Daisy pointed out so delicately, we are all your friends .. . . 
