Ask Mr. Smarty Plants

What you are suggesting, I think, is essentially cloning (à la Dolly, the sheep) or producing an identical copy of a plant. There are much simpler ways to produce clones in plants.   In fact, many plants produce clones on their own.  For example,  Populus tremuloides (Quaking aspen) reproduce by seeds and by root sprouts.  The ones that reproduce by root sprouts are clones.  This article from the US Forest Service says:

"Aspen is noted for its ability to regenerate vegetatively by shoots and suckers arising along its long lateral roots. Root sprouting results in many genetically identical trees, in aggregate called a "clone". All the trees in a clone have identical characteristics and share a root structure."

Other examples of plants that produce identical copies of themselves are strawberries and many grasses that send out stolons (modified aboveground stems) or rhizomes (modified underground stems) that take root to form new plants.

For most plants, cloning is possible by taking cuttings and rooting them in a proper medium.  Here are detailed instructions for cloning plants from cuttings.   A more complicated and time-consuming way to produce plant clones uses very small pieces of plant and tissue culture.  In fact, recently a Russian scientific team, using tissue culture, was able to reproduce a plant, Sylene stenophylla, from tissue that had been frozen for 30,000 years in a squirrel's burrow in the Siberian permafrost.

Interspecific grafting (and even intergeneric grafting, although not generally successful) is also possible.  This involves connecting shoots of one species to the root stock of another species creating a compound genetic system with each species contributing its strengths (e.g., the root stock from the species with a strong root system and the shoot from a species with a desirable shoot system).

Finally, with genetic engineering techniques it is possible to insert genes from another species into a plant species and have them be functional—even genes from a completely different kingdom (e.g., from Kingdom Monera [bacteria, blue-green algae and spirochetes] into Kingdom Plantae).  Here are some of the goals in genetic engineering of plants:

• improving nutrition of food plants (e.g., golden rice that contains beta-carotene a precursor for producing vitamin A)
• making plants resistant to fungi, insects, herbicides and herbivores (e.g., inserting the genome of Bacillus thuringiensis, a bacterium, into plants [potatoes, corn, etc.] to protect them from Colorado potato beetles and corn borers)
• modifying plant genomes to produce a specific product (e.g., coffee beans without caffeine)
• changing the ripening and storage qualities of the fruits of plants (e.g., slow ripening tomatoes)