Here is an article I found
Since chromosome segregation is driven by microtubules, colchicine is also used for inducing polyploidy in plant cells during cellular division by inhibiting chromosome segregation during meiosis; half the resulting gametes therefore contain no chromosomes, while the other half contain double the usual number of chromosomes (i.e., diploid instead of haploid as gametes usually are), and lead to embryos with double the usual number of chromosomes (i.e. tetraploid instead of diploid). While this would be fatal in animal cells, in plant cells it is not only usually well tolerated, but in fact frequently results in plants which are larger, hardier, faster growing, and in general more desirable than the normally diploid parents; for this reason, this type of genetic manipulation is frequently used in breeding plants commercially. In addition, when such a tetraploid plant is crossed with a diploid plant, the triploid offspring will be sterile, which may be commercially useful in itself by requiring growers to buy seed from the supplier, but also can often be induced to create a "seedless" fruit if pollinated (usually the triploid will also not produce pollen, therefore a diploid parent is needed to provide the pollen). This is the method used to create seedless watermelons, for instance. On the other hand, colchicine's ability to induce polyploidy can be exploited to render infertile hybrids fertile, as is done when breeding triticale from wheat and rye. Wheat is typically tetraploid and rye diploid, with the triploid hybrid infertile. Treatment with colchicine of triploid triticale gives fertile hexaploid triticale.
When used to induce polyploidy in plants, colchicine is usually applied to the plant as a cream. It has to be applied to a growth point of the plant, such as an apical tip, shoot or sucker. Seeds can be presoaked in a colchicine solution before planting. As colchicine is so dangerous, it is worth noting that doubling of chromosome numbers can occur spontaneously in nature, and not infrequently. The best place to look is in regenerating tissue. One way to induce it is to chop off the tops of plants and carefully examine the lateral shoots and suckers to see if any look different. If there is no visual difference flow cytometry can be used for analysis.
It would be interesting to treat some seeds and see what you get!?! That would be easy to do.