Depends. You can apply for yourself. Plant patents can be several hundred to thousand dollars plus when you add up all of the additional fees. If you want to propagate the cultivar yourself or license to various nurseries, you may want to patent it yourself. However, if the plan is to sell the patent, then you may not need to bother. Some nurseries will buy the non-patented plant from you outright and then patent it themselves, saving you money.