Because land does not depreciate, you cannot deduct anything for the value of land used in business.
You can deduct your out-of-pocket costs for setting up part of your yard as a show room, including materials and any labor that you pay for. These cost should be deducted on the business schedule C as business expenses, maybe under “advertising.” You can’t deduct anything for the value of your own or other people’ unpaid labor, only cost you actually pay.
also, if audited, the IRS will take a dim view of deducting personal expenses as if they were business expenses. So, you would need to show that you would not have had these expenses but for the business use. In other words, you would not have paid to make the yard look as nice if you were not a landscape contractor using it for advertising, And the only part of the cost you can deduct is the part that is in excess of your normal expenses to care for your property.
I do believe that you would have a difficult time proving that your landscaping expenses of your personal property was for 100% business use only. Therefore, I would highly recommend you not even try. Heck, I can't see how you can convince the IRS your landscaping costs of your personal residence was even one percent business use.