I have a home office. Can I include the landscaping expenses as part of the total expenses?

The US Tax Court has allowed landscaping costs as part of the home-office deduction in limited cases where the taxpayer used his home as his sole office and his clients regularly came to his home to conduct business.  If that's your situation, you may claim landscaping as part of your deduction.  Otherwise, it's not advisable.

Where would this expense be appropriately entered?

If you qualified, you'd count it as a maintenance expense on the house, then reduce it by to the % business use.