Should I deduct non-capital business expense of $670 as an annual expense or depreciate?

I think you mean you purchased a greenhouse for your business and want to know if you can deduct it as an expense in the current year or enter it as an asset that will need to be depreciated. It is an asset so needs to be entered as such, but you can choose to expense it since it costs less than $2,500 in 2024. You will see an option for that when you enter the asset in TurboTax:

You  can take the election but it will apply to all similar assets in all businesses you operate for that year:

You could also depreciate the asset using the section 179 allowance that would allow you to deduct the full cost of the asset up to the amount of your net income for the year, with the balance being carried forward to next year. You will see an option for that when you enter the asset in TurboTax.