I don't think this should be a concern. Better they buy something and you get your commission than they buy nothing and you get nothing right?

I think the thing that you should keep in mind is that having the plants you will no longer be "expert" in one product (your garden iron, and ornaments). So, presumably your knowledge of your garden ornaments (which presumably has been the whole product line for the business since it was born) is much more extensive than it is with plants. What if you get someone come to your store and they want to know something from left field about the plants that you have and no-one at your store knows the answer because these plants are a new thing. They may leave thinking that you/your staff don't know anything about your products.

This is probably an over-exaggerated example but I hope you can see that I'm just saying that its best if you stick to what you know best, rather than get a new product line and only kind of half know it.