Question
I am looking at putting some decorative rock in amongst my flower beds for ground cover. Last year I used black wood chips and with the chinook winds of southern alberta, I lost over half of my product. So I need something heavier, like rock. I am looking at either grey limestone or black lava but I want to know if either will be too sharp or too hot for my flowers, I have tulips, lilies, hostas, and some rhododendron bushes. Please help, I need to get the rock ordered asap. Thank you!!

Answer
Hi Kayla.

Certain rocks can also affect plant growth based on their mineral composition. Limestone is a great example of this as it can actually lower the acidity of soil.

As far as being too sharp? I have never had a problem with this, as I always leave a buffer of at least a few inches around the base of the plant.

I am not sure of any affects from lava rock, as I have not used it enough myself to know.

Being in Alberta, many people use Alberta or Montana rainbow which is, nice and round from river erosion, lighter in colour, and has very little mineral content. This will accent all the different colours in your garden.

Rundle is also very available and popular around here. It is darker and provides more of a contrast.  

Burnco sells this as well as most other landscape centers.

Heat should not be an issue in this zone.

A couple of questions for you.

Are you using a landscape fabric or filter cloth of any kind? If so, what kind is it?

Do you have irrigation?

I also want to note that I am more specialized in hardscaping than gardening. I would like to see a specialized gardener chime in on this as well.

We can put this out to the answer pool. I am not sure if you have to ask the question again though?

Please get back to me and thanks for the question.

Hi Kayla. Thanks for asking the question again. I have now sent it through to our question pool. Hopefully it will be responded to with someone that has had this specific situation before, so they can expand on what we discussed. Best of luck to you with your garden this year.