Growing Things: How best to apply rock around tree beds

Q: We live in a new development and we had our yard landscaped last fall. Around all our newly planted trees, the landscaper put about 7.5 cm depth of 2 cm rock over landscape fabric. Is this a good idea? I feel that the roots will not get any air, and the soil will remain cold all summer long. I would like any comments from you, please.

A: Depending on who you read or listen to, the expert opinions can vary on the recommended depth of rock mulch application. The consensus is that a depth of 5-10 cm should be safe. In my humble opinion, I never mulch to more than a depth of 5 cm. Having said this, if the soil drains well the 7.5 cm of rock mulch you describe should not be a problem. I would have a concern with the landscape fabric around the base of the trees. I have found that the fabric can easily get clogged with soil or dust, impeding the flow of water and not allowing the roots to breathe. My opinion is to remove the fabric around the base of the trees and leave the stone.

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Q: We have a large mayday that has been topped in the past to control its size due to the restricted area. Consequently, it has grown numerous cross branches that should come off to tidy it up. It would be much easier to prune it now before the leaves appear. Would that be OK or is there a danger of frost damage?

A: As long as the leaf buds have not begun to open, pruning would not harm the tree. Pruning maydays is best done in the early spring or late fall. I have just a brief word to those of you who are considering topping your trees. Topping a tree can be a very effective way of controlling a tree, especially if you have size issues. Be aware that this procedure does encourage a lot of extra growth on the tree. Wherever a branch is cut on the top framework of the tree numerous side branches are sent out. This method of containing growth is sometimes called pollarding. Pollarding an older established tree can sometimes result in the tree’s demise but it can be effective with younger trees.

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Q: I really enjoy your column! We have a vegetable garden that is old and depleted. For years I have been adding compost but I suspect it hasn’t been of any benefit to the patch as the soil is powdery and dry. So, what do I add to restore the soil? The patch is approximately 6 m by 9 m.

A: My first question to you would be to ask how much compost you are adding? From your description I would guess that you are not adding enough organic matter. Compost is an excellent choice in getting tired soil re-energized. I would recommend adding 15 cm of compost on top of the existing soil and working it into a depth of 20-30 cm . Normally I would advise adding 10 cm of organics but in your case 15 cm would probably be better. This means you would need approximately 8 cubic meters of compost. That would be approximately a tandem axle dump truck load.

Every week, Growing Things Outdoors runs online at edmontonjournal.com or, if you prefer an epaper format, epaper.edmontonjournal.com

Learn more by emailing your questions to filipskigerald@gmail.com, reading past columns or my book Just Ask Jerry. You can also follow me on X (Twitter) @justaskjerry01.

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