Hi, I live in East York. I am building a raised garden bed. It’ll be about 32inches above ground, and I am using panels with chicken wire on top for rodents trying to climb in. I am wondering how concerned I should be about rats or voles or moles tunneling under. I haven’t seen any signs, depressions in the ground in spring or piles of dug dirt.
It is important to protect the garden from rodents that may try any means to get in! From your description, it sounds as though the top of the bed will be well-protected by the chicken wire.
There are two main types of raised beds. One sits directly on the ground, while the other is elevated and entirely raised off the ground (e.g., on legs). As you mention that the bed will be 32 inches above the ground, this sounds like an elevated bed.
Where a raised bed sits directly on the soil, it is very vulnerable to entry by tunnelling rodents. With elevated beds, burrowing should not be a concern, although if the bed somehow is accessible from the bottom or sides (e.g., through holes), the critters might be able to climb in from underneath to get at the tasty plants.
If you feel that the bottom/sides of the bed are not animal-proof, it would be wise to also line the entire bed – bottom and sides – with poultry wire or hardware cloth.
A note for those with raised beds sitting on soil: with hardware cloth, it is important to use a product with appropriate sized holes (e.g., ½ inch holes to protect plants from moles, ¼ inch holes to prevent voles from getting at the plants).
The following site shows what different rodent holes look like and will give you an idea what to watch for if a rodent starts visiting your garden. If you do begin having a problem you may want to enlist the help of a professional exterminator.