Hi,
Those spikes disturb the gophers, BUT if the gophers smell food and food is straight forward in that direction, they'll pass even through the spike.
So it can help a bit, but won't avoid the damages.
Normally those spikes are sun powered, so after some hours in the night ... You're left with no protection ...
The only thing that works is trapping them, especially now before the females start their new batch. Welcome to the world of trappers !
Gopher cages or buried containers ( 80liters/20 gallons trashcans ) work of course. The gophers will make their tunnels around the containers, but won't get inside.
Near the containers, they often surface. That will help you in spotting their galleries for trapping.
I just got the confirmation of why one of my rose bush did crumble last year ... The foot got chewed. It is recovering, and if rodents don't bother it too much, it should grow back.
I have one common milkweed (Asclepias syriaca) - one of my child's dream - we call it the parakeet plant - The tunnel goes from the rose to the parakeet ... I'm p*ssed !
Killed two beasts in that tunnel. I keep it opened and trapped. I'm sure that there is at least one (?last?) beast in activity in that tunnel... My parakeet is young and has not blossomed for the two last years.Should do this year or Should have done this year ? That is the double question for now . Hope it gets back after the winter ...
So, help yourself and use the gopher cages. Don't get light with them, or they'll take the higher price on your plants.
Rodents, gophers here already got lettuces , tomato plants, a young cherry tree, one fig tree, two rose trees ... and I'm taking care of them. Just imagine what they would do, if I left them unmonitored ...
Good luck !