How to keep cats off my seed starting shelf?

[jal_ut]

" Unfortunately my maw who is 85 and don't ask for much insists that she Not Have To go out when its -10F to feed her 3 cats."

Ummmm...... perhaps you could feed them for her when its -10F ???

[Hillbilly Homer]

...She insists on doing HER chores!..

[jal_ut]

"My growing spot is in the old garage that's attached to the house."

Hmmmmm, I have a refrigerator in the garage for summer use to hold veggies. I put a cardboard box on top of the fridg with some padding in it for the cats. There is a chest freezer next to the fridg, the cats can jump onto the freezer then up onto the fridg and sleep in the box. Cats do seem to like high places.