I would like to set them in my garage that gets cold.
Unfortunately, your garage probably isn't cold enough. You'll have to keep them in the fridge for several months to give them the cold period that they need to germinate. After this, it will probably be another few months before they will germinate. I'd harvest and plant more than you need. It could take a year or two for some of them to pop.
Care of new Holly Plant outside?
There are several choices that can be suited, but there are two that stand out a little more. There is one deciduous and one evergreen. The winterberry is cold hardy and will lose its leaves. The blue holly will remain green during winter.
https://www.gardeningknowhow.com/ornamental/shrubs/holly/winterberry-holly-care.htm
https://www.gardeningknowhow.com/ornamental/shrubs/holly/growing-meserve-blue-hollies.htm
Im trying to sprout holley seeds. Can they tollerate being below freezing.
Yes. They will need this freezing temperature to break dormancy, and will not germinate without it.
This collection of articles will offer more information on holly shrubs.
Hi my holly tree has been thinning over the last year, it had new shoots but it really quite bare, i don't know what is wrong with it. It is about 40 years old. I have attached some photos. Please can you help me diagnose what is wrong with it? Thank you
It could be an environmental, pest, or disease issue. These articles should help pin it down:
https://www.gardeningknowhow.com/ornamental/shrubs/holly/holly-leaf-loss-in-spring.htm
https://extension.unh.edu/blog/2018/02/how-can-i-help-my-holly-bush-brown-leaves-dead-branches-it