Very slow growing holly saplings

elderberry

We've got about a dozen small holly saplings which have self-seeded in the garden, but they are very slow-growing, maybe as little as 1cm per year. Is this normal for holly? I'd quite like one of them to get to a decent size, but it won't happen in my lifetime at this rate.

gjautos

Our holly was very similar. Really slow growth, then all of a sudden it took off and seemed to double in size almost overnight.