One leader is always what you want in almost all conifers, especially arborvitaes. Multiple leaders will tend hold snow loads while a single leader tends to have less snow build up and shed snow easier.

Cut the double leader babies back to one leader. Pick the strongest one to save.

Dave

Thanks so much for your answer Dave. That was my instinct so will do it! I passed over the larger ones, besides being more expensive, they had 3 or more leaders! Years ago I saw a TV show that tied the leaders together in the winter, and I certainly didn't want to have to do that to 18 of them. This year I admired a 20+ year old screen of them at a nursery/gardens, and every single one of them was tall and straight and looked like there was only one leader.

Funny you should bring this up, I have them on both sides. I lost quite a few of the original ones that were here when I moved here twenty five years ago. About half were replaced about twenty years ago They are taller than my house now and two years ago during a very mild winter we had a very wet heavy snow that bent one of them over badly they all have several trunks. So today my son and I tied it up.I hope it stays .

I read in Willian Cullina's book on Native trees and shrubs of North America "I was always puzzled as to why such a cold climate tree would be so snow breakage prone. until I spent some time in northern Maine during the winter.Wild trees are much more diffusely branched and stocky,sheding most of the snow and preventing breakage.Sometimes natural and human selective pressures are completly at odds"

Brings up one of my peeves-the selection of unbelievably crap arborvitaes over the years. I live in the native home of this plant, and it handles snow with ease. But some of the junk that is sold for landscaping is probably best left to split apart under load. Then the homeowner can replace with a decent cultivar.

+oM

Emerald arborvitae does better with snow. But it is still better to find one leader.

Actually, Emerald arborvitae (Thuja occidentalis 'Smaragd') is one of THE MOST prone of the arborvitae cultivars for splaying open due to heavy snows. This is because the wholesale plant producers need to produce their plants as quickly as possible for maximum profit potential. A nice full plant will also sell much quicker/be more attractive to consumers and so the growers allow many low stems to develop and those stems ultimately become multiple leaders that splay apart in heavy snows.

Thuja occidentalis 'Hetz Wintergreen' is one of the best of the arborvitae cultivars for handling heavy snow loads because it tends to grow naturally with only one leader being produced.

Any of the arborvitae cultivars can become plants that can tolerate snow loads as long as you start with small plants and allow only one leader to develop. Unfortunately, most of the plants that can be found in the nursery trade are already multiple-leader plants when purchased - with the notable exception of 'Hetz Wintergreen'.
Mike

Below is a link to a post in this forum that shows mature Thuja occidentalis 'Hetz Wintergreen' growing at the Bickelhaupt Arboretum in Iowa. There is also a link to a place that sells small plants at a very reasonable price. This cultivar grows fairly fast 2' - 3' per year once established and with good moisture.
Mike

Here is a link that might be useful: Link to pics of T. o. 'Hetz Wintergreen'

If you have deer, then snow load is only one worry. Arborvitae are dessert for deer. You will definitely want to research it before winter.

Thanks to you all for this discussion! I'll have to find my tags in my garden box file to find what I actually have, but when I was picking out my "babies(18-24") I tried to find those with single leaders. I was mostly successful except for 3 of 18, so I will prune out the 3. I live in deer country, but where they are shouldn't be a problem, unless we have extremely odd weather. Yes, the industry has certainly sprung up to the demand of non native trees and shrubs and alot of us are trying to grow stuff that we likely shouldn't, but with the help of all the gardenwebbers we ARE getting smarter!