blue spruce tree with double top trunk

[mikenospam72]

Is it recommended that one of the two top tips be cut off and if so, which one. the lower or the upper.

[bamboo]

How big is the tree?

[bamboo]

How big is the tree?

[mzamborini]

The tree is roughly 4 feet tall.

[bamboo]

Remove the one that will leave the best overall shape. Alternately you can remove 1/2 of one and allow the other to grow larger for a season and then remove the rest of the one you cut half from.

[Stephen Henning]

Yes and always cut off the lower one, never the highest one. Most spruce, and especially Colorado Blue Spruce, have a type of apical dominance that does not transfer to lower branches like it does in most other plants. This means that if you cut the leader off a spruce, you will probably end up with a bush and not a tree.

[Andrew Ostrander]

Your point is overstated. If the leader of a blue spruce is broken or cut off, one nearby young branch will take over as the leader, and the tree will continue to grow like a tree, not a bush. Last year I had 3 twigs vying to be the leader and growing vertically. Now the dominant one has been determined, I wonder how, and the other 2 are turning horizontal.

Sometimes 2 leader candidates both continue to grow vertically and you get 2 trunks. Apical dominance seems to be effective only near the very top, and once they grow long enough with side branches, neither will turn horizontal.

[Stephen Henning]

The highest bud becomes dominant and releases auxins that prevent the lower ones from becoming dominant or growing vertically. It is an especially strong response in Colorado Blue Spruce. An older spruce can take several years to recover and develop a new leader. There are documented cases where removing the leader without creating a dominant bud has resulted in such stiff competition among buds on the highest whirl that a new leader never formed and the Blue Spruce were essentially turned into bushes.

Apical dominance is caused by the upper most bud releasing auxins that keep lower buds from becoming dominant or growing vertically. When pruning Blue Spruce Christmas trees, care is taken to cut at a 45 degree angle just above a bud so only one bud gains dominance and only one leader forms. Any time that dominance is transfered, vertical growth is stunted. Since Blue Spruce are slow growing trees, this stunting can be a problem.

In Christmas tree production, pruning is done both to control size and shape but to also insure a dominant bud.

[Andrew Ostrander]

[Stephen Henning]

Because it doesn't have it's dominance stopped by any other terminal buds.

All terminal buds try to release auxins that travel down and only down to other buds below them and keep them from being dominant. Since there is no bud above the top bud, it keeps its dominance. Buds that are nearly side by side have trouble preventing dominance in each other. The higher the dominant bud is above any other buds, the better shot it has at establishing dominance over the other buds.