I planted 10 American holly trees that were all around 7-8' about 3-4 years ago. They are all doing well (except one and I rerouted the pool hose so it seems to be hanging on). They are all about 10' currently (except the one that was chlorinated). They have not been pruned, except some of the bottom branches to open them up underneath. Since they are in a tree shape right now, I was wondering if I could just cut the tops off each one (about 6 inches) to increase the growth/height/bushiness that I want. I planted them as a screen from a parking lot behind us. I don't necessarily want them bushy, just taller (quicker).
Cutting the tops off will make the bushier, but will not make them grow taller faster. The best way to get them to grow taller faster is to encourage them to put energy into growing upwards. In the spring, when you see new growth, trim off all the new growth that is not growing in the direction that you would like. This will focus the plants' energy on the growth that is growing in the right direction. This will produce somewhat leggy growth, but once it reaches the height you would like, you can trim some of the top branches to bring about the bushiness.
I have American holly bushes. What type of trimming tool is best for the job?
Loppers or pruning shears are fine.
This past fall (in CT) I transplanted several holly bushes. They greened nicely but this spring, the leaves on several have begun to lighten, and in some cases, go brown all together. This is not on all, but a few, and seems to be getting worse as weather warms. I am unsure if it is a disease or transplant shock. I have a good pH soil and water frequently, but they do not want to bounce back. Several are in full time sun while others are in 6 to 8 hours of sun, but all seem to have this issue.
How has the weather been where you are? Has it been unusually cold? Are the leaves that are turning light green or brown dropping? Let us know this and we can better advise you on how best to fix the issue.
If you have had a few nights where it was near or below 10 degrees F., the tree may start to go dormant and would act like a deciduous tree, changing leaf color and dropping leaves. This could be especially true of newly planted shrubs/trees, as the weather change would cause some confusion. However, it should recover on its own and grow new leaves once the weather returns to normal.
My American holly bush gets full of berries in the spring, then they shrivel up, turn black and fall off. What's the problem?
Oftentimes, this is due to poor pollination. If not properly pollinated, the berries will drop before they are fully mature. Lots of times changes in temperature, lots of rain, or a lack of pollinating insects are the cause. There is probably nothing that you can do for this year, but next year you need to take steps to make sure that the shrubs can be properly pollinated. These articles will offer suggestions for improving pollination: https://www.gardeningknowhow.com/garden-how-to/beneficial/insect-pollination-process.htm
My holly bushes are bare in the middle and only have leaves and berries near the ends. How can I improve them?
If the shrub has leggy growth like this, it usuallly indicates that the shrub is in need of some pruning. Hollies, as with most shrubs, can be pruned back by a third of their growth. Any more than that will likely harm the plants. This article should help: https://www.gardeningknowhow.com/ornamental/shrubs/holly/trimming-holly-bushes-how-to-prune-holly-bushes.htm
I had an old American Holly tree cut down. I was told that the suckers from the stump would form a Holly bush if I left them in place. Is this true? How long would it take to grow a bunch of suckers? How would I prune these suckers to make them bushier?
Yes, you can grow a new plant from the suckers, provided the plant was not a graft. It is unusual for hollies to be grafted, so you should be ok.
Select a few of the strongest looking suckers and prune out all the rest. Then allow the suckers to grow. As long as you are cultivating just a few of the strongest, they should fill out on their own and you can treat them as you would a small "normal" holly. No need to prune until they are at the desired height.
I have American holly bushes in front of my house and we had a really bad snow storm this winter and now my bushes are looking like they are dying with lots of brown leaves on them and the berries have turned black. What can I do to bring them back looking good again?
Here is an article that you may find helpful: https://www.gardeningknowhow.com/plant-problems/environmental/tips-for-saving-cold-damaged-plants.htm