Some bark from redwood has separated from the tree. Squirrels and possibly rats have made nests in the space between the bark and the tree. Can these sections of bark be removed?
As long as this bark is ready to peel, and not securely attached, then it should pose no threat.
Normally, this will happen in nature, and it won't disturb the tree too much to have some creatures using it as a home. Leaving, or removing will be completely up to you.
This article will give you information on Redwood Care: https://www.gardeningknowhow.com/ornamental/trees/redwood/redwood-tree-information.htm
This can be normal, but excessive bark drop would indicate a dying tree. Unfortunately, your photo did not come through, so I cannot see the damage.
Likely, you are seeing the signs of root rot. There are many types, but they are all fungal or bacterial. Armillaria and Ganoderma will be two of the most common things that many will see this time of year.
The problem is that by the time you notice symptoms of the diseases, it is already too late. You can try to correct with fungicides. This article will help: https://www.gardeningknowhow.com/garden-how-to/info/using-fungicides-in-garden.htm
These articles will help you to understand root rots:
I have a 80-ft sequoia gigantica (big tree redwood). Currently there is grass under the tree that is not doing well. I would like a little more of a natural setting and get rid of the grass. What companion plants are recommended or should I just the replace the grass with mulch? I live in the Vancouver WA area.
The best thing to put under a tree is mulch out to the dripline.
Redwoods will outcompete anything growing under the tree, even grass, for water and nutrients.
ain trunk and continue growing taller? Tree is 8 yrs old. Approx 30-35' tall. Healthy green. Live in East TN.
You may want to have an arborist come out and look at it because they normally are not prone to disease. Japanese beetles will eat the foliage and canker has been noted. Here is more about dieback:
Tree is well established. Well over 20 years old. Has small buds evident. Branches are green inside when scratched with my fingernail and supple. We had an abnormally cold spring with temps dropping into the 30’s. Tree has some leaves but less than 10% of tree. Tree was fine last year
Redwood trees tend to do this when the climate is not, quite, what it should be. Unfortunately, as we move into the brunt of the Grand Solar Minimum, this is what you will come to expect from the tree. They do not do well with cooler than normal temperatures.
Here is an article that will offer more information on the tree:
We have three well established redwood trees ~30 years old in our backyard. In the shade underneath them, and given the needle drop, is there any shade-loving plant that I can plant under them? Ferns, hosta? Thanks1
Sure, you could do those, Rhododendrons, Blueberries, and other acid loving shade plants. This article will help offer some more suggestions:
Giant Redwoods,what is the process to plant from seed?
This will be done in container, outside. In order for the seed to germinate, you will need to provide conditions that the tree would grow in, natively. This can be unreliable, though. They have a low germination rate, and even under perfect conditions may not spark.
You can try and help it along. Scarification and soaking will help to improve germination rates, but you will be at the mercy of luck with this one.
Here are some articles that will help: