Older, mature tree in Sun City AZ, which usually provides an abundance of large, sweeter grapefruit in normal conditions.
If the tree doesn't get fertilized once per month, then this will be the most likely case. This article will give you more information on why a grapefruit can fail to fruit properly: https://www.gardeningknowhow.com/edible/fruits/grapefruit/grapefruit-tree-not-producing.htm
I have a grapefruit that bears prolifically but the fruit does not mature
This can take nine months or longer sometimes. If it is well passed that, and still not ripening, then I would suspect that there is, either, too much nitrogen in the soil, or not enough phosphorus and potassium.
If this is not the case, then I would chalk it up to a pH imbalance in the soil. You can mitigate this by adding dolomitic lime, and iron sulfate to the soil along with your regular fertilizer in the spring.
Can you trim a grapefruit tree way back - taken a lot of the main branches off?
No, only broken or damaged branches should be pruned.
https://www.gardeningknowhow.com/edible/fruits/grapefruit/growing-grapefruit.htm
I have a pot grown grapefruit tree approx a metre tall bought four years ago -- has one pea sized fruit from last year and masses of bud that never sseem to open completely
These articles should help you with care.
https://www.gardeningknowhow.com/edible/fruits/grapefruit/growing-grapefruit.htm
https://www.gardeningknowhow.com/edible/fruits/grapefruit/hand-pollinating-grapefruits.htm
https://www.gardeningknowhow.com/edible/fruits/grapefruit/grapefruit-tree-not-producing.htm
The growth is on my grapefruit tree, orange tree, cactus claw and oleanders. I live in Phoenix Arizona
Those are galls! They are caused by fungal and bacterial infections, specifically spread by insects. They won't cause serious issue to the tree, but you may want to remove as many as possible in order to allow the trees to be as productive as they can. You will also want to treat with insecticides to prevent the issue.
These articles will help: https://www.gardeningknowhow.com/special/organic/what-are-organic-pesticides.htm
https://www.gardeningknowhow.com/category/edible/fruits/citrus
https://www.gardeningknowhow.com/category/ornamental/cacti-succulents/scgen
https://www.gardeningknowhow.com/.../oleander/oleander-growing-tips.htm
We have lived at this home since 2004 and our grapefruit tree was a mature tree when we moved in. Up until 2016 it produced the most beautiful, sweet Ruby Reds and in abundance. Starting in 2017 the quantity and quality of the fruit has degraded to the point you see now in the picture. The fruit is undersized and we have a total of 12 grapefruit this year. I have tried fertilizing with stakes, Mircle Grow for citrus, more water, less water but nothing seems to work. There are some dead branches among the leaves but I cannot figure out what to do. Like me, the tree is getting older, do they eventually old and stop producing? HELP PLEASE!
The general consensus is that they live for about 50 years when cared for flawlessly. They have much less of a lifespan with less than perfect care.
I would expect to get about 30 years from the tree. It could be that it has met its lifespan. It could also be that it is overfertilized. They do not feed heavily, oddly enough!
If letting some of the nutrients leach out of the soil for a year does not help, then you may look to trimming the tree some. This can help restore production if the tree is not at the end of its lifespan.
Here are some articles that will give you a little more insight: https://www.gardeningknowhow.com/edible/fruits/grapefruit/grapefruit-tree-not-producing.htm
https://www.gardeningknowhow.com/edible/fruits/grapefruit/growing-grapefruit.htm
When we cut the fruit it gives off a sulphur smell...The fruit is juicy and pink in color but has a strange odor....not very pleasant...We did just buy this home and tree was full of fruit in yard and is very old tree say 20 years...it is in Palm Desert CA We water regularly and it is very healthy tree any ideas?
Depending on how regularly, watering could be the cause. Once established, they will only need water during times of severe drought. The leaves will curl inward long before any drought damage is done, as this action will conserve water.
Unless it is showing these symptoms, then it will not be necessary to provide extra water.
Saturated soils, and citrus need for sulfur will make for the perfect environment to invite sulfur reducing bacteria. These will acidify the soil, and cause the smell that you are experiencing.
There won't be much need for action. If you would like, you can add just a little DOLOMITIC LIME sprinkled to the area to raise the pH slightly. Otherwise, just let the area dry out thoroughly between waterings, at least down to 4 or 5 inches before it gets any water at all, when possible.
This article will help you with grapefruit care: https://www.gardeningknowhow.com/edible/fruits/grapefruit/growing-grapefruit.htm