This may be caused by several factors:
- high soil salts
- chronic water stress
- high temperatures
- windy conditions
- high light exposure
When excess soil salts are present and taken up by the plant, they accumulate at the leaf tip and leaf margins. When concentrations become high enough, toxicity and leaf necrosis occur.
Chronic water stress will often cause a plant to reduce transpiring leaf surface. Since the tip and edge of leaves are the “end of the line,” those tissues dry out first.
High temperatures and/or (4) windy conditions can cause excessive water loss, so again the tip and edge of the leaves would run out of water first, and the plant – as in water stress – would start to lose leaf tissue.
High light exposure could also be a cause. Dogwood in its native habitat is usually an understory tree, or is at least in the shade of taller trees for much of the day. Again light exposure is related to transpiration and excess water loss.
In your letter you suggest the leaf tip dieback is an annual problem. Therefore, I would tend to rule out #3. However, #1, #2, #4 and #5 could, one or all, be contributing to the leaf tip necrosis. You will have to determine which factor(s) is the likely cause.
You should also realize that plants with thin, tender leaves (ex. Dogwood, Japanese maple) are not well adapted to desert climates. Santa Maria with its winter rains (average 12.3 inches), summer drought and persistent afternoon breezes (winds) is in reality a desert climate (dry air).