Relax, it could be normal. Starting in mid-July and throughout the month of September, a customer will call at least once a week concerned about their redwood tree because they think a significant amount of foliage is turning orange-brown.
Most times the browning foliage is completely normal
Natural exchange of needles
Redwoods are evergreen trees, meaning they keep their foliage all year round like most conifers. Even though evergreens do not lose all their foliage each year like deciduous trees, they will perform what is known as an “exchange of foliage” and will eliminate the older needles closer to the trunk in late summer. If the tree is healthy, it should have produced new, spring foliage at the tips of the branches to, theoretically, replace the older needles.
But they are dropping A LOT of needles!
That’s because redwood trees are cladoptosic (there’s your botany word of the day!). Cladoptosic trees drop not only individual needles but the accompanying shoot they are growing on. If, when the shoot falls, it doesn’t make it all the way to the ground but ends up resting on the tips of lower branches, it can make the look of the browning needles on the lower branches seem excessive. However, if you can reach one of the low branches and shake off the brown needles, you will see that the branch looks instantly better. A couple of good windy days will blow the shedding needles to the ground and slowly eliminate the browning look of your redwood.
But my trees have never done this before!
If this is supposedly an annual event, then yes, you would expect your redwoods to drop needles every year, but with nature, there are many variables that go into a tree’s life cycle and changes in those variables affect how trees respond each year. Many of our clients will tell us they have never seen their redwood do this before. Water is one of those variables. If the tree did not receive the same amount of water as in previous years, due to either low winter rainfall or a change in irrigation, then the redwood might drop more needles than before.
Are there are other reasons redwoods branches would turn brown?
Unfortunately, yes. Root diseases such as Armillaria (which takes advantage of poor soil drainage) may be present in the soil and will cause branches to brown and die. There is also a disease called canker that kills the tips of the branches. Insects such as the Cypress Tip Miner and Redwood bark beetle also attack the tips of branches and cause them to turn brown. However, in all the years we have been looking at browning redwoods in Contra Costa County, rarely are any of them caused by these factors. Redwoods, if well cared for, tend to be fairly disease and pest resistant.
Providing optimal care for your redwoods:
By providing good cultural care you can help your redwood avoid the diseases or pests listed above.
Full Sun: Redwood trees thrive in areas of the landscape that offer full sun, although young trees need the partial shade to get started.
Water: Redwoods are native to the Coastal Ranges from southern Oregon to Big Sur in California, where they get most of their water from the fog. When they are planted inland, away from the coast, they need regular water. For best growth, maintain moist, well-drained soil. One of the best planting locations is directly next to a lawn. If planted far from a lawn, be sure to provide regular summer water (for at least the first five years). Redwoods will continue to grow during periods of soil wetness but standing water may encourage fungal diseases. And lastly, do not allow sprinklers to blast directly against the trunk of the tree.
Be patient with your browning redwood. By Thanksgiving, your redwood should be back to its healthy evergreen self. However, if you are unsure, we are happy to have one of our arborists stop by to (hopefully) confirm that the brown foliage you see is normal!