La Verne Resident Suffers from Redwood Blues

Q. I spoke with you about a week ago on the phone regarding some declining sequoia trees in La Verne. You were kind enough to offer your help by reviewing a few things. You  requested I send you pictures, watering information and treatment information. The pictures are attached and the watering and treatment information is below. The trees were planted in late 2008/early 2009.

Watering:

The trees are watered 7.1 MIN 4 Start times 2 days a week the sprinkler is a spray head. It was changed out about 6 months ago to the sprayers. Previously it was bubblers.

  

Treatment:

The sequoias/redwoods trees were treated on 2/29/16, 3/25/16, 5/6/16, 5/27/16 and 7/1/16 and the service was suspended in August. Each service was a deep root injection with the following chemicals/fertilizers:

Companion 2-3-2 high rate

Essential plus 1-0-1 high rate

PH reducer high rate

Arbor care 15-8-4

Iron max 6%

A. From what I can see your redwoods are not doing badly; considering they are growing in an environment that is not conducive to their growth  (that is, anyplace that is not the central and northern California coastal region) . There are some problems however:

1.       Their skirts are hiked up. Redwoods, especially those growing in inland areas, prefer not to trimmed at all during their lifetimes. The‘skirts’ are those branches which hang down to the ground. They provide both a humid environment underneath the tree that allows for a more gradual shift in moisture of the root zone between irrigations and protection from bark chewing deer. They also prevent people from holding activities in the very sensitive root zone of the trees that could damage them.

2.       They’re suffering from compulsiveness. Redwoods prefer a deep layer of their own refuse (needles, bark etc.) that they produce over their lifetime. This thick layer of spongy organic material provides for an even more gradual drying out of the important ‘root zone’ soil underneath the trees. The redwood has particularly shallow roots so this, along with the protective skirt, creates a growing zone for the tree that is necessary for it to survive. Also, the breakdown product of this needle and bark layer is beneficial to those organisms in the soil that are beneficial to the tree. Removing the needles from the trees (or planting a lawn under them) can be a death sentence.

So what can you do?  Do not trim your redwoods. Also, until they can produce a layer of their own mulch, put down a six-inch-thick layer of small fir bark or gorilla hair fir bark in an area that represents their eventual canopies.

Start changing the water schedule gradually to once a week for 20-40 minutes (remember you changed from a bubbler (good) to sprinklers (not so good)).  Do not feed them, and remove either the lawn or the tree in it as redwoods and lawns are not compatible in your situation.  And of course, limit any traffic under the redwoods.

Feel free to contact me if you have any other questions.

Cheers,  Frank

Drought Has Culver City Resident Singing the Redwood Blues

Q. I live in the Culver City 90230.  We have a small grove of coastal redwoods, three trees about 50' tall and two saplings about 10' tall.  They evidenced considerable twig die-back, I assume in response to prolonged drought and reduced irrigation in the name of water conservation. However now all but one seem to be recovering with the help of winter rainstorms, with new foliage appearing on most branches and some stump sprouts.  Last summer we received an arborist's opinion that the trees were a lost cause and should be replaced, but now we see signs of new growth that inspire a certain optimism.  Can you give a prognosis?  If we are more generous with water, will these trees continue to recover or is this a lost cause so that we should have them removed and replaced with less thirsty trees?

A. It is normal for Redwoods to die back under drought stress and then re-foliate later once the drought is over in their native habitat, however Southern California is not their native habitat. When they recover from drought here they may not recover completely and you might have some top die-back -keep an eye out for it. Also their reaction to drought, which is to die back until conditions are better, becomes more amplified the larger the trees get. Several things can help your redwoods deal with not only drought stress, but the stress they receive being trees that are growing in an area that rarely provides their ideal conditions (foggy mornings, cool nights).

1.       Restrict traffic underneath the trees. Redwoods have shallow, sensitive roots that are damaged by human activity underneath them.

2.       Do not trim their 'skirts'. The apron of branches that occurs if you do not prune them acts as a buffer to the dry, sunny conditions that cause the soil harboring the trees' roots to dry out to rapidly and place great stress on the tree.

3.       Place a 6" layer of bark mulch under the canopy of the trees. This helps keep weeds out, and, most importantly, helps the buffer the drying out of the soil. The decomposition of the bark provides nutrients essential to the health of the redwoods.

4.       Water regularly. Although actions #2 and #3 will help keep your tree hydrated, they do need regular watering. About once a week for 20-40 minutes should be more than enough for most systems.

Also you might want to consider starting over again with the 'Aptos Blue' variety of Redwood. 'Aptos Blue' is more drought tolerant, having been collected from a grove of redwoods far inland from the central California coast. Staring over would allow you to keep the skirts on and restrict traffic underneath the trees.