garden Azalea & Rhododendron California Gardening

are my Rhododendron sick? or normal? zone9b

T Y

2 years ago

I live in Northern CA zone 9b. I planted 12 Rhododendrons two weeks ago around mid March.

There are two plants showing discoloration at the leave tip.

Please see the pictures:

One plant is Rhododendron
Anah Kruschke, the tip of some leaves are turning pinkish brown.

The other is Rhododendron Anna Rose Whitney, there are brown spots and pinkish brown tip on some leaves.

There other 10 Rhododendrons do not have such obvious discoloration so far. Are these situation normal? What can I do to cure, if these are due to sickness?

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Comments (7)

westes Zone 9b California SF Bay
2 years ago
You planted them in ground? In what kind of soil?

What is the sun exposure over the course of the day?
T Y
Original Author
2 years ago
Yes, these two Rhododendron were planted into the ground, same as the other 10, all at the same time.

Anah Kruschke (leaf tip discoloration) has a label indicates full sun or partial. It is at southeast side of the house and sees morning sun until about noon ish, then in the shade of the building.

Anna Rose Whitney (leaf tip discoloration + spots) also has a label indicates full sun or partial. It is at northeast side of the house and sees morning sun until about 10-11am ish, then in the shade of the building.

I have a Jean Marie De Montague right next to Anah Kruschke at Southeast side of the building and Nova Zembla right next to Anna Rose Whitney at Northeast side of the building, so far these two Rhododendrons show no discoloration, fingers crossed!

The soil is purchased from garden center Topsoil. I mixed in Dr.Earth acid lover organic fertilizer.

https://drearth.com/product/acid-lovers-dry-fert/

My area soil is more like clay type than like sand type. But the other 10 Rhododendrons are in the same soil. So I am wondering if the discoloration for these 2 plants were from "moving shock", i.e. they will eventually get over with overtime? Or due to some sort of sickness infections? or other?

Thanks so much for experts' help!
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westes Zone 9b California SF Bay
2 years ago
last modified: 2 years ago
It is not clear what soil these plants are in now. You purchased topsoil, but how specifically did you use that? Did you:

* make a raised mount of just the topsoil

* mix that into the existing soil

* build a planting hole in the clay and dump topsoil into that hole

I want to hear the details of the planting before giving any opinions.
luis_pr
2 years ago
last modified: 2 years ago
The soil looks awfully dry. Do youwater them as soon as the soil feels dry at a depth of 4" or so (the typical depth for rhodies' roots)? I would not put rhodies in full sun in areas with a lot of harsh sun. They are not used to being outside so acclimating to more sun and less water than they got at the nursery might be beneficial. The soil should be acidic, well draining and they should not be planted deeply.
T Y
Original Author
2 years ago
Thanks for the suggestion, Luis! I will increase watering and monitor.

Westes, they were planted along the line of - "build a planting hole in the clay and dump topsoil into that hole". I made sure their root top is exposed.

I am more concerned about the dots on the leaves than the leave tip browning as in "Anah Kruschke" picture. I am thinking maybe the tip browning was due to dryness / sunburn? But what can cause the dots on "Anna Rose Whitney"? I am quite concerned!

Expertise please help. So far, the other 10 Rhodos seem to do fine....
westes Zone 9b California SF Bay
2 years ago
last modified: 2 years ago
@T Y I do not think those plants can survive with the soil you have, or in the manner you have planted them. Let me break this down into parts.

Let us consider how do Rhododendrons grow in the wild. Commonly in the Pacific Northwest, these plants live in the canopy of large Conifer forests. This implies a few things:

1) They get dappled light, not full sun

2) They live in acidic soil, typically with a pH of 4.5 to 6. Garden topsoil might typically have a pH from 7 to 7.5.

3) The soil in the forest is lots of organic material that falls from the trees, sitting on top of well-drained sandy loam soil. Rhododendrons are shallow-rooted plants that live in this well-drained organic material, and whatever water does accumulate at the bottom of the organic material quickly drains out through the sandy loam.

Now let's consider the problems in your planting:

1) These plants are getting full sun for much of the day. You need to either put them in the shade of larger plants or on the North side of a building that stays in shade all day long. I have mine under the canopy of a large tree, but even that gives too much light for the more sensitive species.

2) Your soil is simply the wrong pH. You probably can adjust it with peat moss, but there are additional problems because you planted the soil into a hole in the ground. If you did amend the soil, the planting should be on a raised bed above your soil level, a minimum of 18 inches high, preferably 24 inches.

3) Your clay loam soil is a poor draining soil if yours is anything like mine. That will simply drown Rhododendron roots. By opening a hole in the ground and planting topsoil with high organic content into that hole, you have the worst of all possible combinations. The amount of water in that planting hole will be controlled by the clay soil around it, not the topsoil. But the topsoil itself is likely highly water absorbent. So you will have a bathtub in high water conditions. Rhododendrons need moist soil that breathes all the time. What you can easily do to remedy this is to put the pH-adjusted topsoil above the clay loam, as described above. That will help to ensure well-draining soil and good oxygen exchange in the soil area above the clay loam soil.

What city are you in?
westes Zone 9b California SF Bay
2 years ago
@gardengal48 (PNW Z8/9) should probably be in this thread.

are my Rhododendron sick? or normal? zone9b

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westes Zone 9b California SF Bay

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are my Rhododendron sick? or normal? zone9b

Comments (7)

westes Zone 9b California SF Bay

T YOriginal Author

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westes Zone 9b California SF Bay

luis_pr

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westes Zone 9b California SF Bay

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T Y
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