Thane, do they look healthy? If so, the moss carpet cannot be diverting water away from the rhodies.

Is there some specific reason you feel you need to fertilize, a symptom you are addressing? Rhododendrons have a fine network of surface roots, and normally cultivating soil under them is not recommended. These are low nutrient requirement plants, much more so than most shrubs. Grown in soil with an acidic ph fertilizer is rarely needed.

Mine have never been fertilized, but I do top dress with compost in Spring.

Moss growing around/on rhododendronds is an indication that your soil is somewhat on a wet side. While Rh. do love moisture they resent to live in boggy conditions.
If they are overall healthy then you have a perfect case of symbiosis when moss consumes excessive moisture that otherwise might be fatal to rhododendrons.
I have a similar situation where fairly old Pieris happily grow in a middle of the moss patch.

EGO, this is Washington State. Our deck furniture grows moss :)

MorZ, sorry, didn't pay attention to where poster was from. :-)

> Is there some specific reason you feel you need to
> fertilize, a symptom you are addressing?

The lady at the nursery said that I should feed them a couple of times a year, so I was planning to. It does look healthy and happy, but when it was blooming (before we bought the house) my mother-in-law remarked that it looked like it could use a bit of food, and that would make it bloom a lot more. (It wasn't blooming as vigorously as the neighbor's.)

I haven't had the soil tested yet, but my neighbor says we have very acidic soil.

Thank you for the comments, EGO and MorZ8.

Thane, it seems to me in the PNW, lack of late summer water when plants are setting buds for the next years bloom is more commonly reason for low bloom, along with failure to deadhead spent blossoms, then of course too much shade. Interestingly, overfertilization is another reason plants can fail to bloom. You'll enjoy your yaks, they are among my favorites.

EGO, your input is always appreciated, I hope you read the tone in my post. Our moss does have a life of its own...I heard someone from here ask Martha Stewart how to deter it once, and MS replied...but it's so charming and quaint, why would you want to eliminate moss? Ummmm, because its persistent and slippery underfoot in winter, and tiny slugs hide in it...

I have a large hidcote lavender, SE exposure on a sharp slope that is many years old and still going strong. It grows moss in winter.

MorZ8, thanks for the advice. Do you have any tips on watering frequency as we enter the late summer months? These rhodies have been largely ignored for about 2 months as the house changed hands.

We have a stronger ocean influence here, so cooler, but I have drip irrigation installed in my beds. Shrub and perennial beds, including rhododendrons, are given one slow deep soak per week when we haven't had rain.

If the beds were containing only established rhododendrons and other shrubs and not packed tightly with perennials like mine are, a deep watering every 10 days could be enough. I do approx 7 days here, 10 for the shrub beds I tend next door...there is nothing newly planted there (and summer water isn't free even here).

Mor, would you mind addressing a little bit of an aside? I don't think thane will mind.

When I first read this post, my very first (and second and third) reaction was that this person was seeing lichen. Spoken from a person in the Southeast! Lichen might be one of the most common occurances on azaleas and rhododendrons in the east.

My question is this: does lichen appear frequently in the PNW? If so, what kinds of plants does it seem to set up housekeeping? I've never been to that part of the country and am truly fascinated by it.

Breathtaking. When is the best time of year to visit this part of the country?

Rhizo, I suppose that would depend on what you enjoy doing. In Spring, crocuses and daffodils begin to bloom as early as late February, and the trees begin to bud and flower. The rivers flow fast from winter runoff, problematic if you are a hiker. But keep in mind that the weather can be maddeningly cool and damp this time of year, with the same gray, 50-degree days in February continuing right up to the first of July. particularly here on the coast.

From the 5th of July (notice I didn't include the holiday, the 4th) to the end of September, the weather is typically gorgeous , averaging 75ish. Thanks to daylight savings time and northern latitudes, summer sunlight can extend well past 8:30 p.m.

June is typically the most disappointing month, weather-wise  you keep expecting summer, and the gray lingers; July and August are the best if you can schedule then.
The leaves begin to turn color in October, with beautiful, almost New England-like landscapes to explore. But keep in mind that the end of daylight savings time means that darkness drops on us before 6 p.m., and gray, cloudy weather begins to move in for days at a time by mid-October.

(Winter isn't necessarily cold, you can walk on the beach (raingear)...better yet, curl up in front of a fire with a good book in a cabin somewhere...not a lot of gardening to view during this period.)

My older mature Rhododendrons have thick moss/lichens on the larger/older mature trunks/branches. I've pruned them and want to encourage new branch growth in these areas but am comcerned that the initial budding process may be hampered by this covering. Should I remove it by hand, or take a soft brush to gently remove it?

Usually growth on trunks and branches is lichens. It is more scaly and will grow in full sun with occasional moisture. Moss is fuzzy and requires shade and moist conditions.

Here is what the NC Extension says:

"Gardeners sometimes get excited when they notice lichens on the stems of dying rhododendrons. Lichens are a gray or green fungal/algae combination that grows on anything including plants, fences and rocks. Lichens won't kill the plants. It doesn't kill fences or rocks either. Lichens often thrive as the rhododendron canopy thins from another problem."

We have a rhododendron that is over 50 years old, Trilby, a gift from my husband's mother. That rhododendron and other ones have moss growing on the trunks and branches, green and soft moss. Some of our azaleas also have the moss. There are branches that are dying. Our weather is very moist and rainy. Until last year it looked healthy, but noticed some branches were starting to die. There is an ivy growing underneath it, so I plan to rip it out. I plan to trim all the dead growth off. Is our rhododendron just at the end of it's life span. Is there any way of saving this rhododendron? It's too large to move, so I plan to find a healthy growth underneath that has rooted and move it to another area. This rhododendron is very special to us because my husband's mother gave it to us and we have moved it with us three times. It has been in front of our forever home for the past 40 years and is as tall as our house and very wide. It has been the most beautiful rhododendron all these years and we would like to do whatever it takes to save it, but moving it would be impossible for us. It has been healthy in that same area all these years, so I wonder if it's just at the end of it's life or if it's because of the rainy weather causing the moss. We would appreciate your help!

You are on the right track. Rhododendrons have shallow roots so the ivy growing underneath is definitely detrimental. Pulling it out may disturb the roots of the rhododendron too much. A carefully applied application of Roundup would be more gentle on the rhododendron roots. Actually what would be best would be to trace each ivy vine back to its trunk and cut it off there and treat the stump with concentrated roundup. The roundup should be applied immediately after cutting the stem off. I use an old rubber cement jar with a brush attached to the lid to carry around my Roundup concentrate.

Moss is supposedly harmless, except it adds considerable weight to the branches and weakens them. It indicates shade and moisture and lack of ventilation. When cutting out dead wood, you might keep an eye toward opening up a little ventilation to reduce the shade and moisture.

I would keep a nice mulch layer underneath after you remove the ivy. Besides keeping down weeds, this is good for the roots and helps the plant through drought and cold snaps. The best mulches for rhododendrons are conifer barks or conifer needles.

One last concern, make sure no walnut leaves or roots are near the rhododendron. Walnut kills rhododendrons.

Thank you for your help! I also noticed today 1 branch with lichen, so I will trim that. The ivy is just a tiny indoor variety and hasn't put down roots under the Rhododendron yet, so I will pull it out and then use Roundup where the ivy roots start. I have been researching about moss and lichen and found that a little moss can be beneficial, but seeing the ivy is starting to slightly cover the ground underneath our Rhododendron I will remove it before it really gets going. Do you think fertilizing it will be good at this point? 🤔 It blooms the first week in June and I thought it may be beneficial now since it is having a difficult time. Thank you for taking time to help!!

If the ivy is just tiny, pull it out and be done with it. No need to use any RoundUp! And it is important to understand that lichens are different from moss and lichens pose no threat to the plant. If I were to remove all the branches that had lichen on them from my trees and shrubs, there might not be much left :-) Moss really doesn't cause any harm either although it can indicate that growing conditions may be off.

You never want to fertilize a stressed plant. And as was mentioned several times upthread, they are not needy plants in this regard. Other than mulching with a light layer of compost, I have never fertilized any of mine and several are easily 50 y.o. If you do feel a need to fertilize, wait until after the normal bloom cycle and use a light hand.

Thank you so much for answering my question so quickly. I will hold off on fertilizing and use compost which I have a lot. I think just getting rid of the ivy and trimming dead branches should help a lot. Thanks for your help! This Rhododendron is very special to us. My husband's mother bought it for us in 1970, she passed away in January of 1974 and the Rhododendron bloomed when she died, instead of it's normal time in June. We have moved several times and always took it with us to our new home. 🥰

For a rhody with that much sentimental significance, I'd consider starting some additional plants from cuttings. Since cuttings are a form of clonal propagation, they will essentially be the same plant as you now have.......just in a much younger form :-)

And cuttings not all that hard to do - Propagating Rhododendrons