Sleuthing in the garden – Rhododendrons part 2

Previously on Botanica Chaotica I was dealing with a sad chlorotic, root weevil ridden mess of a rhododendron. As a reminder.

The darn thing has looked this way for years. Then, last year, a discovery. Our well water has a pH of 10 and rhododendrons prefer a soil pH in the range of 5 to 6.5 (American Rhododendron Society). I had been fertilizing with an acidic fertilizer, but what is the actual soil pH?

First, let’s recheck the pH of the water in the well. On May 12, it was 9.02 and for those who care, electrical conductivity (EC) was 519. EC is a measure of dissolved ions in the water – generally the higher EC is, the less pure the water is. So, although the pH today is slightly less than it was in midsummer last year, it is still too high and the water isn’t very pure.

How does that compare to the water in the stream? The pH there was a much more reasonable 7.5 and EC was quite a bit lower at 117. Obviously, there is some basic/alkaline bedrock 200 feet down where our well resides while the water here aboveground is almost neutral.

Now the soil. The pH of the soil near the rhododendron was 6.71 and EC was 89. This was a lot better than I thought it would be. The rhododendron is under a grand fir (Abies grandis), so the decaying needles probably provide some acidity as well as the acidifying fertilizer I add. And, even though this is really close to the pH level that rhododendrons like (only slightly above 6.5), this rhododendron is not happy. A second soil sample from under an apple tree about 30 feet away showed a pH of 6.05 and an EC of 42. Time to think about the evidence.

  1. This rhododendron has been a lot of work. It requires watering twice a week during the summer to keep it from wilting, I am fertilizing it with an acidic fertilizer and it still is unhappy, and it gets lots of root weevil leaf damage on the leaves. It is ugly. Maybe moving it somewhere else on the property would make it happier?
  2. Most rhododendrons planted around the yard have had similar problems. Chlorotic, wilting leaves – need constant attention to look marginally acceptable. This tells me that the site is not moist enough nor acidic enough for rhododendrons. Seems to me that perhaps this is a losing battle trying to grow a plant that is simply not adapted for our yard. I need a plant that is better adapted to the winter muck/summer concrete clay soils and pH that I have now, not more these time suck plants that look like crap.
  3. A tour of the remaining rhododendrons and other plants on our property that also like acidic soils provides some additional evidence.

My two camellias. One, a tea plant from a friend (Camellia sinensis ‘large leaf tea’) and Camellia sasanqua ‘Yuletide’. Both are looking pretty good with normal green leaves and haven’t required almost constant watering. A quick look at the International Camellia Society website shows that they are fine with a similar pH (5.8-6.5) as rhododendrons, so why are my camellias doing so much better? No weevil damage on the leaves either. Just, for some weird reason, the rabbits are irresistibly drawn to chomping the heck out of my tea plant.

Blueberries. Have been a complete and utter disaster. They also have been an ugly, chlorotic mess. Not only that, but several of the plants we bought came in with Phytophthora root rot and end up dying back periodically. Between that and fighting with intense bird pressure for the berries, they were too much work. These are going away and will probably be replaced by a greenhouse at some point. Right now, the blueberry area serves as a holding area for newly propagated plants (table on right).

Most of the other rhododendrons on our property show signs of chlorosis. These in the south stream garden.

Typical slow limp to the death. That is one plant that has a sad flowering branch in the upper left, another one in the lower left, and another in the lower right. It was happy until I got my mitts on it. Blech.

And, lastly, out in the deer garden. Yuck, yuck, yuck. You would think that since I like the color chartreuse, I would like these chlorotic rhododendrons. But, I don’t. It’s a gross, dull, sickly green, not a vibrant, lush, fresh green.

The two exceptions have been this one, Rhododendron ‘Superflimmer’. I think part of the reason that it looks so good is because the leaves are variegated and that hides a lot of the chlorosis. But, if I squint closely, I do see some yellowing between the veins.

And this, Rhododendron pachysanthum. This is the only rhododendron that has really thrived here on our property. I will have to try and propagate this one to see if it does well in other spots around the yard. What makes this one different than all the others? I don’t know.

All of this leads to one thing. The evidence points to the fact that my site is not adapted for rhododendrons and I am not going to fight it anymore. Even if I move the native rhododendron to another spot, the evidence suggests it is going to be just as unhappy. I am ripping it out this year. This also leads to a common theme that I am going to be touching on in future posts. Many times gardeners get frustrated and blame themselves for their plant failures. The truth is, sometimes, it’s NOT your fault. My rhododendron scenario is a prime example of this. As a gardener, I was becoming frustrated by my lack of success with rhododendrons. I kept thinking what am I doing wrong? Why am I so bad at this and why are all of my garden friends so much better at growing luscious, healthy rhododendrons? I needed to take a moment, reflect on the situation, do some investigation, and listen to what the plants were telling me. They weren’t happy and I wasn’t happy. Now, I have the answer. It’s not me (it’s them!). My site and my environment are not the correct ones for growing rhododendrons.

So, take a look around your garden. Are there plants that you have tried over and over that just won’t succeed and it’s bringing you down? What are your plants telling you? I can say, it really has been quite liberating to get rid of a problem that has been bugging me for years. I can now invest that time and energy into something that might be better…

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