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The rhododendron pictured below used to live in Vancouver BC, zone 8ish, and was cut back and moved a few years ago to the northern end of the British Columbia coast, about 30 miles south of the Alaskan border. Although the plant is not losing its new leaves they have a yellowish cast that does not look right. There are other largish rhododendrons in the area that don't have the problem so we don't think it's a problem with the very long summer days and very short winter days. It's planted in sand that was trucked in to replace the forest duff so it has good drainage (1.5 meters of rain annually) but perhaps is lacking organic material.

Sorry, I don't know the variety.

yellowish rhodo leaves

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  • do you mean its planted into actual sand? Or sandy soil?
    – Bamboo
    Jul 10, 2018 at 23:22
  • @Bamboo Actual sand, I was told they removed 3 feet of forest duff replacing it with construction grade sand. You can't build on the forest floor there, it's too thick and compressable.
    – Al Maki
    Jul 10, 2018 at 23:37
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    How about an acid based fertilizer with Manganese, Magnesium and Iron Chelate?
    – kevinskio ♦
    Jul 11, 2018 at 1:06
  • Rhododendron like acidic soil, and sand is absolutely not the right medium for them to be happy. Seek out the type of fertilizer mentioned in the comment above by Kevinsky - the Iron Chelate element is critical because your plant is chlorotic. In the UK, I'd use Sequestrene Iron tonic, which is a solution of just iron to sort out the chlorosis, with a separate general purpose acid based fertilizer, but see what you can find. Light applications of composted materials around the plant ongoing would be helpful, but don't let it sit against the trunk or stem.
    – Bamboo
    Jul 11, 2018 at 10:02
  • So this stuff will make the sand acidic? major grins.
    – stormy
    Jul 12, 2018 at 4:10

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Sand? Pure sand? Forest duff is better. Sorry, all soil is great soil the only caveat is that one learns how to manage that soil. Us humans thinking we can make soil better has been one of our worst downfalls in horticulture.

Three feet of forest duff? That says an awful lot about your environment. I made vegetable gardens in caliche clay just by dumping decomposed organic matter on the surface and a preliminary double dig to make a 'raised' bed that would never need any more 'tilling' but most certainly will need to be watered and fertilized.

The sand is a done deal, your rhododendron will just have to make do. Rhododendrons evolved with clay soils, partial shade. Slow growth to allow the forest debris to decompose enough that there might be a bit of chemistry to add for the plant in addition to the great tilth of the soil.

Your Rhody needs a balanced fertilizer in the worst way. Regular water. Sand, sigh, why do we humans think we know stuff about drainage, plants, soil ecosystems when we don't? Careful with mulching. Their roots are very shallow and adding more than 1/2 inch might smother the roots and their access to oxygen.

So they told you that they could not BUILD structurally on the forest floor because it is too thick and compressable? Wow. Compression is necessary for building structures. The duff is not compressable. It is pure undecomposed organic matter that is very very flammable. A fire can be started by a spark that will smolder for months with no signs of smoke before it bursts into fire. I actually tested this and by golly, no smoke at all. Looking closely into the duff you most certainly can see embers, hot red burning stuff with no smoke!

Duff is amazing and I would have removed the duff and then double dig to fluff up the soil the original indigenous soil, then plant and add a bit of balanced fertilizer. Decomposed organic matter thinly on top of shallow rooted plants. This is acid loving so I would do a pH test for sure.

Plants are amazing that they can survive what we humans throw at them. Chop them completely down, plant them in sand and hope for the best? And look at this guy! He is mightily trying to survive with NO chemistry, no comfy clay and organics, sitting out there in bright hot sunlight surrounded by hot gravel. This is a forest floor plant. Partial shade, cool soils, clay soils SOME chemistry with which to do photosynthesis is all they ask and this plant has none.

And I see signs that glyphosate was sprayed in the last month. Is this true?

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  • It belongs to a family member who has a fishing camp in the Queen Charlotte's. I was up visiting. It's folk wisdom there that you can't build on the duff. When you walk in the woods you typically sink several inches in the moss and duff. It rains about 9 months of the year. From the air it looks like a sponge. I should have thought of the pure sand angle, but there's plenty of organic matter available to lay on top of the sand so it should be easy to amend. As to the glyphosate, I don't know, but it's possible. What are the signs and how would it affect the rhodo?
    – Al Maki
    Jul 11, 2018 at 2:23
  • Just looks as if all that gravel has been sprayed with glyphosate, hey not a big big deal but this rhododendron is not a happy camper. Duff is amazing stuff. I would definitely scrape it back before beginning to build. Duff is NOT decomposed. Once it finally gets decomposed the soil organisms will be able to use it for energy until then it is a mat of organic matter. Give that Rhododendron some balanced fertilizer as well as a thin top coat of decomposed organic matter. You can purchases this stuff, look for 'decomposed mulch'. A thin coating of this and a bit of balanced fertilizer...
    – stormy
    Jul 11, 2018 at 10:16
  • Duff also called detritus, duff and the O horizon, is one of the most distinctive features of a forest ecosystem. It mainly consists of shedded vegetative parts, such as leaves, branches, bark, and stems, existing in various stages of decomposition above the soil surface. So, not decomposed at all, huh? There are literally dozens of other sources that describe duff as decomposed. This just scratches the surface of why this answer and comment are incorrect.
    – Tim Nevins
    Jul 11, 2018 at 14:12
  • One of the main definitions of decomposed is to not look at all like it was before decomposition. Duff is pine needles and leaves and sticks but not much decomposed. As soon as that stuff decomposes it is eaten by the life in the soil and gets 'decomposed' even further as well as pooped out in the top soil, being mixed into that top horizon. I am not sure I understand your logic and conclusion. Why would you think I don't understand duff?
    – stormy
    Jul 12, 2018 at 4:08
  • Do you know why duff is so flammable? Because it ISN'T decomposed. It still has all those energy bonds intact. I am discussing duff in the high desert. Not in the tropics. If there is such a thing. My goodness, I am surprised at your comment.
    – stormy
    Jul 12, 2018 at 4:14

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