Wood ash around rhodies

6 years ago

The house I moved in to Nov. 2019 has 3 well established rhodies and 3 equally established gardenias. 20+ yr old specimens.
My new roommate has been discarding the wood ash from his meat smoker around the bases of them in relatively undispersed piles. I have removed as much as possible from the soil surface, minding the shallow roots. I have also swept the ash from the rocks that protect the base.
They do not look horribly affected. They do, however, look what I consider to be "stunted", from my canna cultivation days. Slight chlorosis up top, noticeably minimal new growth considering 2 weeks of nice, cool spring sunshine. Some necrosis on the edges of a few more mature, mid/low canopy leaves.
While I await soil test results, please help me contemplate my best strategy to negate any effects of the ash and readjust soil pH if necessary. Is an approach differing from one used to acidify a "normal" alkaline soil necessary?
Thank you for your time and knowledge!

Featured Answer

gardengal48 (PNW Z8/9)

6 years ago

Using wood ash directly in garden is rarely advised (best composted first to neutralize) and never around acid loving plants. The ashes are excessively alkaline (pH of 10-12) and can make the growing conditions for rhodies, azaleas, blueberries and similar plants extremely inhospitable.

btw, despite ken's assumption to the contrary, wood ashes are a way of increasing a soil pH in areas were it is excessively acidic. So yes, they can and do have a significant impact on pH.

I'd agree with flushing the plant(s) liberally with water. And if necessary, using a soil acidifier to counteract.

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Comments (6)

Embothrium
6 years ago

Try liberal watering
ken_adrian Adrian MI cold Z5
6 years ago
pH is an exponential function ... i doubt a little ash made any significant change in such ... unless he is one of those insane smoker dudes.. that have smokers on wheels and actual drag this huge machine with him.. where ever he goes ... lol ...

but of course.. the testing is the way to go ... when you took the soil sample.. i hope you got down a few inches.. and didnt just test the surface ...

what i wonder about.. is if he threw them under there.. still hot ... that might burn or heat the surface roots .. injure the roots ....

where are you.. big city name .... was winter anything out of the ordinary.. including very mild ... sometimes you get damage in milder winters.. than you do i what you think are bad winters ....

you might also consider ... that with 20 year old plants.. the important feeder roots... might not be all that close to the trunks ...

i dont know about your comparison of a canna background to shrubs .... other than it is good to know.. you arent a total newb to horticulture ...

im wondering.. also .. if you might not be a bit hypersensitive to finding problems .. now that you have found this .... i always like to err on the side of seeing what how it develops.. rather than over reacting and trying to love something to death ... to be clear.. you are on the right path ... testing ... but we are not dealing with annuals or perennials... that have a much shorter life cycle ...

this is where i ask you for a few pix.. and when you load them ... the plants are obviously in bad shape.. and all my presumptions are moot ... lol.. could you favor us with with such???

ken
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Embothrium
6 years ago
With the soil acidifier being a last resort due to how quick jumps in pH points are murder on soil microlife. Because there is actually a huge difference in acidity or alkalinity between each pH point.
ogdirtbeard
Original Author
6 years ago
gardengal48 (PNW Z8/9)
6 years ago
They don't look as bad as I expected. But they do look stressed, most likely due to the pH being off somewhat and the resulting lack of nutrient availability to the plants. It would not hurt to apply a dose - according to label directions - of an acidic fertilizer, like HollyTone or MG Azalea, Rhododendron and Camellia fertilizer. Both will help to acidify the soil as well.