Gravel causing K imbalance?

[Foggy Paul]

Hi all. I posted a few months ago about our sickly Howea belmoreana. @Darold Petty correctly diagnosed it as a K deficiency and recommended I put greensand down. I did, and the new leaves look much, much better. More recently I posted about our sickly Euterpe edulis, which I thought was due to sunburn (in the middle of the winter). I think there is some burn, but as the leaves get worse, they are starting to look like the Howea leaves did. The common denominator is that both are in beds with a dark grey gravel mulch. Is it possible that something is leaching out of the gravel, causing a K imbalance? I put down greensand at the Euterpe as well and hope that if this really is the problem, maybe it will help with the two leaves that are just now starting to open.

Howea:

Euterpe:

[Merlyn]

@Foggy Paul do you know the type of rock?  Granite is mostly silica and may not dissolve much, but marble chips are mostly calcium carbonate and dissolve much faster.  I don't know if it would be enough to really affect the palms or not.  Two things come to mind:  too much of one nutrient can inhibit absoption of others with "nutrient antagonism"

So too much N or Mg = K deficiency.  The other is soil ph:

But it looks like Potassium is only affected by really low pH, which is probably not an issue.

[sonoranfans]

Potassium is the most soluble nutrient, the most easily washed away by rain or irrigation.  If you have high drainage you may need to put potassium down more often.  I use sulfate of potash or sulpomag(lanbgeinite) for the potassium hogs in my yard.  As you stretch fertilization intervals potassium will become deficient first in high drainage.  Rocky soil has low nutrients and minimal cation exchange to maintain the potassium from fertilizer.  Green sand contains potash so yes it will be a source of potassium that helps a K deficiency.   Perhaps adding some soil with cation exchange will help.

 

In addition to Merlyns information I would add that high sodium in soil can inhibit potassium intake.  Sodium and potassium are electronically similar and potassium uptake transporters cannot tell the difference.

https://onlinelibrary.wiley.com/doi/abs/10.1002/jpln.201200417

 

[Jonathan]

It looks like it could be cold damage possibly? 

Does E edulis generally do ok in SF?? I tried the orange crownshaft variety here and found it pretty wimpy...our climates are reasonably similar if you're in the cooler parts of SF. 

Just a thought.

[Rivera]

I haven't attempted to grow this species, but I would've assumed (perhaps wrongly) that Euterpe edulis would not get enough consistent warmth here in San Francisco. 

I have been top dressing my H belmoreana with a bit of azomite and lots of kelp meal. I use kelp meal a lot in the garden, along with a broad spectrum organic fertilizer mix. Generally no nutritional issues, though deficiencies may take time to present themselves and my garden hasn't been around that long. 

Not sure about the gravel, but if you're on native SF sand, it's mostly volcanic in origin, which is good. I've certainly adulterated my soil with quite a bit of gravel (including cheap orange box store purchased pea gravel) around my H belmoreana, and haven't noticed any ill effect. 

[Silas_Sancona]

2 hours ago, Rivera said:

I haven't attempted to grow this species, but I would've assumed (perhaps wrongly) that Euterpe edulis would not get enough consistent warmth here in San Francisco. 

I have been top dressing my H belmoreana with a bit of azomite and lots of kelp meal. I use kelp meal a lot in the garden, along with a broad spectrum organic fertilizer mix. Generally no nutritional issues, though deficiencies may take time to present themselves and my garden hasn't been around that long. 

Not sure about the gravel, but if you're on native SF sand, it's mostly volcanic in origin, which is good. I've certainly adulterated my soil with quite a bit of gravel (including cheap orange box store purchased pea gravel) around my H belmoreana, and haven't noticed any ill effect. 

PLENTY of gravel in landscapes -and elsewhere- around here and like you, absolutely no ill effects on 98% of plants planted..

As far as any potential deficiency issues related to Gravel / rocky soil, all comes down to the chemical make up of the rock / gravel..

Volcanics like Lava / Pumice ..and rocks like Granite /  Granitoids can contain lots of K ..depending on their origin.. Look at Hawaii,  plants grow like weeds right out of the Lava in many areas..

Sedimentary rock types ( Limestone / Sandstone / Shale / Mudstone, etc, ) can contain lots of Calcium  ..and / or Gypsum.. Too much of both can cause issues w/ plants not already adapted to growing in those types of soil..

Outside of specific areas like parts of S. Cal, most of the deserts,  Nor' eastern CA, Sierras, ..and the coastal / central valley areas -which often contain a lot of alluvial " stuff "  ...and  Clay..  soil in numerous spots in coastal CA can contain lots of Serpentine / Serpentinite < Metamorphic in origin >  ..Soil derived from it ..if there is any..  can contain high levels of stuff like Cadmium, Cobalt, Iron,  and Nickel / is often severely deficient in Calcium and other,  more essential nutrients.  A lot of plants that did not evolve in it, don't like it / often will perform poorly when grown in it.

 

[Foggy Paul]

22 hours ago, Merlyn said:

@Foggy Paul do you know the type of rock? 

No. It's dark grey and looks kind of lava-ish, which of course is the look we want. But it doesn't have surface pores like the boulders we have, which I think might actually be lava, even though the guys at the landscape yard don't call it that. Thanks for the detailed response though! I got a C in college chemistry and decided the subject wasn't for me 🙂

[Foggy Paul]

4 hours ago, Jonathan said:

It looks like it could be cold damage possibly? 

Does E edulis generally do ok in SF?? I tried the orange crownshaft variety here and found it pretty wimpy...our climates are reasonably similar if you're in the cooler parts of SF. 

Just a thought.

Originally I thought it was sun damage. It's possibly a bit of a stretch here, but I have consistently seen it on lists of "cool tolerant" palms and thought I'd give it a go.

[Foggy Paul]

4 hours ago, Rivera said:

Not sure about the gravel, but if you're on native SF sand, it's mostly volcanic in origin, which is good. I've certainly adulterated my soil with quite a bit of gravel (including cheap orange box store purchased pea gravel) around my H belmoreana, and haven't noticed any ill effect. 

There seems to be quite a bit of variation in our small yard. Parts of it are very sandy, other parts are actually somewhat clayey (although nothing like what I grew up with in SoCal). There also seems to be construction debris, probably from when the house was built in 1924. Drainage is generally really good but I always test a location before planting a palm there.

Anyway, thank you all for the responses. Seems like it's probably not the gravel and more likely similar soil composition in the two locations.

[BayAndroid]

5 hours ago, Silas_Sancona said:

PLENTY of gravel in landscapes -and elsewhere- around here and like you, absolutely no ill effects on 98% of plants planted..

As far as any potential deficiency issues related to Gravel / rocky soil, all comes down to the chemical make up of the rock / gravel..

Volcanics like Lava / Pumice ..and rocks like Granite /  Granitoids can contain lots of K ..depending on their origin.. Look at Hawaii,  plants grow like weeds right out of the Lava in many areas..

Sedimentary rock types ( Limestone / Sandstone / Shale / Mudstone, etc, ) can contain lots of Calcium  ..and / or Gypsum.. Too much of both can cause issues w/ plants not already adapted to growing in those types of soil..

Outside of specific areas like parts of S. Cal, most of the deserts,  Nor' eastern CA, Sierras, ..and the coastal / central valley areas -which often contain a lot of alluvial " stuff "  ...and  Clay..  soil in numerous spots in coastal CA can contain lots of Serpentine / Serpentinite < Metamorphic in origin >  ..Soil derived from it ..if there is any..  can contain high levels of stuff like Cadmium, Cobalt, Iron,  and Nickel / is often severely deficient in Calcium and other,  more essential nutrients.  A lot of plants that did not evolve in it, don't like it / often will perform poorly when grown in it.

 

There's a possibility I may move to a property which appears to have serpentine / serpentinite, would this mean I would have trouble growing in this area, despite fertilizing with a palm focused fertilizer? 

[Silas_Sancona]

7 minutes ago, BayAndroid said:

There's a possibility I may move to a property which appears to have serpentine / serpentinite, would this mean I would have trouble growing in this area, despite fertilizing with a palm focused fertilizer? 

Depending on how much is present / depth of it on that future site, definitely possible and not sure the challenges faced by growing in soil derived from it can be successfully altered long term since the levels of  " toxic " metals / elements present are forever in the soil, rather than being something you might be able to flush out over time. ..Obviously, talk to more people about that aspect to get their take..

Would look through the following information:   While not perfect, 2nd link lays out the various challenges Serpentine presents pretty well., as i'd learned about it back in high school.  Numerous other papers out there as well, though many focus on the the role Serpentine / other highly unusual soil ( or rock ) types  can play in helping to understand plant evolution / endemism. 


https://www.fs.usda.gov/wildflowers/beauty/serpentines/adaptations.shtml

https://shuncy.com/article/why-cant-many-plant-species-live-in-serpentine-soils


 

[Jonathan]

8 hours ago, Foggy Paul said:

Originally I thought it was sun damage. It's possibly a bit of a stretch here, but I have consistently seen it on lists of "cool tolerant" palms and thought I'd give it a go.

I thought the same thing...you never know till you try. 

Good luck with it!

[sonoranfans]

1)High drainage check, 2) green sand worked to help the appearance, check.  Its a potassium deficiency but there could be other problems as well.  When we talk of sand or gravel changing the soil chemistry two factors matter.  Solubility in water, and surface area.  SUrface areas of gravel decrease rapidly with gravel size.  Therefore granite 3/4" will do nothing on both counts, its big so has a low surface area/lb and its not appreciably soluble (dissolvable).  Limestone is another matter its quite soluble in water for a stone.  I would expect that unless you have limestone or dolomite, minimal chemistry changes will occur from gravel.  But the low surface area also means low cation exchange especially if the gravel is deep into the soil.  Low cation exchange in high drainage soil is exactly what is in my yard.  White/grey sand is  the worst soil, bring on the ammendments to up the cation exchange and moisture retention.  Lack of moisture retention means more frequent watering which can lead to a hardness accumulation from irrigation water if it is of a significant hardness.   That further prevents soil wetting and water/fertilizer uptake.  I would go straight to sulpomag(langbeinite) and consider some soil ammendment, perhaps turface MVP.

[Foggy Paul]

Thanks again for the detailed response. It's just a mulch, about 1" thick. There is no gravel mixed in with the soil. But yes, it seems like we might need some amendment. Our water isn't overly hard (piped all the way from Yosemite).

[BayAndroid]

Have you since resolved your issues? @Foggy Paul

[Phoenikakias]

On 3/3/2025 at 8:41 PM, sonoranfans said:

1)High drainage check, 2) green sand worked to help the appearance, check.  Its a potassium deficiency but there could be other problems as well.  When we talk of sand or gravel changing the soil chemistry two factors matter.  Solubility in water, and surface area.  SUrface areas of gravel decrease rapidly with gravel size.  Therefore granite 3/4" will do nothing on both counts, its big so has a low surface area/lb and its not appreciably soluble (dissolvable).  Limestone is another matter its quite soluble in water for a stone.  I would expect that unless you have limestone or dolomite, minimal chemistry changes will occur from gravel.  But the low surface area also means low cation exchange especially if the gravel is deep into the soil.  Low cation exchange in high drainage soil is exactly what is in my yard.  White/grey sand is  the worst soil, bring on the ammendments to up the cation exchange and moisture retention.  Lack of moisture retention means more frequent watering which can lead to a hardness accumulation from irrigation water if it is of a significant hardness.   That further prevents soil wetting and water/fertilizer uptake.  I would go straight to sulpomag(langbeinite) and consider some soil ammendment, perhaps turface MVP.

This the reason I crush down to smaller pieces larger lava chunks! Tom, is there any ideal size of gravel for drainage?

[sonoranfans]

5 hours ago, Phoenikakias said:

This the reason I crush down to smaller pieces larger lava chunks! Tom, is there any ideal size of gravel for drainage?

Drainage of 3/4" gravel mixed with clay will be slow compared with 1/4" mixed iwht clay.  Drainage is about the soil mix, when you have multiple components its more complicated.  Clay has the most surface area of all since it has the smallest particles.  At some point the capillary action and microfluidics will really slow the drainage rate as the granular size gets small.  I dont know how to optimize this for different mixtures.  I could design an experiment to learn but there are lots of soil components.  I would not want larger gravel to sink too far into the soil column over years as it will create a drainage gradient that could be undesirable.  Smaller gravel should have less of an issue. 

On top as a top covering in a place like the arizona desert, the larger gravel is better for moisture retention when the sun bears down on it.  Larger gravel heats more slowly and leaves less surface area for evaporation.  In the desert gravel is so superior to mulch or any other top covering for growing plants, you rarely see anyone doing anything else.  As a top covering in the desert, larger gravel has much better water conservation than mulch with soil that is part clay underneath.  Your environment/palms may present unique demands of drainage and water conservation.  I have been in dry hot desert with clay soil base 10 years and in sandy florida soil with humidity and good amounts of rain for 16.  Each has its challenges and growers will be wise to understand their own challenges and adapt.  I killed a bunch of small palms when I first moved here thinking the rain would be consistent enough so I didnt have to watch them closely when small.  In arizona it was easy to keep the soil wet, hard to account for heat and dry air.  In florida the air is fine, its the dry soil that can kill your plants, the need for mulching never stops as the organics are consumed in the soil by microbes. 

[Foggy Paul]

10 hours ago, BayAndroid said:

Have you since resolved your issues? @Foggy Paul

@BayAndroid I now realize that my entire back garden is more or less K deficient and I add a lot of greensand when I plant anything, and at intervals thereafter. I also have issues with B deficiency, especially on my C. costaricana  and supplement with borax every now and then. On @Darold Petty's advice I am trying to rely less on synthetic fertilizers and more on organics, but that is a longer term project. The Euterpe I mentioned in the OP got replaced with a C. ambositrae, definitely a better choice. I still have it in a pot but it looks terrible and will go to compost soon.

[rprimbs]

That's interesting.  We don't have a potassium shortage down here.  My soil is DG.  And the granite is orthoclase (potassium feldspar, K Al Si3 O8) based.  Unfortunately the orthoclase based granite does not tend to have gold like the quartz based.  Our problem is that orthoclase breaks down into clay.  So our soil does not drain like quartz DG.

Do you have clay soil?  Some of my palms look a bit like yours, but not because of deficiencies.  They lack drainage,  and have root rot issues -- especially those planted almost into straight granite.

 

[Foggy Paul]

2 hours ago, rprimbs said:

Do you have clay soil?  Some of my palms look a bit like yours, but not because of deficiencies.  They lack drainage,  and have root rot issues -- especially those planted almost into straight granite.

 

There is some clay, but our soil is very free draining. The only way to get it to pond is to open a hose on it. BTW I found out what our gravel mulch is—it’s basalt. 

[rprimbs]

I don't think the basalt gravel would affect the soil much.  The main difference between granite and basalt is that granite is igneous rock that formed underground -- so crystals had time to grow.  Basalt forms above ground and cools too fast to get crystal formation.  And basalt that flowed out over the ground is generally low in silica, or quartz.  

[BayAndroid]

12 hours ago, Foggy Paul said:

There is some clay, but our soil is very free draining. The only way to get it to pond is to open a hose on it. BTW I found out what our gravel mulch is—it’s basalt. 

I wonder if you're on a serpentine belt. I am and I can see some K deficiencies right now. I'm going to start introducing compost into the soil around my palms and work it into the top layer. I'll also add SulPoMag as well.