fourteener
Omono
I always use haydite that is the size larger than the mix used in the soil. Just enough to cover the bottom of the pot if room is limited. More if I have a deeper pot or a pine that really wants less water.
can you overwater in mostly inorganic soil?
- Thread starter HazMatt
- Start date
I always use haydite that is the size larger than the mix used in the soil. Just enough to cover the bottom of the pot if room is limited. More if I have a deeper pot or a pine that really wants less water.
HazMatt
Seedling
wow, thank you everyone for the information in this thread. I expected it to be a simple answer, and it turns out it was, and it wasn't at the same time 
. but i think i have a better idea of what to watch for with my watering and my 'soil', and probably have enough information to make educated changes if the need is there.
Thank you to everyone
. but i think i have a better idea of what to watch for with my watering and my 'soil', and probably have enough information to make educated changes if the need is there.Thank you to everyone
Paulpash
Masterpiece
Isn't your substrate your 'drainage layer' if it's the right size and composition? As small particles tend to retain water molecules more than larger (drainage layer) particles you are just extending the perched water table in your container. I enclose an article on drainage dynamics in containers by Paul Cumbleton, lecturer at RHS Wisley:
This brings us to the old myth. "Put a layer of grit or other coarse
material at the bottom of pots and containers to provide drainage". You will
hear such advice repeated again and again in books, on websites and TV
programmes. Materials recommended for such use may include gravel, grit,
sand, broken up clay pots or polystyrene bits, all to be added "for
drainage". If you ask the person giving this advice as to EXACTLY why they
think this will work, they often don't know - it's just something they have
been taught or read about and they have never stopped to think why it might
work. If they do have an explanation, it is usually to point out that coarse
materials have large air spaces that drain more easily than small air
spaces. This is of course correct as we saw earlier. HOWEVER this applies to
the materials ALONE. They don't stop to think what happens if you start
putting materials in layers. What actually happens is that drainage is
HINDERED by this practice and water tends to accumulate at the boundary
between the two layers. This happens for two reasons:
a) As we learned earlier, small pores hang on to water more strongly than
large ones. Because of this, when you have a medium with smaller pores above
one with larger pores, the water has difficulty crossing the boundary. There
is insufficient "strength" in the larger pores to pull the water out of the
smaller ones above where they are held more strongly by capillary action. So
instead of the water draining evenly from the pot, it drains to the
interface between the two layers then slows down or may even be stopped
altogether until a sufficiently large hydraulic head has built up again to
force it across the boundary. This of course means when the media above is
completely saturated! Since the stated goal for using a layer of coarse
material is "to improve drainage", it is ironic that this practise actually
causes the very state it is intended to prevent!
b) Secondly, the natural "perched water table" we learned about has now been
forced to form higher up the pot giving what is called a RAISED perched
water table. This leaves even less of the volume of the pot which contains
well-drained and well-aerated compost.
I should conclude by saying that the hindrance effect of putting a drainage layer at the bottom of pots is a small one; most plants will not care if you do it or if you don't. But for sensitive plants the effect can be enough to make the difference between success or failure in growing it successfully. But in any case, be it is a large or small effect, this technique does not work and I believe we simply shouldn't passing on
ideas which are false.
Good growing everyone"
Paul Cumbleton
This brings us to the old myth. "Put a layer of grit or other coarse
material at the bottom of pots and containers to provide drainage". You will
hear such advice repeated again and again in books, on websites and TV
programmes. Materials recommended for such use may include gravel, grit,
sand, broken up clay pots or polystyrene bits, all to be added "for
drainage". If you ask the person giving this advice as to EXACTLY why they
think this will work, they often don't know - it's just something they have
been taught or read about and they have never stopped to think why it might
work. If they do have an explanation, it is usually to point out that coarse
materials have large air spaces that drain more easily than small air
spaces. This is of course correct as we saw earlier. HOWEVER this applies to
the materials ALONE. They don't stop to think what happens if you start
putting materials in layers. What actually happens is that drainage is
HINDERED by this practice and water tends to accumulate at the boundary
between the two layers. This happens for two reasons:
a) As we learned earlier, small pores hang on to water more strongly than
large ones. Because of this, when you have a medium with smaller pores above
one with larger pores, the water has difficulty crossing the boundary. There
is insufficient "strength" in the larger pores to pull the water out of the
smaller ones above where they are held more strongly by capillary action. So
instead of the water draining evenly from the pot, it drains to the
interface between the two layers then slows down or may even be stopped
altogether until a sufficiently large hydraulic head has built up again to
force it across the boundary. This of course means when the media above is
completely saturated! Since the stated goal for using a layer of coarse
material is "to improve drainage", it is ironic that this practise actually
causes the very state it is intended to prevent!
b) Secondly, the natural "perched water table" we learned about has now been
forced to form higher up the pot giving what is called a RAISED perched
water table. This leaves even less of the volume of the pot which contains
well-drained and well-aerated compost.
I should conclude by saying that the hindrance effect of putting a drainage layer at the bottom of pots is a small one; most plants will not care if you do it or if you don't. But for sensitive plants the effect can be enough to make the difference between success or failure in growing it successfully. But in any case, be it is a large or small effect, this technique does not work and I believe we simply shouldn't passing on
ideas which are false.
Good growing everyone"
Paul Cumbleton
Marie,
I'd be concerned about the materials the author was referring to: "Grit, gravel, sand", etc. You are in the UK so, there may be a language difference, but here in the USA, "Grit" and "Sand" generally mean fairly small grained particles. Yes, they may be "sharp" as opposed to "round" in shape but sand and grit can become quite tightly packed, thus inhibiting drainage.
I think the key features we should be looking for is "open". Material with a large amount of air space between particles promotes fast drainage.
Also, if you look at Brian Van Fleet's first photo, you see a mass of roots. Look closely, and you do see the large particles, but the inter-particle space has become filled with root and mychorazzae (excuse my poor spelling).
Like Brian, I too sift my soils, and use whatever won't pass thru my coarsest screen as drainage layer. I discard anything that passes thru the finest screen, which is basicly window screen. I end up with two sizes of good material, the larger I use for conifers, and the smaller for deciduous trees. The smaller soil mix (all inorganic) holds more water because of its greater surface area.
I'd be concerned about the materials the author was referring to: "Grit, gravel, sand", etc. You are in the UK so, there may be a language difference, but here in the USA, "Grit" and "Sand" generally mean fairly small grained particles. Yes, they may be "sharp" as opposed to "round" in shape but sand and grit can become quite tightly packed, thus inhibiting drainage.
I think the key features we should be looking for is "open". Material with a large amount of air space between particles promotes fast drainage.
Also, if you look at Brian Van Fleet's first photo, you see a mass of roots. Look closely, and you do see the large particles, but the inter-particle space has become filled with root and mychorazzae (excuse my poor spelling).
Like Brian, I too sift my soils, and use whatever won't pass thru my coarsest screen as drainage layer. I discard anything that passes thru the finest screen, which is basicly window screen. I end up with two sizes of good material, the larger I use for conifers, and the smaller for deciduous trees. The smaller soil mix (all inorganic) holds more water because of its greater surface area.
I've noticed the same in my area Dave. I use 100% inorganic for my trees, with the exception of my wisteria and bald cypresses.
An inorganic mix with small particle sizes can hold a lot of water. I think it's still important to get the pot size, particle size and drainage right even when using inorganic mixes - I made the mistake of overpotting a scotts pine a few year ago, and was surprised at how much moisture was retained by the inorganic mix.
Last edited:
Jason_mazzy
Chumono
ok so is the lesson here use about the same size particulate throughout your mix?
example 1/4 inch DE and granite and pine bark (all 1/4)?
example 1/4 inch DE and granite and pine bark (all 1/4)?
Jason_mazzy
Chumono
ok so is the lesson here use about the same size particulate throughout your mix?
example 1/4 inch DE and granite and pine bark (all 1/4)?
example 1/4 inch DE and granite and pine bark (all 1/4)?
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