What is "Sharp drainage"?

6 years ago

I was researching moisture needs for some plants I just bought. One said "Sharp drainage is a must". But the SAME article also said "Evenly moist" . To me, those two things are different. I thought sharp drainage meant that when it rains, the soil dries out rapidly. Like on a slope. I don't see how that can be "evenly moist". Thanks.

Featured Answer

gardengal48 (PNW Z8/9)

6 years ago

I hate to say it but adding peat and sand to clay will not improve drainage.....in fact, they are quite likely to make it worse! Drainage is improved by adding a coarse textural element - partially finished compost, decomposed wood or bark chips or similar. Something with a much larger particle size and irregular form than peat or sand. Incorporating these into a clay soil will add porosity or spaces in between the soil particles that allow for good drainage as well as oxygen penetration. And they tend to help retain some moisture while letting water drain through easily.

A great many plants prefer soil conditions described as "fast draining yet moisture retentive"! It does sound like a contradiction in terms but the best friable, loamy and organically amended soil will offer these features.

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Comments (7)

dbarron
6 years ago
last modified: 6 years ago
I know of plants like that. They like well aerated roots, so water must NOT stand and stagnate. However, they like frequent water.

Outdoors that seems to correspond to areas with sandy soil, slopes, decomposed granite/mineral soils and the like...and often with snow melt or seeps to provide some degree of moisture constantly.

Ie, these are difficult plants (for most people).
linnea56 (zone 5b Chicago) thanked dbarron
ken_adrian Adrian MI cold Z5
6 years ago
i would sum it up this way ...

what you put in the top of a pot... seems to all go out the bottom ... but with just enough peat [or whatever] to hold what the plant needs ...

when you are doing it in the ground ... you can see how hard it gets to manipulate it all ...

when i dabbled in alpines decades ago ... i bought a yard of scree .. and planted on top of it ... now that was drainage ... a hosta friend of mine.. used chicken grit in his pots.. for this purpose .... the only downside was.. his pots were ridiculously heavy ....

i guess. ... the bottom lline.... is you want full complete drainage .... whatever they are.. they are not bog plants ...

ken

scree

https://duckduckgo.com/?q=scree&t=ffcm&iax=images&ia=images

chicken grit as scree

https://duckduckgo.com/?q=chicken+grit&t=ffcm&iar=images&iax=images&ia=images
linnea56 (zone 5b Chicago) thanked ken_adrian Adrian MI cold Z5
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deanna in ME Barely zone 6a, more like 5b
6 years ago
Short version--no clay. I also found it surprising that plants would want ample fresh water, but heaven forbid any water hang around too long. They like a fresh rain to come and drain away, and then another one to come before too long. If you have clay soil, add lots of good soil-draining amendments, like peat and sand.
linnea56 (zone 5b Chicago) thanked deanna in ME Barely zone 6a, more like 5b
deanna in ME Barely zone 6a, more like 5b
6 years ago
I take back my recommendations! Thanks, gardengal.
linnea56 (zone 5b Chicago) thanked deanna in ME Barely zone 6a, more like 5b
gardengal48 (PNW Z8/9)
6 years ago
Deanna, hope that info helps you out with future amending issues!!

btw, mixing sand with clay generally results in a substance much like adobe. And that will not tend to offer very sharp or fast drainage :-)
linnea56 (zone 5b Chicago) thanked gardengal48 (PNW Z8/9)
linnea56 (zone 5b Chicago)
Original Author
6 years ago
Thanks! I’ve been amending most of my beds for decades. Mostly compost but also leaves and bark. So I think I’ll opt for one bed with a slight slope for these fussier plants.

I have one bed I’ve only been working on for a few years. So that soil will not be as good. I will only put the less fussy ones there.