Drainage in pots

[Darren]

Darren I am not so sure that's a myth:I have had that on hydrangea leaves by doing so and no it was not the water that was very hot due to the hose left in the sun.
Some other suggestions???

I'd be interested in other views on this one as well. Unlike John I've never personally seen any evidence that this is true (and I don't grow Hydrangeas). In fact I've frequently heard the view expressed that this is a myth. That said - the view is expressed usually by alpine experts who point out that showers and strong sun together are frequently encountered in the mountains. I could accept that for woodland plants with sensitive leaves that sun + water drops = scorch.

One mistake I won't make again is watering the larger hardy geraniums overhead when they look like they are suffering on a hot day - the weight of the water often makes them collapse and they never seem to stand up and look tidy again!

[Heinie]

I was also advised by my parents to put large stones, broken tiles and what ever is large to create good drainage in the pot. I applied that "trick" all my life until I found an article of Paul Cumbleton about Drainage Mythology somewhere on the internet a few years ago. It took me a while to properly understand the principle of the "perched water table" because my Dad was right in what he taught me. No he was wrong once I was convinced by the article which was very similar to what you wrote above. I am now using that article to promote the correct method of drainage to plant collectors as well as my Clivia growing friends because we always have differences in the correct medium to use.

Paul, I hope you do not mind that I am using your expert advice when I send the method to my friends to make hard copies. I copied the method into a Word document which makes it easy to print and your name is at the bottom of the document.

Thank you for teaching me a very important lesson about drainage in that article.

[Maggi Young]

Ian returned to the subject in his Bulb Log this week http://www.srgc.org.uk/logs/logdir/2011Nov161321442879BULB_LOG_4611.pdf

If only the message could get through to the "experts" on TV and radio and writing books ......

[Katherine J]

I also thank you Paul and Ian!
I've learnt from older bonsai growers and other gardeners to put a layer of grit, than a layer of peat and then the potting mix. The peat would hinder the potting mix to mix with the gravel. Sincerely I did not think too much of why this does not work as we wanted to, but I realised many times that it didn't. And for some years I have not used it any more.

Last year I've got a flowering Pleione in a pot, from a friend. It was planted in some soil mixed with sand and he told me he put a good layer of polystyrene particles on the bottom, "for good drainage". I also bought a Pleione bulb which I planted in a mix made by me, following Paul Cumbleton's advice on his website (http://www.pleione.info/). During summer both of pots were plunged in one of my miniature gardens, which is a little "woodland". The first Pleione in the pot with soil and drainage layer rotted by the end of summer. The second, with the compost made by me is fine, with 3 large bulblets I hope will flower next year (during winter I put them of course in a dry, frost-free cellar).

[Anthony Darby]

Thank you all.
Maggi says that there are several other horticultural myths like this one .
Can you name another one?

Planting snowdrops "in the green"?

[ashley]

Deadheading rhododendrons

[Maggi Young]

Deadheading rhododendrons

exactly! Of course, NOT deadheading rhodos can make them look a bit untidy but most types will only hold back on making their new growth for a very short time after the flowers are dead as opposed to when they make the new growth when deadheaded.
Since some ofthe tiny rhodos seem to keep their dead, papery flower on them, making them look scruffy, I like to tidy those up, not by dead heading as such but by giving the bushed a rough rub over to dislodge the spent flowers.  It has the same instantly gratifying effect of cutting the edges of a lawn  

I have deadheaded some rhodos, such as R. rex fictolacteum in the past because he just looks neater that way, but now he's much bigger I can no longer manage to do that from a step ladder so his flower heads get left on.

I cannot tell you how many hours I spent thoroughly dead-heading bushes of small flowered rhodos VERY thoroughly in the the dim and distant past... before I realised I was wasting my time!

[Neil]

This layer of grit to aid drainage, which is false, in a pot I presume that the same could be said of raised bed. I have 600mm of soil well mixed with grit etc to help drainage, then a layer of crushed brick 60mm then the soil of the garden.  I don't really want to remove 12 cubic metres, it was bad enough putting it into the bed! to remove the brick and disposing of it. 

[Maggi Young]

The world is full of folks who have taken the opportunity of needing to raise a bed to get rid of rubble and junk, Neil..... We've done it ourselves!

With a bit of luck you will find that the large weight of soil above the rubble, as will be the case with your bed, will be enough to force the soil down into... and through... the rubble layer and so (in time) provide a continuous "wick" for drainage throughout.

Don't panic !

[Martin Baxendale]

Thank you all.
Maggi says that there are several other horticultural myths like this one .
Can you name another one?

That snowdrops need "wet" soil!!! I see this in a gardening magazine or newspaper feature at least once a year.

[Neil]

Thanks  Maggi

[Rick R.]

'Don't water in sunshine because the water drops act like a magnifying glass and scorch the leaves'

If indeed a water droplet magnifies light to the point of scorching, would this heat not also be transferred to the droplet itself?  And since the evaporation of water, occurring at "all" temperatures (and increasing exponentially at warmer relative temps) cools a surface, would this not keep the droplet cooler than one might think, thereby possibly preventing scorching?  Would it be enough to make a significant difference?

John, is the "scorching" of those hydrangea leaves actually necrosis, or a discoloration of another sort?  It is known (I am told) that African violet leaf water spots are caused by a  certain threshold of difference in temperature of the leaf itself relative to the water that contacts with it.  Where leaf and water are the same temperature, spotting does not occur.  Where leaf and water tempertures differ by 10C (or whatever that threshold is), spotting does occur.   Could this phenomenon also apply to the hydrangea?

[Ezeiza]

That the only solution for a perched water table in A pot is to place it in a plunge bed!

[John85]

Maggi
I am just building more raised beds.Do you think it will be right to put the draining mixture(soil+sand+gravel) straight on the existing soil(a heavy loam) or is it better to increase the proportion of soil bits by bits.Till now I have put stones between as was adviced nearly everywhere but if I can avoid it...nice :savings!
Darren
It left yellow spots(about 5 mm) here and there on the leaf .
I have seen the same thing after a very short shower in summer followed by a bright sun.And then many more plants with a soft foliage suffered the damage.

[Ezeiza]

A big mistake would be to fill the bed in layers of different materials: it has been shown over and over that water collects in a table when passing from one material to another, actually impeding drainage. Mixing all the materials together improves drainage comparatively.

If you can not  (and if you can) obtain crushed rock, gravel, etc. to mix with the clay base make sure to install wide drainage pipes at the base of the raised bed to force any water collecting there out. Not completely horizontal but slanting to the outside of the bed.