Wednesday, 11 July 2018

Hot Weather Watering: Part 3: Pots

Earlier this week I started a short series on Watering in Hot Weather: the other pages being...

1: General Principles.
2: Don't waste water on plants that don't need it
3: Pots
4: Resuscitation

Today, then - POTS!

Oh la, and fie, and horrors in general: pots in hot weather are Trubble with a capital T.

They are getting all the very worst of drought, for these reasons:

1) they have restricted top openings, so they don't catch any rain that might arrive, and they don't catch much water from random sprinkling either.
2) they don't have access to the water bank in the soil.
3) the sides of the pots get scorched by the sun, drying out the roots.
4) they are usually filled with compost (as opposed to "soil"), which is very hard to re-wet once it dries out.
5) they are frequently left up on their "feet" all through the summer.
6) they are totally reliant on their owner to water them... and they are easily overlooked!

I must just add a word of explanation about watering: in Part One, I went on at length about not flooding any individual plant, and how to move the hose to and fro to give the water time to soak in.

With pots, it's all different: their soil is usually hard and compacted, and they often have a dreadful surface pan, so with pots, it is permissible to flood the top of the pot, then leave it to soak down.

So how can we help our poor pots?

Firstly get them off those feet, and get them standing in saucers: plastic ones, terracotta ones, the deepest ones you can find: or use large trays if you don't have any saucers: and if you are desperate, get a biggish cardboard box (or a plastic tray) and line it with plastic: a bin liner, or a compost/bark bag if they are in reasonable condition. Then sit as many pots as you can fit in, inside it.

Why? If, when you water them, the water runs straight through and out of the bottom: and/or if the soil or compost has shrunk away from the sides of the pot, then your compost has dried out and - as per point 4 - it's very hard to re-wet it.

And pouring more and more water into them doesn't help, because the water runs straight through, without being absorbed.

By putting a saucer or tray underneath the pot, that runaway water will sit at the base of the pot and will gradually, by osmosis, be sucked back up into the pot.

Secondly, try to group your pots together during hot weather: this allows them to form their own little micro-climate. Instead of each pot being fully exposed to hot sun and drying winds, they will shelter and shade each other. Not much, but it might be enough to make a difference: and it makes it a lot easier for you to water them, if they are all in once place.

These two points can easily be incorporated together: move all your pots into plastic-lined trays or boxes!  You could even make a decorative arrangement of them, perhaps with a line of empty pots to hide the front of the box... or some trailing foliage.

But just be aware that you are creating a Slug Hotel, so it's worth checking it every so often, and evicting any interlopers. On the other hand, you are also creating a safe environment for frogs, newts, and other small damp-loving amphibians.

Thirdly, how much to water: take note of the expression "it takes one inch of water on the top of a pot, to penetrate eight inches down". So as most plants have roots of 4-8", you'll need to aim for getting up to an inch or so of water on the top of the pot, as it were. If the water starts to sink into the soil as soon as  you start to pour it on, well, that's good: but you can still see for yourself that you need quite a lot of water to soak the soil to the right depth.

If you are not sure how long it takes to add this much water, stand a shallow straight-sided bowl or container on top of a pot, then water it as much as you would normally do. Look in the pot. Gasp in horror at the bare quarter of an inch of water that has accumulated. Go back and water it properly!

This - incidentally -  is why planting instructions always say "leave a gap of at least an inch between the top of the soil, and the top of the pot."  It's to accommodate the amount of water necessary to properly soak the pot.

If it helps, I hold my hose or watering can over a largeish pot for a count of between 5 and 12, depending on the size of the pot. And that's quite a slow count, but remember that I turn my hose pressure way, way down to avoid jet-blasting.

Those are the three important elements of saving your pots in hot weather: saucers, grouping, and sufficient water.

There are also a few other things you can do,  to help your plants-in-pots.

Clear away any weeds, moss, algae, etc on the top surface. They are cheekily sucking up the best of the water each time.

Rough up the surface: break up that "pan" or crust on top, to make the water more likely to get down inside the soil, rather than running to the edge and sneaking away down the sides of the pot.

Add a mulch of something like gravel, small stones, slate chips, anything like that: a hard mulch prevents weeds, prevents a surface pan forming, and slows down the water that you slosh on top, giving it more of a chance to soak into the soil, rather than running straight through and away. I'm not a big fan of hard mulches on pots, but in hot weather they have a role to play, and many people find them decorative as well.

Finally, remember that pots are totally dependent on you for their water, and in this very hot weather, you might need to water them at least once a day, maybe even twice. It's a small price to pay!

If you missed any of the other articles in this series, you can either go back through the archive list, or jump:

1: General Principles.
2: Don't waste water on plants that don't need it
3: Pots (this one)
4: Resuscitation 


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1 comment:

  1. As a water conservation measure - only use square pots. Why? - no gaps between pots means no water wastage!


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