Garden School:


Garden School:
Teaching this week: Rose pruning (as always!) and leaf mold.

Saturday, 8 July 2017

What to do when water puddles on the surface of the flower beds.

Earlier this year I helped a friend to set up some new flower beds in her back garden: she'd had the garden completely landscaped with new raised, shaped bed edges, a beautiful summerhouse to sit in, new turf lawn, and a super new patio.

The builders had piled the old soil back into the beds, but of course had left all the weeds, and had trampled it all down flat, so our first job was to dig over all the beds, digging out the roots of the perennial weeds (couch grass mostly) and aerating the soil again.

We then replaced the plants which had been temporarily potted up, and my friend bought a whole lot of new plants, which we planted: it all looked lovely, and I left her with strict instructions to water the new plantings, even if it rained.  And a good thing too, bearing in mind that we've had the driest spring/early summer for years, and the hottest June in decades!

However, there's a problem: when watering, the water is now forming puddles on top of the beds.

This is not a big problem: it is absolutely typical of "old" soil in a "new" garden, for a couple of reasons. Well, three main reasons, anyway!

Firstly, the builders: obviously they had to stand on the ground both inside and outside the beds while they were laying the walls, causing compaction. Having built the walls and levelled the lawn area, they threw all the excess soil into the beds, not worrying about getting topsoil on top and subsoil below it, just mixing it all up and very probably walking all over it again while they laid the turf.

We dug it over to a depth of a spit and a half (nothing to do with expectorating, that means one and a half times the depth of a spade) which aerated the soil again,  but there will still be some compacted soil underneath, and the "soil" will be mixture of topsoil ("good") and subsoil ("horrible") which will make the soil less free-draining than it could/should be. This is not necessarily a bad thing: the normal action of worms and bugs will eventually sort it all out, and in the meantime at least the soil is not immediately drained of all the water!

Secondly, the soil was already a bit "tired": the house had been rented for many years, the various occupants were not really into gardening, and they would have not have been adding manure, digging in compost, mulching, moving plants (thus aerating the soil) and so on every year. It takes a while to get back on track, but the sooner you start, the sooner  you'll get there, and you can tell the quality of your soil by the colour: it should be brown, and preferably dark. If it's kind of grey, then it is "tired", or what gardeners call "lacking heart".

It's easily remedied:  just add organic matter. Make this an ongoing part of your garden routine: do it now (whatever time of year you are reading this!) and aim to add more as often as  you can - at the very least, twice a year, in spring and again in autumn: but frankly I'd add organic matter whenever I came across any.  Don't worry if you already have plants in place - just add the organic matter on top of the soil, taking care not to pile it against the stems of the plants,  and let the worms do the work in pulling it down into the soil.  You can help them by gently digging it in - use a small hand tool and just turn over the soil enough to mix the new - which will be delightfully dark - and the old - which will be pale and grey.

When I say "organic matter" I mean any of the following:

- Home made compost from your own bins. Usually  lovely rich stuff!
- Horse manure: if you have a friend with a horse, they will usually welcome you with open arms if you ask for some, although  you will probably have to go and dig it out yourself. This is a good thing, as it means you can get the well-rotted manure from the oldest part of the pile, which is the best stuff.
- Cow/chicken/pig/anything else manure: again must be well-rotted. See below.
- Bought-in manure in bags from the garden centre: expensive, but lovely stuff.
- Leaf mould: does not add much in the way of nutrients, but is fantastic soil conditioner, for improving the texture and the water-holding capabilities.

Now a quick word about manure and the phrase "well rotted": it's essential to get well rotted manure, as fresh manure is not good for the garden, for several reasons. Firstly, because it needs to absorb nitrogen in order to rot down. We don't want to give any of our precious nitrogen away! We want more of it, not less! Secondly, too-fresh manure can also "burn" the stems of plants, as it creates heat as it rots. This, in combination with the concentration of nutrients, can dehydrate plants. Thirdly, most fresh manures are high in nitrogen (N, for lush green foliage) whereas most of our garden is filled with flowers (requiring P,  Phosphorus, and K, Potassium) so it always better to wait until the manure is mature, as it were, then it can be mixed with the soil. Fourthly, fresh manure is very prone to forming a crust or pan on the soil, if you spread it on too thickly: just think of a cow pat. You wouldn't want a continuous sheet of cow-pat on the beds, would you? And fifthly, if there is such a word, fresh manure is STINKY!!

So how do you  know if what you are being offered is well-rotted? Two ways: if it is STINKY then don't touch it. And if you can see "clods" then it's not ready: just like our home-made compost, if you can still recognise any constituent parts, then it is not ready for use. Of course, if you have a largeish garden, you can accept any sub-standard manure, stack it out of sight somewhere and in a  year's time, it will be well-rotted and ready for use. Don't add it to your existing compost heap, just leave it to rot down by itself.

Where were we? Oh yes, the soil:

Thirdly:  due to the dry spring and hot early summer,  all garden soil everywhere became very dry earlier this year, and it takes a long time to "re-wet" it thoroughly. You would think that a bone dry soil would just suck up all the water, wouldn't you? Well, no it doesn't: normally, when you water a bone-dry soil, the water disappears like magic but it is not making the top soil wet, it is actually vanishing down cracks in the soil, and it's not doing the plants - whose roots are in the top 4-8" of the soil  - any good at all.  The other end of the same problem is when the too-dry soil forms a pan or crust on top, such that the water can't get in, and sits there on the surface, sulking.

Normally, "one" would have been watering the garden throughout the dry spring, but as my friend had builders trampling about, the garden was not watered at all - so the soil has no water banked, as it were, and very dry soil, like shop-bought compost, is hard to "re-wet".

Right, we now know what conditions can lead to water puddling on the surface: compaction, mixing of sub-soil, tired soil, over-dry soil. So how can we fix it?

Firstly, water gently: only turn the tap enough to get the water coming out the end of the hose, not so fast that it sand-blasts everywhere. Think of the phrase "it droppeth like the gentle rain from above" and hold the hose pointing upwards, so the water falls on the plants from above, not from the side: you can also shake the hose nozzle, to create a light shower of big drops.  Move the hose from side to side in elegant sweeps (pretend that you are a sprinkler), so that each set of droplets has time to soak in before you get back to that section. Watch for the water to soak in - as soon as puddling starts, stop watering that area - move the hose on to the next area.

In between waterings, use your hoe to break up the surface: this will prevent a crust or "pan" forming, as crusts make puddling much worse.

As mentioned above, add organic matter whenever you can - your own compost, or well-rotted manure or bought in bags of farmyard manure. Don't add "multipurpose compost" as that doesn't really improve the soil. Over time, this will enrich the soil and will make it hold water better: new rainfall will soak in quickly and evenly, and it will stay moist for longer.

So there you have it,  what to do when water puddles on the surface of the flower beds!

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