Soil confusions!

We have a thick chalk base under our soil. But our soil does not seem to follow characteristic 'chalk' properties.

It seems very 'claggy' when wet. Yet, as soon as it begins to dry out it cracks. I have just heavily dug a bed, weeded it, dug in manure, and planted garlic. Two weeks later, after very wet weather, it is cracking.

Is this usual? And what should I be doing?

 

It sounds like you have a typical boulder clay soil over a chalk substrata. My son has the same sort of situation in Cambridgeshire.
You need to dig in plenty of organic material and something to bind the clay particles together. Usually this is sharp sand and 5mm grit. On an acid clay you would add lime, but with a chalk substrate I would imagine you do not need it.

 

That is really interesting. And explains why we have so much trouble with the soil! It has always seemed an odd chalky/clay mix with some characteristics of both!

Can you tell me what that means for us as gardeners? For example, we have a pieris which is looking sickly, so I presume we are not quite 'clay-like' enough for that. Although we bought it as a bargain plant which was pot bound last year, so it could just be sickly in its own right! Does it mean we still buy chalk loving plants, or clay?

Any information you can give me would be hugely appreciated - I only started gardening last year, and I'm on a huge learning curve. Just as I think I'm becoming a bit more knowledgeable something else creeps up on me and shakes me again!

 

Well, we have been gardening for over 40 years and just as I think we are getting somewhere something new appears.
The best thing you can do is to go to a G/C and buy one of those cheap Soil pH testing kits. I do not mean the expensive electronic meter, they are a waste of money. Follow the info on the packet and you should see if your soil is acid or alkaline. Now Pieris like an acid soil (ie no lime). If your clay is limey (no guarantee either way) then the Pieris is going to be unhappy. Grow it in a big pot of ericaceous compost.
About the only good thing one can say about clay is that it does hold nutrients well. Our first ever garden was what I call 'grow taller' clay. As you walked across it you got taller, 'cos it stuck to yer boots!

 

Hmm.. Ok that sounds like a good idea. I will test the soil. Presumably the packet will tell me how to interpret the results and what they mean.

I will invest in a large pot and pot up the pieris.

Thank you for your advice. I will let you know what the results are!

 

clay soil grows marvelous Roses

 

you beat me too it. My road is clay heavy, and all gardens (except mine :() have gorgeous roses permanently in the front gardens.

 

Good info on the roses - our back garden is elevated about 10 feet up from the base of the house - and is solid chalk under about two inches of 'dirt'. The front garden which is level with the house is pure clay......of the 'grow taller' variet that Pal speaks of! So roses eh?

 

I am struggling to get my head around this one!

When I look up clay soil nearly everything suggests acid soil - which I am pretty sure the test will show I don't have. They also suggest clay holds moisture and is poor draining. Which to an extent mine is, but it seems, due to the chalk, that although it is slower to drain, once it does it dries out very quickly. I don't get big deep cracks, but I get lots of small cracks.

So I guess soil types are much more variable than it first seems.

I'm just struggling to work out what a chalk base under a clay soil means in practical terms.

I have mulched with forest bark (the rotting down kind not the big lumpy kind) after watering well, so I hope that will help keep moisture in, and in the long term improve the soil structure.

But I'm presuming when buying plants, I still buy for chalky soil (ie alkaline) but work on the organic matter and drainage issue. I can't dig in big amounts of sand currently as I am planted up in many areas, although I suppose I could work a bit into the surface before mulching the main beds?

 

Mulching is as good an alternative to digging in as you can get. It encourages worms who take the organic material down into the soil and their tunnels help drainage and water retention. Take care when improving the soil in small planting pockets that you do not reate water retaining sumps in which the plant's roots get waterlogged. IE Make bigger planting holes!
It is hard to say about alkalinity/acidity until you do a soil test. However, the vast majority of plants do not care that much one way or the other. It is only a few lime lovers or haters which react badly to the wrong conditions.
Finally, there are as many soil types as there are gardens!

 

Another quick question re mulching. In my two perennial beds I have some bulbs still to show - gladioli, iris etc. If I mulch over them will they find their way through? Or should I mulch thinly until they are through?

 

They will move themselves up and down in the soil to suit the conditions, so mulch away. Just remember that you cannot hoe off weeds once you have mulched, so hand weeding is about all you can do.

 

Well - I have not got the ph testing kit yet, job for the weekend.

But I have half filled a jar with soil, topped up with water and shaken for three minutes to really break it up. I saw a test you can do to see the layers within the jar when it has settled, and find out the make up of your soil.

In theory there should be a sand layer at the bottom, the first to settle, then a silt layer, then a clay layer.

The odd thing is that I only have two layers.. sand, then half as much silt, then just really cloudy water.

 

Despite what you think, clay is the first to settle out normally. This is because of the size and shape of the pieces. To help, rub a bit of the bottom layer between your fingers, it hould feel 'soapy' if it is clay. If it is sand then it will feel 'gritty'.
Sand actually takes a long while to settle because the pieces are very tiny and float longer.
Lots of organic material, ie silt, in your sample is a good sign.
And now you are taking me back to 40 odd years ago Rural Studies! So, don't shout at me if I misremember it.

 

Despite what you think, clay is the first to settle out normally. This is because of the size and shape of the pieces. To help, rub a bit of the bottom layer between your fingers, it hould feel 'soapy' if it is clay. If it is sand then it will feel 'gritty'.
Sand actually takes a long while to settle because the pieces are very tiny and float longer.
Lots of organic material, ie silt, in your sample is a good sign.
And now you are taking me back to 40 odd years ago Rural Studies! So, don't shout at me if I misremember it.