What is well drained clay soil?

hiacedrifter · March 2023

I'm using the RHS plant finder website, as I have a north facing area (clay soil) that I'd like to have shrubs/hedges in. Several say they tolerate well drained clay soil ... isn't clay soil by its definition NOT well drained?

My garden was squelchy after we had weeks of rain, but did dry off after a couple of weeks. I don't know if that counts as well drained!

punkdoc · March 2023

Sounds impossible doesn’t it? Well drained clay soil really just means it has been improved by the addition of organic matter.

nick615 · March 2023

..... or maybe sloping so that rainwater runs away?

hiacedrifter · March 2023

punkdoc said:

Sounds impossible doesn’t it? Well drained clay soil really just means it has been improved by the addition of organic matter.

Aaah ok. Let's say I dig in loads of organic matter, and then plant hedges/shrubs. Once the plants are established I can't dig in any more organic matter ... if I spread it on top of the soil can I rely on the worms to do the rest?

punkdoc · March 2023

Yes.

Fairygirl · March 2023

A slope isn't really a game changer with clay. Water soaks in to the ground - it doesn't just run down the surface like it would on a road. Over time, yes - the bottom of a slope will be where the excess will gather if there's no other planting to take it up, or burns and tributaries for it to feed into, and the top is more exposed so will dry out more quickly, but it isn't that simple.
There wouldn't be any bogs at the top of hills if the water all just ran downhill.

Extra organic matter is the only way to get clay to improve in terms of structure and drainage. What you can't change is the amount of rain that falls on it, so that's why it matters for the plants. In drier areas it bakes and cracks when there isn't rain/snow to keep it moist. The organic matter helps to hold onto the moisture in those dry spells .

padmeister · March 2023

There’s a lot of variety in clays. My garden is clay but it’s had a lot of compost and manure dug in over the years. It still cracks in very dry spells and the low spots can get soggy. The clay in my son’s garden on the other hand is the thick red stuff you could make pots from!

Personally I’ve found that the list of plants I can’t grow is quite small so I don’t set too much store by the labels. Most shrubs and hedging plants do fine. It’s the more delicate plants that don’t stick around. Any alpine won’t survive in it. I’ve tried Pulsatilla and astilbes without success too.

Camellias, rhododendrons and azaleas are very happy in mine (have you tested the pH? If it’s slightly acidic they’ll be ok). Weigela love it as do Sambucus nigra. My neighbour has a couple of laurels that do well.

Sharp sand can help break clay up too, but avoid builder’s sand (smaller particles which may actually make it worse)

bédé · March 2023

I have gardened on clay soil. It can be very rewarding.

My first garden was north of the chalk downs, the soil was called London Clay. But on former woodland and then an orchard, it was marvellously fertile, workable, moisture retentive and free-draining.

My daughter's garden is in the Chilterns. The soil is called Clay-with-flints. Difficult, but free-draining. It was to my surprise ±pH 6. It moved more towards garden No1 with my organic additions, a bit of digging, and frost

My Belgian rented property was on clay. There was the tiniest season when I could work it. Mostly like concrete. A rose garden was impossible to keep weed-free and attacked you if you tried hoeing. I eventual left the problems to the landlord.

Redwing · March 2023

It may come as a surprise to some but clay soils do vary and even more importantly what is underneath the clay, geologically speaking, is very important. For example, Essex clay soils are under layered by gravel, hence will be well drained where this occurs. On the other hand my Wealden clay can be up to 200 feet deep of solid clay and not well drained and never will be, unless it is bone dry in drought conditions. These are only examples and there will be endless variations in between.

I don't know where you live @hiacedrifter but you could research how deep your clay is.

For my deep heavy clay the only way to manage it is lots and lots of every kind or organic matter you can apply. Then grow plants recommended for clay, of which there are a lot.

GardenerSuze · March 2023

You can dig a hole in my garden four feet deep and you will find thick red clay. Bricks were made locally.
Even with thirty years of improvement what will grow has limitations.

Fairygirl · March 2023

It's why it helps to have raised beds @GardenerSuze

I always do them as it enables me to have some plants thriving a bit more quickly.
Obviously, a solid layer of rock under a small amount of clay topsoil is never going to be great, as is sandy soil over solid ground, but even a small raised area makes it easier to get a better growing medium, and a better choice of suitable plants. There's no real shortcut though. Organic matter, and lots of it is the best solution.
I do grow the aforementioned Pulsatillas and Astilbes, and most of the shrubs too @padmeister, plus many other shrubs, but the pasqueflowers are in raised beds. Astilbes and lots of other similar plants like Dicentras, Camassias, Primulas and Acteas thrive no problem, as they get consistent moisture.
We don't have the droughts here that many areas get though, so that makes it easier for lots of shrubs and trees to establish and thrive. However, there's lots of plants I can't grow because it's too cold and wet for them, even in the raised beds, and the season's shorter.
It's always a combination of factors when choosing plants.

What is well drained clay soil?

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