How to increase soil depth in a planted bed?

JMagic · October 2018

Good morning! I am a first time poster so please forgive any errors I make.

I have a long and narrow (12m x 2m) sloped bed which is proving very difficult. The soil depth is only 15-20cm (6-8") and it sits on clay under very thirsty lime trees. I believe the most significant factor preventing successful growth is retaining moisture in the soil, so figure the best way to do this is to increase the soil depth (plus irrigation etc).

The problem is that the bed is planted up with some 200 plants (Liriope, Ophiogogon and Pachysandra), so I imagine my options are as follows:

Remove every plant, add soil, replant. This sounds like a lot of work.
Mulch every year and in 5 years it might get to a suitable depth.

Does anyone have any additional ideas please?

Many thanks
JM

Hostafan1 · October 2018

Welcome to the Forum @JMagic .
I'd add layers of mulch,as best you can between the plants.
Those listed root as they spread so should cope with additional material and none of them really need deep soil, so I see no reason why you need to dig stuff up.

JMagic · October 2018

Thank you Hostafan1, I was kind of hoping someone would encourage the lazy option(!). Probably an amateur question, but would any mulch type do the job?

Fairygirl · October 2018

I think I'd do the same as Hosta suggests. Jmagic. It would be hard work taking those all out at this stage. I'd also agree that those plants won't be greatly affected by soil depth.
Otherwise, if you fancy the challenge, you could remove the plants, and add a decent sized retaining edge, so that the bed has less of a slope, and you can then backfill with extra soil to make it deeper.

Are your trees quite heavy low down? You could also remove some of the lower branches which would let more light and rain in [if you get plenty] and slightly reduce the take up of moisture too.

JMagic · October 2018

Thank you Fairygirl.

Unfortunately adding a retaining wall isn't possible. I am lucky in the at the trees aren't heavy low down. I have actually just had them put right back so now the area is flooded with light (it only gets direct sun in the early morning).

I just wish plants grew quicker!

jm

Fairygirl · October 2018

Patience is the hardest thing to cultivate in a garden JM

Once your plants are established, they'll soon spread and knit together. Have they not been in very long?

JMagic · October 2018

About two years. Due to budget constraints they were all 9cm pots - therefore they have plenty of growing to do!

Fairygirl · October 2018

They might have been suffering a wee bit from lack of moisture then. I would have expected them to have spread a reasonable amount in that time - even from a small pot.
I think a deep mulch, after they've had plenty of rain would really help. Maybe in a month or so, they'd be damp enough then inmost parts of the country. If you're in a wetter part of the country, you could mulch now. My soil is soaking, so I could easily do it now if I needed to, but it depends on your conditions.
Take a look - poke your finger down and see how damp the soil is, then make a judgement on whether to mulch yet or not. You can reapply before summer too, after some decent spring rain, to help through the drier months. Just leave a little gap round the plants when you do it, to prevent too much moisture sitting against stems/crowns of plants.

Rubytoo · October 2018

Are you leaving the leaves on the bed, that will eventually help raise the level, although I imagine if you get a lot you need to clear some off so the plants do not disappear.
But if you can stack the leaves somewhere you can have a free mulch and deepen the soil layer at the same time after a bit for free with the leaf mould.
You can lay them on the lawn and run a mower over them to break them up a bit and speed up the process.
Leaf mould is one of the best things for retaining soil moisture.
Welcome from us too.
Edited for spelling and forgetfulness...

Fairygirl · October 2018

Rubytoo said:

Edited for spelling and forgetfulness...

But at least you remembered you were forgetful Ruby2

Good point about the leaves. They're not called black gold for nothing. Wonderful resource.
If you're unsure how to make it - collect the leaves [ideally they should be damp, not bone dry] bung them in black bin bags, tie them up, stab a few holes into them for drainage, and stack somewhere out the way. As Ruby says - you can shred them a bit with the mower to help them break down quicker. By next winter, you should have a usable mulch

You can make a 'bin' for them, with chicken wire and a few posts, but no need if you don't have the time or the room.

JMagic · October 2018

Wow, blown away by all the helpful suggestions, thank you.

I look after the bed (time and money) for our communal block. The rear garden has a compost heap the size of a bungalow - I will dig into it and see if the stuff is any good (it is not maintained, it just sits there). I might post a picture to get your advice on whether the stuff is usable, or whether it isn't rotten enough (and so would rob the Nitrogen).

Rubytoo - I do pick up the leaf litter that falls on the beds as I was worried the Pachysandra were being killed by blight.

I appear to be the only person on Earth who struggles to grow Pachysandra, perhaps I should take a hint!

jm x

How to increase soil depth in a planted bed?

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