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Newbie raised bed!

Hi there,

I live in N. London and I am about to start a 8x4 ft / 12” deep vegetable raised bed in my back garden and just want to make sure my plan is ok and confirm a few areas I’m not to clear on. Any help would be rally useful! 

So firstly sowing indoors soil I have ordered a mix of seed compost with vermiculite and Shamrock Moss Peat (as well as some extra louse vermiculite to add as well). Will this be OK for just indoor sowing? Anything else I should add that is not to expensive?

After the seeds have sprouted I need to keep them warm still but ass light so the best (cheapest) option is to put them under some I.e. normal fluorescent 50w fixtures? Can they be any type of fluorescents and blubs? What will be enough watts for the standard vegetables? What is a good average temperature for vegetables & strawberries?

Once true leave appear transfer to larger separate pots and keep them under light.

After awhile start to introduce them to outside for hardening.

Now, the thing that I am finding hard to be clear on is the actual soil in the raised bed. For a soil mix is this ok:

All in liters for a rough total of 900liters excluding some parts like newspaper.

- 200lt Vermiculite

- 300lt “Sandy loam top soil”

- 300lt Mushroom Compost (The topsoil and compost comes alrady mixed in a 50:50 ratio.

- 100lt Moss Peat

- Fertilizer – How much (in KGs) do I need and what are good types? Again not to costly.


Anything else I should add to this?

The plan is to find a grass section and cut a small trim so the wooden bed fits nicely into it. Then dug up some thin layers of grass lawn close by and put that in the bed grass side down. Put a thin layer of newspaper over than then fill with some mulch or just put the soil mix strait on it. Then cover that with a bit of mulch. – I will be planting in this probably within the month. Will that be too soon?


According to weather there is a short end of march frost coming to I was going to cover it with poly until I planted the first outdoor sowing such as carrots.


  • Busy Bee2Busy Bee2 Posts: 1,005

    I think nobody has answered your question because you haven't really said what vegetables you are going to grow  You have clearly put a lot of thought into what you are putting into your bed, and I don't know of any reason why it wouldn't work, but I am no expert and have to tell you that I just put some fallow topsoil and a bit of compost in mine to begin with, and have put manure and some wood ash in this year to give them a bit more oomph.  So I have obviously not put as much effort or thought in as you have.  All I can tell you is that most vegetables will surely grow, and I don't know any that I would use vermiculite or 50 watt bulbs for - I think they are for degree level gardening, and I am just a GCSE student, if you get my meaning?  A good sunny windowsill and regular watering should be enough for most vegetable seedlings - a propagator to get tomatoes, chillies, peppers, cucumbers etc. going is not a bad idea.  (If you don't have a greenhouse, make sure you grow outdoor varieties).  Outdoor things like carrots and lettuce and rocket and radishes and onions don't need too much thought.  Brassicas a bit harder (cauliflowers not too easy).  Potatoes a doddle (but cover up in case of frost).  Strawberries will take up quite a bit of space - if you only have room for one raised bed you may be better putting them in a strawberry planter.  Quite a lot of stuff is reasonably hardy - you can use fleece if a late frost threatens to be severe.  What were you thinking of growing?  I am no expert, but I get a good old crop of stuff - my advice would be don't imagine growing vegetables is harder than it is.  Just grow what you like to eat.

  • My raised bed is full of multi-purpose and nothing else more complicated. The base is on grass layered with thick layers of old newspaper which must have rotted a couple of years ago. Remember, raised beds or the ground, soil is just a medium in which to grow plants. Feed regularly with a long-lasting fertiliser and you will be fine. Don't get too complicated, especially at first. And I agree with all that Busy Bee2 above says, good advice.

    Onions and beetroot also do well in my raised bed as does garlic.

  • BobTheGardenerBobTheGardener Leicestershire, UKPosts: 11,067

    I wouldn't bother with the vermiculite in the raised bed.  Together with all of the other ingredients you mention it would make for a very light weight growing medium making it difficult to grow many vegetables, especially brassicas.  I would suggest that 800l of good quality topsoil (or the pre-mixed topsoil/mushroom compost you mention) and 100l of composted farm yard manure (as supplied in bags by garden centres etc) would make a good basic soil suitable for the majority of vegetables.

    A trowel in the hand is worth a thousand lost under a bush.
  • greenjudegreenjude Posts: 64

    Vermiculite is good as a covering for seeds sown indoors, but I wouldn't use it outside. It's so light it'll blow away. Besides, it's way too expensive to use outside and not in the least necessary. I also wouldn't recommend peat. It's an environmental no-no, contains no nutrients and is expensive. Organic matter is a very good idea but you'll have plenty in the mushroom compost. (As a bonus, you may get a crop of mushrooms too!)

    A box of bonemeal for slow-release fertiliser, and blood,fish and bone for faster acting, both good and fairly cheap. Maybe too a box of sulphate of potash as a booster. There are instructions on dosage on the packets - don't be tempted to overdo it. Your mix of sandy loam and mushroom compost will be fine without peat or vermiculite - don't waste your money on them.

    Don't be in too much of a hurry to sow if you don't have a greenhouse, though I admit the temptation is to crack on asap. If you wait until light levels and temperatures are higher, they'll grow stronger and will soon catch up. Fleece is great for protection, but if outdoors make sure you peg it down firmly.

    Best of luck and happy vegging!

  • We started our raised beds about 4 years ago now in April... they are about 2 ft high so I dont have to bend down... but we started 2 Lasagne beds (Youtube helps)... it seemed to me the easiest thing to start off with, layering it all like a lasagne with cardboard on the base, then manure, garden and green kitchen waste, straw, bought bags of compost... it didnt take long to fill, then the top layer was compost/soil and straw... I just moved the straw out of the way and could plant seedlings immediately in May.  We had lovely beans, tomatoes were over 6 ft high, salad etc... after a while when the planting had finished the compost in the bed had shrunk so we just carried on as before for next year with root veg..  The compost is lovely now.  We moved 3 years ago, took the beds with us as well as the compost!  I wasnt going to leave that lovely stuff behind was I?

  • KevinMKevinM Posts: 22

    Just built one of my own, and went for a similar mix as Bob above says - about 2/3 topsoil, a bag of mp compost, a bag of manure and some compost from my own compost bin. Added in some chicken manure pellets, but I think you can use any good fertilizer depending what you want to grow - nitrogen richer for leafy/brassicas etc, more potassium for fruiting types I think is right.

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