Blocking Up – experimenting with peat-free soil blocks

I can’t quite remember where I first came across the idea of soil blocks for seed sowing, but they’re a rather neat idea. Compacted cubes of growing medium are used instead of pots or modules, freestanding seed trays with narrow air gaps between the blocks.

Big claims are made about the benefits of soil blocks for raising young plants in terms of reduced root disturbance and how ‘air-pruning’ of the roots prevents root binding of seedlings, all of which may well be true – I haven’t really got the horticultural background to say! But actually the thing that really attracted me to soil blocks was practicality.

Sowing seeds into soil blocks

I really don’t like module trays – they’re a pain to wash and re-use, if nothing else, they tend to degrade badly and crack up so that they only last two or three seasons, and are expensive and enormously wasteful if you’re using them only once. While it makes sense  to start certain seeds directly into 3″ pots, that takes up an awful lot of window sill space – something that’s definitely at a premium in my house at this time of year. And as we’re aiming to be completely peat free in the new garden, those little peat jiffy pots are right out (and the cost adds up quickly). A useful compromise has been home-made newspaper pots, but there’s quite a lot of effort involved in making these and I don’t always have time (also, my paper potter tool seems to have gone astray in the house move)! I’d more or less settled to using plain seed trays and pricking out seedlings at a small size, but that’s quite a lot of work and it can be rather traumatising for the seedlings, and has to be done at just the right time when inevitably I have too much else to do. So, no perfect solution.

Half trays of soil blocks in heated propagatorSoil blocks combine the convenience of the plain seed tray with the ‘modularisation’ provided by plastic module trays or individual paper pots – so could they be the best of both worlds?

Despite a real lack of cash just now, I decided to dig deep and find the twenty pounds for a four-block two inch cube soil block maker, which I bought from GreenGardener.co.uk. Only after diving in feet first with the purchase did I stop to consider the peat free problem; almost everything I read suggested that a peat-based seed compost was essential for making functional soil blocks. So had I just wasted my money?

Unwilling to compromise on our principles, I set about mining websites and gardening forums in search of a peat free recipe for soil blocks. None was quite right but some themes kept recurring. A base of peat free compost (fine textured seed compost ideally), something to help drainage (sand, perlite and vermiculite were variously mentioned) and loam or topsoil to help bind the mixture.

I’ve mentioned that money is a bit tight; going shopping for extra growing media is not on the cards, but I have a reasonable supply of New Horizon peat free organic multi-purpose compost and a rather soggy old bag of vermiculite (I generally use the New Horizon compost mixed 3:1 with vermiculite as my seed mix). We also have an almost inexhaustible supply of molehills, as the efforts of Mr Mole to create a ‘des-res’ for Mrs Mole are in full swing on our paddock!

So with a ‘make-do and mend’ attitude I did a few experiments and have come up with the following mix that seems, so far, to be working well for me. It will be the basis of my soil blocks for this season, while I get a handle on how things go germination-wise, and consists of –

  • Dry soil block mixture4 parts peat free multipurpose compost (you could sieve this to take out the biggest bits – but I’m fundamentally lazy and don’t own a garden sieve)
  • 1 part vermiculite, and
  • 1 part molehill (you should ideally sterilise this to get rid of weed seeds, I suppose, though it seems like faff) or substitute with bought topsoil (being careful it’s not been mixed with peat compost, as it often is!)

Wetted soil block mixMix the components thoroughly and then add water, a little at a time, until you reach a consistency that holds well together when you take a handful and give it a good squeeze. I find this is at the stage that you can just squeeze a tiny bit of water back out of the mix. Any wetter and the blocks slide straight out of the block maker – drier and the blocks tend to crumble. If you find you’ve over-wet the mix just add a bit more compost to dry it out again. A little trial and experimentation and you should get a good idea what you’re aiming for.

Filling the soil block makerTo make the blocks, level the wet compost mix about two and a half inches deep and as even as possible. Push the block maker down firmly into the compost until it hits the bottom, then push down on the handle without moving the press, to squeeze down on the blocks. You may squeeze a out a little water (if you’re seeing a lot, your mix is too wet). Then, release the handle and carefully pick up the block maker, tilting it on it’s side to reduce the risk of blocks falling out.

Making up soil blocks in seed trayPosition it where you want your blocks to go, and then press down on the handle again pulling the block maker up at the same time. If it’s all worked perfectly, you will have four even, neat little cubes each with a dimple in the middle. I find I can fit three rows of four blocks (12 blocks in total) into a half sized seed tray or seven rows of blocks (28 in all) in a full sized tray.

Half seed trays of soil blocksNow you’re ready to sow your seeds. Pop one seed into each dimple (or more than one if they’re small seeds and you plan to thin any extra seedlings) and cover loosely with a pinch of dry compost or vermiculite – or leave the seed uncovered if light is required for good germination. Then place the seed tray in your desired spot. I currently have two half trays of soil blocks in my heated propagator with tomato seeds in, and two full trays of salad leaves and brassicas in the unheated greenhouse.

Completed tray of soil blocksThe soil blocks are supposed to contain enough water to allow the seeds to germinate without further watering being required, but this depends on preventing excessive evaporation.

Covered seed trays in greenhouseI wrap the seed trays in the greenhouse with cling film (wetting the edge of the seed tray like a pie dish gives a good seal) and those in the heated propagator are under a closed lid. But if they do get a bit dry, don’t panic – mine held together fine when I watered them with a normal watering can and medium rose, just be gentle! Obviously you can’t use normal plant markers easily if you’re using cling film, so I label my trays using masking tape stuck to the seed tray. Keep your eyes open for signs of germination and remove the cling film before the seedlings reach it.

I’m waiting to see how things germinate in them now, and how they grow on, with no small degree of excitement!

Are you experimenting with soil blocks this year? How are you getting along?

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Something’s Rotten in the Garden Centre

Something has been happening in our garden centres. This blog post, I’m afraid, is a bit of a rant.

Recently, I had the most depressing experience. We were out and about, and with seed sowing season upon us, we needed to pick up a few bags of peat free compost for the garden. As it happened, we knew there was a garden centre just up the road – the glossy signage at the roadside bragged of it having won awards, and the car park, on a sunny February Saturday, was crowded.

Garden CentreThe bad omens started at the entrance. ‘No dogs’, said the sign. This was a nuisance because Dave dog was with us, of course. So he would have to wait outside with Hubby while I popped in to pick up the compost. And maybe one or two other bits and bobs. Even better, I had some National Garden vouchers in my wallet, so it was the best sort of shopping, the kind that doesn’t feel like it involves spending ‘real’ money.

The ‘information’ desk at the entrance (‘This is Not a Till’) was a bit odd, but the man in a suit standing behind it was able to confirm that they would indeed accept my vouchers. Oh goodie! I looked around. A few BBQs. A chimnea or three. A garden swing. Nothing really unexpected, and surely the good stuff would be just through there…

The sight that greeted me through the door, instead, was rather startling. A large hangar of a space, it was filled from side to side with tat. Not so much as a houseplant, as far as the eye could see. Instead, nick-nacks piled up on tables like some sort of demented car boot sale. I’ll admit, it took me a few moments to take it all in. A second adjoining cavernous space seemed to be filled with even more of the same. But where on earth were the plants?

Garden centre tat

In the distance I spied a door that seemed to lead outside. Perhaps, this was where I might find what I needed? After weaving through tables piled with clocks, picture frames, porcelain rabbits, and oversized tea sets, I stepped out into the sunshine. Here, finally, I found the plants, set out on staging. I could have danced. And there, against the fence, half-hidden by heaps of discarded wooden pallets, were piles of promising looking plastic sacks. At least I’d be able to pick up the compost I needed, and escape from this very perplexing place.

Compost SacksI couldn’t spot the peat free compost we normally buy, so I walked along the row looking to see what they had instead. It dawned on me, slowly, that the answer was ‘nothing’. Not a single bag of peat-free compost. I walked back along the row, slightly disbelieving, and checked all the labels carefully. But apart from the topsoil, wood chip, and the farmyard manure, all the potting mixes contained old-school peat.

Now, I’m not a peat free zealot. I understand that some gardeners, familiar and comfortable with its properties, find it hard to give it up. A bit like fossil fuels and global warming, it can be hard to link the bag of compost in your shed to the destruction of rare and fragile wetland habitat. I’ve made the personal decision to finally make the break, and our new garden will be peat free as far as it possibly can be – but I understand that not everyone is ready or able to make that jump just yet. It is surely a remarkable moral failure, though, to be denying your customers even the possibility of making the right choice.

Rather shocked, I turned around and tried to find the exit. On my way out, I spied the seed racks – the ultimate impulse buy for any keen gardener, and my personal retail kryptonite – hidden so far out of the way that I wasn’t even tempted to browse, let alone buy. A tiny range of cheap plastic propagating trays was piled haphazardly nearby, almost hidden behind a giant selection of multi-coloured welly boots.

I left, gift vouchers resolutely still in my pocket.

What has gone wrong when a garden centre can’t part a keen gardener with a pocket full of gift vouchers from even a penny their cash?  The failure to stock even one peat free multipurpose compost is beyond disappointing – actually I think it’s unconscionable; presumably it result from some bean-counter’s profitability analysis but surely it’s the bean growers’ needs that should matter?

Discussing this with friends on Twitter, I’ve been asked to name and shame, but that’s not my style. And depressingly, I don’t really need to – wherever you live in the country, unless you’re very very lucky, it’s likely your local garden centre, be it a chain or an independent, is somewhere rather like this. Some make a better job of pretending to care about the gardener than others, but a cursory look at the square footage is enough to make clear that the cafe, food court, interior decor, ‘giftware’, crafting supplies, pet shop, outdoor clothing (and indoor clothing for that matter), garden buildings, children’s soft play areas, and fishing tackle are more important than seeds, plants, and essential garden provisions.

This sad state of affairs appears to result from a nasty loophole in planning law which allows horticultural businesses – which real plantsman (and woman) nurseries absolutely are, but these garden centres are not – to be developed on agricultural land where permission would never be given for an out of town shopping centre. It’s the worst of both worlds, then – over-development of inappropriate sites, and the horticultural purpose, sadly, long forgotten. Instead, we get this rambling, low-rent, mixed-retail mess. And a mess which, to add insult to injury, now often fails even to fulfil its original purpose, of offering plants and horticultural supplies for gardeners.

So what are we to do? Well, you could do as we did, and visit the good guys.

Nursery PolytunnelIndependent local plant nurseries are the gardener’s friend and still hang on in most places despite competition from the big boys of the garden centre and DIY warehouse worlds. They probably don’t sell BBQs  – they may not have a cafe – but what they know, and excel in, is plants, and the knowledge and gear that you need to grow them successfully.

Fresh from our disappointing experience at the garden centre, we went along to Bodmin Plant and Herb Nursery. We immediately found the compost we needed, along with a very nice selection of pots, right outside the entrance. In the small inside space (into which Dave dog was welcomed), a good selection of seeds, seed potatoes, pea and bean seeds sold loose by weight, little bunches of snowdrops ‘in the green’ ready for transplanting, and a good selection of tools, along with tree ties, rabbit guards, and so on. Second-hand module trays, too, saved from landfill and a bargain addition to our potting bench. And not a nasty nick-nack in sight.

Plant selectionOutside, even in very early spring, a great range of fruit trees and bushes, and a really good selection of shrubs and bedding plants. I can’t wait to go back in a month or two when I expect a riot of colour and fresh growth. The staff don’t wear suits; they were helpful, knowledgeable and clearly cared about the quality of their plants and the needs of their customers.

I went home with my peat free compost, and a couple of other little bits that caught my eye (yes, there might have been a seed packet of two…) and left a nice bundle of gift vouchers behind me. In fact, the only slight cause of sadness was the relative emptiness of the car park, with only a handful of vehicles parked when we arrived.

Honourable mention also goes to Burncoose Nurseries near Redruth, which we visited last week on the way back from an outing to the Lizard. A great ‘pure’ plant nursery with a fabulous selection of specimen plants and shrubs, where I finally found the Tasmanian Snow Gum I’ve been looking for for about a decade. Don’t expect to find tools or supplies here, but for plant selection it’s one of the best I’ve seen.

So, even if you’re not ready to go peat free, why not reject the tat-merchants and DIY barns and make it your resolution to go garden-centre free this growing season, and instead, give your support – and your hard-earned cash –  to your local independent nurseries?

[The photos used in this post are Creative Commons licensed images sourced from Flickr (see image pages for details) – they are for illustrative purposes and do not represent the products, nurseries or garden centres discussed in this blog post.]

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