Raised Garden Beds En Masse 2 - Saving Money at the Gardening End

    If you've read my other articles about raised garden beds, namely:

    Pros and Cons of Raised Garden Beds

    Raised Garden Beds En Masse

    ... You'll notice that I talk about them in a pretty general way, outlining the pros and cons and general construction overview in one gardening article. In that same article, I later depict a simple method of using full-length and half-length sleepers in my design to build two garden beds. My second article approaches it from a wood working angle, noting the unusual ways I've designed some beds to minimise required (and wasted) materials, and the challenges I faced in making beds as a larger-scale project. Simply put, that wood adds up, and it doesn't get any lighter!

    This is a continuation of that theme, once you've moved ten frames to make five garden beds into place, you've still got to prevent weeds from taking them over, fill the beds with soil, get all the irrigation in, and of course, most importantly, plan and get those plants in there as well.

    Weed Prevention:

    While prevention is indeed better than cure, the simple fact is that weeds are everywhere and if you have particularly... enthusiastic plants like mint, perpetual basil, blackberries, and lemon balm/lime balm, then this is going to be a gladiatorial death match of epic proportions, and the mere construction of a few garden beds is not going to get in the way....

    Ren and I opted for a carpet mulch approach. We took large sheets of cardboard and laid them down on the ground to block sunlight, and to stop the roots/runners of other plants from clawing their way up into the garden bed from below (at least for a little while).  Then to ensure that the cardboard didn't move, and to reduce the large amount of soil needed to fill the beds, we filled the lower half of the garden beds with woodier compost on top of the first layer of cardboard. By "woodier" compost, I mean twigs, half rotted branches, larger stuff that will break down in the bed themselves eventually and add important carbon, the wood also absorbs and stores water in hotter months. (Burying logs, branches and twigs below the top soil is called Hügelkultur, it's worth looking up online). We filled the gaps with some gravelly/clay/generally low quality soil, then placed another another layer of cardboard on top of that. Now with the lower half of the beds taken care of, we filled the top half of the garden beds a large amount of higher quality compost and soil which provides weight to crush the weeds and an immediately-available bed for shallow rooted plants.

    Sounds like overkill? No, not really.

    Filling the beds on a budget:

    Now anyone who has spent time in the local Bunnings/hardware store and bought potting mix by the bag will tell you, that bags are ok if you have a few pots to fill, but gets very expensive if you need a lot of soil. Low-priced bags of "Tomato and vegie mix" start at around $4 mark for a mere 25 Litres of volume. Premium potting mixes can go as high as $11 for the same volume. Specialist or organic mixes (for example: citrus, natives, or certified organic mixes) can be significantly higher priced than that, and supply less volume.... a double "whammy" of added expense.

    Bags have appeal, especially to those who have a few pots, don't have a trailer, might only have a small car, and might not even own a wheel barrow. They are a convenient way for people to cart soil in any less-than-ideal circumstance. But that convenience is something you pay heavily for.

    Here's a small sample of the types and prices at Bunnings. They can be noticeably cheaper than specialist shops and proper nurseries too.


    Ok, so let's break the cost and effort down for a single garden bed.... assuming we didn't half-fill the beds with compost, twigs and low-grade soil:

    My garden beds have a soil volume (in this case) of 1.5m long, and 1.05m wide (1200 - (2x75mm)) and roughly 0.4m high. Total volume = 0.63m3 or 630L. A bed with 630L volume requires 25.2 bags if each bag holds 25L.

    Think about that for a moment, 25 bags is a lot for a single bed and it gets very expensive.

    Total cost is going to be $105 per bed if you buy the cheapest offering in Bunnings. That' $525 for all five beds. If you used the $11.98 bags, that's $301.90 per bed, or $1509.48 for all five beds. Most people who are growing their own vegies aren't willing to spend that much.

    If you're trying to grow your own tomatoes, think about that for a second. You really want a return on your investment (ROI) Do you think you could possibly eat $1509 worth? At $4-9 per kilo in the supermarket, that's at least 150Kg of produce. This also assumes your crop goes well. If your plants die, you get a ton of soil and expense and very little benefit for your money.

    What about that effort side?

    I just happen to know that the most amount of bags you can fit into a 2004 model Ford Focus hatch back is 32, assuming that two people are occupying the front two seats. Let me tell you that the Focus is more spacious than many newer models, and that if you do this, the car will be riding on it's axle. (As 32 bags weigh in at 460Kg or so, and most hatchbacks don't have anywhere near the typical 1 ton carrying capacity in the back of some utes/SUVs. Also, your car will smell like compost/manure/etc and that can last for weeks.

    Each bag weighs around the 13Kg mark, so you need to carry 325Kg of bags to fill one single bed. That's loading the car, unloading the car, moving the bags to the right site, cutting them open, shaking out every last scrap of dirt out (you paid a lot for it after all), that's not easy on the back, especially if you're a typical office worker that doesn't run a farm or does other strenuous exercise.

    Surely there's a better way!?

    There is. As mentioned above in the weed suppression section, keeping the weeds down is a major consideration. However, by using decomposing "filler" to reduce the volume of "good soil" needed is great and has the added benefits of being an easy way to deal with garden waste and save money.

    The simple fact is that most plants that I grow (outside of trees and established vines) don't actually need topsoil deeper than a 20-30cm right now. I have only raised the bed higher than this to make gardening easier, and to have some leeway when the soil level drops in the beds as plants absorb nutrients. So filling in the bottom half with compost and woody branches offers significant savings, and some gardening benefits as well. 

    Ultimately the biggest cost saving advice is: "Don't buy bags".

    There's a lot of ways to do this. Ren found a guy on Gumtree (an online classifieds system) who was getting his whole garden re-landscaped professionally, and he was digging out a lot of "old" dirt and wanted it taken away. In short he was offering it for free. The in-laws turned up with their trailer, and we got about 1.2 metres cubed of gravelly/clay soil. Now it is not the most fertile medium to grow in, and I found a few weird odds and ends in it, (nail file, a pen, a few bits of weed mat), but as filler it's ok.

    However, that's not going to get you up and running.. for that, you'll need some "good" soil.

    Visit your local landscape supplier, and get them to deliver soil to you by the cubic meter. You'll find that the prices are much cheaper. Many of them don't bother to post their prices online (why? I don't know) so here's a sneaky shot I took when I was in the office of one local supplier.

    Let's compare that price to the bags, just to make sure I'm not leading you astray...

    Remember that cheap Bunnings stuff that was priced at $4.20 per 25L? That comes out to be $168 per cubic metre. The "good stuff" at Bunnings would cost $479.20 per cubic metre. The average price for the same amount of decent soil at the landscaping supplier was just $55. That's a savings of at least $100 per cubic metre. (That more than covers the delivery fee). $424.20 is saved per cubic metre if you're buying bags at $11.90 each. (Now you know how Bunnings makes so much profit).

    Cubic metre too much? Note the smaller amounts in the price list above. Also, there might be some sense in talking to your neighbours and pool resources, get a big delivery, and split the delivery costs.

    If you have your own trailer or ute (or know someone who does), things get even easier. You can go back if you need more, so just buy what you need without worrying about whether or not you ordered enough. If you get it delivered, the fee will probably be the same if you ordered half a cubic metre or ten. So make sure you know how much you require to save unnecessary multiple delivery fees. If you have room, it might be worth making a pile somewhere and keeping it aside and using it up over the spring-time rush.

    Ren's parents are well versed in traveling across the countryside, so they keep a lot of interesting stuff in their boot so they can spontaneously help with gardening, building retaining walls, fix a roof, or clean out a house.. they're extremely capable people and they're scarily efficient at getting stuff done.

    So given that I would have needed 5x 630L of soil to fill five beds. That's 3.15 cubic metres of soil. Filling half of each with filler and free soil, that meant I needed only to add 1.6m3. In the end I bought three "half" metre loads...(the limit of the trailer) but one was extremely generous, while another... less so. I had actually transferred some soil from the previous stone beds, into the "filler" to further save costs. Now I know that adds up to more than the 1.6m3 needed. So we just used the excess to "top up" other beds.

    All in all, I spent about $160 on three loads, spent about 2-3 hours shoveling dirt, and with Ren and her parents on board, we did that quickly, yet casually paced over a day or so. The savings are considerable, but I have not accounted for the fuel and other costs Ren's parents have paid to help.

     Any issues?

    The biggest concern I have is the free soil. We're starting to see weeds pop up and mint is turning up in places that could potentially be a problem. Also, because the soil was free, we have no clue what if any pesticides or herbicides were used. Right now, that's all separated, but it will take time for the chemicals (if present) to break down/leach away. Also, I'm finding broken glass in places, so I have to wear puncture resistant gloves to garden safely. In retrospect, I should have just skipped the free stuff and bought another load of landscaping supplied stuff.

    Another note: While we're seeing mint grow in unexpected places... we got a sneaky little bonus. We have had tomato plants (that we didn't plant) come up in places due to the free dirt.... we'll take the tomatoes.... probably weed the mint.


    Irrigation is a combination of 13mm dripper lines and adjustable drippers on 4mm lines. Each bed also has a spray head for the germination of seedlings. I put a tap to control the flow to each bed, as well as a hose connector to the end of each bed (with tap) for flushing each branch of the main lines. I re-purposed an irrigation zone on my system... formerly used to irrigate the grass that grew where the beds are located. So this did not require the extensive piping efforts of two zones into the distant front garden as discussed in a previous article.

    I also did something I've been meaning to do for ages, and that's put the back hose on one of the spare zones of the irrigation system. That way I can turn the tap on and off with my phone and monitor my "manual" irrigation times to ensure that I don't drown my plants. I don't know if this is a problem for you, dear reader, but I tend to zone out while watering and I've been known to over-water because of it.


    Ren transplanted some of our lettuce to the new beds and that has gone pretty well. However, Ren went a little.... err... nuts when she sowed our tomato seeds. You see, we had some aging seeds that needed to be planted. So anticipating a lower-than-average germination rate, she planted over 1000 tomato seeds in a variety of heirloom species. Some of these seeds grow to 5m tall... as we had in a previous season. When we had 30 plants in the previous season... that was more than enough. It's been quite cool of late, so we've only got 100 seedlings or so.... but more pop up every day....

    Ren then went a bit nuts again on the carrots.... she planted them all at once... so we'll be having a bit of a carrot inundation in the future. I hope we can find ways to preserve them... probably dicing and freezing will be the order of the day.

    I on the other hand have been somewhat less insane, by planting lots of staggered crops of beetroot, thyme, parsley, onions, blueberries, and some other stuff I just can't quite recall. However, I'm really looking forward to what will crop up.... literally.

    Here's just one batch of beetroot we harvested. There's a lot more where that came from, and we harvest about this much every day for a week, each time the crop comes through. The lead time is about 14 weeks, and I've staggered it over a couple of months. We really like making beetroot relishes with caramelized onions and/or black garlic. It goes on everything from sandwiches, is a great dip by itself, it works on barbecue meats, it's also amazing as a marinade... and that's when we don't just bake it and eat it plain.


    This project has been big... far bigger than you might think for an additional 5 beds that only raise 7.87m2 of garden area by a whopping 40cm. However it has made management of the entire back yard significantly easier, I can reach almost any point of the garden with ease (something that wasn't always as simple). I think the long-term benefits will outweigh the shorter term workload. I've also incorporated cheap soil, existing compost, as well as cuttings into the beds, saved money on bulk purchases of soil, re-purposed existing irrigation lines, and suppressed some serious weeds. So all in all it has been done with some considerable cost savings as well.

    There are advantages with doing so many beds at once, but you have to have the space needed to not only place the beds, but build them as well.

    I hope this helps you to improve your garden, or at least provide some alleviation of boredom.

    Stay safe and happy gardening!



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