Vegetable gardening with raised beds
You'll find the information in this feature is the flip side to
our no-dig garden feature.
What are raised beds?
Raised beds give your vegetables extra root growing room and are
vital for good drainage. Free draining soil is extremely important
to growing vegetables so raised beds are definately the way to go.
Do you want raised beds or just hilled
Some gardeners will suggest that when setting up your vegetable
beds you should start shovelling the soil to make paths, building
up the beds. Then you can start adding manures and other goodies
to each bed in appropriate amounts depending on what you're growing.
Or you can think ahead, planning where each particular bed will
be and pouring old manures, blood and bone and compost in appropriate
amounts to where each bed will be. This way if you do have a rotary
hoe you can automatically till the good stuff into the soil. Then
hill up the beds by shovelling your paths.
These types of raised beds are really just hilling the soil up
above the existing soil level. You can also make things tidy by
pouring saw dust or pebbles over your paths.
Nothing appears to be wrong with this method at the start. Sounds
enticing but we wouldn't recommend it. We did this twice in former
vegetable gardens. The problem starts around six months after your
garden has been going when you start noticing that your 'raised'
beds don't look very raised any more. Rain and watering causes soil
erosion, losing extra height in your beds. This means a lot of back
breaking movement of soil in an established garden. Get it right
from the start. Go with raised beds with a bit of support.
Think ahead about timber
as raised beds
A Queensland organic gardener's research
shows railway sleepers can be okay if you do your research.
We recently purchased sleepers for a raised
bed garden and only afterwards thought about the fact that
they would have been chemically treated.
We had difficulty finding out what they
were treated with and so did a heap of research into CCA
and creosote on the Internet. We aslo made heaps of phone
calls to all sorts of places including the National Testing
Authority, CSIRO, the Biological Farmers Association etc
etc. We had just decided to get rid of the sleepers (and
had in fact made an order for untreated timber at our local
mill) when the guy we bought the timbers off returned our
call and told us that our timbers were not treated. Apparently
railway sleepers were only treated for one year in Queensland
and the treated railway sleepers are marked in 2 ways -
they have a metal plate on one end (which could, of course,
come off) and they also have "pockmarks" in them
which were made to help the creosote soak in. We rang Queensland
Rail and they confirmed this.
Apparently they only treated the sleepers
for one year about 15 years ago. They had so many workers
getting skin irritations and having time off work and/or
claiming compensation that they decided to stop treating
the timbers. Rather than treating the timbers, they use
I'm not sure whether sleepers in other states
and countries have been/are treated, but according to Queensland
Rail the sleepers have not been should be safe to use if
there is no evidence of the "pockmarking" on the
timbers and so should be safe to use.
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You've got a couple of options when it comes to raised beds that
give a bit of support. But it pays to do a little research especially
if you're thinking about building wooden frames around the beds.
The American magazine 'Organic
Gardening' has been leading the fight against using pressure
treated timber in the garden for the last few years. They often
refer to scientific research showing that CCA treated timber leaches
arsenic and chromium into the soil. And from the soil it goes into
your homegrown vegetables and then according to OG into you. For
some more info on this check out their web
site. Even the American
Consumer Product Safety Commission and the Australian
Pesticides & Veterinary Medicines Authority (a Commonwealth
Government body) are now looking at banning the use of CCA treated
timber in playground equipment.
For more info visit the
Australian Pesticides & Veterinary Medicines Authority
Think about it, if CCA treated timber is not safe enough for kids
to play on, it's hardly safe enough to build your vegetable garden
in. Me, I think I'd prefer not to be digesting arsenic and chromium
thankyou very much!
Until recently I used to also consider old timber railway sleepers,
but recent studies have also shown problems with these and their
chemical treatment from years ago. For more information about researching
whether your local old timber railway sleepers were treated chemically,
read Kathy Reed's research in the right hand column.
Of course you could find some recycled timber. Not only is it good
for you (versus the arsenic tainted pressure treated wood) and the
environment (no trees to cut down), its old weathered look is more
Just remember that recycled timber is a product of nature. This
means it will break down over time, so you might have to replace
the beds in 5, 10 or maybe 15 years time.
Our old vegetable patch used besser blocks to form raised
beds 5 inches above the soil level
Strong blocks, strong character
But here in sub-tropical Queensland old recycled wood isn't the
answer. Non treated wood encourages our local termites to start
a march on the house. One of our solutions? Besser blocks, like
what is used in landscaping retaining walls. They look great, are
hardy and get around the arsenic and termite problems.
Non treated timber
In our new vegetable patch, we've gone back to timber, but unlike
CCA treated timber, what we've done is 100% safe. Well
tell you how to do this below.
Getting down to business
Now that you've decided to invest in raised beds with some decent
support it's time to plan the bed placement and put down some thick
layers of newspaper to kill off the grass underneath. To stop it
blowing away we wet it deeply. Then we built our raised bed. We
dug deep into our pockets and trucked in some wonderful organic
soil. We also poured heaps of old manures into the appropriate beds.
Confused about what manures, the quantity and what beds you should
plan? Don't be. It's all in our crop rotation
Why should you put all of this animal manure, compost and organic
matter into the beds you might ask. Well its all about organic gardening
and feeding the soil. Organic matter improves the condition and
structure of the soil. According to James Stephens on the University
of Florida, it boosts your soil's ability to hold water and nutrients
which are slowly released. It also helps support the soil's microbiological
activity and helps your vegetables survive stress periods. James
says organic matter really helps boost your vegetables' ability
to grow. Micro-organisms, like fungi, algae, bacteria, moulds and
earthworms decompose organic matter, gradually converting insoluble
and unavailable nutrients into simple useable nutrients for your
vegies. For more information about organic fertilisers click
One thing to always remember when handling manures, soil or any
organic matter is to always wear tough gloves to protect you from
bacteria getting into any cuts.
So how much organic matter should you add to the soil? I think
as much as you can get your hands on! Here's a few reasons. Dig
a foot deep hole in one of the beds you've just created and pour
into it a bucket of water. Walk away for half and hour. After this
time if there's any water still in the hole you've got poor drainage
and vegetables hate wet feet. The answer, dig in more organic matter.
This will mix with your clay soil, improving its texture over time
and its ability to drain properly. The same rules apply if you've
got sandy soil. Sandy soils don't retain water or nutrients for
that matter. Answer, dig in more organic matter. Over time, with
the help our friend the earthworm, organic materials will help improve
your soil's texture and composition, until you've got a healthy
loam soil. So overall, organic matter improves the quality and health
of your soil. Remember as J.I.Rodale said, healthy soil means healthy
vegetables and healthy people.
Throw a good fistful of blood and bone into each square metre
of your beds. Don't forget to mix in one part potash to ten parts
blood and bone. This way you'll get healthy leaf, stem, root and
perfect! You can use most aged manures in your
vegetable patch, like sheep, cow, horse and poultry manure. The
secret though is to only use matured manure (sounds like a good
bottle of red). If you use anything reasonably fresh it'll "burn"
your vegetables, either killing them or making them very sick. So
compost the fresh stuff instead. And don't use cow pats (or similar)
which have been sitting out in the open for a while. Any nutrients
in them would've been leeched out a long time ago. Mix your aged
manure into the soil at the rate of half a bucket per square metre
and put as much homemade compost or mushroom compost into the beds
as you can. Peat moss is good too but tends to be expensive and
isn't too good for the environment (afterall they have to dig up
old peat bogs).
Another important indicator of your soil's health is its acidity
or alkalinity level. Different vegetables prefer different levels
of acidity or alkalinity. Tomatoes, capsicum and eggplant like an
acidic soil while onions prefer a sweet alkaline soil. High acidity
or alkalinity will "lock-up" essential nutrients so its
important to get your soil's pH balance right. Invest in a pH soil
testing kit from your local nursery and test the pH in each bed.
Australian gardeners are likely to find that their soil is slightly
acidic with a pH around 5.0 to 6.5 (1 is highly acidic, 7 is neutral
and 14 is highly alkaline). This has a lot to do with the Australian
continent's old age and will make it generally easier for you to
grow your vegetables. That's because it's a lot easier to boost
the alkalinity of soil compared to increasing the soil's acidity.
Adding calcium in the form of lime, limestone or dolomite will increase
your pH level. I'm not too sure about what organic materials to
use to boost a soil's acidity. I've heard pine needles, saw dust
and tea leaves, but don't hold me to that!
One way or the other raised beds do have their benefits; improved
drainage, less stooping over and they tend to warm up quicker in
spring (which means earlier crops!) When this is all finished water
the beds deeply and leave it for at least two weeks. This helps
reduce the volatility of the beds, lets unhealthy gases escape and
lets the beds settle. Your vegetable beds will stink to high heaven
for at least a week. And I mean stink. I'd personally prefer to
describe it as a "wonderful earthy aroma" but your neighbours
may not refer to it in such flattering terms, so a word of advice.
If you're going to locate your vegetable patch anywhere vaguely
near your neighbours talk to them first. They should be accommodating
if you give them a warning (and the promise of future harvests).
You mightn't want to start your vegie patch though in summer when
their windows are open
try late winter or early spring instead!
(This is from personal experience).
Sheet composting involves a thick layer, or sheet, of compostable
materials being applied over the soil. This can include straw, sea
weed, sugar cane trash and grass clippings. This organic material
acts as a mulch. Natural fertilizers (like blood and bone and aged
manures) are sprinkled in, hastening its decomposition and improving
the soil below. As this rots down it becomes a feeding mulch. In
much the same manner as the no-dig garden the sheet compost conserves
moisture, reduces the soil temperature, smothers weeds and feeds
the soil. The big advantage of this method compared to the no-dig
garden is its ability to warm the soil. You shouldn't mulch vegetables
until its starting to get hot and stressful. This way your soil
warms earlier in spring and doesn't stay as cold in winter compared
to the no-dig garden. The only other time you should mulch is when
a particular vegetable, like sweet corn, tomatoes or leeks, prefers
to be mulched. The only vegetable which hates being mulched is onions.
Their bulbs go mouldy and rot.
Our latest secret
to a healthy and cheap raised bed garden!
As I mentioned before, in our new vegetable patch, we've gone back
to timber, but unlike CCA treated timber, what we've done is 100%
It involves using a rotary hoe (you can hire one or get a guy in)
to churn up your soil, and any goodies like trucked-in organic soil
and manures, etc. Then you dig paths around your beds with a shovel.
We then 'reinforced' the walls of the beds with sugar cane mulch.
It's worked great and has prevented soil erosion. To stop grass
growing into the vegetable patch we've put a two inch deep border
of untreated pine timber around the whole bed. Covering around 20
metres (about 60 feet) cost us a whole $14. At that price almost
anyone can afford for all the timber to be eaten by termites and
replaced every few years, knowing full well that you won't be polluting
your body with arsenic and chromium leaching from CCA treated timber
So which method is better? The no-dig garden or raised beds? I
think it really depends on what you're growing and your lifestyle,
but generally I prefer raised beds. I haven't even touched on the
square foot method of gardening or container
gardening. But they're articles in themselves!
23 October, 2008
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