by Wally Richards
RAISED GARDENS
Raised beds for gardening is a great way to make gardening easy and at the same time produce a good range of vegetables or flowers.
The advantages as I see them are; less bending, tidy gardens, attractive gardens, less weeding, no digging, superior produce or plants, ease of watering, great drainage, ease of harvesting and a pleasure to garden even if you are not really into gardening.
I have viewed some excellent raised gardens over the years and have always been very impressed with the layout and the thought that the owners have put into their work.
To obtain really good crops you need about 30cm of good humus-based soil to allow plants to root deep. Deep rooting plants will produce greater amounts of foliage when compared to shallow rooting ones.
When this is applied to brassicas, lettuce, silverbeet and similar foliage crops, the more tops the better harvest.
Plants that can root deep require less spacing giving you greater production on each square metre. Root crops such as potatoes, carrots, parsnips, beet root etc, fare better and bigger when they can easily penetrate deeper into the soil.
A raised garden can be of any height over 30cm tall built on top of the ground in a fairly sunny situation. An ideal height would likely be 70cm tall and at that height a person in a wheelchair is able to garden.
A raised garden should not be too wide with one metre being ideal, as long as you have access from both sides; 900 wide allows three rows of potatoes or brassicas, two of which are planted near the sides with one in the middle.
The length of the raised garden will depend on your needs and the amount of room available.
As with anything new, it is better to start in a small way and extend over time as your enthusiasm for this way of gardening increases. A starting raised garden would likely be a metre wide, 70 cm tall and between 1 metre to 2 metres long.
A combination of timber and corrugated roofing iron for the sides is the best by far and has the advantage of collecting heat from the sun to warm the growing medium.
The added heat will speed up maturity times for harvest.
For this structure you simply need 2 sheets of corrugated iron 1.8 metres long and another sheet cut into half for the ends and two square fence posts 100x100mm 1800cm long cut in halffor the four corners to screw the roofing iron to.
The wood used should be ground treated and tanalised to ensure the structure has a long life. We do not want the chemicals from the tanalised process leaching into our garden so the first step is to paint them all over with a couple of coats of acrylic paint.
The raised garden is free standing and a structure that could be dis-assembled if need be in the future. This also avoids the need to dig holes and cement posts into the ground. The structure will be very stable once it is filled with our growing medium.
Rather than nail the iron to the wooden uprights (posts), drill holes through the iron and screw it to the posts.
How to construct: Lay the posts on the ground and place a sheet of iron over them so that there is a post at each end flush with the iron.
Now drill your holes for the screws and screw it up. There should be one screw at every place where the iron touches the post.
Repeat the same with the other 2 posts and the one remaining 1.8 metre length of iron.
Now move these two sheets and their posts to the spot where you are going to have your raised garden.
The spot should be in a sunny area with either the end or one side facing towards the north.
One side facing north will be best for maximum heat to the growing medium.
Now on the remaining sheet of iron mark at 900 mm and cut the iron with tin snips. Repeat for a second one metre length being the two ends.
Lay one of the sides on the ground with the iron on the ground and the posts exposed, drill and screw the two ends to the outside of the exposed posts.
Once done stand this side where you want the structure to be and raise the other side to match keeping it squarely in shape. Drill and screw the remaining side to the iron ends.
We now have an oblong box 1.8 metres long and a 900 wide.
Now this is most important either make a concrete pad to sit the raised garden on or when the structure is sitting on bare soil or lawn pour a concrete onto the soil to make a layer about 50mm thick.
If you dont do this then likely invading roots from trees, shrubs or vines many metres away will find and fill the garden with fibrous feeder roots and ruin the garden for growing any thing in.
To fill this structure firstly place a layer of twigs and branches over the concrete.
Some even use a layer of fire wood.
This will aid in initial drainage and provide carbon. Next cover this with untreated saw dust or wood shavings to further increase the carbon content.
Next a couple of inches (5 cm) of top soil.
From this point upwards a number of materials maybe used in layers such as straw, animal manures, kitchen scraps, wet newspaper, grass clippings, green waste, top soil and compost.
You need not fill the raised garden to the top at this stage; in fact with the materials just mentioned take it to about 40 cm deep.
Now sprinkle Ocean Solids, BiPhos and Unlocking your Soil, for the extra minerals they provide, at the recommended rates on the containers.
Take Wallys Calcium & Health and also sprinkle this over the area at the rate of 100 grams per square metre.
Finish off with 5 to 10 cm of compost and you are ready to start planting or sowing seeds.
You should end up with 20 cm of air space from growing medium to the top of the roofing iron.
This creates a micro-climate where wind will pass over the top and no disturbance of plants growing.
When you harvest crops, disturb the growing medium as little as possible, and with foliage crops and weeds just cut them off with a sharp knife just below soil level.
Root crops should be carefully lifted with little as possible disturbance.
To plant seed potatoes take a round pole 100 mm wide with a sharped point and press this into the mix to a depth of about 20 to 30 cm.
Drop the seed potato into this hole and push some mix in to just cover the potato. When the new shoots appear in the bottom of the hole, sprinkle a little compost to just cover.
Repeat till the foliage breaks free of the top of the mix. A little mounding may be done as required after this. When you harvest use your hands, so once again the medium has minimum disturbance.
The reason for non disturbance of the soil is to not upset the soil life and beneficial fungi.
When a crop is harvested you simply cover the area with some fresh compost after adding the products mentioned above and plant up again.
If you wish to grow tall crops such as corn or tomatoes place them on the southern side of the raised garden so the lower crops are closer to the north for sun and do not get shaded by the taller plants.
You can grow runner beans up the stalks of the corn, once the corn is up 20 cm tall, plant the bean seeds.
To keep the area around the raised garden tidy lay a strip of weedmat and cover with pebbles or bark chips or lay some paving slabs.
Later on you may wish to construct more raised gardens after you have success with the first one; it’s a nice project this time of the year so that it is ready for spring planting.
A WORD OF WARNING; if you are using the new Spray on Frost Protection then do not use Liquid Sunshine, MBL or Mycorrcin on the frost treated plants.
These products effect the microbes and you lose the valuable frost protection.
Liquid Sunshine, MBL or Mycorrcin should be used at this time of the year only on hardy plants such as vegetables and strawberries. Plants that do not need frost protection.
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