by Wally Richards

TIME TO MAKE RAISED GARDEN BEDS

Raised beds is a great way to make gardening easy and at the same time produce a good range of vegetables. The advantages as I see them are: less bending over, 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 thought that the owners have put into their work.

To obtain really good crops you need about 30 cm (12 inches) 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, silver beet 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. With root crops such as potatoes, carrots, parsnips, beetroot etc they fair better and bigger when they can easily penetrate deeper into the soil.

A raised garden can be of any height over 30 cm tall built on top of the ground in a fairly sunny situation. An ideal height would likely be 70 cm tall and at that height a person in a wheelchair is still able to garden.

The width of the raised garden should not be too great with one metre being ideal as long as you have access from both sides. A metre 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. Roofing iron is a good material to use for the structure. The combination of timber posts and corrugated iron for the sides which has the advantage of collecting heat from the sun to warm the growing medium. The added heat will allow harvesting much earlier.

For this structure you simply need 2 sheets of corrugated iron 1.8 metres long and another one cut into two for the two ends. Using 100 x 100 mm fence posts, these are cut to the same width of the corrugated roofing iron sheets and will be the four corner posts that the roofing iron is screwed too.

We do not want the chemicals from the tanalising processed posts leaching into our garden so the first step is to paint them all over with a couple of coats of acrylic paint after the posts are cut to the correct size.

The spot where you place the raised garden should be a sunny area with one side facing towards the north. Facing north will be best for maximum heat to the growing medium.

Now this is very very important… you either sit the raised garden onto a concrete pad or if sitting on soil you pour about 50mm of concrete onto the soil inside the structure.

This is to prevent invading roots from trees or plants entering the raised garden and destroying it with a massive amount of feeder roots which will fill the whole raised garden to within about 15cm from the top of the bed. These roots will suck out all the goodness and then nothing will grow in the future.

To fill this structure firstly place a layer of twigs and thin branches over the bottom or, as I have seen some do, a layer of firewood logs. This will aid in initial drainage and provide carbon. Next cover this with a few centimeters of untreated saw dust or wood shavings to further increase the carbon content. Next a few centimeters of top soil.

From this point upwards a number of materials may be used in layers such as straw, animal manures, kitchen scraps, wet newspaper, grass clippings, green waste, topsoil and compost.

You should not fill the raised garden right to the top at this stage in fact with the materials just mentioned — leave about 30 cm from the top of the structure.

Over this spread any animal manures, chicken manure, sheep manure pellets that you have available.

Now sprinkle Ocean Solids, unlocking your soil, Wallys Calcium & Health and BioPhos for the extra minerals they provide, at the recommended rates on the containers.

Then place a nice layer of purchased compost such as my favorite, Value Compost, about 5 to 10 cm deep. The gap between the top of the garden and the growing medium creates a micro-climate and wind passes over the structure.

You are ready to start planting seedlings or sowing seeds. If you have a worm farm or worms in the garden collect some and add them to the raised garden as you are putting the later layers, in but do not put them directly onto lawn clippings or green waste.

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 disturbance. To plant seed potatoes take a round pole 10 cm 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 again sprinkle the products mentioned above then cover the area with some fresh compost 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 you then plant the bean seeds. Later on you may wish to construct more raised gardens after you have so much success with the first one.

It’s a useful project this time of the year so that it is ready for spring planting.

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