River Cottage Australia

How To Make a Self-Watering Vegie Bed

There is nothing more rewarding than growing your own vegetables. Here, we look at the advantages of growing your own vegie bed in your backyard.

I love my vegie garden but there is always the worrying question: who can I trust to water my vegies? The answer is to construct a wicking garden bed — a bed with a water reservoir that will water my plants when I am away.

Even if you only have a balcony to garden on, a raised wicking garden bed can produce delicious organic food that waters itself while it grows. 

Constructing a garden bed in a container has many advantages. Perhaps your back (like mine!) doesn’t bend as well as it used to. If you want to be able to take your vegie garden with you when you move, containers are portable. If your outdoor space is completely paved, you can build one straight on top; or if the ground is so poor or contaminated, a raised garden bed can hold superior soil.

 

How do they work?

We all know that fine-textured soils such as clay hold water tightly, while coarse gravels allow water to flow through them. By utilising a sealed container (such as an old bath), a layer of coarse stones such as scoria, blue metal or crushed bricks can act as a reservoir to water an upper layer of good soil in which you grow your vegetables.

The two layers are divided by a sheet of shadecloth to keep them separate. The water in the gravel reservoir is held very loosely and is attracted to the finer-textured soil, thereby watering your plants from below.

Not only does this mean you will have fewer weeds, as the surface soil is drier, but less of the water is prone evaporation. The water is wicked up to the root zone and taken up by the plants, not the summer heat. The ultimate self-watering and water-saving vegie bed!
 

How to construct a small raised wicking bed:

 

1) Rummage through your recycling bin and select some plastic bottles that will fit snugly into the bottom of your box. Milk bottles are ideal; cut out one side of the bottle.

 

2) Select a long plastic bottle such as a litre water or detergent bottle, rinse well and remove the base.

 

3) Lay the milk bottles open end down in the box. Make a hole for the neck of the water/detergent bottle in one of the milk bottles to act as a pipe to the base of the box.

 

4) Pierce the sides of the box where the upper part of the milk bottle and soil meet. This will ensure that the soil does not become waterlogged.

 

5) Fill your box with the best soil you can get your hands on. Some of the soil will flow to the base through the gaps in the bottles. This will act as the wick that waters your garden bed box. Make sure the depth of the reservoir (in this case the bottles) matches the depth of the soil.
 

How to construct a medium - large raised wicking bed:

1) Make sure the container is absolutely level. Use a level to be certain as the bed will not work if it is tilted in any way.

2) Once you have a watertight container, snake some 100mm agricultural drainpipe over the base of the tub or box and attach one end to a pipe that rises vertically from the base to just over the top of the proposed garden bed.

3) Fill the base of your planter with gravel, blue metal, scoria or any 25mm-minus gravel that is available. Very coarse woodchip will also do but it does degrade over time and will need to be replaced. Fill to a maximum of 300mm deep as water will not wick against gravity at greater heights.

4) Next, drill some drainage holes at the top of the gravel layer. This will prevent the bed becoming waterlogged if there is heavy rain. It will simply flow out of the top of the reservoir.

5) Use some shadecloth to provide a division between the gravel and the soil. If you have a wooden planter, staple it firmly to the sides of the box.

6) Fill your garden bed with a good organic soil mix — potting mix with some well-rotted manure can form the bulk of it. Incorporate some of your own compost or garden soil as this will introduce the micro-organisms that are essential for a healthy soil. Fill to a maximum of 300mm deep so the water can be drawn up. Top with a layer of mulch.

7) Sound the trumpets and fill the gravel reservoir by pouring water down your vertical pipe. Now you can plant.

 

Planting

Plant your seedlings as you would normally. They will need to be watered in as the water in your wicking bed would not have had time to rise through the soil. If you are sowing seeds, keep them moist until their roots move down through the soil. Remember that the top of the soil will always be drier than the base.
 

Fertilising

Always feed your plants with composts and well-rotted manures as well as some potash — but don’t overdo it. Your wicking garden bed is virtually a closed system, so plant nutrients can build up to toxic levels. Nutrients such as nitrogen are easily washed through the soil and in this system they will end up back in the reservoir at the bottom of your bed/box. So be careful with high-nitrogen fertilisers such as blood and bone or chook manure.

Once your plants are established they can be safely left with just a top-up of water. So off you go and have a break! 

 

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