Raised Garden Beds
Raised beds are a brilliant way to garden, especially if your soil is heavy clay, poorly drained or full of tree roots. You build up rather than dig down, and you get to fill the bed with exactly the soil you want.
They warm up faster in spring, drain freely after our heavy rain, and save your back from constant bending. For many Kiwi gardeners a couple of raised beds is the easiest way to start growing food.
Why raised beds suit NZ gardens
Much of the country sits on clay that holds water and turns to concrete in summer. A raised bed lets you skip all that and start fresh with good soil. The free drainage is a real advantage through a wet winter.
The contained soil also warms earlier in spring, which gives you a head start in cooler regions and the South Island. And a tidy edge keeps couch grass and other creeping weeds out.
Building your bed
A bed about a metre wide lets you reach the middle from either side without standing on the soil. Make it as long as you like, and aim for at least twenty to thirty centimetres deep, deeper if you are building over concrete or hard clay.
Use untreated timber, macrocarpa, corrugated steel or recycled bricks. Avoid old treated timber for food crops. In windy and coastal spots, fix the bed down well and keep it lower to the ground so it does not catch the wind.
- Width: around a metre so you can reach the middle from each side
- Depth: at least 20 to 30cm, more over hard surfaces
- Materials: macrocarpa, untreated timber, corrugated steel, brick
- Avoid treated timber against soil used to grow food
Filling and feeding the bed
Fill the bed with a mix of quality garden soil and compost. A blend of roughly two parts soil to one part compost gives a rich, free-draining base. Tui compost and sheep pellets dug through at the start give plants a strong send-off.
The soil in a raised bed dries out faster than the ground, so mulch the surface with pea straw to hold moisture, and keep the water up in summer. Top up with compost each season as the level settles.
Frequently Asked Questions
What should I fill a raised bed with?
A blend of good garden soil and compost, roughly two parts soil to one part compost. Mix in sheep pellets or aged manure for richness, and finish with a mulch on top to hold moisture.
How deep should a raised bed be?
Twenty to thirty centimetres suits most vegetables. If you are building over concrete, paving or compacted clay, go deeper so roots have room, especially for carrots and other root crops.
Do raised beds dry out faster?
Yes, the free-draining soil dries quicker than ground level, more so in wind. Mulch the surface and water regularly through summer, and the better drainage still works in your favour the rest of the year.