The Gordon Gnohm

Be sure to read my article, Future Farmer in The Braidwood Bugle every Wednesday. 

Raised Beds

Raised Beds have become very popular but are they really worth it?

What it’s made from matters. Most beds are made from corrugated iron. Simple enough to transport and construct. Strong enough to stay in shape. I’m sure these perform well in a mild climate, perhaps nearer to sea level, but we don’t live anywhere near that kind of climate.  

If you’ve ever stood next to a shed in summer, or metal fence, you’ve felt heat transfer. In a raised metal garden, the heat is transferred to the soil and plant roots, ok for spring but not summer, or winter.

Freezing temps will transfer into your raised soil. Smaller beds might freeze through stunting winter veggies and if your raised beds don’t get morning sun, they might stay frozen all winter!

To prevent temp transfer, you could insulate between the soil and the metal, or you could go for wood sleepers. Wood is a great thermal break, 50+mm is a good thickness. Avoid treated sleepers, go for Australian hardwood fresh from the mill. 

What about thermal mass? Bricks, stone or concrete will soak up the heat from low winter sun and release it overnight. In summer the thermal mass stores the excess heat and stabilises the temperature.


To maximise the bed size make it double reach. Measure the arm of the gardener from chest to knuckles in an outfront stretch. Double this measurement for the optimum width of the bed so the middle is reached from each side.  

The height of your raised bed is critical and will determine your water inputs. Raised beds of 20-30cm are my preference, and require less water than a 1m high bed, because Gravity. 


A tall bed of 1m will require considerably more water than one sitting on the ground. Gravity will assist water to find its way to the ground and back into the water table. Water can only wick uphill 25cm through soil. So, if the ground is wet the low bed will take up that water. The tall bed will only wet the base layer requiring you to top water even after light rain. The material inside the bed will also determine the water holding capacity.

Filling It

A high bed of 1m will require a lot of soil to fill it. A low bed will just require a Bed Prep as in Ed #173 (Hyperlink please alex) I have seen all manner of materials thrown in to save on soil, but none of them really help, except tree trunks. 

Add subsoil to bottom ¼ of bed. Fresh prunings of 100-150mm logs, are stacked the length of the bed to halfway. Cover with subsoil to ¾ of the bed.

This is my approximation of a Hugleculture. Moisture will stay in the soil as the logs decompose and the food web colonises. On top of this material, use my Weed Free Veggie Bed preparation. These two networks will team up rapidly and feed your plants for many years.

Do you really want a high bed?

When folks ask for a raised bed, I always ask, ‘why do you want it raised and how high?’

Generally, folks don’t want to bend over. But what bending, when?

Weeding. We’ve learnt that weeds don’t need to be a part of our garden, if our soil prep is good, and our surroundings are sympathetic to our overall garden vision. 

Planting/Harvesting. Each vegetable is planted and then you watch and wait until harvest. As you are not a market gardener, you won’t be planting hundreds of seedlings or harvesting all your produce at once. Picking or bending once or twice a day can be very good therapy, even if you have damaged back/knees.

The problem with most people’s desire to have a raised bed is their ability to deal with the plants they wish to grow in them.

Tomatoes, unless you are growing dwarf varieties, it will be difficult to harvest except from a ladder. My favourite Tommy Toe grows in excess of 2m, add a 1m bed and it’ll be hard to tend.

Corn, the ears will be towering over you requiring a step ladder to check when to harvest.

Pumpkins, will drape over the edges to sprawl making it difficult for you to approach your beds. 

Spaces between the beds should be wider than you think. A wheel barrower should pass without getting elbows covered in morning dew. 

If you live in a swamp or have high rainfall, raised beds will work for you preventing soggy roots, otherwise they will cost you water. Summer is upon us, and I don’t think anyone can afford to waste a drop.

This week

My tomatoes are in! Feels like Summer. No frost forecast this week and with the soil temp climbing it’s time to get your summer vegetables. Bombay Seed Traders will be at the Braidwood Markets on Saturday with tomatoes, pumpkins, zucchini, cucumbers and more, so get in early. 

Cauliflowers I planted in July are producing tiny heads, mostly because I didn’t hand water. The great thing about cauliflower and broccoli is that they produce edible parts before they go to seed. Plant them in winter, and you can be eating from your garden next spring too.

There is one Noisy Friar sitting in a tree calling for his friends. He appears to be the first of his kind to arrive for the summer. In a week or two the dominant call in the forest will be Noisy Friars. A very similar sound to wattlebird calls, but a bit more rattly. The two are never visiting at the same time.


My Cercis canadensis is covered in purple flowers. I love a plant that flowers before they set leaf, and this one nitrifies the surrounding soil to help all the plants in the garden. Cherries have started popping flowers, so xmas yums are coming if the Rosellas will share them.

The Kunzea hedge in the main garden has popped its first flowers for the year. Its an experiment to see how high nutrient affects natives. This hedge has survived the high nutrients for 4 years and is not showing any signs of giving up. The tiny kunzea leaves make a fine mulch that doesn’t blow away in the wind. This fine mulch is a great boost to the topsoil on our property and the key to a thriving ecosystem. 

Next week Mulch

Stay Awesome,

The Gordon Gnohm

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