Using Raised Garden Beds : 6 questions answered.

raised garden beds in yard

Over the last few years, we have installed ten raised beds and cannot speak highly enough of them, but people still have questions when they see them. It is as if they need total convincing that they are the real deal.

This post is about these questions.

Will manure rot metal raised garden beds?

Manure can rot metal garden beds if the manure is corrosive, like fresh chicken poop.

The solution is to age the chicken manure or compost it before using it on garden beds.

If the raised garden bed is wooden, there is little to no risk of rot from the manure.

Any rot in a wood garden bed will come from over-watering and having soil in the bed that is not freely draining or poor quality lumber. We use metal raised garden beds because of the climate where we live, so we use the metal garden beds as described in “Why use corrugated steel raised garden beds? “

Good quality soil with plenty of organic matter will retain enough moisture for the plants without you having to water constantly and potentially cause trouble.

We recommend good quality garden beds no matter what soil you place in them; if you start with second-grade construction, then expect issues earlier.

Everything rots or rusts, and the trick is to prolong the inevitable for as long as possible.

Wood shavings from our side hustle business with chicken poo from the roost.

Do metal raised garden beds dry out faster?

Raised garden beds can dry out quickly if the soil is too free-draining.

To help avoid this problem, mixing plenty of compost and organic matter into the bed will help with moisture retention. The soil drainage is a disadvantage in these garden beds, as discussed in “Organic raised bed gardening, what are the disadvantages? “

You should place mulch on the soil surface to stop excess evaporation.

The raised garden bed is a manufactured process. It does not gain any natural benefits that a ground-level garden can have, so it is up to the gardener to create the conditions for optimal plant growth.

Layering different soil types in the raised bed column can help with drainage issues, as can geotextile fabrics.

Soil quality drives water needs.

How much topsoil do I need in a raised garden bed?

Vegetables only set roots down to about 8 inches or 200mm, so having 10 inches or 250mm of good quality topsoil should be enough for the typical raised garden bed.

There are gardens planted on bare concrete that are only 8 inches deep, and they supply a harvest ok, so the raised bed with a little deeper soil will be fine.

As you grow in these beds, you will find that each season you need to top them up with more soil and compost because the soil settles in the bed and sinks.

Some of our beds need top-ups, which will be the third time, including the initial filling. Be prepared to do the same.

It may be a pain in the butt, but after a few years, the result is a deep fertile soil column that allows you to grow crops with longer, deeper roots.

Do tree roots get into raised garden beds?

Tree roots can invade a raised garden bed, but it is not something that happens often.

It will depend on the tree near your bed and how aggressive it is in its growth behavior.

Some trees send roots out a long way and will chase nutrients and moisture if they require this and are not readily available.

More often than not, the roots that may end up in your beds are adventitious feeder roots, which may only be small in size.

It should be rare to have primary structural roots competing with the lettuce plants, and if they do end up there, then the choices are simple. Move the bed or move the tree.

If you are working on being self-sufficient, it will depend on what that tree has to offer against the productivity of the garden bed over time.

If the tree loses the deal, mulch it and compost it down for adding to the beds next season. Keeping as much green waste on the block where you live is a step towards sustainability in soil creation.

Why pay for soil when you can make it.

Will dirt make metal raised garden beds rust?

Yes, in particular circumstances, dirt can rust a garden bed; however, the dirt, or soil, will need to be acidic and strongly acidic at that.

It is, therefore, unlikely in a healthy garden.

Acid soil is a self-curing problem because the acidity required to cause a bed to rust is unlikely to grow a decent amount of food.

You will either replace the soil or do something to the soil to bring it back to a level where plants will grow in it again.

Acid-loving plants like blueberries can be the case that proves this wrong, though, but generally speaking, the soil shouldn’t cause rust in the short term but may play a part in 10-15 years.

Everything breaks down eventually.

If the soil does not grow crops because of acidity, then you can amend the soil with lime or replace it and start again with better quality soil with plenty of organic matter. The organic matter helps buffer large pH movements in the soil.

To understand pH in soil, “How safe is your soil?” explores hidden dangers to avoid.

Can raised garden beds be used in tropical areas?

Raised garden beds can be used and are great for the tropics. As you have discovered above, metal garden beds are good but can rust. Timber is an alternative that some people like to use, but it also has issues. “Does timber edging for gardens last?” explains it for you.

Soils in the tropics can be quite acidic and may hold many plants back from performing. We live in the tropics, so we have first-hand knowledge of this.

The way to counter this effect is to use plenty of good compost and a good layer of mulch. The compost will bring the soil pH closer to neutral, which benefits most of the plants we all love to grow.

It does become an annual event to top up the beds and dress them with compost and mulch, but that allows us to fine-tune each bed to suit the type of plants we want in that bed for that season.

The new season sprouts are popping up. This is a snake bean beginning its life.

Tropical soils can also be very clay-heavy, and because we build and then fill the beds with the soil of our choice, we can develop very fertile patches within these beds over time.

To learn how to create fertile soil using chickens, we have an article titled “Making organic soil for raised garden beds” that explains our process.

We cannot think of any reason that would argue against using raised beds in the tropics.

We have ten raised beds here with plans on adding a few more over time, and the ability to control the soil quality is too good of a chance to pass up.


Raised garden beds are great for many reasons. As you grow older, less bending is involved, and gardening becomes much more enjoyable when there is little to no pain involved with sore backs and bent knees.

Understand that no raised garden bed will last forever unless it is concrete or stone.

Last minute hint…

You better get the garden bed position right if that is the type you put in and I would suggest mapping your yard for sun and shade for the whole year before building those concrete beds. We hope the info above has helped in some way, and thanks for dropping in.

Article by Tim Blanch for He is a qualified Permaculture designer.