Empty Concrete Planters: Why They Kill Plants and How to Style Them

The Scenario

A homeowner recently asked:

I'm in Melbourne with a modern house and these two empty rendered planter boxes right by the driveway—what should I plant in them?

The GardenOwl Diagnosis

The Assessment

You have a sharp, modern home in Melbourne with a clean rendered facade and a concrete driveway. It looks great, except for those two white geometric boxes sitting by the entrance. Right now, they are just vessels for dirt, actively hurting your curb appeal. If you want to avoid The Synthetic Heat Island, you need them to be a feature that complements the architecture, not a thermal trap that functions as a weed trap.

The Trap: The "Concrete Oven" Effect

Most homeowners see a planter box and think, "Great, I'll just pop a plant in there." That is a mistake that will cost you money.

First, look at that dirt. I guarantee you that is construction fill—leftover clay, concrete dust, and rocks from when they poured the driveway. It has zero nutrients and drains like a bathtub with the plug in.

Second, those rendered concrete walls absorb heat. In the summer, especially with the reflection off that driveway, the soil inside those boxes is going to cook the root systems of delicate plants. In the winter, if they don't drain perfectly, the roots will sit in cold mud and rot. You aren't just planting a flower; you are engineering a micro-climate.

The Solution: Prep, Drainage, and Structure

Here is how we turn these boxes into the highlight of your front yard without killing three rounds of plants first.

1. The Excavation

Get a shovel and dig out everything that is currently in those boxes. I mean all of it. You need to get down to the bottom to check for weep holes. If there are no holes drilled at the bottom for water to escape, you need to drill them immediately (use a masonry bit). Without drainage holes, you are building a swamp, not a garden.

2. The Soil Mix

Do not use "Garden Soil" or "Topsoil" from a bag. Those are too heavy for containers and will compact into a brick. You need a high-quality Potting Mix.

Potting mix is designed to be lightweight and free-draining. Since you are in a hot spot (surrounded by concrete), mixing in some perlite or pumice will help keep the soil aerated even when it gets hot.

3. The Plant Choice: Go Architectural

Because your house has strong, modern lines, you need plants that match that geometry. A messy "cottage garden" mix will look cluttered here. You want structure.

The Focal Point: Since you are in Melbourne (roughly equivalent to USDA Zone 9/10), you have the perfect climate for soft succulents.

• Agave attenuata (Fox Tail Agave): This is the gold standard for modern planters. It has a big, bold rosette shape, it's spineless (so it won't stab guests walking to your front door), and it loves the heat.
• The Native Option: If you want to keep it Australian, go for Kangaroo Paws (Anigozanthos). The 'Big Red' or 'Yellow Gem' varieties add vertical height and look stunning against that dark brick. They are tough as nails once established.

The Underplanting: To take the edge off those sharp white corners, you need a "spiller."

• Dichondra 'Silver Falls': This is my go-to. It has silvery, coin-shaped leaves that cascade down the side of the planter. It handles the heat well and contrasts beautifully with the white render.

Visualizing the Result

Imagine walking up the driveway: instead of staring at dirt, you see a sculptural green Agave rising out of the top box, with silver foliage trailing down the side. It softens the concrete without fighting the modern architecture. It looks intentional, expensive, and finished.

If you want to test this on your own yard, upload a photo and see what this design would look like using our Exterior Design App. It’s a lot cheaper to test a plant combination digitally than to dig it out three months later.