How to Fill Large Planters: A Guide to Creative and Budget-Friendly Solutions

Filling large planters can seem daunting. All that space to fill with soil means buckets of heavy potting mix and a hefty price tag. But your back and wallet don’t need to take a hit when planting your oversized containers. With a bit of creativity you can find cheap or free materials to fill the bottom of large planters before topping them off with potting soil.

In this guide, we’ll share plenty of innovative ideas and tips to fill your large pots inexpensively. We’ll also cover what to avoid using as planter fillers. Read on to learn the best tricks for planting on a budget!

Know Your Planter Size and Plant Needs

The first step is determining how much space you need to fill, Measure the height and width of your planter to calculate its volume,

Next, consider the root depth of the plants you intend to grow. Shallow-rooted annuals like petunias or impatiens need just 6 to 8 inches of soil. Tomatoes, coneflowers, and other deep-rooting plants require at least 12 to 18 inches of potting mix.

Identify how much soil your plants need, then you can fill the remaining bottom space of your planter with filler materials. This ensures healthy root growth while minimizing soil costs.

Use Recycled Plastics

Plastic bottles, jugs, tubs, and plant pots are go-to fillers for large planters. Rinse thoroughly, then add upside down with caps on. Milk jugs, detergent bottles, soda bottles, yogurt cups – virtually any plastic container works.

Opt for lightweight plastics to maintain mobility if you’ll need to move the pot. Avoid chemical containers. While plastic doesn’t biodegrade, recycling it into planter fillers keeps it out of landfills.

Crushed Aluminum Cans

Rinsed, dried, and crushed aluminum cans are perfect lightweight fillers. As an inorganic material, crushed cans don’t decompose so they maintain their filler structure. Their drainage-promoting shape makes this a budget-friendly win.

However, chemicals from soda or food residue may leach into the soil over time. Use caution when planting edibles. Sharp edges are also a minor hazard when handling crushed cans.

Polystyrene Fillers

Polystyrene packaging materials, like Styrofoam blocks, foam peanuts, or pool noodles, are incredibly lightweight. Biodegradable versions are eco-friendly options. Just ensure any foam fillers won’t dissolve when wet. Containing them in mesh bags or landscape fabric helps minimize mess.

While convenient to reuse, polystyrene filler risks compacting or shifting over time as it degrades. This can reduce drainage potential. Non-biodegradable types also carry environmental impacts when discarded.

Inorganic Materials

Rocks, pebbles, gravel, clay pellets, and rubble from broken clay pots are great inorganic fillers. They won’t decompose or impact soil chemistry. You can reuse them indefinitely in other planters too. Arrange with drainage gaps for improved aeration.

However, gravel and small pebbles tend to mix into the soil over time. Landscape fabric barriers help separate filler layers. Inorganic materials add substantial weight, making relocating large pots difficult. Their thermal mass can also overheat plant roots.

Wood byproducts

Wood chips, bark, sawdust, or straw make attractive organic filler options. As they break down, the resulting compost improves soil structure. But decomposition means volume loss over time, so periodic replenishment is needed.

Wood-based materials also tend to harbor molds, fungi, and pests. Use caution and monitor closely, especially with edible gardens. Hardy plants like shrubs or trees better tolerate the changing soil chemistry during the decay process.

Coconut Coir

The stringy fiber from coconut husks, known as coir or coco peat, is a rising superstar as a planter amendment. Coir buffers moisture changes in soil to benefit roots. It’s lightweight yet durable enough to persist for several seasons.

As a natural product, coco coir is completely biodegradable and compostable. Look for sustainably sourced coir versus synthetic versions. It does require extra watering diligence since coir repels water when dry.

Get Heavy With Bricks, Blocks and Pavers

For permanent or freestanding planters prone to tipping, weigh down the base with bricks, concrete blocks, or paver stones. The thermal mass also helps buffer soil temperature fluctuations.

Lay bricks and pavers with gaps to allow drainage and air circulation. Concrete blocks work well arranged in columns to bear the weight while facilitating water flow. But anything extremely heavy sacrifices mobility if you need to relocate the planter later on.

Think Twice Before Using:

• Loose shredded paper or cardboard – Decomposes too quickly into a dense mat that blocks drainage
• Untreated wood – Invites termites and rotting
• Metal items – Rust over time and negatively impact soil chemistry
• Bagged organic matter like mulch or topsoil – Moisture retention causes decomposition and soil contamination

Expert Tips for Success

• Always allow proper drainage by not blocking holes or bottoms of planters
• Add a landscape fabric middle layer to separate filler from potting mix soil
• Monitor soil moisture levels closely and adjust watering practices accordingly
• For permanent installations, use inorganic materials to maintain stable soil conditions
• Research plant root depths and water needs before selecting filler materials

Get Creative Filling Your Planters!

Hopefully these ideas sparked your creativity for inexpensive ways to fill large planters! Raid your recycling bins or take inventory of materials lying around your home and garden.

With a little thought, you can transform what would normally wind up in the trash into functional planter fillers. Your plants will appreciate the improved drainage while your wallet appreciates keeping a few extra dollars. Happy planting on a budget!