Tricks to Fill a Large Planter

This post shares a variety of materials, tips, and tricks to fill a large planter or pot, other than dirt!

If you know me, you know I love a planter filled to the brim with seasonal colors. I have a variety of planters in just about every size on the stairs to and from our home and right outside our screen porch. I collect container garden ‘recipes’ just as I do food recipes. Pop over here to see all my Container Garden Recipes in one place.

With all these pots comes a whole bunch of soil…right?

Nope!

You can easily fill a large planter with an assortment of items that would normally find their way into your trashcan or recycling bin, saving you money…and your back.

Before You Start Filling Your Planter, Ask Yourself a Few Questions:

1. Do I need to move this planter?
2. Will I want to hang this planter?
3. Is it a lightweight planter, like this one?
4. Will this planter blow over without weight at the bottom?

If the answer to questions #1 or #2 is ‘yes’, then you’ll want to consider filling your planter with lighter-weight items. If question #3 or #4 is answered in the affirmative, then you’ll want to add heavier items to the bottom of your planter.

Three Layers to Your Planters

Between layer one and layer two, consider adding a layer of permeable, landscape fabric.

• Layer One will be the top layer of soil that your plants will be growing in and you want to make sure you have enough good, rich soil for them to thrive.
  • Most annuals will have a shallow root system (think vinca/periwinkle, impatiens, begonia, coleus, creeping jenny, verbena), as do lettuces and some herbs, like oregano, thyme lavender, chives, and basil. Make sure these plants have about 6-8″ of soil.
  • For deeper-rooted plants like tomatoes, basil, parsley, black-eyed Susans, and purple coneflower ensure that you have at least 12-18″ of soil.
  • Do a little research to determine how much soil your plant needs, and therefore, how much of the pot you can fill with non-soil.

• Layer Two is optional, but can prevent your precious potting soil from sifting down to your filler layer, thereby reducing the benefit you’ve been striving for! This layer should be a permeable material, such as landscape fabric, newspaper, mesh filter, old window screening, or similar material. Don’t use plastic bags or sheeting as those materials won’t allow water to run through.

• Layer Three will be your bottom layer. It will have an assortment of the items listed below.
  • Once you determine how deep you need your soil to be in layer one, fill the bottom of the planter up to that point. For instance, If you have a 2-foot-deep pot and are planting tomatoes (which need about 12-18″), fill about 6-12″ inches of the bottom of the pot with filler items.
  • If you have space between your items, consider filling in the remaining space of layer one with old soil, bunched-up pantyhose, or packing peanuts (the kind that doesn’t dissolve).

The good GREAT news is that many of these items will cost you nothing and will keep a few things out of the landfill or recycling center. When I am getting ready to plant a new planter, I go through my recycling bin and pull out items like many of these listed below.

Materials, Tips, and Tricks to Fill a Large Planter

Plastics

Plastic water bottles, milk jugs, sour cream, yogurt containers, and soda bottles with lids (you don’t want the water to get in the bottles and stagnate). Avoid bleach, ammonia, and other plastic containers that held harmful chemicals. Also, plastic plant pots (with holes) turned upside down are great fillers.

• Pros: Reuses materials that might otherwise go into the landfill, are lightweight, and can help with drainage. Bonus points for using biodegradable options that are environmentally friendly.
• Cons: As plastic slowly breaks down, the chemicals can be released into the soil. You may choose to use plastic filler for non-edible food plants only.

Crushed Aluminum Cans

• Pros: Crushed aluminum cans (crushed so that they don’t collect water) are another lightweight option that can also help with drainage. Using crushed aluminum cans also keeps them out of landfills. And, unlike organic materials, aluminum cans don’t decompose, maintaining their structure and function as a filler over time.

• Cons: There’s a concern about chemicals leaching from the cans into the soil, although aluminum is generally considered safe and is used in many gardening products. It’s still something to consider, especially for edible plants. Crushed cans may have sharp edges that could pose a risk when handling the filler material.

I know it looks like I’m just dumping trash in my pots, which I kind of am doing. 🤷‍♀️ But, it is just one of several tricks to fill a large planter and just think of all the 💲 I’m saving on soil! 😉

Packing Peanuts, Styrofoam and Pool Noodles

Make sure they are the ones that don’t dissolve in water (grab a few and run them under water…you’ll quickly know if they dissolve or not). Consider accumulating them in a bag so that they don’t get everywhere when you need to repot. If you use a plastic bag, put the bag in your pot so that the bag opening is facing down or has a few small holes poked in it so that it doesn’t fill with water.

• Pros: Lightweight and can improve drainage. Again, bonus points for using biodegradable options that are environmentally friendly.
• Cons: Non-biodegradable types can be harmful to the environment. They may also shift or compress over time, potentially affecting drainage.

Broken Ceramic, Terra Cotta Pieces and Stones

• Pros: Add stability to planters, excellent for drainage, and reuse materials that might otherwise be discarded.
• Cons: Can add significant weight, making planters harder to move.

Wood Chips or Bark

• Pros: Organic and improve soil structure as they decompose. Lightweight and help with drainage.
• Cons: Decomposition can affect the filler volume over time, requiring replenishment. May attract pests.

Expanded Clay Pellets

• Pros: Enhance aeration and drainage, reusable, and sustainable. Ideal for a variety of plant types.
• Cons: More expensive upfront cost compared to some other materials. They may float to the surface if not properly covered.

Coconut Coir

• Pros: Sustainable and lightweight, promotes healthy root growth and improves moisture retention.
• Cons: Can decompose over time, requiring replacement. May hold too much moisture for some plant types, necessitating careful watering practices.

Bricks, Rocks, Pebbles, Gravel and Cinder Blocks

Bricks

• Pros:
  • Durable and provides excellent stability.
  • Can improve drainage when placed correctly.
  • Reusable and can be arranged to create space for better air and water flow.
• Cons:
  • Heavy, making planters difficult to move.
  • May not be suitable for all plant types, especially those requiring deep, unobstructed root growth.
  • Can alter the pH of the soil over time, affecting plant health.

Rocks

• Pros:
  • Improve drainage and prevent soil from becoming waterlogged.
  • Versatile in size and shape for different planter needs.
• Cons:
  • Heavy and can make planters less mobile.
  • Can retain heat, potentially overheating roots in direct sunlight.
  • May be difficult to remove or replace soil around them.

Pebbles

• Pros:
  • Smaller than rocks, offering more flexibility in use and arrangement.
  • Improve drainage and aeration when used as a base layer.
• Cons:
  • May shift over time, affecting drainage and root growth.
  • Smaller pebbles can become mixed with soil, complicating plant removal or pot cleaning. A layer or landscape fabric will be useful.

Gravel

• Pros:
  • Excellent for improving drainage and aeration in pots.
  • Relatively lightweight compared to larger rocks or bricks.
• Cons:
  • Like pebbles, can mix with soil over time, making separation difficult; use landscape fabric.
  • May compact over time, potentially reducing its effectiveness in improving drainage.
  • Requires careful placement to avoid obstructing drainage holes.

Cinder Blocks

• Pros:
  • Highly durable and provide excellent support and stability.
  • Porous nature can help with aeration and drainage.
• Cons:
  • Very heavy, significantly reducing planter mobility.
  • Porous material can harbor moisture, potentially leading to mold or mildew issues if not properly managed.

This is my porch vegetable and herb ‘garden’. I have a tomato, fennel, a pepper, and the last of some dill growing in a large aluminum ‘planter’. I really don’t know what this ‘planter’ is, my husband went to a restaurant supply auction several years ago and brought it home for me.

It makes a unique and good-sized planter, measuring 15″ deep and wide and 25″ long. We drilled holes in the bottom for drainage. (*p.s. If you do know what this ‘planter’ is, please let me know. It looks like an industrial-sized mixing bowl, but the back of it is flat! I’ve never seen a flat-sided mixing bowl, so we are flummoxed!)

I wanted to give the tomato as much soil as possible, so I filled the back with good-quality soil, compost, and ground-up eggshells. But I used broken terra-cotta pot pieces at the front, where the dill and fennel are to reduce the amount of soil I needed there.

What Not To Use to Fill a Planter

• Metal, as it will rust and fall apart, causing air pockets in your soil
• The same is true for any organic matter, like logs, wood, paper, wood chips, cardboard, etc. They may be fine for the short term, but over time they will decompose, you will get air pockets that can damage the roots and the plant will start sinking. No Bueno. 😔
• Sheets of plastic, bubble wrap, etc...

Frequently Asked Questions About Using Fill in Planters

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