how to fill a large pot

How to fill large flower pots?

Having large plants and dwarf trees on your deck, porch and even indoors can add a lot of beauty and interest to your space. However, these pots can take a lot of potting soil to fill.  It will be nice to fill the pots with something lighter and cheaper.  Here are some answers to the question: How to fill large flower pots.

how to fill a large flower pot?

You need to understand the needs of your large potted plants

Before you think about how to fill large flower pots you need to understand the needs of your plant.

Using large pots for annuals and small perennials

If you are using your large flower pots to add height to your garden and using a pot full of annuals and small perennials then the depth of the soil is a lot less important.  In many cases, I don’t even put soil into the pot at all.

Instead, I keep the flowers in a smaller pot.  I stack things inside the large pots like patio bricks or used plastic containers to give the pots hidden height without using soil.

how to fill a large pot

The benefit of this is that you can easily change the plants seasonally without much effort.  Since smaller plants are happy in small containers there is no reason to actually fill the large pots and plant them

Large plants in containers

When you use large pots to give your large plants a good home you need to think about what they need.

Many plants have shallow roots.  These typical potted shallow-rooted plants are:

  • most cacti
  • bonsai trees
  • most herbs
  • annual flowering plants
  • Azaleas

These shallow plants are well suited for containers.  You need to be less concerned about the depth of the container.

Some plants have deep root systems.  The common container plants that are deep root plants include:

  • Black eye Susans
  • Purple coneflower
  • Aloe Vera
  • roses
  • all trees

Deep-rooted plants need to have large containers filled with quality material.

Ways to fill the pot

Plastic bottles

fill large pots with plastic

Many people use old plastic bottles like water bottles and soda bottles.  You can fill the bottom of the pot with layers of bottles until the height is so that the soil will be at the depth you need.

Be careful, make sure that the bottles will not fill with water or soil.  If they fill it can cause algae and root rot issues.  You can help ensure this does not happen by either cutting the bottles into pieces that will not hold water or keep the covers tightly on the bottles.

This is best for shallow root plants.

Old clay pots

fill large flower pots with broken clay

A great way to make use of old broken clay pots is to use the pieces to fill large flower pots.  Simply take the pieces of the old pot and place them in the bottom of the large flower pot.

Break up the old clay into pieces that will be small enough to fill the bottom without stopping the water from draining out.


As I said, I like to use bricks to fill my large pots.  I use them as a base to put the smaller flower pots.  I create a fake bottom at a height that will make it seem that the plants are actually planted in the large pot.  This way I can easily change plants around, always keeping my planters fresh and seasonal.

However, you can also put bricks into the bottom of the large flower pots then you can fill them with potting soil.

Best for shallow-rooted plants.

Clay Balls to fill large flower pots

how to fill a large flower pot

These are one of my favorite container garden tools.  I mix potting soil with clay balls before I put the soil into the pot.

The great things about using clay balls to help fill large pots :

  • you use less potting soil
  • keeps the nutrient-rich soil distributed in the entire pot
  • helps to aerate the soil

This is a great method to use for all deep-rooted potted plants.

Coco Coir

Coco coir is another thing I use a lot of.  It is inexpensive and goes a long way!

Bricks of coco coir expand when you get them wet.  It is amazing the volume that you can easily add to your potting soil with one brick.

The benefits of using coco coir to fill large flower pots:

  • it adds a great deal of volume
  • coco will help keep your plant soil moist
  • keeps your flowerpot lighter and easier to move

This is an easy and useful way to add volume to pots with deep-rooted plants.

Words of caution when filling a large flower pot

Styrofoam and peanuts

Many gardeners say to use styrofoam and packing peanuts to fill large flower pots.  I do not agree.

There is some mixed science on whether these things release harmful chemicals into the soil.  Some reports say that it is completely fine some say it is very hazardous.  Most seem to fall in the middle camp.  The styrofoam and peanuts will take so long to break down that it is found to use in your garden

I feel that there are lots of other options with any risk of contamination so I never use styrofoam or peanuts in the soil.

Keep drain holes clear

Large pots with lots of material will need lots of drainages.  Many large pots come with only one large hole in the bottom.  Whenever possible add more holes.  You can never have too many ways for water to drain off.

The soil should be well-drained.  So there is no purpose in keeping the water in the pot.  It can only cause harm to your plant’s roots.

Potting Soil

Remember never to use “dirt” from the yard to fill your large or small flower pots.  It can be tempting to just fill the pot with dirt from your yard.  This soil will be far too dense for container growing.

You can use dirt from the garden if you do a lot of prep work.

  • Only use very rich dark soil
  • it is a good idea to heat the soil to 170 degrees for 15 minutes to kill any pathogens in the soil
  • add at least 25% of a lighting soil substance like perlite or vermiculite

Often it is just easier to use good quality potting soil.  The additional benefit of potting soil is that many come with a fertilizer designed for container gardens already mixed in.

Large plants in flower pots can add so much color and style to your space.  Don’t let the volume that needs to be filled be a concern.

Thank you for reading.  Please add your comments or questions.

Please read “How to grow citrus in a container” if you love large pot growing.

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