Introduction: Giant Geode Orb Planter

About: Welcome! Pleased to meet you, I am Barb; a Maker. I have been making things AND explaining how to make things for as long as I can remember. I was all about DIY before it was a popular term. I absolutely love …

When I get an idea in my head I am so determined to make it work that I sometimes wonder if it will ‘kill’ me first! This was one of those ideas… I was on a mission to create another orb design; but not just a typical one, I have to be super unique! With the help of a volcano and ingenious thinking see how I managed to make these Geode Orb Planters

Step 1: Make the Mold:

The Spherical Mold:

I wanted to create a casting from the inside of a mold, a sphere of course. Well, if you have ever tried to find a perfect sphere it’s not easy! I bought ball after ball and cut them open. Nope, not smooth enough. Basket balls have wierd seam lines inside. Other balls shrink to a limp skin. Plastic orbs are next to impossible to find… Soooo, I had to do what I usually do; make one.

My ‘Go-To’ method of making a mold always seems to save me.

What you need to make the Giant Geode Planter Mold

  • One box of corn starch
  • One tube of 100% Silicone Caulking
  • Old bowl
  • Gloves and good ventilation (super smelly stuff!)
  • Caulking gun, knife to cut it open
  • A smooth well inflated ball (cheap kids play-ball)

Have your ‘master’ ball ready by sitting on a bowl for stability. Squeeze the entire tube into the bottom of the bowl that is well filled with the corn starch. The intention is to keep it suspended in the starch so that it does not start to stick on the sides. Keep it in one mass, tossing and working in more starch so to get less and less sticky. Try to keep a layer of starch between it and your fingers as well.

After it absorbs more and more starch it will start to become moldable as it won’t stick to the fingers as much. This is so much like making a dough (I guess my years working at a bakery helped!).
Roll in your hands to make a ball of even consistency.

Flatten the ‘dough’ on a flat surface that has a dusting of corn starch to about 1/4″ thick.

The mix starts to set pretty quickly so immediately place it over your form ball and smooth it out. Do not worry about the edges or excess. I was aiming to have a good 1/2 of the ball or bit more covered. It will usually set with in 30 minutes I find. When you you poke it and it feels like rubber then it is set. It popped off easily and I finally had my sphere mold. It is flexible but also keeps it’s shape well – perfect!

Step 2: Making the Rock Sphere:

The Rock:

As you know by now, I love rock! It has to have some character, I’ve always marvelled at the way that lava rock is made, cooled lava from a real volcano. It is available as the internal rock for BBQ’s and also as a landscape type mulch. I used both types, but the bagged lava rock was larger and more colourful.

Which Concrete Mix to use:
I am always trying to get so much done (life of a blogger & maker) so I am happiest if I can use one of my quickset concrete mixes. I used the Quikrete Fastset Allcrete on this project but the Rapidset Cementall will also work here (it ends up lighter colour) Both these mixes can work at various consistencies. I did try a few variations and the results were all great.

If you would rather not see the any of the stones in the final form you can mix a very fluid mix and let it run between the rocks that line the mold. If you want to see more of the rocks you can use it more as a thicker mortar and just have it between the rocks.
You should experiment… I did realize that it is strong and holds the rocks together even if there are some empty voids.

The Method:

This is not a perfection type of orb, it has a lot of character and will be quite unique. There is somewhat of an element of magic here as to how it turns out; but that is what makes it so refreshingly unique.

The ingenious thing about a sphere is that you can work in partial portions since IS all the same curve! Gravity is something that will work against you so working in smaller sections is better. Once one section is set (about 1 hour if it’s warm) you can move it up the side to then work another bottom section next to it.

Place that set section on one side and then add more in the bottom. Slightly mist the existing set concrete to have better adhesion. Add rocks by letting the mix run in between or ‘mortar’ the individual rocks where you’d like them. You are in charge here.

You can continually adjust position to ‘fill’ as much of the form as you like after each addition is set until you have no more room for your fingers. My vision in my mind was to resemble some type of ‘carved-out-of-rock’ orb. The hollow void will be great for the other ideas I have!

Step 3:

I love the flexibility of this mold! It does tend to slightly stick but can be worked lose with a bit of manipulation. I do not really like the gunk that builds up when using a spray release like ‘Pam’.

Once you pull it out of the mold you will be amazed… Isn’t that so interesting?! So many elements of design, form, texture, shape and colour! Yes, colour! You can add some concrete colour to the mix to have some variations of colour. Each one will turn out with it’s own unique pattern.

Step 4: Adding the 'Crystals'

I have been making geodes for quite a while now. Finding suitable glass as crystals can be challenging. I have made my own as in these or also used broken safety glass.


  • glass stones, rocks, broken safety glass
  • glue gun and glue sticks
  • 5-minute Epoxy
  • stir sticks

I use the glue gun to 'tack' the pieces in place but the epoxy is much more permanent as an adhesive.

Plan the placement and colours to mimic nature. Try to be a bit more random than perfectly planned. Fill in small gaps with smaller pieces. You can vary the colours as well or even add some colour.

Once you have it as you like, mix some 2 part 5-minute epoxy and let it run between the pieces. It is a strong adhesive and will set very quickly. I work small batches at a time.

Step 5:

Being an artist I always seem to enjoy some embellishment. You can leave it as is or add some design of rock layers.

It is as easy as 'squiggly' lines of metallic tones! Check here to see a whole geode chair!

Painting the design with acrylics is quite simple.

Step 6: On to the Planting:

I like to be frugal so I am quite resourceful. On my walks through the forest I gather moss. Do not decimate a patch; just take small parts of it so it can regenerate. There are a few varieties that seem to grow here in Canada. I have often used found moss in my terrariums and it lasts for years and does quite well. Moss loves damp shady climates.

I keep my moss collection in recycled food containers so that it does not dry out.

There are plants in my garden that just seem to keep multiplying without any of my help.

My favourite Plants:

This red creeping Sedum is a favourite and never disappoints! Just cut the ends off and stick in some soil; red and green, with dark red flowers. These plants loved my other poured planters as well. Golden Stonecrop is another one of those, and it grows where ever it just falls. I don’t think I have ever even bought any. It’s even happy to find a home between the flagstone. The Yellow flowers are a bonus. Creeping Jenny also seems to just multiply and I love the way it can trail over the edges. That bright chartreuse green can’t be beat! 'Hens & Chicks' are also great little plants!

The Soil:

I lined the inside with some fabric since there were a few holes between the rocks. This will allow drainage and the soil will stay put. As a way of holding moisture I used some sphagnum moss under the good soil layer.
Use fluffy, organic matter soil to keep the mosses happy. Cut or gently rip the moss into shapes to firmly secure all the little sprigs of plants; like a big blanket.

Step 7:

The other awesome thing about orbs is that they can be set however you like. There is no bottom, so you can sit them sideways if you so desire since the moss will keep everything in place. A couple little pebbles will keep it from rolling…

Imagine a few filled orbs set in a pile – instant rock garden in a small space. Maybe for a balcony or tiny porch, or under a glass dome.

I think orbs in the garden are the best thing! The sparkle and bling is unexpected and the concrete and rock ensure that they last 'forever'.

Happy concreting, planting and making! See more unique projects on my site:

Planter Challenge

First Prize in the
Planter Challenge