I have a large pot that sits on top of a pillar, so I wanted to buy some flowers that would hang over the edges of it. We ended up buying a hanging arrangement of calibrachoa. Now I'm wondering if I'm better off trying to transplant the flowers from the hanger into the pot, or if I should simply remove the hanging apparatus and place the bowl on top of the pot. If you do recommend that I transplant them, do you have suggestions on how to do that effectively? The hanging bowl is about twelve inches in diameter, and the pot is about eighteen inches in diameter.
You can actually do whichever you want. I've done both. If the plants are healthy, feel free to take the plastic hanger supports off and set it on top of the other pot or somewhere else in the yard. Make sure there's enough drainage from that bigger pot so that when you water it, it's not sitting in stagnant water.
However, any time you have a bigger pot, my recommendation is to transplant, and this plant will generally look better in a larger container, Calibrachoa likes some some space. The bigger pot also gives you the option of adding more flowers, especially in the center. Something that stands tall is pretty for that.
In Massachusetts, growing zone 6 (−15°F, -26°C), which is somewhat east of you, they grow very profusely and easily. Since a trailing element is often a staple in a hanging plant, nurseries will sometimes use a lot to make the plant more attractive. The hanging plants I buy in the spring tend to be packed very tightly to give them a "finished" look, and, in my opinion, justify the high cost! After a while, they're either too crowded to produce good flowers, something else in the pot has pushed them aside so they become stringy at the base, or you just want to put them somewhere else.
They're an easy plant to transfer, very much like petunias, if you've ever grown those. Some people say that pH and nutrients are important for a healthy outcome. Rather than try to figure out the proper conditions, I just use potting soil that already has fertilizer in the mix, and that's what I recommend if you're transplanting from one pot to another.
Remove the hanging supports. This will make it easier to reach the whole thing and minimize breakage that can occur when extracting the plant. This is a good rule of thumb in general when taking things out of hanging pots, but especially for trailing plants, as they're likely to have wrapped themselves around those supports.
Choose a time of day when the temperatures are on the cooler side, and the plant is not in full sun.
Prepare the new pot by filling it loosely with new soil, to about 2 -3 inches from the top. Even if you're going to transfer all the dirt from the existing pot, the new soil adds fresh nutrients and is free from the surface debris and bugs which may have accumulated in its current home.
Wet it thoroughly. It shouldn't be drenched, like mud, but you should be able to feel moisture all the way through. This is to encourage the roots to spread easily, and minimize the shock of transplant.
If you're moving the entire plant, gently lift it out of its existing pot. If the roots are all tangled, or seem dry, pull them apart just a bit, but be careful not to break them. Leave the existing soil around the root ball, as it's already established.
Set it on top of the dirt you just prepared, keeping the plant level with the pot, or a little lower.
Gently settle the dirt around it so that it's well-supported. If it's leaning sideways, it's more likely to pull out of the pot as it grows. Since, the roots are fairly shallow, a good wind or rain can tip it over. The branches also spread more easily, and look prettier, when rising out of a compact center.
Water again, especially at the root ball, keeping an eye on the new dirt, so it doesn't too far below the level. Again, it doesn't like to be soaked. In fact, it doesn't like to be too wet.
To remove only some:
Gently remove the part you want to separate, being careful not to break roots of the other plants.
Use the same method as transplanting the entire plant.
Add fresh soil to the place in the hanging plant from where you took them, as the remaining plants in the hanger need good support.
This is an extremely easy plant to transfer, and even though it seems like a number of steps, you really don't have to baby it too much.