Hello joy99,
You can transplant the cacti into another larger container and/or move them outside (depending on your climate).
Here are some tips for building a cactus garden:
Materials - Large rocks, potting mix
To start your garden, look for a sunny, well-drained area. For a lot of us, this will be hard to do. Our yards are usually too flat so we have to build raised beds so that there will be no chance of the plants becoming water logged. First draw an outline on the ground of the garden. Don't make it to large, you can always expand. Now take out some of the top soil (6" to 12") deep. Then place a narrow strip of plastic where the rocks will be, let it extend into the hole a few inches, this will help control grass from getting in the garden. Now place the rocks around the hole, don't make it round or square, do a natural look. If the garden is to be facing the street you can go two or three rocks high in the back. Now fill the hole to the top of the rocks with your soil mix. A good cactus mix is: one part potting mix, one part washed sand, and one part large (gravel, pumas, broken clay pots,) most anything that will help keep the soil loose. If the garden is to be level, mound up the mix to make it show better and increase drainage.
Take all your plants and set them in the garden to give you an idea as to where to put them. Dig a small hole in the mix just deep enough to cover the roots, leaving the cactus body on top of the soil. Cactus that are not winter hardy can be used by leaving them in the pot. Just bury the pot so they can be removed and taken in for the winter. Give the plants a small amount of water ever two or three weeks until they root. Then let nature pay the water bill. Feed once a year with a plant food like 10-10-10 or good house plant food. Never overfeed, this is where a little does better. A few large well placed rocks will add protection from the hot sun, and help hold moisture, and it just looks good.
