Indoor plant question

So I have a couple small cactii that need to be transplanted into bigger pots. I am WAY too cheap to go to the garden centre to buy a whole bag of indoor potting soil for the miniscule amount these two plants would need. My mum suggested I just dig up some soil from outside and put it in the microwave to kill any parasites or whatever might be in it. This strikes me as a good way to break down all the nutrients in the soil and make it useless? Opinions?

Go to a store that sells smaller bags of soil?

That. ^^^^^^^^^^

I was expecting a question about lights and heat shields.

You find clean fill dirt or potting soil on cragslist in the free section sometimes.

I've occasionally repotted plants in the UK with some of the soil from outside and I never felt the need to microwave the soil first. Didn't seem to either kill the plants or myself.

Actually for cactii you might want to get a small bag of the appropriate soil instead which IIRC contains a lot of sand. Then again, the soil around Berlin is pretty sandy, too.

Time for a little trip out of town then .

Buy a bag and more plants to "spruce" the place up a bit. House plants are nice decor items and require a lot less attention than pets or swmbo's.

This is going to seem a little convoluted and busy but it works. You can mineralize the soil, getting rid of the stuff you don't want and keeping the stuff you (and the plants) do want.

You take your dirt, mix it with water in a bucket or some other vessel big enough to let you dig around in it. Let the water/mud settle and skim the top of floaters. Stir it up again. Settle, skim.

Carefully poor the water off and spread the mud on a tarp or plastic in the sun and let it dry. Then put it back in the bucket and do the first few steps again.

Do the whole process 3-4 times, it will take a week, and the bacteria that you're producing through the wetting and drying will break down any unwanted organics in the soil that could make the plant unhappy.

It's a process but it grows great plants.

Jay wrote: My mum suggested I just dig up some soil from outside and put it in the microwave to kill any parasites or whatever might be in it. This strikes me as a good way to break down all the nutrients in the soil and make it useless?

Or a good way to mutate any parasites into microwave-sized super-parasites!

I would think soil from outside should be fine, especially if you can get it from a garden bed. Cacti are pretty hardy.

These guys might know!