Why is potting soil deadly to fly traps?

I'm COMPLETELY new to planting. I'm getting some venus fly traps next week and luckily I found some already potted so I doon't have to worry about bare roots or transplanting at the moment, but my research has brought up questions.... What is it in potting soil that makes it supposedly deadly to fly traps? I have 1/2 a bag and it says it has peat, sand, and pumice in it.... they all seem to be the same planting ingredients listed for FTs. It is a fine mixture, so would adding some more pumice or sand be fine and help with the drainage?

 

Most potting mixes have lime added to them. VFTs need acidic soil.

 

If the potting mix had lime in it, it would state that in the ingredients... right?

my bag says that the product is made regionally... and that it may contain hypum peat, forrest products, and compost as well as sand and perilite (not pumice as stated before).

 

I don't think that soil makers have to list ingredients as food makers do. Does the bag say anything about PH?

 

Look for composts marked as 'Ericaceous' or 'suitable for Rhododendrons'.

 

Premixed potting soils are very high in nutrients that is why they are deadly to VFT and other carnivorous plants. Mix of 1 part peat: 1 part send should be OK. And plastic pot.

 

Thanks everyone! The plants are a Christmas present for my husband so I'm hoping not to kill them off before then. :)