Question
Hello there,  i've got approx 20 north american pitcher plants and VFT's, all in pots ranging from 8 inches to 16 inch.   when it comes time to repot them, do they all require spag peat moss and perlite?  or can i mix some fresh spag peat moss (or just spag moss) and perlite in with my potting media from last year?  seems like a waste if i just throw all that away.  please advise.

Answer
Hello Darren,

Eventually your old potting medium will go sour. Old sphagnum peat moss and perlite break down slowly and begin to lose their quality. Fresher sphagnum peat moss contains more iodine and keeps bacterial growth at bay longer. It also is spongier and airier so that plant roots can breathe more easily. Perlite breaks down after a year or so and begins to release chemicals that can sicken some species of carnivorous plants like Nepenthes. About the longest such soil should be used is two years. If you are going to mix some new soil in with some of the better looking old soil you could go with a 50% new and 50% old mix and totally replace it every two years. If you were getting some odd growth or slowing in growth in your plants you would want to totally replace the soil with new to ensure that nothing harmful remains near your plant. Any chemicals or minerals would be picked up and might build up in that soil over time, altering the Ph gradually.

Christopher