Of course it is not ideal... It's just my orchid has sadly passed and I've decided to replace it with a hardy herb I can use to make tea (I'm a dorm student so I only have room for one plant on the counter). What I have now is a bark-based potting mix and a container with drainage proper for an orchid. Of course I'd need to water mint more regularly, but I want to know if the resources I have are sufficient to support mint life. Thanks!
If you are talking about planting mint in the old soil of the Orchid, no do not reuse that soil. There is a hard and fast rule in gardening; never reuse potting soil, especially when a potted plant dies. Never save used potting soil to use for plants in pots ever again. Fine to dump in your garden or compost but to plant new plants in pots, always clean, sterilize the pot and new plants get new potting soil. I have found many Nurseries that do reuse potting soil. Very risky but I guess they save money on sterilized potting soil.
Mint is a voracious plant that can grow pretty much anywhere, anytime, any type of soil. Little fertilizer is necessary but all plants need added fertilizer. ALL. Unless fertilizer was already added to your soil.
If you want success you have to invest a little dough truly just a few dollars...purchase a bag of cheapo potting soil no gimmicks or fertilizer added, use bleach to clean your pot, make sure it has a hole at the bottom and fill the pot 1/3 with the bagged generic potting soil. No rocks or gravel, nada at the bottom of the pot above the hole. Wet and firm that soil then plant your mint plant (I am assuming you've got a nursery grown potted mint in a 4" pot and your orchid pot was 6")? so that the top surface of the soil of your new plant sits an inch from the rim of the pot for proper watering. Lift bottom of pot so that there is a quarter inch between bottom of pot and the saucer. Dump water out of saucer after watering. Get a small container of Osmocote 14-14-14 and apply the beads at 1/2 the directions. You might add this only when you transplant your mint into a larger pot or divide it to make more plants.
Water only when that soil is dry. Pinch the very top newbie leaves once in awhile to help your plant get bushy. Do not 'mist'. Once or twice a year take into the shower or use the kitchen spray to wash the plant leaves of dust.
Mint care is like riding a tricycle. Orchid care is like riding a Harley. If you couldn't keep an Orchid alive (I can't either, I don't have the environment so don't feel bad) you will have success with mint! Do you have covered porch or covered patio? Great to take them outside to sit up off the ground to get a boost of light (light bouncing off objects out of doors is stronger than the light in the house on the kitchen windowsill) although never in direct sun...they come inside before the weather changes having made a lot more food for themselves and a stronger root system. Keep them up off the patio surface so you don't get earth worms, pill bugs, earwigs, slugs...etc. having made a home in the bottom of your pot.
Hope this helps. I am known for TMI. Grins!!
Orchid mix is purposely nutrient poor, and low in organic material. It also drains rapidly as it is designed to support epiphytes that grow on branches, and get their water from the leaves absorbing moisture from the air, and not from roots absorbing from soil.
So, it's completely inappropriate for a soil based plant. You could keep it should you decide to get another epiphyte.