Question
Hello,

I would like to know what is the best soil to buy to repot a large Peace Lily plant.
What I have seen in the stores are bags of different potting soil.
Don't know which is best to use.
The other thing I would like to know regarding the Peace Lily plant is then I don't water it for 2 days it starts to droop, the leases kind of hand down. I is a large plant about 4.5 ft. and the area is not hot, we are in NY.
I water with a 1 lt bottle.
I was told to water once a week, it looks like it needs it every other day?

Answer
Nice to meet you, David.

Your Peace Lily ("Spathiphyllum" to Botanists) grows in the wild  in the shade, under the canopy of tall tropical trees.  It thrives as an apartment or house plant because it is totally at home growing in the shade at 65 to 90 degrees F and cannot take bright light.

Biggest mistake most people make with these: Too much attention.

This is a plant that has to dry out between waterings.  You can't water it on schedule, like a baby; there are just too many variables.  Humidity varies.  Soil water-holding capacity varies.  The size of the leaf surface and the root system varies.  And the pot size and material varies.  All of this together will determine how quickly the soil dries out and when you should water it.

How can you tell?

Touch the soil every day.  That way you will learn what moist soil feels like: Cool to the touch, as water evaporates and lowers the temperature.  As the soil dries out, it does not feel as cool.  Until finally you can tell it's dry and room temperature.

If you can, tilt the pot and see if bottom is also dry. Touch the drainage holes and see if they are dry.  If not, wait a few days before watering.  If the plant wilts, you can water it -- Spaths like lukewarm water, the kind you would give a baby.  Not hot.  Not cold.  Lukewarm.

You'll get the hang of it.  You'll learn.  That's what this is all about.

This being a huge specimen, the roots may be filling the pot to the point where they use up all the water you give it.  Frankly, a plant that large should be getting more than a 1 litre bottle at a time.  Don't measure the water.  Fill the bottle over and over with lukewarm water, and drench the soil.  Don't stop watering until the underdish has water trickling out of the bottom.  In half an hour, if there is no water in the underdish left because it was soaked back into the pot, water it again.  You want the roots to be thoroughly watered and the soil to be moist.  Then you stop.  Test the soil with your fingers and learn how to tell in the dark if that plant needs water.

Spaths do need a reasonably warm situation.  They cannot take full sun and they do need moisture, but the roots also need to dry out completely.

What happens if you water it too much?  If it does not dry out between waterings?

Anaerobic bacteria in the soil multiply and quickly attack the roots.  Your Spath no longer looks green and healthy.  The leaves look a sickly pale green color; they droop and drop.  This SHOULD NEVER HAPPEN to you.  Because if you follow those careful directions I gave you, the roots will always be dry and there will always be Oxygen in the soil to keep anaerobic bacteria from ever growing up.

Of course, we never, never use chemicals on our plants.

Especially because we live indoors with those plants and those chemicals would be terrible for us.

When we get spider mites, aphids, or the unexplained, we write to the Long Island Gardener and describe the symptoms.

Now, What about the soil?

Assuming you are living in a highrise multifamily unit with no free dirt, you will have to buy a bag of this stuff somewhere.  So you are pretty much limited to what you can buy.  And let me tell you, there are all kinds of companies out there just lining up to sell you dirt.  They do market studies to determine exactly what colors to make the bag so that you will not only buy it, but you will pay top dollar for their dirt.

Just get the cheapest dirt you can find.

If it says "African Violet Soil," and it's on sale and it's cheap, buy it.

If it says "Peat Moss," well, Peat Moss is not dirt.  Don['t buy it.  You'll have to mix it with dirt and then you will have a whole mess.  Totally unnecessary.

Just go out and get some dirt.

If I have am wrong -- say you have a nice little house in the Hamptons, or your parents live in New Jersey in a house, go out and visit, dig up some dirt in the back yard, buy a bag of sand and a bag of "Humus" at Home Depot and mix it all up before you take it home, and there's your potting soil.

The pot is more important.

If you haven't got the pot yet, pick a Terracotta pot if you can.  They're porous and healthier.  Make sure you get a matching underdish for water to drain into.  And under that you will need something plastic because I guarantee the water will also soak thru the underdish if it's Terracotta and ruin a wood floor or carpet.  You can also use a ceramic or plastic dish.

Sounds like a stunning specimen you are growing there, David.  Large, lush plants are a spectacular thing to be able to put in a room in the city.  This is one worth keeping.  Good luck and if I was unclear about anything here, let me know.  Again, it was good to meet you.