Judy, I like using Pro-mix it is a soilless mix that enables great drainage and aeration. I took Horticulture at College and they used the same thing I use. Make sure you moisten it real well (but not soggy), just so when you squeeze it in your fist it stays together without water running out. I get it at the Hardware stores, Home depot, Wall Mart might have it, or a different brand. The mixture is peat, vermiculite and perlite. Or you can make your own with approximately 3 parts peat, 1 part vermiculite and 1 part perlite. Commonly known as a triple mix. Janet

For me the key word is light.
As my plants - and the pots they're in - get bigger, I mix the potting soil with more & more Perlite.
Right now, with some pots nearly a foot-and-a-half in diameter, I'm using about 50% Perlite in them, and they're still light enough to move outdoors in the summer.
I figure that by putting even more Perlite, I can keep going until the pots get a couple of feet in diameter, and more.
Over ~80% Perlite though, I guess the soil would be so loose, that the plants won't stand up straight.... But the denser rootball from earlier, smaller pots, should give them some stability, before they send out enough roots to anchor themselves in the new soil.
If fast drainage is a problem, adding some peat moss should fix that, without adding a lot of weight...

Thanks for the great info. I will be sure and try to keep it light .
Thanks again.
Judy

I make my own soil mix, using perlite, vermiculite and whatever brand of soil/compost the store I'm at happens to carry. I like promix but just find the cost is prohibitive. If they carry peat, I will get that too, but it's not always available. I just mix it in a big bucket, get really dirty transplanting and have fun. The only problem I have run into is fungus gnats some times, and that is easily remedied by adding a layer of sand to the top of the pot.

I no longer buy commercial soil for my houseplants - not even promix. Promix has wetting agents in it and that's fine for a plant that's going to be outdoors in the wind and sun - then it needs the ability to hold a bit of extra moisture. But indoors it stays too damp.

So I make my own soil-less mix. It's 1/3 peat, 1/3 perlite and 1/3 pine bark fines. The peat is reduced or left out entirely for some succulents.

This mix drains very well, allows air exchange at the roots, and is easy to remove from the rootball when you want to change the 'soil'. I haven't had fungus gnats in any plant I put in this mix. The only thing you need to do differently is get in the habit of watering more often. This mix doesn't hold a lot of water (holding a lot of water is not good anyway) so you will need to water more frequently. This more frequent watering will benefit the plant by exchanging the air around the roots more often.

Your generic tough-as-nails plants like pothos and spider plants don't really need this extra care, but anything fussier will almost certainly appreciate it.

BP

Curious, what are pine bark fines? I do agree that some types of promixes are too heavy and stay too wet. The supersoil that you can get at Loblaw's, for example, I think is just way too peaty and needs so much water to get it to hold water, that it is useless on its own. That's why I use the vermiculite/perlite, to lighten up the soil. And you can add/subtract depending on what plant it is. The compost or soil I use because I am bad at remembering to water all the time, and I find I don't really have to fertilize very often, or keep track of when I do. And it saves money so I can buy more plants!

Pine bark fines are often sold as big bags of 'partially composted pine bark mulch'. That's how I have bought it in the past (usually in the spring) - however I have had a hard time finding it the last couple of years so I have been using very fine orchid bark. Small bags of orchid bark can get pricey, but a big nursery can probably sell you a big bag for a reasonable amount. It lasts for a very long time - it doesn't break down quickly - so even though it seems expensive at first, it's not so much in the long run. I repoted most of my houseplants into this better soil(less) mix over a period of several years, so it didn't cost a lot at once.

You do have to be good at paying close attention to your plants if you're going to use a mix like mine - it dries out faster and is generally healthier for the plant, but if you're a forgetful waterer, then you might have a few more dead and crispy plants that you'd like :-)

Even if one wants to continue using whatever comercial soil mix they prefer, adding extra perlite would be a smart move.

BP

worry less about the planting mix and more about your watering.

In the winter most plants suitable for cool, Canadian climates rest.

This means they require far less water and fertilizer in the winter months than they do in the summer months.

As a rule I water plants in the summer deeply, allowing much water to drain out the drainage holes to ensure a thorough watering. Indoors in the winter I just give those plants sips. I don't soak the mix, I just give the plants a watering every 2-4 weeks in a much smaller amount and don't fertilize at all.

No matter what medium you put plants in they require less water in winter than in summer. The faster draining mix you use the more often watering is required, but everything being equal it is far easier to kill overwintered plants with too much water than it is with too little.