Perlite helps with aeration and holds moisture, too.

Here is a link that might be useful: Perlite, container growing with 100% Perlite and Perlite/ peat mixes

thanks for the link, very interesting.

anyone have experiencing amending with additional amounts of perlite? or using the 100% perlite mix described in the link?

what are the drawbacks of perlite?

The main drawback I can see with perlite is its cost. Around here I'm paying $18 for a 4 cubic foot bag. Also perlite gets kind of dusty when dry and I'm not sure how badly it breaks down after awhile. It's a very interesting concept however.

I change out about 150 cubic feet of containers each Spring so I might up the average perlite percentage over many years of replanting and recycling potting soil.

mea

Wow! I only pay $9.75 for that size bale of perlite. But I've found a nursery supply company not far away that also sells to the public, so I imagine their markup isn't all that large. Why don't you check out your yellow pages for a nursery supply -- I hope you'd be able to find it cheaper somewhere.

Perlite doesn't break down in the soil, is good to reuse for years. I personally prefer vermiculite because its aeration is slightly better, and it doesn't look like styrofoam. It, however, does break down, sometimes after just one season, so next year I may switch to perlite myself, or at least combine them. They're both very lightweight.

what about the difference in size of the perlite particles and the finer spaghnum peat moss or other organic material? does this hinder drainage? or is the difference negligible?

spmimi

Agricultural perlite (considered to the be "medium" size) is used for planters and containers. The difference in size is not a problem. The perlite aeration and water-holding pores are not invaded by the sphagnum moss particles, and once the mixture is in the container, unless it's flooded to overflowing with water, it'll stay put as you've mixed it. I occasionally find perlite at the top of my windowbox soil after heavy rains, as well as some of the water gels, but I just swizzle that stuff back into the soil.

anney, thanks for the pricing info on the perlite. Perhaps it will be worthwhile to make some phone calls and take a driving trip somewhere. I need two more bags of perlite this year and that pine bark mulch isn't cheap either ($4.50/2 cu. ft.) at the nursery I go to. Unfortunately I live in a densely populated urban area and that nursery is the only one within a reasonable distance that I've found that had the big bags. The small bags of perlite they sell at Home Depot are even more expensive.

anney and mea - thanks for the input!

besides the breakdown issue, what else is the difference between perlite and vermiculite? specifically drainage properties?

also, assuming i do add extra perlite either to my commercial mix or sphaghnum... i should also make sure to use a fertilizer with the micro-nutrients, correct?

and al, if you're around... since the mix above is similar to yours (minus the bark) i wanted to ask you whether or not i still have to add the lime? (which i assume i do)

Vermiculite is essentially heated and "popped" mica. It has a high cation exchange capacity (i.e., takes positively charged ions from the soil and slowly release them) and contains magnesium and potassium. Vermiculite can hold up to 16 times its weight in water and provides good numbers of air spaces. Horticulture grade vermiculite is near neutral in pH. Building or insulation grade vermiculite is alkaline, coarser and often treated with chemicals; it should not be used to grow plants. Vermiculite is an excellent seed starting medium. You should avoid breathing the dust from vermiculite because it contains silica.

Perlite is crushed, heated and expanded lava (actually volcanic sand) that has no mineral nutrients or buffering capacity. Like popcorn, moisture trapped in the lava particles causes them to expand when heated. Perlite retains structure better than vermiculite and has a neutral pH (6 - 8). It is especially good for starting cuttings.

Whether or not you need to add lime depends on what is in the mix & what you fertilize with. I don't think you described the mix - only said you were going back to what you used last year. If it contains no pine bark, why not mix it 50:50 or 3-4 bark: 2 your mix? Saying a mix w/o bark is like the mix I grow in is like saying. "This farm is just like a dairy farm, but it has no cows". ;o)

Cheers - It'll work out for you. My dearest friend is fond of saying, "It's all good." ... and so it is.

Al

al, thanks for describing the different properties of vermi and perlite. i also meant the mix described in the link, 50/50 perlite and spaghnum peat moss.

i wish i could mix in some bark (and use your mix as a model); however i ran into the potential problem with the cedar bark. if i can find pine bark, then it will be a project for next year!

i have one last question if anyone has input - if, indeed, cedar has toxicity issues with plants, how quickly would those toxicity issues arise? bottom line, if i can put of the transplant until next year, my wallet (and my back) would be much happier. but if someone has the experience or knowledge and recommends changing out of the cedar this year, then that would be helpful to know.

all best.

I didn't get involved in the thread for two reasons. First, I've never grown in "cedar" bark, and can't speak from experience. I know it's not commonly used as a grow media, though. Second, it would do no good to research the bark unless you attach a binomial (Genus/species) to the tree from which it came. I can think of at least a dozen different trees in no less than 6 genera that carry the common lable "cedar".

Al

thanks al. i wasn't really fishing for a comment from you specifically. anyone who has had experience would've been helpful (and i always assume that if someone doesn't have the direct experience, then they won't respond).

and thanks for reminding me of the oversight in my "research". i am always a stickler about scientific names in my native wildflower garden, so i don't know why i wasn't with this. at any rate, it is listed as "eastern cedar" which of course gives no identification property at all (red or white? and red isn't even a 'real' cedar but a juniper).

at this point, i've decided to transplant out of my cedar, but i just have to decide when is best according to the needs of my plants. who knows, by the time i decide to do it, maybe i will have found pine bark fines! ;)

FWIW, although I don't grow in 100% perlite I amend my soils with it and it works great (if I had access to composted bark fines I would try Al's recipe). I use a 50/50 mix for cacti and succulents and am going to try this with a few non-succulent plants this year. And, contrary to conventional wisdom, perlite does not "float" to the top of the pot.

thanks andy. glad to know you're doing a 50/50 with success. if i don't find composted fines this week, i think i'm going to try out the 50/50 mix and we'll see what happens!

I just found I have a bigger problem with perlite than price. After running out of perlite I found the nursery where I get mine won't have any more for about a week and this week is the start of planting stuff here in Chicago. So I call almost every single nursery and garden place in the Chicago area and nobody carries the 4 cu. ft. bags of perlite. Most didn't even know what I wanted and some of these advertise they cater to "Container gardeners." Can you have a container garden without lots of perlite? Am I the only person in Chicago mixing my own soil?

Anyway, I'm in a bind right now in that I have to mix soil but don't have perlite so I'm going replace the part perlite in my modified Al's formula with parts pine bark fines (i.e. double pine bark for what I put in for perlite). I'm hoping this will be OK. I have to get some containers planted this week.

Mea - Bummer! How much do you need to get by? I could ship you some tomorrow - you'd have it by wknd.

If you don't mind driving, I could try to get you the name of the supply house N of Chicago where a friend picks up all my fir bark. They would certainly have it in several sizes. Let me know tonight, off forum. I'll call her in AM for the phone & address.

Al

I really wanted to try Al's mix this year, but at the last moment I chickened out and decided to try a compromise strategy. I combined the regular soil that I usually buy with pine bark (labelled as "Bark Mulch"), mixed 50/50. The sizes of the pieces look about right for Al's mix, but I do not know if these are pine or not. The mix drains really well, we'll see how the structure holds up over the season. I have had two squash plants in containers of this mix for about a month now, so far so good, starting to get my first fruit.

Hope you do well, Osprey. ;o)

Mea - I know you said you're all set now, but here's a link to Oak Hill Gardens. They have big bags of perlite and fir bark at very reasonable prices. You can build a killer soil for houseplants with fir bark & Turface.

Another source for pine bark & large bags of perlite near Chicago is Platt Hill Nursery in Carpenters ville. (847) 428-6767.

Al

Here is a link that might be useful: Oak Hill Gardens

Al, I've been thinking of using some of the potting mix ingredients you recommend, and was wondering what you think of Shultz Orchid mix. It contains aged pine and fir barks, arcillite (which I believe is comparable to Turface), and charcoal. Nothing else. I was thinking of mixing this 50/50 w/ a peat-based mix (as I have no desire to water daily, or anywhere near that often). I only have around 30 plants, many of them small, so I really don't want to get into ordering bulk single ingredients, and paying tremendous shipping rates.

Thanks,
Karamy

I don't do orchids, but the mix they're grown in is always plenty airy. I try to limit my mixes for things like veggies & display containers to no more than 15% peat (most of my soils for woody plants have no peat and only 1/3 is pine or fir bark - the rest is inorganic particles), but soils are about compromise. By that, I mean if you can't or don't want to water every day, it's a given you'll have to grow in something that holds more water & less air. That's for you to decide. ;o) All I do is try to relay the relative importance of the physical characteristics of the soil proper, and the choice or combination of ingredients that goes into it.

All soils have inadequacies; none are perfect. Some growers can adapt to them because they have enough info/knowledge to recognize the shortcomings. That you have concerns and are aware of what constitutes a good container soil is half the battle in heading off potential problems. My bet is you'll do just fine.

Al

Al, thanks for the info. With the advances of the Internet it's still very difficult to find places that sell esoteric things like perlite and pine bark. When I get out by either of those places I'll definitely check out them out. Their perlite is $5 cheaper but it would cost me about $10 in gas to drive out to Dundee and back LOL. Maybe next year I'll make a bulk buying trip.

Osprey, I'm recycling regular soil into my mixes. I'm doing about 40% recycled (i.e. regular) soil, 40% pine bark, 10% peat moss, and 10% perlite. When I stick my finger into this mixture after planting I can almost feel the air pockets in the soil which is far different than what I felt in previous years.