1/7 in terms of raw materials.

"Necessary" is a subjective word. Necessary for what?

If you want to use bark and turface, you may as well find some grit and make Gritty.

The fines in 5-1-1 play a secondary, but still important role to the bark and perlite. It's critical to understand that the ingredient particle size in these mixes is as conducive to success as the type of ingredient itself.

If you hybridize between 5-1-1 and Gritty, you run the risk of creating a 'jack-of-all-trades, master of none" setup that is suboptimal to either pure 5-1-1 or Gritty. Then again, people on here are mixing and matching all the time so you really won't know until you try it.

""Necessary" is a subjective word. Necessary for what? "

Moral reasons. Some think it is hurting our environment harvesting the peat. I grow blueberries, and peat is the most important ingredient. If I could not use it, I would not grow them. I use a 1-1-1 mix for raised beds or pots. No lime or gypsum, but some elemental sulfur, and cottonseed meal.

I don't think the sphagnum peat is "necessary" in the commonly understood meaning of the word. Many people have left the peat out when their pine bark fines include a large proportion of dust so the balance of smaller and larger particles is about the same. In that case they use 6 parts PBF to one part perlite. I alter my 5-1-1 for vegetables in large fabric containers in the summer by using some compost for the peat and sometimes replacing the perlite with Floor-Dry. But I stick pretty close to the recipe when growing annuals in hanging baskets and vegetables in plastic nursery pots.

The point of the recipes is to give you an idea about the principles of good drainage. If something else offers similar benefits without any additional drawbacks, you can try substituting.

Some people are talking about the importance of good drainage...and then promoting an experiment with very fine particles mixed with larger ones. This is not sound thinking. If you read a lot of the past posts from people who really are experienced on the subject....you will realize the importance of having your ingredients matched (similar sizes). The finest of sizes... will determine how a pot drains. As one person said "how many bb's does it take to make a cup of pudding drain?". The gritty is fine if you are willing to handle the necessary feeding/watering (labor intensive) schedule. Not to mention the weight factor of larger pots.

Well, it's the eternal struggle between drainage and retention, Fire. Two sides of the same coin. If you live in Seattle, I suppose you're more hung-up on drainage. If you live in Vegas like me, you need some retention. I love the gritty but I just can't use it outside on anything but drought-tolerant plantings or I'd be watering 3x a day in summer even in full shade. The 5-1-1 is much more practical and the fine particles within allow my container plantings to survive 2-4 days in summer without watering.

I understand that peat moss can help acidify the mix and that it also allows it to retain more water.
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to my understanding, it is not the intention of acidification of the medium by adding peat moss. And maybe it is not so much moisture retention either. BUT to provide an environment where the roots have more constant contact with the medium. Hairline roots rather be in contact with something from which the can draw moisture and nutrients without much disruption. Absence of peat moss in medium like 511 will mean TOO MUCH air that leaves the roots naked.

"Absence of peat moss in medium like 511 will mean TOO MUCH air that leaves the roots naked."

Is this just a supposition on your part? If it's true, then wouldn't the gritty mix leave roots even more naked? After all, it has no fine material whatsoever. Even without the peat, the aged bark in the 5-1-1 mix should have a considerable proportion of fine material that would be sifted out in properly prepared gritty mix.

Looks like we could use an Al post on the true function of the peat in 5-1-1...

The primary purpose of peat in the 5-1-1 mix is to increase water retention. If you have well aged bark with a lot of fines, you can reduce or eliminate the peat fraction. If you have fresh bark with few fines, you can increase the peat fraction.

If you're still following this discussion, K-Tex, I've provided a link (below) to a relevant thread from last year.

Here is a link that might be useful: Turface in 5-1-1