Rather than trying to make those ingredients work, you might focus instead on using a less expensive packaged soil mixed with perlite. If you employ the benefits offered by using ballast to eliminate almost all of the perched water the soil can hold, you'll end up with a more productive arrangement than you would with any combination of the ingredients on your list.

Click me and I'll show you how to use ballast.

Al

It's not about the price. How about mixing the "orchid mix" with some perlite? Would that be better?

@Al

is vermiculite interchangeable with perlite?

can i use it instead?

I read many of the plants i need to repot are sensitive to fluoride that is present in perlite.

I wrote this several yrs back - might be helpful. I beg a pardon for the weird formatting:

Tip
Burn/ Necrotic Margins

Plants
with brown tips and/or leaf margins have been known to generate
considerable debate, perhaps because of multiple causal possibilities
- you think? ;-) Dry air, over-fertilizing, air pollution, fluoride,
chlorine - all have been judged guilty, alongside of bad plants, bad
culture, bad water, bad air, bad temperatures, ad infinitum.

Lets
think about this - First, we need to consider it a symptom, and not a
disease or pest. Like a rash, it could be caused by a wide array of
maladies; and like a rash, if we want to get to the offending cause,
we need to do tests or become detectives. I can tell you this - there
technically is no cure (dead tissue cannot be brought back to life),
but you can halt progression in most cases, by looking to cultural
causes.

I
see fluoride often blamed for scorch in plants like spider plant,
Easter lily, maranta, dracaena …. and a few plants are actually
somewhat susceptible to leaf scorch injury from fluoride and
chlorine, but not to the degree for which it’s blamed, and we
really can't avoid it anyway - it’s all around us - in the water we
irrigate with, in super-phosphate (a nutrient added to soils), peat
moss and perlite as well. Coffee and tea, tea being the greater
offender, are reliable sources of fluoride too, so consider that the
next time you read that it’s a good thing to add them to your
plants.

If
I had to pick a plant most often named as the victim of fluoride it
would be the spider plant. Most growers think
brown tips come free with the plant. At the Soil and Plant Lab in
Santa Ana, CA, new spider plantlets were subjected to a barrage of
treatments in multiple grow mediums. Included were heavy
fertilization with super-phosphate, and fluorine applications in
irrigation water at 3 times the concentration of what is normally in
drinking water. None produced any measurable amount of tip burn, and
the short version of the conclusions is that many of the injuries previously
blamed on fluoride would more accurately have been blamed on other,
unfavorable cultural conditions.

Some
growers have decided/concluded that fluoride damage is a
perlite-related problem and have suggested rinsing it in clear water
prior to using it in soil mixes. But testing information still
strongly suggests you can't blame leaf scorch on only perlite or
fluoride.

The
most likely cause of tip burn other than over-watering is an
accumulation of metal (fertilizer) salts in soils. Briefly, high
levels of salts in soil solutions inhibit the osmotic process, making
it difficult, or in some cases impossible for the plants to take up
water and dissolved nutrients. When this occurs, distal plant parts
suffer tissue necrosis due to salt induced drought stress.

Over-fertilization
and softened water are big offenders. When water is too hard, the
standard treatment to “soften” it, is to replace the calcium ions
with sodium, which is essentially what table salt is. You can replace
the calcium and neutralize the sodium in softened water by adding ½
tsp gypsum in a gallon of warm water & allowing it to sit
overnight.

In
recent plantings or repots in fortified soils (those w/fertilizer
added), microorganisms can make toxic levels of fertilizer
immediately available, causing plasmolysis (fertilizer burn) and
leaf/tip burn.

Humidity
can be to blame. Most houseplants are tropicals, and they prefer
humidity in the 60-90% range (most greenhouses operate at around 60%
in winter). We usually keep our home humidity levels, when
controlled, somewhere around the 30-35% range. Unhumidified homes may
often have as low as 10-15% humidity levels, which is lower than the
average relative humidity in the earth’s driest deserts. This can
be a problem.

Though
continued ultra-low humidity can be problematic, an even bigger
problem is that rapid drop in humidity when plants are brought
indoors as the weather turns cold and the furnace is suddenly
employed. This can cause not only tissue necrosis, but loss of blooms
and buds, and the shedding of other plant organs, sometimes so severe
as to cause the death of the plant.

I
know some feel humidity trays are effective at raising humidity in
their immediate area, but I tested this theory. I placed a digital
hygrometer in the foliage of a bonsai tree about 10 inches above wet
pebbles in a large humidity tray. It read only about .4% higher in
humidity than the room air. I attribute the lion’s share of this
rise to normal moisture loss from the foliage through transpiration.

Misting
is also ineffective/inefficient. It only increases humidity for as
long as water remains in liquid form. Humidity levels return to
normal in a few minutes, as soon as evaporation is complete. Misting
can also be counter-productive for two reasons. As dissolved salts
from mist water accumulate on plant surfaces, the salt can actually
“pull” water from tissues, like salt pulls moisture from a ham,
where it is lost to the air via evaporation. Misting also closes
plant stoma, often for many hours, which slows transpiration and
water movement in the plant. When transpiration is slowed, it is also
accompanied by a reduced photosynthesizing ability.

You
can also suspect cold injury as a possible cause of tip burn. Many
tropical plants can leak bio-compounds from cells at temperatures
below 50* or so. Low temperatures can also inhibit photosynthetic
ability. The time needed to fully recover normal ability once more
favorable temperatures are restored varies by plant, but is often
measured in days.

Many
other cultural conditions can cause tip burn, too. Leaf shine, dust
accumulation, a source of ethylene gas or carbon monoxide,
inappropriate pesticides, aerosol propellants (cold), and on and on.

In
an overwhelmingly high % of cases, you’ll find tip burn originates
with something cultural. Most often it can be attributed to a poor
soil that drains slowly and causes drought stress from too much water
in the soil and its accompanying impediment of root function, or from
a poor soil that necessitates the grower water in sips to prevent
root rot, the upshot of which is to guarantee the accumulation of
soil salts and the plant’s inability to take up water.

Al

@AI or others

What is a good ratio of

common potting soil and perlite?

Can too much perlite be harmful?

Have you taken the time to read this yet? (Click me)

Al

Yes. I still don't know.

Is 1:1 perlite:soil bag a good ratio for the plant?

It's mostly about the plant itself. How fast it evaporate water. You can increase or decrease the soil part. Increase water retention for strong mature plant, or reduce it if its still young or weak on evaporate water (cactus for example). You might fail at the beginning, but practice and experience will give you green tumb award, and the most important is, you can use any available common materials around you and maximize their usability for your purpose. Perlite isn't toxic. Perlite, soil bag, bark, rice husk... all have their own characteristics and benefits, and none of them toxic for plants. Best soil mix will be always subjective. None best for everything...nor everyone.

S - When addressing air porosity and water retention, generally speaking you need a very large fraction of coarse material to largely avoid the limitations imposed by perched water or excess water retention. In order to take advantage of the larger air spaces between the larger soil particles, there should be a volume of fine particulates insufficient to fill the larger air spaces between soil particles. As long as you have coarse material(s) on hand, it doesn't make sense to not take advantage of what they offer. There will be a "threshold %" somewhere around 80% coarse and 20% fine materials. For example, if it takes a 25% fraction of fine material to fill the large air spaces between the coarse particles, you'll see the greatest gain in growth/vitality potential when you limit the fraction of fine ingredients to LESS THAN 25%.

Imagine a quart of pebbles the size of BBs in a jar. In the mind's eye, you can see all the beautiful air spaces between the BBs, but add a pint of sand and you will have filled all the large air space between the BBs, such that the net result is the same as though you were growing in sand only.

To SOME degree, the plant's rate of respiration and its mass has an impact on the rate at which water is drawn out of soils; but, air porosity has a very strong impact on how much water a plant can absorb and move from roots to shoots. Very large and mature plantings are not immune to the effects of hypoxic soil conditions. If soils lack air porosity, the plant can suffer a wide array of limitations. It can't be said categorically that the plant is autonomous when it comes to water uptake. For example, A plant watered in sips so it's not forced to deal with soil saturation might use a given amount of water in a week or month; but a plant that is given the same amount of water all at once, might only use a small fraction of the water a plant watered in sips might use. This is because of the limitations imposed upon how much water a plant can absorb when it's forced to suffer prolonged periods of soil saturation.

Al