I mix it a gallon at a time and go through it pretty fast, especially during the winter because my air is dry and I'm paranoid about spider mites. Been awhile (more than a year) since I've seen any but I spray down each and every orchid plant surface every third watering, or so. Mites are just insidious for me. I stupidly spent too much money at Hausermann's yesterday and today I'm repotting everything after a soak in Physan and then a spray-down with the soap mixture.
I do not use Neem oil; the smell makes me blortch. So, the recipe I use is as follows:
1 gallon RO or distilled water
3 tablespoons Dr. Bronner's liquid soap (currently using the citrus scent but you can use whatever you want, or the unscented
2 tablespoons vegetable oil (I use olive oil but have used corn oil and grapeseed oil in the past; it doesn't matter)
That's it. Sure, you can put Neem oil in if you want, some put in cinnamon, some add chili powder. If I didn't have Dr. Bronner's on hand, I'd use classic Palmolive ("look Madge! I soaked in it!). Dawn is nontoxic but I don't like how it seems to separate in the mixture. Of course, ALL these mixtures separate and you have to shake them up to mix them, then shake very well in the spray bottle and spray several times into the sink before you start spraying the plants, and then shake often during the spraying session.
If you don't have a lot of plants, just proportionally mix the soap and oil with the amount of water. I'm terrible at math but it's pretty simple to break it down by hallf-gallons or quarts or ounces.
Recipes online recommend only making what you will use that day; I think this is silly. It's just water, soap and oil. It doesn't go bad.
Good luck!
