Heather, I’m all over the place. I’ve been targeting more balanced fertilizers. I’ve found MSU for pure water to be very aggressive, even diluting it into a gallon sprayer, it carries more TDS than other ferts I have in rotation. But I still use it in the summer. Others on the list include Jacks classic all purpose 20-20-20, this is probably what I use the most year round.. I can really dial in the lower TDS (25-30 ppm) and it’s not nitrogen heavy (it won’t blast the buds). I’ve also started using miracle grow plant food for tomatoes 18-18-21, just this past year and have had good results with the summer and fall blooming cattleyas. My main workhorse for the past few summers has been Peters excel 15-5-15 cal/mag with black iron. It’s been recommended for vandas through mote’s. So I’ve incorporated it into the rotation. I also have K lite for the summers but honestly the numbers scare me (12-1-1) and I’ve previously felt I have not had the best results with this. I should give it another try now that I’ve learned to drive my grow room a bit better. I also have Maxsea 16-16-16, I this is a urea based fert (lots of back and forth on urea, so I cover the bases), and it’s been recommended for use with carnivorous plants in ‘The Savage Garden’ so again I use this mostly in the summers as it also has seaweed and from what I’ve read, fert with kelp can cause bud blast if provided at the wrong time. I also have kelp max as well which I use in the summer.. some other items include Great White Premium Mycorrhizae, also I use Recharge in the summer for Mycorrhizae and trichoderma fungi.. but it also has kelp and a bunch of other stimulants so I use it strictly in the growing months.
Ontop of all this, I also pepper some plants with slow release fert in the early spring, especially after repotting nutricote 13-11-11.
I have a few more ferts that I’ve tried to use on a schedule someone gave me from a vanda nursery, who swears by the table to get the vandas to bloom in a 12 week cycle.. which, I was skeptical of and still am.. I also don’t have their temps. It was handed to me by a senior member of my society years ago. it includes a 12-61-0, 18-16-39 and a 11-36-24 fert at different intervals. I’ve been somewhat successful with this but it’s so difficult to stay on schedule for a particular genus when everything else in the collection won’t benefit from this regiment. Only so much time I can spend tinkering with this.
Really it sounds like a lot and it is. But the application is minimal, we are talking 25-30ppm of balanced fert in the winter and nothing over 50-80ppm at each watering in the summer. I believe in a constant low feed. I need buffer in the water at every watering in order to keep the RO water from stripping the plants.
From what I’ve been presented, orchids are very efficient at taking up nutrients, I want to provide them with small amounts of what they need.. just make everything available so they can grab what they need when they need it.
My main rule is to lower the nitrogen in the periods of slower growth by switching to balanced fert at lower concentrations. And this varies by genus, vandas and phrags right now are getting larger concentrations of balanced fert compared to the rest of the collection because vandas never stop growing and phrags grow the most for me in the fall through spring when the temps are cooler.
Apologies for the long winded response.
You must be older than I am now.
