How much fertilizer?

[Ray]

Originally Posted by mascia

Thanks for all the replies!

I think Ray's approach is really interesting, but I do believe it's hard to compare orchids growing for someone at 40°N with my orchids growing at 24°S or for someone even closer to the equator.

A lot depends upon your selection of plants, and how you're growing them.

For example, I'd bet that in my greenhouse, the conditions are quite similar to those at the equator, except for natural daylength variations....

[terryros]

The fertilizer concentration also depends on how frequently you water/feed. Ray waters/feeds frequently with the 25 ppm N concentration. If you are watering/feeding only every 7-10 days, then you need a higher concentration of N for your feed. I don't think everyone commenting has been specific about their feeding frequency.

[bil]

Originally Posted by terryros

The fertilizer concentration also depends on how frequently you water/feed. Ray waters/feeds frequently with the 25 ppm N concentration. If you are watering/feeding only every 7-10 days, then you need a higher concentration of N for your feed. I don't think everyone commenting has been specific about their feeding frequency.

Good point. However, I have to admit, last winter I was lazy and never got round to upping the fertiliser for the phals when they went from sumer 3x a week to winter 1x a week.
They didn't seem to notice, and are flowering well this summer.

[Ray]

Originally Posted by bil

Good point. However, I have to admit, last winter I was lazy and never got round to upping the fertiliser for the phals when they went from sumer 3x a week to winter 1x a week.
They didn't seem to notice, and are flowering well this summer.

I have routinely considered that by reducing the feeding and watering frequency in winter, I was mimicking the conditions that many of my plants see in nature. However, Bil's comment makes me think that even at the very low concentrations, I was routinely giving the plants a lot more fertilizer than they needed.

Since moving, I have been a poor "orchid dad," and I'll bet my plants haven't been fed more than once a month, yet all are growing and many blooming quite nicely.

[bil]

Originally Posted by Ray

I have routinely considered that by reducing the feeding and watering frequency in winter, I was mimicking the conditions that many of my plants see in nature. However, Bil's comment makes me think that even at the very low concentrations, I was routinely giving the plants a lot more fertilizer than they needed.

Since moving, I have been a poor "orchid dad," and I'll bet my plants haven't been fed more than once a month, yet all are growing and many blooming quite nicely.

Dammit Ray, have you been getting us to use high levels of fertiliser?

All kidding aside, does that mean you will be recommending lower levels?

[terryros]

Ray, what is that saying about your use of Inocucor and KelpMax!! Are you bundling them all up in one monthly blast and only using water the other times? This doesn't sound like you.

[Ray]

When I grew in a greenhouse, fertilizer was metered into the water supply whenever it was used. I added KelpMax once a month via a hose-end sprayer, alternating with Inocucor Garden Solution at two-week intervals.

Now - after 40+ years - I am back to windowsill growing, and my regimen is more hit-or-miss than that. I'm good for a couple of weeks, get onto their stuff for a while, come back to it, etc. I hope I'll get better discipline as I settle into my new life.

[estación seca]

Originally Posted by mascia

Thanks for all the replies!

I think Ray's approach is really interesting, but I do believe it's hard to compare orchids growing for someone at 40°N with my orchids growing at 24°S or for someone even closer to the equator.

I've only been growing them for a year or so, but between last october and march some my cattleyas literally doubled in size. Plants that only had 7 or 8 bulbs would create 5 new bulbs at the same time. During summer I was feeding with ~150 ppm weekly and was thinking this was too low due to how much energy they were spending on growth. I've never had any issues with root burn or anything of the sorts.

Considering I only watered them 2x a week, 25ppm seems awfully low while they are actively growing.

I think I'll make an experiment and get two nearly identical orchids that will be grown side by side, and try feeding one on every watering and the other weekly or every two weeks, and see the results after a few months.

Has anyone ever done something similar?

I agree your vigorous plants, pushing large numbers of new growths, in a wonderful climate, need a lot more fertilizer than a plant struggling to survive on a cold windowsill far from the Equator.