Now nutrient poor doesn't mean nutrient devoid, so some brave people were spraying low doses of fertilizer onto the leaves or into the soil. It turned out well for those that found the right way to do it. Too much and the roots could burn and it could kill the plant or the plant would just stop pitchering and not do well. Too little and it was a waste of time. I passed on trying too find the right way to do it back then as the last thing I wanted to do was kill a healthy growing plant, just to try and make it grow better. However, within the last few years coffee has come up as another way to fertilize them.
Coffee works. I decided to try it after I let those brave, experimental people before me risk their plants first. I didn't have any to experiment on at the time, so waited to see how it worked for others for a while before making any decisions.
Coffee works for Nepenthes for a few reasons:
1. Coffee is acidic, most Nepenthes like their soil on the acidic side. If you use media that doesn't break down quickly, re-acidifying the soil at some point between re-pots isn't a bad idea.
2. There isn't a lot of minerals in coffee, but there is nitrogen and other trace nutrients which Nepenthes can use. Not so much that it can damage the roots, as long as you don't brew the coffee with mineral laden water, that is.
So I've been brewing a pot of coffee at regular strength with distilled water, letting it cool down and then watering some of my Nepenthes with it about once every six months or longer. This isn't exactly the most scientific experiment, as they are different species and my only control are ones I haven't tried fertilizing yet for one reason or another.
Below is newest leaf produced after a coffee treatment on my N. robcantleyi. All the old pitchers had dried up when I moved it to a lower humidity environment indoors for the winter. Now maybe this burst in growth is a coincidence, but the humidity levels in my apartment had gotten worse, not better. This looks like more than it's adjusting to new conditions to me. I've never seen a Nepenthes put out a bigger leaf right away, usually it throws out a smaller one or one that's slightly deformed before going back to growing normally when it has to adjust to a new environment.
|Newest leaf after coffee treatment growing towards the bottom of the picture|
Below are the newest leaves on N. ventricosa. I gave this one a coffee treatment back on the same day as the robcantleyi. The leaf growing straight to the bottom of the picture and the new one that hasn't unfurled yet are post-coffee leaves. N. ventricosa is a faster grower here than robcantleyi anyway, but this one had to endure a move to lower humidity than it likes too. Not quite as big a jump up in leaf size as robcantleyi, but still significant.
|Post coffee leaf #1 growing straight down the picture, #2 not unfurled yet top right|
I'll wait a few months before feeding them or fertilizing again, because too much could still cause the plant to stop making pitchers. A Nepenthes that wants to catch insects makes pitchers, an over-fertilized one won't. Same thing applies if you stuff the pitchers full of insects, it''ll temporarily stop making more. It seems pretty simple a concept when you think about why a plant would grow the way it does. Everything in nature happens for a reason.
Small Disclaimer: Coffee isn't a substitute for normal fertilization. I wouldn't recommend it for any other plants as it does not have all the nutrients the vast majority of other plants need.