In my book The Revised Savage Garden I discuss the feeding of one's carnivorous plants various insects, both living and dead, such as dried insects from pet shops. I also discuss the application of various plant fertilizers, usually applied in a very diluted form as a foliar spray to avoid enriching the soil with excess minerals, which can certainly harm carnivorous plants.
Charles Darwin was the first to do extensive experiments in the feeding of flesh or insect-eating plants, which he published in his 1875 book Insectivorous Plants. Nearly half of the book concerned his detailed experiments with the common round-leaved sundew, Drosera rotundifolia, but also with Venus flytraps and butterworts. He did not study any pitcher plants although he strongly suspected them of carnivory as well.
Darwin found that plants like sundews and butterworts reacted strongly to both nitrogen and protein. He found no reaction when he fed the plants sugar, olive oil, starch or tea. However the plants reacted strongly to milk, albumen (egg white), somewhat evaporated human saliva, as well as urine and bronchial mucus. Ugh! Darwin also found the plants were semi-vegetarian at times. They would eat some seed and pollen, and he also fed them infusions of protein rich cabbage and peas. I imagine if you wish to grow your sundews as vegetarians, some cooked Brussel sprouts (very high protein) would make a good start! Haha!
While other growers have done this in the past, at California Carnivores we have recently experimented with simple, easy non-insect food. I was amazed at the reaction of a cape sundew when I fed it a small piece of goldfish food. In just a few hours the leaf jelly-rolled around the flake ravenously. The flakes can also be pressed upon butterwort leaves.
On John Brittnachers recommendation, Axel has been feeding all of our Nepenthes with slow release Osmocote Flower and Vegetable pellets with fantastic results! Nepenthes that have limped along for years almost instantly started to grow faster! Pitchers developed much more quickly and they opened much, much bigger than the previous ones. We have also noticed a huge difference in peristomes. They are wider and more colorful when the plant is eating. (See photo below of pitcher before and after feeding)
Osmocote pellets are a plant fertilizer that is usually added to or laid atop house plant soil. With a permeable hard casing that slowly dissolves, the minerals contained within are slowly released when the soil is watered. This makes them an excellent, hassle free food for Nepenthes, Cephalotus and Sarracenia purpurea. For small to medium sized pitchers less than three or four inches tall, one pellet dropped into a newly opened pitcher works. Larger pitchers can be fed two or three pellets. Axel put as many as 10 pellets into a two inch N. x miranda pitcher. The top of the pitcher burned away in a couple of days, but the bottom remained alive. This "overfeeding" is rough on the individual pitcher but is still for the greater good of the plant. It is difficult to "overfeed" thick walled pitchers like N. lowii but thin pitchers like N. chaniana and N. glabrata uppers can burn easily, so tiny pellets are best.
Axel has also tried them on Heliamphora. It does seem to help them too, but it seems easy to overdue and make a brown patch at the base of the fed pitcher. Avoid using it on dry pitcher plants like the tall Sarracenia species and Darlingtonia.
I'd love to hear from growers who have tried unusual food on their plants. firstname.lastname@example.org!