Q. Can you please tell me if it is possible or not to use volcanic rock dust on a Venus fly trap to promote its growth?
A. Rock dust is a marketing term which means a very finely ground powder from different sources that contains dozens of minerals in small quantities. It is thought that soils which are used for a very long time become depleted of some minerals that cannot be replaced with fertilizers. Recently, this term has become a hot topic among gardeners in the social media like YouTube and some gardening internet blogs.
I became interested in it because I was getting questions regarding its use. I experimented with three different kinds of rock dust and compared them for one growing season in some raised vegetable beds. All of the raised beds were composted, as they would be, normally, at the start of a growing season.
Perhaps it promotes growth in soils that do not have enough nutrients but I did not test that. I have not seen any advantages to vegetable growth when it is applied to raised beds and the soil has been composted and amended correctly.
It does not hurt anything to apply it in small quantities and it can be inexpensive insurance if you want to be sure. You don’t need much.
Venus flytrap in nature grows on very poor soils. It gets its nutrients primarily from the soil when it can get it. Alternatively, they also take nutrients from small insects that walk or fly into their trap. They evolved this way because of the poor soils. But catching insects and devouring them is an alternative to getting nutrients from the soil or leaves.
Regardless, the soil must drain well when growing these plants. Lava rock, perlite or pumice will help in that regard. They like high humidity so growing them in an enclosed terrarium will help. Adding rock dust to the soil will not hurt it. But help it? Perhaps if the soil is lacking in any of the plant nutrients found in the rock dust.
Personally, I would use liquid fertilizer sprayed on the foliage much like you would orchids. This plant would like very much compost tea applied this way. They do not like rich, wet soils.