I was given the details of a mix used for Oxalis in a conservation collection at a local botanical garden; it is a coarse mix designed to hold moisture but not stay waterlogged. I thought this may be useful for Drosera and other CP's that sometimes like to be moist but not permanently wet. Given my knowledge is mostly on South African dews in the wild, this may apply to the montane non-seep species (ramentacea, hilaris, cuneifolia, glabripes etc) that rely on frequent fogs or mist to keep the soil damp, or the winter growers (cistiflora, zeyheri, pauciflora etc) that grow when it rains frequently. This is similar to the many Oxalis that grow in winter here. They like moist but not waterlogged soil.
The soils are rarely peaty as bogs are, rather just nutrient poor. Therefore I thought this mix or something similar would be ideal for those dews. It consists of, with notes on its function from the designer:
2 parts silica sand - graded to avoid fine particles that could compact the mixture
1 part perlite - aeration and drainage
1 part milled bark - provides some nutrients and retains moisture
1/2 part compost - Less coarse component, more rot prone if used in high volume
1 part vermiculite - some water retention, does not rot
1/5 part biochar - Keeps some nutrients and slowly releases them
This mix is free draining and low in nutrients. I suspect for drosera it may be better to:
-Replace milled bark with peat or chopped sphagnum to reduce rot if used for more water loving species. I have heard that composted bark sometimes work but can rot
-Reducing compost due to high nutrient amounts
I intend on experimenting with this once I have sundews again. If the bark was replaced entirely with peat that would still only be 1/6 peat which is less than the 1/2-1/3 composition often used. If using large amounts of peat could be avoided that would also be useful.
What thoughts are had on this?
Carnivorous plant explorer from South Africa