FlytrapCare Carnivorous Plant Forums

Hi everyone.

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?

I think the problem you would run into is the milled bark, compost, and biochar. Any nutrients that are released that the roots may take up could prove detrimental to a plant evolved to live in nutrient poor/nutrient zero media.
It might work on some of the SA dews you've described, but those plants aren't very common. You'll have to let us know your results if you're able to experiment with it.

Thanks for your insights! I think any proportion of those could definitely be reduced. I think composted bark is more acidic and peat-like than regular milled bark and compost. Replacing it with chopped sphagnum may work but it's quite expensive here. The issue is finding low nutrient components that don't rot which is possibly why peat is so heavily relied on.

Given that these species do not live in bogs, they may be more tolerant of nutrients. Will have to experiment!

Hi,
I have never used such mix or anything similar, however I think it may have potential to work for non bog sundews.

Sand - ok, but use clean one, I use washed sand dedicated to aquariums. Sand taken from a forest was a disaster, probably because it contained to much iron.
Perlite - I made some tests with it, for some time few of my plants grew in pure perlite. Perlite did not affect pH or water EC. Perlite is much lighter than water so it has a tendency to travel upwards in the pot.

Milled bark - what bark would you like to use? Pine bark or something similar potentially may be fine, but I have no idea how fast it will decompose and release nutrients. Somewhere in the internet a saw that somebody tried to grow CP in sawdust and it seemed to work, at least in short term.

Compost - I would definitely avoid it

vermiculite - I have never used it

biochar - also never used it.

I think that nobody used such mix for sundews so you have to test it yourself. Maybe prepare a small amount of such mix, plant strong sundew like D. capensis in it and see what happens. If it dies or grows poorly then the mix is inappropriate. Also test if the mix does not desiccate to quickly.

MarcinS wrote: ↑Wed Jul 07, 2021 6:13 pm Hi,
I have never used such mix or anything similar, however I think it may have potential to work for non bog sundews.

Sand - ok, but use clean one, I use washed sand dedicated to aquariums. Sand taken from a forest was a disaster, probably because it contained to much iron.
Perlite - I made some tests with it, for some time few of my plants grew in pure perlite. Perlite did not affect pH or water EC. Perlite is much lighter than water so it has a tendency to travel upwards in the pot.

Milled bark - what bark would you like to use? Pine bark or something similar potentially may be fine, but I have no idea how fast it will decompose and release nutrients. Somewhere in the internet a saw that somebody tried to grow CP in sawdust and it seemed to work, at least in short term.

Compost - I would definitely avoid it

vermiculite - I have never used it

biochar - also never used it.

I think that nobody used such mix for sundews so you have to test it yourself. Maybe prepare a small amount of such mix, plant strong sundew like D. capensis in it and see what happens. If it dies or grows poorly then the mix is inappropriate. Also test if the mix does not desiccate to quickly.

Thanks for lending your thoughts!

-I use silica sand, same as for aquariums, as well. Great substrate
-I think pine bark is the standard based on availability, I must look at the composted variety as well which may do better with water. The bark may last well if not constantly waterlogged with non-bog species
-Compost, in full agreement. Perhaps peat can be used

I am getting some capensis cuttings next week, once established I will try some medium and report back. It is not the best test species for a non-bog mix so hopefully I will be able to get more in-depth results with winter growing plants.