June - from the 'Year at Robie Creek' series

Originally published in the:

Well, there’s been a little change of plans with the pond. We’ve decided to follow the wisdom of the fishes and just build it around the spot they like best already, which is much more conveniently located for humans than the other spot as well, but also much more prone to filling in with sand and silt. That can be dealt with without disrupting the workings of the creek, and the work we already did at the first location leaves us with a nice little shady sit-n-chat spot so no great loss.

But speakin’ of ponds, let’s talk about duckweed. We can’t grow this little miracle plant on the natural waterway here, in part because it’s too fast-moving, in part because it wouldn’t be able to withstand the winter temps even via turions, and in part because there just aren’t enough nutrients in the water for it. What plants call nutrients, aquatic creatures and humans call pollution. Robie Creek has two water-quality issues: High oxygen levels and suspended particulate sediment. The former makes it excellent for fish and people but not great for plants, and the latter is a natural side effect of its turbulent journey to the lake six miles down from us. The sediment isn’t visible, doesn’t impact the water’s clarity, but if you fill a container and let it settle there will be a small amount of particulate matter at the bottom in a few minutes. Nothing that makes it non-potable (in fact it’s excellent drinking water with the high oxygen and mineral levels), but also not much for plants to grow on, even in the quiet spots where the sediment settles out naturally.

So since we can’t grow it the natural way, we have duckweed tubs in our side yard that we move into the utility room in winter and allow it to mostly go dormant, and we keep some stocked in each of our mulm/snail/worm nursery buckets, the fish tanks, and the paludarium. Over the summer I skim some off every few days for drying so we’ll have lots to use over the winter, as it won’t actually reproduce in any of our indoor receptacles and if it does it’s a sign I need to do some husbandry or we’ll lose the critters that live in ‘em. This is a rare occurrence even in our heavily-overstocked (with high-waste fish) twenty-gallon tank, thanks to a low-tech setup, heavy planting, and a deep sand bed – it’s actually more often an issue in the ‘appropriately’-stocked ten-gallon, but that’s not surprising as it’s always more challenging to maintain an ecosystem in a smaller volume – but the duckweed is a good indicator should things go out of whack, and when our power goes out and the filters stop running it’s part of what prevents a tank crash even if they have to go days without that extra aeration. In any case, if you’re not familiar with the wonder-weed, I hear you asking, “Why? Why would you want that? I only hear terrible, horrible things about it!”

We keep it for many reasons, beyond just its use as a water cleaner and quality indicator.

• Duckweed is excellent food for fish: Some can be raised on it almost exclusively although we prefer to provide a varied diet from the natural source just outside our door. (This does at times result in parasites, but of those that survive in our tanks’ tannin-rich water – the Creek runs very clear so parasites carried in it are not adapted to resisting the effects of tannins – and manage to attach to our robustly healthy fish most can be dealt with with a few salt dips.)
• It’s a protein- and nutrient-rich feedstock for grazing animals and composting worms as well as for live foods (both insects and rodents) one might feed to various herps who then in turn benefit from the higher nutrient content in their food than what they’d get if it was fed usual recommended diets.
• It’s a great supplement for domestic pets – even obligate carnivores with its high protein content – and it’s also edible by humans; some varieties are said to be quite tasty although frankly we haven’t chosen to test that for ourselves. Most varieties, people who eat it say, taste of nothing.
• It’s easy to grow, and once a system is established it replenishes itself endlessly.
• There’s strong indication that it not only prevents mosquitoes from laying eggs in still water, but may produce toxins that actually kill those they do lay in any open patches, although this is still being studied.

The best way to dry duckweed, either for storage (which can also be done by freezing it in a tray of water, then cutting the ice sheet into cubes for later use; this method preserves the highest nutrient levels but requires more freezer capacity than we currently have) or for use in applications where a dry feed is more desirable than a wet one, is through sun-baking out of direct sunlight. A solar oven works for this, or as we prefer to do (since the higher the heat the greater the destruction of the good parts) so does spreading them in a thin layer – about a quarter-inch thick works well – on a screen under an opaque covering with good airflow below and full sunlight all day from above. By the end of summer, along with the other greens we gather and dry along the way, we have enough to get everyone through the winter quite nicely. In spring we’ll take our tubs outside again – most of the duckweed will have gone dormant – and in a matter of hours they’ll have a nice new green carpet on top and we’ll start all over.

As always, it’s fantastic to be here with you at the OCG. Thanks for havin’ us, we’ll see ya next month, and from Robie Creek to Owl Creek, take care, be safe, have fun!

With much love,

Peace & the Dudes Jaway

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