Today is a gloriously sunny winter day, and while I know spring isn’t that far away, there is still a meter of snow on the ground, and I am missing the green. So much so that I have spent yesterday sowing seeds for the coming spring, and repotting a number of plants which have started to wake up from their winter sulk. I’ll post some about that once the seeds sprout, but for now it’s a pretty boring sight with a bunch of pots in a plastic greenhouse, and also some covered with soda cut-off soda bottle tops (best makeshift pot greenhouse ever, even comes with a nice vent you can close!). So, to beat the I’ve-had-enough-winter-now-thanks mood, I would like to talk about a plant I have, that you may not have yet, but that – if you like coriander (the greens, not the seeds) – you probably also will want to get and keep. Why? Because as anyone who has ever tried to grow true coriander (cilantro) knows, it’s a pain in the head, and you have to do successive sowings to keep the supply of greens going, and it’s prone to bolting when weather is sunny, or sulking when it is not. In short, outside of its native range, coriander is a fickle primadonna.
So, here’s the awesome news – Persicaria odorata, also known as Vietnamese coriander, laksa leaf, and Rau Ram (and a lot of other names in SE Asian languages) – is not. In fact, it’s about as easygoing as a houseplant can get – on the same order of ease as a Wandering Jew (Tradescantia zebrina) plant, and perhaps more so. And it tastes a lot like coriander, maybe with a bit of arugula-like pepperiness thrown in (it’s related to Japanese water pepper, they are both in the knotweed, aka buckwheat, family).
How easy it is to grow? Easy enough that it’s an unproblematic plant to keep going and multiply under central heating conditions through a dark Nordic winter, and still nibble some leaves now and then even during said winter. Why is it easy to grow? Well, being a knotweed, it propagates like nobody’s business, which is why some of the knotweeds are invasive in some parts of the world, but provided you have winters with below-zero temperatures, or keep the pot indoors, you are not risking anything with P. odorata (it doesn’t tend to bloom outside the tropics and is frost-tender).
So, to propagate it, all it takes is cutting a few pieces long enough for some nodes to be under water and some out of water, cutting the leaves off the bottom half (carefully so not to injure the stem), and sticking the cuttings in a glass of water. Roots will appear in less than a week, at which point you can either continue to grow them in water (they seem happy to grow in water culture with or without any fertilizer), or you can plant them into some nice potting soil in a plastic pot, and put that pot into an outer pot (cachepot) which is waterproof, and fill the outer pot with water nearly to the brim of the plastic pot. And … leave it. Persicaria is a water plant, and it cannot be overwatered (it will get sad and wilt if you let it get too dry, but mine recovered pretty well after that happened and I watered it – but not being a cactus, it will die if you let it dry out entirely). All you have to do is keep the water topped up, fertilize lightly and occasionally, and it will sit there and grow shoots you can clip and use. The growth will slow down if your winter is really dark and you don’t have grow lights, but a fairly well-lit window should be enough to get it through the darkest part of the year.
It’s February, which here in Norway means not a whole lot of sunlight per day yet, and spring isn’t quite around the corner as you can see from all the snow (the window is triple-glazed, though it may be hard to see in the photo, and I have the window vents shut in the kitchen). I have a thermometer sitting on the corner of that windowsill, and it reads about +17C indoors on a cloudy day, and warmer on a sunny day like today. My Persicaria has already broken the winter-sulk and is growing vigorously and crawling up the window glass. I have even started harvesting and using some of it. I currently have three pots (after one survived the December move in subzero temperatures, and two propagated from it) – one in pure water culture, and two, including the survivor, in soil-in-plastic-pot-in-water, and they are all happy.
Using it is also rather easy – I just grab a pair of shears, snip off a twig, rip off the leaves and chop them up if needed, then use as I’d use regular coriander (or as you’d use laksa leaf in SE Asian cooking). You can even clip the leaves off the bottom of the twig you cut, use those, and put the twig with a few leaves left on top in water to propagate. In fact, the only thing that you may find even moderately difficult about this plant is getting your hands on it to begin with (though you really only need 1 twig). I got rather lucky (and was rather surprised!) when I found a pot in a local nursery last summer, mixed in with other Asian herbs (lemongrass, etc.), but if you can’t find it at your local garden centre, and no locally-shipping suppliers have it, you have another recourse – you can go to an Asian store which has refrigerated vegetable cabinets, and check in there, or ask your local Vietnamese restaurant – if you can find a packet of twigs, you are all set – just take it home, and put them into a glass of water, and … we’ve been over this. You will have roots, and you will have young plants. In fact, remember those cuttings in a glass of water from one of the photos above?
They’re planted in soil-in-water setup now, and once I see new growth (they look like they are already growing but I have only planted them yesterday and that growth was from being in a glass of water), I will cut them short to encourage them to bush out as I’ve done with the water-and-leca culture pot.
I have heard that excessive sunlight may cause the leaves to go bitter. It hasn’t happened to me yet, since last summer the plant sat under shade of a North-facing porch, and it’s pretty unlikely to occur indoors during the Nordic winter, but I suppose you (or I) shouldn’t stick them outside in full sun come summer. I will probably put at least one pot out on the SE-facing balcony by the side pillar where they will be shaded after the (rather long) morning hours of sunlight, and see how that goes, but as easygoing as Persicaria is, I really don’t foresee any problems. Note – some of the varieties appear to have an attractive dark purplish-green heart-shaped spot on the middles of their leaves. Mine doesn’t seem to have it, but perhaps once it gets more sunlight come summer, that may appear. I do not know whether this is a cultivar or a sun exposure difference, but don’t worry if the plant you get has those.
So, this is it, in short. Plant is awesome and easy to grow, tastes great (unless you are genetically predisposed to taste coriander as soap and then I am sorry for you), and is actually not bad looking as houseplants go. Get one, keep one, rejoyce in the easy availability of coriander-flavored leaves. And to those who area already experiencing spring, I’m envious of you. But only a little, and only till the snow melts off.