Here is what I have found available at the local Hong Kong Market and a few others:
Chinese Water Chestnuts - These are smallish bulbs that look to me a lot like gladiola corms - 'bout the same size too. They are very dark, almost black and always look muddy - even after you wash them ten times, they look muddy. They grow a grass like plant - actually more like a really thick chive plant with hollow leaves. These are sometimes available in the grocery as well, but the best ones are the really fresh ones in the market. Sometimes they even have little green tips on them.
Taro - I've seen taro bulbs in all sizes from about 1" in diameter to over 6" in diameter. The bigger bulbs grow really huge plants. They are sold like potatoes, and they don’t cost much – about 90 cents for a 6” bulb. They are rounder and rougher than potatoes and not as uniform brown. They are almost always labeled as taro.
Planting taro from the market: First, do not submerge them until they have sprouted. Since this process can take a few weeks, they will rot if they are in water. I plant them in the pot they are going to be in when put in the pond in pond type dirt and then set the pot by the pond and water it. I do not use the pond pots without holes because the dirt will get too wet and they will rot, I use regular nursery pots with something lining the holes (found that paper towels work better than newspaper and cloth works best). If you can figure out which end is up, put it up, but don't worry about it too much as they will sprout either way. It will take a lot longer to see the sprout if the bulb is upside down, but you'll get about ten plants that way, don't ask me why. Be patient as they take a while to get started - but once they sprout, they grow like gangbusters and get very huge very fast.
Arrowhead - These seem to be available only in the very early spring. They look a bit like onions - round and white - and almost always have a green growing tip on them. I've never seen them marked as anything other than arrowhead. Be careful - the markets also sell arrowroot which is not the same thing.
Watercress - This is sold in bunches like spinach or other herbs. It is usually clearly marked. I've also seen it in the produce section of the grocery store. Just trim the stems to give them a fresh cut and put them in a glass of water and they’ll root. I have even rooted them in the pond itself. It’s a nice plant for a waterfall or the rockery around the pond. Be careful with it in the falls though because it can be invasive and I’ve heard people say it caused their waterfall to flow over the sides and drain their pond.
Water Spinach - this is a member of the morning glory family. It is sold in bunches like spinach or watercress. They only sell the new shoots, and they root easily. Usually the shoots are between 6" and 12" long, and have narrow pointy shaped leaves that are about 3" long - pretty dark green. You can grow a nice vine from these, but they like to climb on all your other water plants and can escape the pond. I found that these root best if you give the stem a new cut and then put each stem in damp sand or dirt – they don’t do as well in water as watercress does. I liked the way the vines traveled all over around the ponds and covered the rock wall I have around my pond.
Lotus - I have seen cleaned and uncleaned lotus tubers at the market. The smallest ones were about 4" long and the longest were about 12" long per tuber with two sections attached making each almost 2' long. I have never ever seen any with any viable growing tips.
Malanga - This is a food crop from cuba and South America. These tubers come in varying sizes, with the smaller ones shaped more like a sweet potato and the larger ones becoming more round. The plant looks like a taro, but the leaves are a little thicker and less pointy at the tip and the heart is sometimes right side up and sometimes upside down. Malanga leaves are held more horizontal than vertical and they are shaped slightly different from taro. It also seems to be shorter - much shorter and fatter than taro - and a bit lighter green. I found one last year with red stems. They would be grown the same way that taro would be - start in dirt and sink in the pond when they have their first leaf. Here is a pic of one growing.
Sensitive plant - This seems to be available only fairly late in the season. It is sold in bunches of tips that are about 12" long each. They usually have no roots and none of the white styrofoam looking stuff that makes them float. But if you put the end in dirt and float the stem in the water, most of them grow. I have seen this plant sold in water gardening stores in exactly the same condition as it is in the market - only for a lot more $.
Lemon grass – This plant grows near water, but doesn’t like to be too deep in water. It’s usually sold without roots and with all stems trimmed. It doesn’t look like it will grow, but it will. A bunch of 5 stems usually costs 99 cents. I peel the outside leaves off and put the stem in a glass with about an inch of water in the bottom. I change the water every few days. It takes a week to ten days before you’ll see roots starting to appear and if you leave the stem in the water, it will start to put out side shoots shortly after you see the roots.
Water Chestnuts, Trapas - These are very strange looking things and are most widely available in the fall but can easily be stored till spring. They do need to be kept damp throughout the time they are stored or they will not grow. They grow into a floating plant that has a rosette of leaves and a long dangling stem. They can be attached to roots in the dirt but will often break off and float free. I take one of the 6" pots and put in a little dirt then stuff in absolutely as many of those bats as I can. Then I put more dirt in the pot (to cover the bats) and sometimes a second or third layer of seeds and more dirt, then some sand to keep the dirt from floating. After I've done that I sink the pot at least 18” deep because the shoots grow straight up and will come out of the water, dry up and die if they are in shallow water. Be aware that koi and turtles love to eat the tender new growth when the seeds first sprout, so protect the plants till they get started.
