LA
Onion plants (Crinums). Not impressive when starting out.
Origin.
With a name like Crinum thaianum, you might suspect (correctly)
that these guys originally came from Thailand (Siam to you folks that didn’t
get Anna’s memo).
Incredibly Tough.
You usually find crinums bobbing on the surface like corks. We’ve
seen them bob about for six weeks or so before seeing them
deteriorate. In fact, they deteriorate much less floating than when
planted incorrectly. We have the most problems with onion plants
when we get a 100-pack and get sloppy in planting them.
Start
out Like Onions. Just like an onion, shuck off that brownish
“skin.” Get out your
underwater garden shears. Trim off all those short, misshapen, or
ratty looking leaves. Snip off all those long roots. If you
leave them, you encourage them (and the bulb) to rot.
LA
Here's the onion (Crinum) bulb and extensive root system.
Root
Comments. It’s
really tempting to leave those long (eight-inch) roots -- especially if
they’re a nice healthy
white color. If you can spread them out in a nice
“fluffy” substrate (see below),
keep them. Otherwise, snip them off. They grow back fast.
LA
Use a small gravel for best results.
Excellent
Substrate. Smaller gravel mixed with lots and lots of
vermiculite makes a perfect substrate. Soak the vermiculite about a
week or it floats like a cork. Onion plants really root into this
mixture. They do fine in this substrate without fertilizer.
LA
Onion plants grow from a bulb. They will reach six feet in length.
Planting Depth.
Plant your bulbs shallow. You want to be able to tell they’re
onion bulbs by looking at them. But the main reason is to discourage
bulb rot. Rotting bulbs are nasty and smell nastier.
LA
And here's the onion plant's six foot-long leaves. They grow longer.
Long Leaves.
If you have a 10-gallon tank, step away from the onion plants. They
grow to the top of a 55 fairly fast. Then they arch across the top
and make an attractive frame that shows off your fish.
LA
Great root growth but plecos mowed down these leaves.
Strong Threat.
We made the mistake of tossing a half-dozen rhino plecos in a tank of 20
or so onion plants. We couldn’t figure out why these guys never
seemed to grow. Then we pulled one out and saw very good root growth
with curled over leaves. By then it dawned on us about the plecos --
the rhinos plus an atabapo pleco, plus a red cactus pleco.
Duh. We scissored off all the curly leaves, cut their roots in half,
and re-planted them in a shallow tank.
Fertilizer?
When you mix in vermiculite, you’ll find onion plants grow like a
weed. Otherwise, you probably want to add a good leaf
fertilizer. Any leaf that grows two yards long needs extra
nourishment.
Lighting?
Standard aquarium bulbs grow your onion plants like a weed -- up to the
top and across. Unfortunately, when they grow across the top, their
long leaves get very close to your lights. You guessed it. As
the bumper stickers say: Algae Happens. Add otocinclus and
algae-eating shrimps to control it. Severe algae? Get out
those underwater shears again. Cut off the algae covered leaves.
New leaves will grow to replace them.
LA
Good start. They grow quite long.
LA
Two onion plants on the left. Jungle val to the right.
Background Plant.
You know you cannot put your onion plants out front unless you’re
striving for an impenetrable jungle. Some of us love jungles.
But on
the whole, onions look best in back. They grow thick enough to hide
filter stems and heaters. And they grow taller than any other plant
-- unless you include anacharis, hornwort, and vallisneria and bog plants
and ... well, let’s say longer than most aquarium plants.
LA
Dwarf onion plants floating on top of a 10-gallon tank.
Not so Close Relative. Dwarf onion plants, Zephyranthes
candida, look like green onions (or scallions) and reproduce like
shallots -- lots of small bulbs in a cluster. You plant the
“momma” bulb and she grows daughter bulbs right next to her.
Dwarf onion leaves and bulbs never grow as large as Crinum thaianum.
LA
Momma dwarf onion bulb with one daughter bulb.
LA
Twins?
LA
If not planted, chlorophyll eventually covers the bulbs also.
LA
Crinum calamistratum -- fairly rare,
Unusual Crinum.
Same bulb style, totally different leaves. Everyone who sees Crinum
calamistratum remarks on their appearance. They are expensive,
hard to find, tough as nails, and take up a lot of room for such a small
plant. See below.
LA
Crinum calamistratum grows horizontally as well as vertically.
Propagation.
John Deere has yet to build a commercial planter, cultivator, or harvester
for any of these onion plant species (yet). It’s pretty much still a
hand process. By the way, you may find a Crinum natans out
there. Treat them like the Thai guys. Their leaves are
wrinkled looking, like they’re made out of green seersucker. LA.
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