Water Hyacinth

Water hyacinth

Water hyacinths, Eichhornia crassipes, are common ornamental pond plants that are relatively safe to grow in the north, but that can spread to natural ponds and waterways in the south and become invasive. They don’t survive cold winters in the north.  For northern gardeners who want plants in a small water feature water hyacinths may be ideal.  The water hyacinth produces showy flowers that are lightly fragrant; its roots filter water and provide hiding spots for tiny fish after hatching. Having water hyacinth in a water feature also helps control algae growth.  In northern water features water hyacinth is an excellent, easy to grow addition.

Water hyacinths are native to South American, from the Amazon basin. They grow only in fresh water.  Most sources say they cannot grow at temperatures below 50 degrees and are killed by frost or freezing. There are some reports that the plant can survive short freezes and some people believe that seeds of the plant might survive the cold in the right conditions.  No known cases of it over wintering in native waters that freeze have occurred.  However the water hyacinth has spread around the world where the water stays warm year round and has caused considerable trouble.  It chokes and shades out native plants, impedes boating and fishing and can become a major problem in warm areas with its aggressive growth.

Food for hippos and manatees?

After water hyacinths were introduced to the US in the late 1800’s they quickly became horrendous invaders of natural waters in Florida and other warm places.  A bill was even introduced into Congress to import hippos to eat them.  That bill didn’t pass. However, just this spring researchers in the Sacramento, California delta area released a herd of hippos in an isolated area to munch on the plants.  Hippos can be very dangerous to humans so that solution won’t work everywhere. 

One of the favorite foods of the endangered manatee is the water hyacinth.  It may be keeping some of the manatees from disappearing in the south.  Manatees have also been imported to California and other places to deal with the plants.  The water hyacinth can also be eaten by humans and is sometimes used in place of other salad greens.

And just as we have discovered that many invasive plants can have valuable traits, it was recently discovered that water hyacinths can filter heavy metals and other pollutants out of water.  China is using them for this purpose.  They can also discourage algae by absorbing nutrients and preventing algae blooms.  Ironically some areas of Florida that had nearly eliminated water hyacinths are re-introducing them under controlled conditions to clean water and remove algae overgrowth.

What water hyacinths look like

Water hyacinths are floating plants; their roots do not need soil.  They have thick, glossy green rounded leaves with a bulb like base.   The bulbs act like a balloon or life preserver and keep the plants floating.  Leaf stems may be reddish.  The roots are long and feathery and a deep reddish or purple color, sometimes black looking, that dangle in the water.   Roots will grow into natural muddy bottoms if they reach them but they don’t need soil.  The plants can grow up to 3 feet tall above the water in ideal conditions but in most ornamental situations they remain much shorter than that, generally 12 inches or less.

It’s amazing how quickly the water hyacinth grows.  One plant can easily become 600 plants in four months if conditions are right.  It reproduces by seed, but most of the quick multiplying of the plant is done by daughter plants being developed along the root system.  Pond owners may need to periodically thin out water hyacinths to keep some open water surface in their ponds.

The plant is equally quick in how fast it blooms, one day it suddenly develops a bud stalk and the next it blooms, and the flower dies in a day or so.  The flowers are produced in a cluster on a stalk held above the water and are pale blue or lavender.  One petal of each flower has a small yellow spot on it.  They are lightly fragrant with a pleasant smell not unlike their namesake.  The flowers attract water insects and bees and may produce seed pods.  Flowering occurs on and off throughout the warm months. 

Growing water hyacinths

Many northern garden stores sell water hyacinth plants.  You’ll only need one or two plants even for fairly large ponds as they spread so quickly.  Simply throw the plants in the pond.  Water hyacinths will grow in any fresh water a foot or more deep.  They prefer calm water but adapt to fountains and pool filters.  If you want them to bloom the pond must get 6 or more hours of sunlight a day.

If the leaves of water hyacinths turn yellow while it’s warm they probably have exhausted the nutrients of your pond.  If you don’t have fish in the pond you can add a water soluble fertilizer occasionally.  If you have fish you can remove some of the plants to a large bucket with some liquid fertilizer for several days, and then rinse the roots and return them to your pond, removing some other plants for their fertilizer treatment.  There are also some pond plant fertilizers that are said to not harm fish.

While water hyacinths provide some food for goldfish and koi and give them some shade and hiding spots they may also hide mosquito larvae.  Periodically moving the plants around helps dislodge hiding mosquito larva for the fish to eat.  You can also use a floating mosquito briquette with BT mosquito control in your water feature.

If you want to share your water hyacinths, simply cut or break off daughter plants.  Transport the plants in water.    

Saving water hyacinths through winter

You can over winter water hyacinths if you have the space and dedication.  You’ll need a warm room (70-90 degrees) with bright light, or a warm space where you can suspend grow lights over your water container.  Choose just a few small, very healthy plants to bring inside.  It’s probably best to keep them separate from fish inside, since they will need frequent fertilizing.  A room where dumping water, water spills and high humidity isn’t a problem is best.

Water hyacinths need very bright light to thrive inside; you may need to suspend grow lights, full spectrum lights, only a few inches above the water.  Buy an aquatic plant fertilizer if you can and use it according to the label directions.  You could use a water soluble fertilizer for other plants but you may have to experiment a bit.  You will need to change the whole water container about every other week using water that is not chlorinated or softened and that has been brought to room temperature.  This is to avoid a buildup of waste products and salts.

Water hyacinths are interesting and helpful plants in the right situations.  Please don’t dump your unwanted plants in natural water ways.  Compost them on dry ground.  That way we avoid any unwanted invasive behavior and keep the plants available for ornamental gardeners.