I pulled one rosette out of the half-barrel water garden on my sunny patio. A thick curtain of dark feathery roots came up with it. They hung a full foot below the leaves, dripping and trailing like wet hair. I turned it over in my hands and found nothing else attached. No pot, no mud, no dirt at all. I planted nothing to get that plant going, and it had been thriving in there for weeks.
So can water hyacinth grow in water alone? Yes, it can. It is a free floating aquatic plant, so it never needs to sit in soil to live. The roots you saw hanging down do all the feeding for you. They pull everything the plant needs straight from the water around them, which is exactly why you can grow it in a plain bowl.
Here is how your plant pulls it off. Those dangling roots you saw draw nutrients right out of the water column below the surface. The swollen leaf stalks handle the other half of the job for you. Each stalk is packed with air, almost like a tiny built-in float. That trapped air keeps your rosette riding high on top of the water. So your plant feeds from below and floats from above, and it does both on its own with no help from you.
This is why it makes such an easy no soil pond plant. You set it on the surface and you walk away. It behaves the same in a wide pond, a stock tank, or a small fountain bowl on your deck. As long as the rosette can float free and reach the light, it will spread across the top and push out new offshoots. You never have to anchor it or bury anything. In my own barrel I just drop a few rosettes in and they take over the surface on their own within a few weeks.
Warmth and calm water are what your plant wants most. Water hyacinth thrives in still water around 77 to 86°F (25 to 30°C), the kind a sunny container holds through summer. Cold water and hard wind both slow it down. So give it a sheltered, warm, bright spot and you get the fastest, most lush growth from it. A shady corner will leave it pale and stalled.
Its hunger for nutrients is no small thing. Your plant pulls food in so fast that treatment systems use it to strip pollutants out of wastewater. Those same roots that scrub dirty water clean are the ones feeding the leaves in your barrel. The richer your water is, the faster your plant grows. A bowl with your fish waste or some runoff in it will turn into a green carpet in no time.
A small container or fountain bowl of plain water is all you need to start. Skip the soil and skip any pot. Float one healthy rosette on warm water in full sun and let the roots do the rest for you.
That fast growth has a flip side you have to stay on top of. Rich water fuels the plant so well that a few rosettes can double and cover your whole surface in a couple of weeks. Pull out a handful every week or two to keep it in check. This frequent thinning stops it from choking the open water and the fish swimming below. The plants you scoop out compost well too.
So you do not need a pot, gravel, or one scoop of dirt to keep it happy. Float a healthy rosette on warm, still water in full sun. Scoop out the extra now and then. Do that and your water hyacinth will run strong all summer on water alone.
Read the full article: Water Hyacinth: Menace and Resource
