>> Also see the main feature, “Waterlily Pests and Diseases: A Ten-Year Update.”
Waterlilies are fairly low maintenance, especially compared to equally gorgeous terrestrial flowers. However, they do require some regular care to stay healthy and bloom well. Here are the basics.
Rinse & Observe
Whenever you add water to your pond or display tanks, thoroughly spray all the plants. This keeps the foliage clean and looking good. It also washes off any pests before they become a problem. If you have an automatic top-off system, use the hose to manually spray everything at least once a week.
While you spray, methodically check the lilies and other pond plants for any signs of damage — pests, holes, discolorations, etc. If you see anything suspicious, cut it off and discard it. (Old-time water gardeners burned all pest-infected or diseased foliage to eliminate chances of contagion.) Pests and diseases are infinitely easier to control before they start to reproduce and spread. Make “rinse and observe” a weekly routine. It is also the perfect time to check your fish and take a relaxing break from screen time.
Trim
Pads on water lilies live four to nine days (depending on the variety) before they turn yellow and decompose. But the good news is that each lily only needs four to nine pads to grow. Regularly trim off the oldest leaves — those farthest from the growing tips. Those are the weakest and most attractive to pests. Removing them from the pond also helps maintain good water quality and reduces the load on your filtration system.
Cutting off flowers that are done blooming is called deadheading. When left on the plant, faded blooms sink below the surface, may form seeds, and then decay. Deadheading keeps the water much cleaner and has another important advantage — it diverts the plant’s energy from making seeds to making more flowers.
Fertilize
The majority of water gardeners plant waterlilies in containers without any holes. This means each lily must get all its nutrients from soil in that pot. Nutrients from the original planting can be quickly utilized during the growing season. How fast that happens depends on the lily, pot size, and climate.
Many efficient (or lazy) gardeners repot their most vigorous lilies every spring to ensure they’ll have plenty of space and nutrients all season long. They incorporate a controlled-release fertilizer with micronutrients and NPK. This provides a steady food supply over the entire growing season, resulting in healthy, happy waterlilies.
If you have to fertilize a lily mid-season, use aquatic plant tablets that also contain micronutrients. Poke holes into the soil, insert tabs, and then cover the holes with soil. (This prevents upsetting the water balance and growing healthy algae.)
A lily that has run out of space is easy to identify. Try poking a stick or pencil into the soil. If there is no available room, it is root bound. It’s time to repot and maybe to divide the plant.
Repot & Divide
When the time comes to repot or divide your lily, please contact someone who has done it. The ideal person is someone from your neck of the woods and climate zone. Listen carefully to what they say; it is important. Repotting and dividing waterlilies is very different from terrestrial plants. Without guidance, you could screw things up and set the waterlily back a year or worse.
