Reduce nutrients in waterlily pond to prevent growth of algae

Backyard Q&A

July 31, 2005|By Jon Traunfeld and Ellen Nibali | Jon Traunfeld and Ellen Nibali,Special to the Sun

Our waterlily has a bright-green mosslike substance growing on the roots. It pulls out of the water in large sheets and grows quickly. What is this?

You have filamentous algae in your pond. This algae is stringy, hairlike or threadlike and very common. For small ponds, the recommended control is physical removal. Twirling it around a stick like spaghetti on a fork works well.

To prevent algae growth, reduce nutrients dissolved in the water. Fertilize potted pond plants with tablets pushed down into pot soil, limit the number of fish because their excrement is a potent source of nutrients, and grow more water plants to absorb excess nutrients.

The 'Lord Baltimore' hibiscus bush in my front yard has a myriad of little holes in the lower leaves. Upon turning over affected leaves, I see thin, little green worms eating voraciously. Any treatment to eradicate this plague?

The "plague" on your hardy hibiscus is actually not worms or caterpillars, but the larvae of sawflies. Sawfly adults look like small flies. The larvae can cause significant feeding damage. To control, pick the larvae off by hand or spray them with horticultural oil or insecticidal soap.

I planted pumpkin seeds a little late this year. Can I get them to set fruit faster if I pollinate them myself? How is this done?

Hand-pollinating is helpful when you see few pollinators such as bees near the plants, you have few pumpkin plants or you use pesticides regularly.

To hand-pollinate, first identify the male and female flowers. There are more male than female flowers. Males grow on thin stems above the main vine. Their pollen is on the center stamen. It's mature and ready to use when it comes off easily when touched. The female flower is identified by the round bump (unfertilized ovary) between the flower and its stem. It is ready to be pollinated when the flower opens fully.

Pollinate in the morning of the day the bud opens. Remove the stamen from a mature male flower and gently rub it all over the stigma and inner segments of the female flower. The bump will develop into a pumpkin on a pollinated flower. If pollination does not occur, this bump or immature pumpkin will shrivel up and die.


1. Avoid spraying pesticides on hot, humid days. Pesticides can burn foliage. Store pesticides in a cool location and mix only the precise amount you need for a single application.

2. Start broccoli, cauliflower and cabbage plants for planting in late August. Snap beans, cucumbers and squash still can be planted.

Jon Traunfeld, regional specialist, and Ellen Nibali, horticulture consultant, work at the University of Maryland Cooperative Extension's Home and Garden Information Center. The center offers Maryland residents free gardening information and answers to plant and pest questions. Call its hot line at 800-342-2507 (Monday through Friday, 8 a.m.-1 p.m.) or e-mail questions through the Ask a Question feature on the Web site at (You can also download or order publications and diagnose plant problems online.)

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