A jewel in the water garden but invasive in waterways, water hyacinth is a pond fish’s best friend, providing shelter and feeding area. Rosettes of glossy green leaves float leisurely across a pond, gradually covering the surface and sending down thick roots that shelter fish. In warm weather, the plants send up lavender bloom spikes that last about a day. It should be planted early in the season so its spread outpaces algae, and thin out old plants every year to reinvigorate growth. Because it’s a tender plant, it requires overwintering indoors in an aquarium to survive from year to year. Note: This plant can be invasive in warm-weather areas. Check local restrictions before planting it.