Get the weeds

The gardeners try to use the least toxicity possible when controlling weeds. Organic herbicides (such as plant extracts plus acetic and citric acid) are tested for weed control in turf plots. For flowerbeds, the gardeners often use preemergent herbicides once the plants are established, and then they follow with mulch immediately.

1. Testing things out
2. Again.

But mulch doesn't work everywhere, Stendahl notes, pointing to a bed of 1,400 irises, which need their crowns above the surface. "We've managed to grow exhibition-size dandelions in there," she laughs. "We're still looking for the perfect solution."