QUESTION: To get my gingers to bloom more, should I cut the flowering stalk once its pau blooming?

— Mimi Bornhorst Gaddis, East Oahu

ANSWER: Mahalo for this great question. My theory is to make sure the stalk is pau blooming, then check the moon calendar to calculate the next full moon. I cut the flower stalk a week after the full moon. This allows nutrients from the stalk to be naturally recycled back to the ginger rhizomes (modified stemlike special roots).

First, I cut the leaves off in three pieces, then I cut up the stalk into 6-inch-long pieces. I mulch all of this back onto the ginger bed. Thus, the nutrients are doubly recycled, and you have the benefits of a leafy mulch (water retention, weed suppression and not overfilling our landfills).

(You can do the same with the banana (or maia) plant. Once a trunk has fruited, use a bolo knife to cut the trunk into pieces and mulch to protect the banana patch.)

Gingers are “heavy feeders” and benefit from rich compost soil and regular watering. Like most flowering plants, they will bloom best in full sun.

IS GINGER A WEED?

Volunteers and conservation workers who have tackled gingers at higher elevations know it can be a pest. On a recent Tantalus hike with fellow horticulturist and University of Hawaii at Manoa graduate Rachel Morton, we observed invasive yellow, white and kahili gingers growing in the native forest.

All kinds of alien pests have grown and taken over the lovely forest up there, especially with the hot, wet conditions of the last few years.

However, there are weeds more harmful than ginger such as miconia, thorny tree ferns and Australian tree ferns, which are spread by spores and invade pristine forests and watersheds, along with toxic poisonous plants like the pencil tree.

The amount of weediness all depends on the location of your garden. Gingers do not spread easily down in low elevations where most of us live. In fact, they need a lot of nurturing by adding compost and organic matter to the soil, watering and fertilizing.

It’s a different story in the mountainous rainforest regions. In places such as Kokee on Kauai, Volcano on Hawaii island, upcountry Maui, Lanai and Molokai, ginger plants are serious weedy pests. At higher elevations the roots are more vigorous, and they set seeds. The seeds have an orange aril that attracts birds, which eat them and spread the seeds. The plants are also larger and healthier, forming dense patches, which can overwhelm native forests and take over vast areas of land.

An example of this invasive spread was in Kokee after the devastating hurricanes Iwa in 1982 and Iniki in 1992. The hurricanes wiped out native forests, buffeted and knocked over trees and opened up land to sunlight. Weeds from gardens in Kokee moved into the devastated and open areas. Today you can see huge patches of yellow ginger as well as kahili ginger along the roads and in dense stands. No native plant could replant itself amid such ginger patches.

A similar situation exists in the Volcano area on the Big Island. People like lots of alien plants (we used to call them exotics) and plant them in their gardens. Some of them go wild.

Lots of weed-control work and volunteer projects help attack ginger and other plants that have “jumped the fence” out of gardens and into the wild.

One way to help control them is to pick every flower and blooming stalk in your garden. Don’t let them go to seed.

If you are lucky enough to have a garden in mauka rainforests, it’s best to plant natives or noninvasives.

Heidi Bornhorst is a sustainable landscape consultant specializing in native, xeric and edible gardens. Reach her at heidibornhorst@gmail.com.