Ginger (Zingiber officinale) is a tropical plant native to the humid, partly shaded habitats in moist tropical and subtropical forests of Southeast Asia. By mimicking these tropical conditions in high tunnels, ginger is becoming an increasingly popular specialty crop in the eastern U.S.
Although it’s often referred to as ginger root, it’s actually a rhizome or an underground stem. When harvested in high tunnels, it is most commonly sold as fresh baby ginger, often with its lush lance-shaped leaves still attached to the rhizomes. The growing season is not long enough in the eastern U.S. to harvest the cured, large and fibrous pieces seen in grocery stores.
High tunnel ginger plants are typically grown in a greenhouse and then transplanted into high tunnels. The first step to raising the transplants is to find a source of disease-free rhizome seed.
During a presentation, Dr. Reza Rafie, Extension specialist and professor of horticulture at Virginia State University (VSU), said each piece should be at least two ounces. Seed is often sold as larger pieces which must be cut into multiple pieces (ideally, each piece will have two to four well developed “eyes”). After each cut, the knife or pruners should be sterilized to prevent the spread of disease. Then, the pieces should be sterilized in a 10% solution of household bleach (one part bleach to nine parts water) for 10 minutes. Finally, the seed pieces should be cured for three or more days before planting.
The next step is to sprout the rhizome pieces; it must be at least 65º – 75º for this step to be successful. At VSU, they grow the seedlings in one-gallon pots using a soilless potting mix composed of two parts compost, two to four parts sphagnum moss, one part perlite and one part vermiculite. Other growers spread out multiple pieces in shallow plastic trays. Either way, the rhizome pieces should be buried about two to three inches deep and kept slightly moist as they are sprouting.
When soil temperatures in the hoop house reach 60º, the ginger plants are ready to be transplanted. At VSU, they are planted in shallow trenches with three feet between rows and two feet between each plant. This spacing allows for air circulation and helps prevent foliar diseases. Shade is critical to ginger, but Rafie said that the high tunnel is sufficient because the plastic provides 25% shade.
Even though it’s a tropical plant, ginger can be grown in the eastern U.S. – given the right growing conditions. Photo courtesy of Becky Sideman
Ginger has high nutrient demands and can quickly deplete the soil of nutrients, so at VSU they put mushroom compost into the shallow trenches before planting. They also add triple super phosphate and a 3-2-3 poultry manure fertilizer. According to Rafie, the goal is to provide a lot of nitrogen early in the season to encourage the foliage of the plants but switch to potassium later in the season to boost rhizome growth.
Drip irrigation is used to supply a consistent water to the plants. When the pink rhizomes begin to show, they should be mounded to keep them from turning green, which could impact their saleability.
Rafie suggested walking through the high tunnel frequently and parting the plants to more easily find rhizomes beginning to stick up past the soil surface. Plants can be mounded with soil, mulch or other organic materials.
About four to six months after it’s been planted, baby ginger is ready to be harvested. The crop cannot tolerate soil temperatures below 50º. To harvest, gently lift the thin-skinned rhizomes from the soil with a spade or a digging fork. The tops can either stay on or be trimmed off. Either way, everything should be lightly rinsed following harvest. Topped ginger will store for about 3.5 months and should be kept refrigerated in an airtight environment.
Rafie stressed the importance of crop rotation when growing ginger, particularly to prevent bacterial wilt. Bacterial wilt is the most common disease of ginger and spreads by infested soil adhering to hands, boots, tools and equipment, water from irritation or rainfall and infected ginger rhizome seed pieces.
According to Rafie, it infects ginger rhizomes through openings where the lateral roots emerge or wounds caused by handling. If a grower suspects bacterial wilt, they can cut a stem and place it in water. If bacterial wilt is present, a milky ooze substance will be visible in the water. The streaming begins only a few minutes after placing the cut rhizome in water.
Ginger is also susceptible to bacterial soft rot, bacterial leaf blight, Fusarium yellows and Pythium soft rots. Pests tend to be less of an issue, but the plants can be affected by root knot nematodes and army worms.
In terms of fungi, Rafie has witnessed leaf spot but was able to control it with an application of a fungicide.
by Sonja Heyck-Merlin
