Bok choy (Brassica rapa subsp. chinensis) is a leafy green vegetable prized for its tender leaves and crisp, white stalks. This cool-season crop matures quickly, making it an excellent candidate for kitchen scrap gardening. Regrowing the plant from its leftover root base is a straightforward technique that allows home cooks to yield a second, smaller harvest. This process encourages dormant cells in the root crown to sprout new foliage and roots using water, before transplanting the new growth into a permanent medium.
Preparing the Bok Choy Base for Regrowth
The initial preparation of the bok choy base determines the potential for successful regrowth. Begin by making a clean cut across the bottom of the stalk, ensuring that approximately one to two inches of the root crown remains intact. This section, where the stems converge, is the plant’s meristematic tissue and contains the cells necessary for vegetative growth. Remove any damaged or yellowing outer layers from this remaining base to prevent decay and improve air circulation around the tissue.
Once the base is prepared, it should be placed in a shallow dish or bowl containing fresh water. The water depth should be carefully regulated, covering only the very bottom of the base—typically about one to two inches. It is important to avoid submerging the entire crown or the cut ends of the stems, as this can encourage rot and fungal growth. The base should be positioned with the cut side facing up, allowing the upper portion to remain exposed to the air.
The container should then be situated in a location that receives ample light, such as a bright windowsill. Bright, indirect light is often preferable during this initial rooting phase. Maintaining the proper light exposure encourages the base to initiate the development of new roots from the bottom and new leaves from the center of the crown. You should start to see small, pale green growth emerging from the center within a few days.
Sustaining New Growth and Transplanting
Sustained growth requires consistent care of the water environment to keep the developing roots healthy. The water must be changed daily or at least every other day to prevent stagnation and the buildup of bacteria or algae. Using fresh, clean water ensures that the emerging root tissues have access to necessary oxygen and minimizes the risk of the base becoming slimy or decaying. Mist the exposed top of the base occasionally to keep the new, tender leaf shoots hydrated, especially if the air in the room is dry.
Within one to two weeks, the base will exhibit two significant signs that it is ready for the next stage: the development of new, visible roots and the emergence of several new leaves from the center. The presence of established new roots, ideally one to two inches long, indicates the plant has built a functional system to absorb nutrients from the soil. Transplanting to a growing medium at this stage is necessary for the plant to achieve a size suitable for a future harvest, as water alone lacks the required macronutrients.
A well-draining potting mix is the best medium for transplanting the bok choy base, and the container must have drainage holes to prevent waterlogging. Plant the base so that the new roots are covered by the soil, with the original base buried about an inch deep, leaving the new leafy growth exposed above the surface. After transplanting, water the container generously, allowing excess water to drain completely. Post-transplant care involves keeping the soil consistently moist but never saturated to prevent root suffocation. Bok choy prefers temperatures between 45°F and 75°F and benefits from full sun or partial shade.
Troubleshooting Common Root Care Issues
Root rot is a frequent problem encountered when regrowing bok choy, particularly during the water-based stage. Root rot results from the base being submerged in stagnant, oxygen-depleted water, which creates an anaerobic environment favorable for pathogenic bacteria. The solution is to strictly adhere to the schedule of changing the water every one to two days, ensuring the water level touches only the bottom of the base. If the base develops a slimy texture, an immediate water change and a gentle rinse of the base can help mitigate the issue.
Premature bolting is a challenge for bok choy regrowth, representing the plant’s shift from vegetative growth to flowering. Bolting is often triggered by temperature stress, specifically when the plant experiences a cold period followed by a rapid rise in temperature, or when temperatures exceed 75°F to 80°F. Once bolting occurs, a tall central flower stalk emerges, and the leaves become stringy and bitter, effectively ending the harvest. To prevent this, the plant must be kept in its preferred cool temperature range and shielded from intense afternoon sun.
If the base fails to produce new leafy growth or roots, the problem is most often insufficient light or the age of the original base. The base requires a minimum of four hours of bright light daily to initiate photosynthesis and fuel new cell division. Ensure the container is placed near the brightest light source available to encourage the plant to break dormancy. New growth can also be stunted if the roots are damaged during the transition or if the soil is allowed to dry out.
Pests can target the root crown, even in container settings. Fungus gnats thrive in perpetually damp potting soil and their larvae feed on tender root hairs, while vegetable weevil larvae can chew at the roots underground. Ensuring proper soil drainage and allowing the top inch of soil to dry slightly between waterings helps manage these moisture-loving pests. Additionally, slugs and snails are highly attracted to the tender, new foliage and must be managed quickly.