Rhubarb, with its vibrant crimson stalks and tart flavor, is a culinary delight, particularly in pies, crumbles, and jams. While typically grown outdoors under the sun’s warm embrace, the intriguing question arises: can rhubarb be grown in the dark? The answer is a resounding yes, through a fascinating process called rhubarb forcing. This technique unlocks a different flavor profile and yields a unique product that’s highly prized.
Understanding Rhubarb: A Perennial Vegetable
Rhubarb is a perennial vegetable, meaning it lives for more than two years, regrowing each spring. Its large, leafy green foliage is toxic, but the stalks are edible and delicious. Rhubarb thrives in cool climates and requires a period of dormancy in the winter, which is crucial for successful forcing.
Rhubarb plants store energy in their roots, called crowns, over the growing season. This stored energy fuels the growth of new stalks in the spring. The forcing process manipulates this natural cycle to produce earlier and more tender stalks.
The Magic of Rhubarb Forcing: Growing in Darkness
Rhubarb forcing is the practice of growing rhubarb indoors, in complete darkness, to encourage early growth and produce tender, sweeter stalks. This method prevents photosynthesis, resulting in stalks that are pale pink to red and have a milder, less acidic flavor compared to their sun-grown counterparts.
Why Grow Rhubarb in the Dark?
There are several compelling reasons to embrace rhubarb forcing.
- Early Harvest: Forcing allows you to enjoy rhubarb weeks or even months before the outdoor crop is ready. This provides a welcome taste of spring after a long winter.
- Tender and Sweeter Stalks: The absence of light inhibits chlorophyll production, resulting in stalks that are more tender and less tart. The sugars are also more concentrated, leading to a sweeter flavor.
- Unique Culinary Experience: Forced rhubarb offers a distinct culinary experience, with its delicate flavor and texture making it a prized ingredient for desserts, sauces, and even savory dishes.
- Extending the Rhubarb Season: Forcing allows for an extended harvest period, supplementing the main outdoor crop.
The Science Behind Rhubarb Forcing
The success of rhubarb forcing hinges on manipulating the plant’s natural dormancy cycle. After a period of cold exposure, the dormant rhubarb crown is brought indoors to a warmer environment. The darkness prevents photosynthesis, forcing the plant to draw upon its stored energy reserves in the crown to produce new stalks.
Because the plant is not producing chlorophyll (which requires light), the stalks remain pale and tender. The plant also converts starch into sugar, contributing to the sweeter taste.
How to Force Rhubarb: A Step-by-Step Guide
Forcing rhubarb is a relatively simple process, but it requires careful planning and execution.
Selecting the Right Rhubarb Crowns
Not all rhubarb plants are suitable for forcing. Choose well-established crowns that are at least three years old. These crowns have accumulated sufficient energy reserves to withstand the forcing process. Look for healthy, vigorous plants with multiple buds. Ideally, select a specific variety known for its forcing ability, such as ‘Timperley Early’ or ‘Valentine’. Avoid forcing newly planted or weak plants, as this can weaken them significantly.
Preparing the Crowns for Forcing
In late fall or early winter, after the first frost has killed back the foliage, carefully dig up the chosen rhubarb crowns. Remove any excess soil and trim the roots slightly. Ensure the crowns have experienced a period of freezing temperatures (ideally below 40°F for at least 8 weeks) to break dormancy. This chilling period is crucial for successful forcing. If your climate doesn’t provide sufficient cold exposure, you can chill the crowns in a refrigerator (not the freezer!) for the required duration.
Planting the Crowns in a Forcing Container
Choose a large container or pot with drainage holes. The container should be large enough to accommodate the entire crown without crowding. Fill the container with a well-draining potting mix, such as a mixture of compost, peat moss, and perlite. Plant the rhubarb crown so that the top of the crown (where the buds are located) is just above the soil surface. Water thoroughly after planting.
Providing Darkness and Warmth
The key to successful rhubarb forcing is complete darkness and consistent warmth. Place the container in a dark, warm location, such as a basement, shed, or closet. The ideal temperature range is between 50°F and 60°F (10°C to 15°C). Cover the container with a light-proof material, such as a black plastic sheet, cardboard box, or upturned bucket. Ensure that no light can penetrate.
Maintaining Moisture and Humidity
Keep the soil consistently moist but not waterlogged. Check the moisture level regularly and water as needed. You can also increase humidity by misting the foliage occasionally. Be careful not to overwater, as this can lead to root rot.
Harvesting the Forced Rhubarb
After several weeks (typically 4-8 weeks), the rhubarb stalks will begin to emerge. Harvest the stalks when they are about 10-12 inches long and have a vibrant pink or red color. To harvest, gently pull the stalks from the base of the plant. Avoid cutting the stalks, as this can damage the crown. Leave a few stalks behind to help the plant recover.
After Forcing: Plant Recovery
Forcing rhubarb is stressful for the plant. After harvesting, it’s essential to allow the crown to recover. Do not force the same crown for consecutive years. Plant the forced crown in a well-prepared garden bed with fertile soil. Provide regular watering and fertilization to help the plant regain its strength. Avoid harvesting any stalks from the plant during the first year after forcing to allow it to rebuild its energy reserves.
Troubleshooting Common Rhubarb Forcing Problems
Even with careful planning, problems can sometimes arise during the rhubarb forcing process.
Lack of Growth
If the rhubarb crown fails to produce stalks, it may not have received sufficient cold exposure to break dormancy. Ensure that the crown has been chilled for at least 8 weeks before forcing. Check the temperature of the forcing environment. It should be consistently between 50°F and 60°F (10°C to 15°C). Also, ensure that the crown is receiving adequate moisture.
Rotting Stalks
Rotting stalks are usually a sign of overwatering. Reduce watering frequency and ensure that the soil is well-draining. Provide adequate ventilation to prevent fungal diseases.
Weak Stalks
Weak, spindly stalks may indicate that the plant is lacking energy reserves. Choose well-established crowns for forcing and avoid forcing the same crown for consecutive years. Fertilize the plant regularly after forcing to help it recover.
Pests and Diseases
Rhubarb forcing is generally less susceptible to pests and diseases than outdoor cultivation, but it’s still important to be vigilant. Inspect the plants regularly for any signs of infestation or disease. Treat any problems promptly with appropriate organic or chemical controls.
Beyond the Basics: Tips for Rhubarb Forcing Success
Here are some additional tips to enhance your rhubarb forcing experience.
- Choose the Right Variety: Select rhubarb varieties that are known for their forcing ability, such as ‘Timperley Early’ or ‘Valentine’. These varieties tend to produce more tender and sweeter stalks.
- Use a Dedicated Forcing Pot: Consider using a dedicated rhubarb forcing pot, which is a tall, narrow container that helps to exclude light and retain heat.
- Monitor Temperature and Humidity: Use a thermometer and hygrometer to monitor the temperature and humidity levels in the forcing environment. Adjust as needed to maintain optimal conditions.
- Provide Gentle Air Circulation: While complete darkness is essential, gentle air circulation can help prevent fungal diseases. Open the forcing container briefly each day to allow for some air exchange.
- Harvest Regularly: Harvest the stalks regularly as they mature. This will encourage the plant to produce more stalks.
- Be Patient: Rhubarb forcing takes time and patience. Don’t be discouraged if the first few attempts are not entirely successful. Keep experimenting and learning, and you’ll eventually master the art of growing rhubarb in the dark.
The Culinary Delights of Forced Rhubarb
Forced rhubarb is a versatile ingredient that can be used in a wide range of culinary applications. Its tender texture and delicate flavor make it a perfect addition to desserts, such as pies, crumbles, and tarts. It can also be used to make sauces, jams, and compotes.
In savory dishes, forced rhubarb can be used to add a touch of acidity and sweetness. It pairs well with pork, chicken, and fish. It can also be used in salads and chutneys.
The pale pink color of forced rhubarb makes it a visually appealing ingredient that can elevate the presentation of any dish.
Conclusion: Embracing the Dark Side of Rhubarb Growing
Growing rhubarb in the dark, through the process of forcing, is a rewarding experience that allows you to enjoy this delicious vegetable earlier in the season and with a unique flavor profile. By understanding the principles behind rhubarb forcing and following the steps outlined in this guide, you can successfully grow tender, sweet stalks in the darkness of your basement, shed, or closet. So, embrace the dark side of rhubarb growing and discover the culinary delights of forced rhubarb.
Can rhubarb be grown entirely in the dark?
Yes, rhubarb can be grown entirely in the dark through a process called “forcing.” This technique involves depriving the plant of light to produce tender, pink stalks that are sweeter and less acidic than those grown outdoors in sunlight. While the initial growth and establishment of the rhubarb crown typically occur in a sunny location, forcing takes place in a dark, heated environment, such as a shed or cellar.
During the forcing process, the rhubarb draws upon the energy stored in its crown to produce stalks. The absence of light prevents chlorophyll production, resulting in the distinctive pale pink color and sweeter flavor. This method allows for an earlier harvest than traditionally grown rhubarb, often yielding crops in late winter or early spring when other fresh produce is scarce.
Why is rhubarb forced in the dark?
Rhubarb is forced in the dark primarily to produce sweeter, more tender stalks. The darkness inhibits the production of chlorophyll, which gives rhubarb its green color and contributes to its tart, sometimes bitter taste. By forcing in the dark, the rhubarb stalks remain a pale pink to red hue and develop a more delicate flavor.
Furthermore, forcing rhubarb in the dark accelerates its growth cycle. The warm, dark environment tricks the plant into thinking it’s spring, causing it to push out new shoots much earlier than it would naturally. This allows growers to harvest rhubarb in the late winter or early spring, providing a valuable early-season crop.
How does forcing affect the flavor of rhubarb?
Forcing rhubarb significantly impacts its flavor profile. When grown in the dark, the plant produces stalks that are notably sweeter and less tart compared to those grown outdoors in sunlight. This difference is attributed to the lack of chlorophyll development, which reduces the bitter compounds typically associated with rhubarb.
The resulting flavor is more delicate and nuanced, making it highly sought after for desserts, jams, and other culinary applications. The tender texture of forced rhubarb also contributes to its appeal, as it requires less cooking time and breaks down more easily than its sun-grown counterpart.
What conditions are necessary for successfully forcing rhubarb?
Successful rhubarb forcing requires specific environmental conditions. The rhubarb crown must be well-established before forcing, typically after at least two years of outdoor growth. The crown needs to be dug up in the late fall or early winter after the foliage has died back and the plant has entered dormancy.
The forcing environment should be completely dark and maintain a consistent temperature between 50°F and 60°F (10°C and 16°C). Humidity is also important, so the roots should be kept moist but not waterlogged. Providing these conditions will encourage the rhubarb to produce tender, flavorful stalks.
How long does it take to force rhubarb in the dark?
The forcing process for rhubarb typically takes between 4 to 8 weeks. The exact timeframe depends on the size and health of the rhubarb crown, the temperature of the forcing environment, and the desired length and thickness of the stalks. Regularly checking the plants is essential to monitor their progress.
Harvesting can begin once the stalks have reached a desirable size, usually around 12 to 18 inches long. It’s important to harvest the stalks gently by pulling them from the base, leaving the crown intact for potential future forcing or to be replanted outdoors.
Can any rhubarb variety be forced in the dark?
While most rhubarb varieties can be forced, some are better suited for the process than others. Varieties like ‘Timperley Early,’ ‘Stockbridge Arrow,’ and ‘Valentine’ are known to be particularly productive and yield high-quality stalks when forced. These varieties tend to produce more tender and sweeter stalks in the dark.
It’s crucial to choose a variety that is well-adapted to your local climate before attempting to force it. A healthy, vigorous crown will be more likely to produce a successful crop when forced. Also, consider the flavor profile of the variety, as some are naturally sweeter than others, which can further enhance the results of forcing.
What happens to the rhubarb crown after forcing?
After forcing, the rhubarb crown is typically weakened and should not be forced again for at least two years. The forcing process depletes the plant’s energy reserves, and it needs time to recover before it can be forced again. Replanting the crown outdoors in a sunny location is essential for its recovery.
The crown should be planted in well-drained soil and provided with adequate water and fertilizer. Over time, the crown will rebuild its energy stores and can potentially be forced again in the future, although it’s generally recommended to give it several years to fully recover for optimal results. Some gardeners choose not to force the same crown twice, opting instead to have separate crowns specifically for forcing.