Rhubarb, with its vibrant pink stalks and tart flavor, is a culinary delight, particularly enjoyed in crumbles, pies, and jams. Forcing rhubarb is a technique used to produce an earlier and more tender crop than would naturally be available. But the key to successful forcing lies in understanding exactly how long you should force rhubarb for. Let’s delve into the factors that influence the forcing duration, the process itself, and what to expect at each stage.
Understanding Rhubarb Forcing
Forcing rhubarb essentially tricks the plant into producing stalks earlier than it normally would. By excluding light and providing a slightly warmer environment, the plant draws upon its stored energy reserves to produce long, slender, and delicately flavored stems. The resulting rhubarb is typically sweeter and less stringy than that grown outdoors in the regular season.
The method relies on mature rhubarb crowns that have already spent at least two years establishing themselves in the garden. This ensures that they have adequate energy reserves stored within their roots.
The Science Behind Forcing
Rhubarb, like many plants, requires a period of dormancy during the winter months. This period of cold is crucial for breaking down growth inhibitors within the plant. Once the dormancy is broken, the plant is ready to resume growth when exposed to warmth and light.
Forcing bypasses the natural light requirements by keeping the plant in complete darkness. This encourages the plant to elongate its stems in search of light, resulting in the characteristic long, pale pink stalks. The slightly elevated temperature, compared to the outdoor winter conditions, further stimulates growth.
Factors Influencing Forcing Duration
The duration of forcing rhubarb isn’t set in stone. Several factors play a crucial role in determining how long the process will take. Understanding these factors will help you optimize your forcing schedule and achieve the best possible results.
Crown Maturity
The age and maturity of the rhubarb crown are paramount. As mentioned earlier, crowns should be at least two years old, preferably three or more, before forcing. Younger crowns may lack sufficient energy reserves and will produce weaker, less productive stalks. Forcing immature crowns can also weaken the plant permanently.
Temperature
Temperature is a critical factor influencing the speed of growth. Ideally, you want to maintain a consistent temperature range. Too cold, and the rhubarb will be slow to emerge. Too warm, and the stalks may grow too quickly, resulting in weak and spindly stems.
A temperature range of 50-60°F (10-15°C) is generally considered optimal for forcing rhubarb. This can be achieved in a dark shed, garage, or even a basement. Using a thermometer to monitor the temperature is essential.
Light Exposure
Complete darkness is essential for producing the desired elongated, pale pink stalks. Any light exposure will trigger chlorophyll production, resulting in green stalks that are less tender and more tart. Ensure your forcing environment is completely light-tight. If necessary, use black plastic sheeting or other opaque materials to block out any light.
Variety of Rhubarb
Some rhubarb varieties are naturally more vigorous and responsive to forcing than others. ‘Timperley Early’ is a popular variety specifically bred for early forcing. Other suitable varieties include ‘Stockbridge Arrow’ and ‘Victoria’. Researching and selecting a variety known for its forcing capabilities can significantly impact the success and duration of the process.
Crown Size
The size of the rhubarb crown also influences the forcing duration and yield. Larger crowns naturally have more stored energy and will produce more stalks over a longer period. When selecting crowns for forcing, choose the largest and healthiest specimens.
The Forcing Process: A Step-by-Step Guide
Before diving into the timeline, let’s review the actual process of forcing rhubarb. This will help contextualize the timeframes we discuss later.
Preparing the Crowns
The process begins in late autumn or early winter. After the foliage has died back naturally, carefully lift the rhubarb crowns from the ground. Ensure you dig deep enough to avoid damaging the roots. Gently remove any excess soil.
Chilling the Crowns
Before forcing, the crowns need a period of chilling. This further breaks dormancy and prepares them for growth. Place the crowns outside, exposed to frost, for a minimum of two weeks, preferably longer. A period of four to six weeks of chilling is ideal.
Planting/Potting
After chilling, bring the crowns indoors and plant them in large containers or directly into the floor of your forcing shed or basement. Use a well-draining potting mix or garden soil. Water the crowns thoroughly.
Providing Darkness and Warmth
Place the containers in a completely dark location with a temperature range of 50-60°F (10-15°C). Cover the crowns with an opaque forcing pot or a large bucket to exclude all light.
Maintaining Moisture
Keep the soil consistently moist but not waterlogged. Check the moisture level regularly and water as needed. Avoid overwatering, as this can lead to root rot.
Harvesting
Once the stalks have reached a suitable length (typically 10-12 inches), they are ready for harvesting. Gently pull the stalks from the base of the plant, twisting slightly as you pull.
Typical Forcing Timeline: From Start to Finish
Now, let’s address the core question: how long should you force rhubarb for? The typical forcing duration is 4 to 8 weeks. However, this is just a guideline. As we’ve discussed, several factors can influence the actual time it takes.
Early Stages (Weeks 1-2)
During the first two weeks, you’ll likely see little to no visible growth. The plant is acclimatizing to its new environment and beginning to mobilize its energy reserves. Keep the soil consistently moist and maintain the correct temperature.
Mid Stages (Weeks 3-5)
This is when you should start to see significant growth. The stalks will begin to emerge from the crown, elongating rapidly. Monitor the stalks closely and ensure they are not becoming too crowded.
Late Stages (Weeks 6-8)
By weeks six to eight, the stalks should be approaching harvest size. Continue to monitor their growth and harvest them as they reach the desired length. Remember to harvest the largest stalks first, allowing the smaller ones to continue to develop.
Factors Affecting the Timeline
- Lower Temperature: If the temperature is consistently on the lower end of the recommended range (around 50°F), the forcing process will take longer, potentially extending to the full 8 weeks.
- Higher Temperature: A slightly warmer temperature (closer to 60°F) can accelerate growth, potentially shortening the forcing duration to as little as 4 weeks.
- Crown Vigor: Vigorous, well-established crowns will generally produce stalks faster than weaker crowns.
- Variety: Some varieties are simply faster growers than others.
Knowing When to Harvest
Knowing exactly when to harvest is just as important as knowing how long to force rhubarb for. Harvesting at the optimal time ensures the best flavor and texture.
Signs of Readiness
- Stalk Length: The stalks should be at least 10-12 inches long.
- Color: The stalks should be a pale pink to light red color.
- Thickness: The stalks should be reasonably thick and firm.
- Ease of Pulling: The stalks should pull easily from the base of the plant.
Harvesting Technique
To harvest, gently grasp the stalk near the base and twist it slightly as you pull upwards. Avoid cutting the stalks, as this can leave a stub that may rot and damage the crown. It is better to twist and pull to separate the stalk entirely.
Post-Harvest Care
After harvesting, you can leave the crown in the forcing environment to produce another flush of stalks, but be aware that each subsequent harvest will yield smaller and weaker stalks. Eventually, the crown will exhaust its energy reserves.
What Happens After Forcing?
It’s crucial to understand that forcing rhubarb puts a significant strain on the plant. After forcing, the crown will be depleted of energy and needs time to recover.
Resting the Crown
Do not attempt to force the same crown for at least two years, ideally three. This allows the plant to replenish its energy reserves and ensures it remains productive for years to come.
Replanting
After forcing, replant the crown in a well-prepared bed in the garden. Choose a sunny location with well-draining soil. Amend the soil with compost or other organic matter to provide the plant with essential nutrients.
Ongoing Care
Provide the replanted crown with regular watering and fertilization. Monitor for pests and diseases and take appropriate action if necessary. Mulching around the plant will help retain moisture and suppress weeds.
Troubleshooting Common Problems
Forcing rhubarb can be a rewarding experience, but it’s not without its potential challenges. Here are some common problems and how to address them.
Weak, Spindly Stalks
This is often caused by insufficient light exclusion or temperatures that are too high. Ensure your forcing environment is completely dark and that the temperature is within the recommended range.
Slow Growth
Slow growth can be caused by temperatures that are too low or by immature crowns with insufficient energy reserves. Ensure the temperature is within the optimal range and that you are using mature crowns.
Rotting Stalks
Rotting stalks are usually a sign of overwatering. Reduce watering and ensure the soil is well-draining.
Pests and Diseases
Rhubarb is generally resistant to pests and diseases, but it can occasionally be affected by slugs, snails, or crown rot. Take appropriate action to control any pests or diseases that may arise.
Conclusion
Forcing rhubarb is a rewarding way to enjoy an early harvest of this delicious vegetable. By understanding the factors that influence forcing duration and following the steps outlined in this guide, you can successfully force rhubarb and enjoy a bountiful crop of tender, flavorful stalks. Remember to be patient, monitor your plants closely, and provide them with the care they need. The key is to observe and adjust your approach based on the plant’s response. Happy forcing!
Why is forcing rhubarb a beneficial practice?
Forcing rhubarb offers several advantages, primarily resulting in an earlier and more abundant harvest. By manipulating the plant’s environment, we trick it into producing stalks weeks or even months before it would naturally do so outdoors. This allows gardeners to enjoy the delicious flavor of rhubarb much earlier in the season, extending the harvest period and providing a welcome source of fresh produce after a long winter.
Furthermore, forced rhubarb stalks are typically more tender and sweeter than those grown outdoors under normal conditions. The lack of sunlight during the forcing process inhibits the production of chlorophyll, which contributes to a less acidic taste. This results in delicate, pale pink stalks that are ideal for pies, crumbles, and other culinary creations, making forcing a highly desirable practice for rhubarb enthusiasts.
What factors determine the ideal forcing duration for rhubarb?
The optimal duration for forcing rhubarb depends on several interconnected factors, including the variety of rhubarb being forced and the ambient temperature surrounding the plant. Some varieties are naturally quicker to respond to forcing conditions than others, while warmer temperatures accelerate the growth process. Constant monitoring is crucial to prevent spindly, weak stalks.
Additionally, the pre-treatment of the rhubarb crown plays a significant role. A well-established crown that has experienced adequate frost exposure will generally force more quickly and vigorously. Factors such as the crown’s size and the overall health of the plant also influence the duration. A larger, healthier crown will usually produce a greater yield in a shorter amount of time compared to a smaller, less vigorous specimen.
How can I tell if my rhubarb is ready for harvest after forcing?
The primary indicators of ripeness in forced rhubarb are the size and color of the stalks. The stalks should be at least 10-12 inches long, although some varieties may naturally produce longer stalks. Look for vibrant, pale pink stalks that appear plump and juicy, indicating they’re full of moisture and flavor.
Furthermore, the leaves will typically be small and yellowish-green. Avoid harvesting if the leaves appear significantly larger or greener, as this indicates that the plant is redirecting energy towards leaf production rather than stalk growth. Gently tug on a stalk, and if it pulls away from the crown easily, it’s ready for harvesting. Never harvest more than two-thirds of the stalks at once to avoid weakening the plant.
What happens if I force rhubarb for too long?
Over-forcing rhubarb can significantly weaken the plant and negatively impact future harvests. Allowing the forcing process to continue for an extended period depletes the crown’s energy reserves, leaving it unable to recover adequately for subsequent seasons. This can lead to reduced yields and smaller, less vigorous stalks in the following years.
Moreover, excessively long forcing periods often result in spindly, etiolated stalks that are lacking in flavor and texture. The prolonged absence of light causes the plant to stretch excessively in search of it, producing weak and pale stalks that are not as desirable for culinary use. Proper monitoring and timely harvesting are essential to prevent these negative consequences and maintain the plant’s health.
Can I reuse a rhubarb crown after it has been forced?
While a forced rhubarb crown can be replanted, it’s crucial to allow it at least two years to recover before forcing it again. Forcing is an energy-intensive process, and the crown needs ample time to replenish its reserves before being subjected to another round. Replanting it in a fertile, well-drained location and providing adequate care will facilitate its recovery.
During the recovery period, prioritize regular watering, fertilization, and weed control to promote healthy growth. Allow the plant to produce leaves and stalks naturally, but avoid harvesting any for at least the first year after replanting. This will give the crown the best chance to regain its strength and vitality, ensuring a successful future forcing cycle.
What are the ideal temperature and lighting conditions for forcing rhubarb?
The ideal temperature range for forcing rhubarb is between 50-60°F (10-15°C). This temperature range encourages stalk growth without causing the plant to bolt or produce excessive foliage. Consistent temperatures within this range promote uniform and high-quality stalk development.
Complete darkness is crucial for achieving the desired pale pink stalks and tender texture. Blocking out all light prevents the production of chlorophyll, resulting in the characteristic color and taste associated with forced rhubarb. Ensure the forcing container is completely light-proof to achieve optimal results.
What are some common mistakes to avoid when forcing rhubarb?
One common mistake is harvesting too many stalks at once. Over-harvesting weakens the plant and reduces its ability to recover. Always leave at least one-third of the stalks on the crown to ensure its continued health and productivity. Also, failing to provide adequate moisture during the forcing process can hinder stalk development and result in poor yields.
Another frequent error is not allowing the crown sufficient time to rest and recover after forcing. Re-forcing a crown too soon depletes its energy reserves and diminishes its vigor. Remember to allow at least two years of undisturbed growth before attempting to force it again, and provide it with proper care during the recovery period to ensure its long-term health and productivity.