Light deprivation (light-dep) is a technique used by growers to manipulate plants’ day and night lengths using blackout tarps and artificial lighting. This technique forces plants to flower faster or grow plants outside of their natural season. Short-day plants require long nights and short days to initiate flowering. In contrast, long-day plants need shorter nights and longer days to start flowering. By manipulating the day and night lengths, light-dep can accelerate or delay flowering in short-day and long-day plants at any time of year.
Light Deprivation for Short-Day Plants
Short-day plants, such as rice, hops, onions, camellias, violets, and winter-blooming ornamentals, are exceptionally responsive to light-deprivation techniques. Using blackout tarps to increase dark periods, growers can simulate fall and winter seasons and stimulate early flowering or tuber production.
The strategy for maximizing your harvest of short-day plants with light-deprivation is relatively simple:
Start Early: Start seedlings indoors under a grow light to ensure healthy and robust plants.
Create Long Nights: When plants are large enough, use a light-deprivation tarp to shield plants from light for 12 hours while allowing light exposure for the remaining 12 hours. This schedule mimics the fall equinox at the end of September. The increased night length signals to the plants that it is later in the season, triggering flowering. Continue this light-deprivation technique until harvest.
Start another batch of seedlings as soon as you bring your flowering plants outside. This close timing permits a second harvest.
Harvest your first batch of plants and replace them with the second seedlings. The second batch will not usually require light-deprivation techniques as they will be exposed to seasonally shorter days, naturally triggering flowering.
Light Deprivation for Long-Day Plants
Long-day plants, such as asters, hibiscus, lettuce, spinach, radishes, carrots, and some strawberry cultivars, require supplemental lighting to reduce periods of darkness during fall and winter. A shortened night promotes more prolonged foliage and root development, resulting in larger, healthier, and more productive plants. Timing and consistency are especially crucial when implementing light-deprivation techniques with long-day plants.
Here are some key considerations for using light management techniques with long-day plants:
Supplemental lighting: For long-day plants, growers typically need to combine light-deprivation techniques with extra lighting to minimize periods of darkness and promote vigorous growth in long-day plants.
Timing is crucial: To prevent premature flowering, it is essential to time the implementation of light-deprivation techniques correctly. Begin using supplemental light when the days shorten, typically in late summer. Extending light exposure and limiting dark periods extend the vegetative phase and maximize foliage and root growth.
Consistency is key: Maintaining consistently short dark periods is vital to successfully cultivating long-day plants. Any inconsistencies in coverage or timing can induce bolting, shock the plants, and make them susceptible to pests and diseases. It is often beneficial in these cases to use automated systems and timers to ensure consistent and reliable results.
Day-Neutral Plants
Day-neutral plants are not strongly influenced by the duration of night or day hours. They can flower regardless of the day length and rely more on environmental conditions such as temperature and plant development cues. While these plants can flourish in a controlled greenhouse environment, particularly during the cold months, light-deprivation isn’t a helpful technique for them.
Potential Challenges and Considerations
While light-deprivation techniques offer numerous benefits, they also present some challenges that growers should be aware of. It is essential to address these considerations to ensure successful cultivation:
Pests and diseases: While light-deprivation can create a more controlled environment for plant growth, it can also create favorable conditions for pests and diseases. Reduced light exposure and increased humidity can attract certain pests and promote the development of pathogens. Growers should implement appropriate pest management strategies and ensure proper ventilation to mitigate these risks.
Cost: Implementing light-deprivation techniques may require additional investments in equipment, such as blackout tarps and automated systems. Growers should consider the associated costs against the potential benefits and increased yields.
Crop selection: Not all plants respond equally to light-deprivation techniques. It is essential to select crops known to benefit from this practice. Conduct research and consult with experienced growers to determine the suitability of specific plants for light-deprivation.
Conclusion
Light deprivation techniques offer growers a powerful tool to manipulate growth and flowering processes and optimize plant production. By controlling the duration of light exposure, growers can mimic seasonal changes and induce early or delayed flowering in plants. This technique allows for multiple harvests, increased yields, and extended cultivation seasons. However, it is vital to consider the specific requirements of each plant species and address potential challenges associated with light-deprivation. By combining scientific knowledge with practical application, growers can harness the benefits of light-deprivation to maximize their crop production and meet market demands more effectively.
