Hydroponic Herb Light Cycles For Beginners

As a hydroponic gardener, understanding the importance of light cycles in the growth and development of your plants is crucial. If you’re just branching out into the realm of indoor herb gardening, you might wonder how many hours of light to give your new basil sprouts, or lettuce leaves, because this is a very common question. Most vegetative herbs such as basil, parsley, cilantro and dill thrive under 18 hours of light per day, but there are some plants, or life cycles of plants that require different light phases. This guide will help you navigate the world of light cycles in hydroponic herb cultivation.

1. The Essential Role of Light Cycles

Light cycles play a critical role in the development of your hydroponic plants. They aid in photosynthesis, the process by which plants convert light energy into chemical energy for growth. But what exactly is a light cycle?

1.1 What is a Light Cycle?

In the context of plant growth, a light cycle refers to the recurring pattern of light and darkness that plants experience each day. The duration of light and dark periods influences how plants grow and whether they will flower. The aim in your hydroponic system should be to simulate a natural light cycle as closely as possible.

In the natural world, plants experience a daily rhythm of light and darkness, as well as an annual cycle where the ratio of light to dark hours changes with the seasons. In winter, days are shorter with long periods of darkness. As spring approaches, the hours of daylight increase. Summer brings the longest days, while autumn signals a return to shorter days and longer nights.

In a hydroponic environment, you can control the light cycle to influence the growth and flowering of your plants. This control over light cycles is one of the benefits of hydroponic gardening, especially in climates where outdoor growing can be challenging.

2. Emulating Natural Light Cycles in Hydroponics

To replicate the natural light cycle, hydroponic growers often use a pattern of extended light hours followed by dark hours. A common light cycle for vegetative plants is 18 hours of light and 6 hours of darkness, mimicking a summer day’s light cycle.

During the vegetative stage, plants require plenty of light for healthy growth. Leafy plants, in particular, need an abundance of light in the blue and red frequencies of the color spectrum. This range can be achieved using full-spectrum LED grow lights.

In a hydroponic setup, aim to provide around 14 to 16 hours of artificial light, followed by 8 to 10 hours of darkness. This pattern should be repeated daily. The duration of darkness plays a significant role in determining how a plant behaves, influencing its progression from the vegetative stage to the flowering stage.

2.1 Using Electric Timers for Light Cycles

To maintain a consistent light cycle, an electric timer can be invaluable. It allows you to automatically switch your grow lights on and off according to your desired schedule. This is particularly useful when growing different types of plants with varying light and dark cycle preferences.

3. Catering to Different Light Requirements of Different Plants

Different plants have unique light and dark cycle needs. Some plants prefer longer days, while others thrive with shorter days. And, some plants are less fussy about light cycles.

3.1 Long Day Plants

Long day plants require up to 18 hours of light per day. These plants, like lettuce, wheat, spinach, potatoes, and turnips, tend to flower in the summer and thus prefer longer days.

3.2 Short Day Plants

On the other hand, short day plants like strawberries, chrysanthemums, and cauliflower need fewer than 12 hours of light per day. They require longer dark periods to photosynthesize and flower. These plants usually bloom in the spring and thus prefer shorter days.

3.3 Non-Flowering Plants

Non-flowering plants, including corn, rice, and roses, are less particular about light cycles. They don’t produce flowers or fruit, so the light/dark cycle doesn’t significantly impact their growth.

If you’re growing a mix of long and short day plants in a limited space, a compromise may be necessary. Aiming for about 14 hours of artificial light per day could be a good middle ground.

4. Manipulating Plants’ Growth Cycles

In some cases, you may want to delay a plant’s flowering stage. This can be achieved by keeping the plant in its vegetative stage for an extended period, achieved by providing shorter periods of darkness.

Conversely, if you want to encourage flowering, you can trick the plant into thinking it’s time to bloom by reducing the hours of light and increasing the hours of darkness. This can be done by switching from an 18-hour light and 6-hour darkness cycle to a 12-hour light and 12-hour darkness cycle.

5. The Impact of Continuous Light

While it might seem logical to provide plants with light 24/7, doing so can be detrimental. Constant light can confuse plants, disrupt their flowering stages, and hinder other essential growth processes. Therefore, it’s essential to maintain a balance of light and dark periods in your hydroponic system.

6. Lighting Systems in Hydroponics

Choosing the right lighting system for your hydroponic set-up can be a daunting task, but it’s crucial for success. The main components of a hydroponic lighting system include the bulb, reflector hood, remote ballast, and timer.

6.1 Types of Bulbs

The most commonly used bulbs in hydroponic systems are LED, fluorescent, metal halide (MH), and high-pressure sodium (HPS) bulbs. Each type has its advantages and is suitable for different stages of plant growth.

  • LEDs (light-emitting diodes): LEDs are a cost-efficient and energy-efficient lighting option. They’re available in a variety of forms, including square panels and tubes.
  • Fluorescent bulbs: These bulbs are perfect for starting seeds and growing salad greens and flowers. They emit low heat, reducing the risk of burning or drying out the plants.
  • Metal halide (MH) bulbs: MH bulbs provide robust all-around light, making them suitable for long-day plants and the vegetative stage of plant growth.
  • High-pressure sodium (HPS) bulbs: HPS bulbs are ideal for the flowering stage of plant growth. They are more expensive but last longer than MH bulbs.

6.2 Reflector Hood

A reflector hood is a reflective casing around the bulb that increases the bulb’s effectiveness by reflecting light onto the plants from multiple angles.

6.3 Remote Ballast

The ballast is a power box that powers the light. It’s typically the most expensive component of the lighting system, so it’s important to keep it off the ground to prevent water damage in case of a flood or leak.

6.4 Timer

A timer is crucial for maintaining a consistent light cycle. It can be either manual or electric and should be heavy-duty and grounded.

7. Frequently Asked Questions

  • Is a lighting system required for hydroponic gardening? A lighting system is required for INDOOR hydroponic gardening. The amount of light varies depending on the type of plants you’re growing.
  • What are the main components of a lighting system? The main components of a hydroponic lighting system are the bulb, reflector hood, remote ballast, and timer.
  • What are the different types of bulbs for the system? The most common types of bulbs are LED, fluorescent, metal halide (MH), and high-pressure sodium (HPS).

In conclusion, understanding and effectively managing light cycles is crucial to the success of your hydroponic herb garden. By mimicking natural light cycles and adjusting them according to the needs of your plants, you can optimize their growth and flowering. Whether you’re a beginner or an experienced gardener, mastering light cycles can help you overcome even the toughest of climatic challenges and enjoy a flourishing hydroponic garden.


Located in Portland, Oregon, Tim started gardening in his 20's and after a couple of decades felt like he had some things to share.

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