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Last Updated on April 24, 2025 by Alaina
Urban gardening isn’t just a trend, it’s a solution. Whether you’re growing tomatoes on your balcony or herbs in your kitchen, space is limited and conditions are far from perfect. That’s where supplemental lighting steps in to save the day. While most folks rely on full-spectrum grow lights, there’s a secret sauce to really supercharge your plants: UV and IR light.
Let’s break down exactly how adding these specific light wavelengths can help you grow healthier, stronger, and more productive plants in your urban garden.
What Are Supplemental Grow Lights?
Supplemental grow lights are not your average grow lights. Instead of covering the full light spectrum (like the sun or full-spectrum LEDs), they target specific wavelengths. This article focuses on UV (Ultraviolet) and IR (Infrared) light, two powerful tools that can dramatically impact plant growth when used correctly.
What Is UV Light?
UV light sits just beyond the violet end of the visible spectrum. It’s divided into three types:
- UV-A (315–400 nm) – Safe in low doses; helpful for plant development.
- UV-B (280–315 nm) – Triggers stress responses and increases potency.
- UV-C (100–280 nm) – Harmful and not used in gardening.
What Is IR Light?
Infrared light lies just beyond the red end of the visible spectrum:
- Far-Red IR (700–850 nm) – Promotes flowering and stem elongation.
- Thermal IR (850–1000+ nm) – Generates heat and helps regulate plant temperature.
Why Add UV and IR Light to Your Garden Setup?
1. Boosting Nutritional Value and Flavor (UV)
UV light, especially UV-B, encourages the plant to produce flavonoids, antioxidants, and resins. This doesn’t just protect the plant—it enhances taste, smell, and nutritional content. Imagine herbs that are richer in oils and tomatoes with a deeper flavor.
2. Triggering Flowering with Precision (IR)
IR light stimulates the phytochrome system in plants, signaling that it’s time to flower. This is especially useful for growers who want to control bloom cycles or speed them up. It’s like giving your plants a nudge to start showing off their flowers.
3. Enhancing Stress Resistance (UV)
Exposing plants to short bursts of UV creates a controlled stress response. The result? Stronger, more resilient plants that can fend off pests and handle urban gardening challenges like inconsistent temperatures or poor airflow.
4. Managing Growth Stretching (IR)
In tight spaces, vertical growth can get out of hand. IR light helps you direct and control plant stretching, which can be especially useful for fruiting plants like peppers and strawberries.
How to Use UV and IR Light Effectively
Using UV and IR grow lights can seriously improve your plant growth—if you use them right. These types of light aren’t like your regular full-spectrum grow lights. They’re powerful tools that can boost flavor, flowering, and plant strength—but if you go overboard, they can also cause stress or damage.
Optimal Usage Timing
UV light needs to be used carefully. The best way is short sessions of 1–3 hours a day during the middle of your light cycle. This mimics how the sun naturally gives off the most UV at midday and gives your plants time to recover. Too much UV can cause bleaching, damage, and stress, doing more harm than good.
IR light works differently. It’s best used during the start or end of the light cycle—early morning or late evening. That’s because IR helps set the plant’s internal clock and encourages natural stretching and blooming, without interfering with photosynthesis.
Strategic Light Placement
UV lights should be 12–18 inches above the plants. That’s close enough to work, but far enough to avoid burning the leaves. IR lights need to be 18–24 inches above, because they give off more heat. This height lets the light spread out and avoids overheating your plants. Keep an eye on leaf temperatures—too much heat can undo the benefits.
Integration with Primary Lighting
UV and IR lights are extras, not your main light source. They’re like vitamins for your plants, working alongside your full-spectrum grow light. The main light gives your plants everything they need to grow. UV and IR lights fine-tune that growth by improving things like resin production or flower development.
They usually make up 10–20% of your total lighting, but even that small amount can make a big difference when used right.
Final Thoughts
Urban gardening is all about making the most of what you’ve got. When you add supplemental grow lights to your setup, you’re not just growing plants—you’re crafting an environment where they can thrive, not just survive. It’s a next-level hack that separates casual hobbyists from intentional, high-yield gardeners.
So if you’re ready to upgrade your grow game and get more out of your urban jungle, give UV and IR light a try. Your plants and your taste buds will thank you.