Herbs are flavorful, fast, and easy to grow – making them a staple in the indoor kitchen garden. Outdoors, herbs need a fair amount of sunlight, so most of the time we try them inside they don’t just get enough light to thrive. In this blog, we’ll review the light needs for the different herbs, how to see if you have enough natural light, and how to set up a simple but effective grow light.
Light Needs for Herbs
Herbs use light to make the essential oils that give them their flavor. If you get it right, you’ll be rewarded with a constant stream of fresh, pungent herbs. If you don’t give them enough, the flavors will fall flat – if the plant even grows at all. The minimum and ideal hours of direct sunlight for the culinary herbs are:
Generally, 6 to 7 hours of sunshine hitting their leaves will provide all herbs with enough light to grow well. However, 6 hours is alot of direct light to get in any window, so depending on your conditions you might want to look at the lower light herbs (like Cilantro & Parsley). While it’s a must to hit the minimum, you’ll get faster growth as you give the plant more light. If you want more herbs, the #1 thing you can do is give your plant more light.
Do I have enough sunlight to grow leafy greens?
Sunlight is excellent for plant growth (and free!) so we recommend it whenever it makes sense. It can be tricky to know exactly how much light you have – it changes day-to-day and season-to-season. The best way to know that you have enough natural light is past experience: has a “Full Sun” plant grown well in the same spot / same season? We find that most windows benefit from grow lights, but if you want to explore before taking the leap we’ve got exercises to understand your natural light environment [coming soon].
Season & Window Direction
South facing windows are typically the brightest, and thus your best chance for growing indoors with just natural light, though you will need to understand some seasonal shifts. In the fall and spring, bright, unobstructed southern windows work well for growing herbs. In the winter, your southern window is still your best bet, but the weaker sunlight might need to be combined with a grow light. In the summer, southern windows can get too hot (over 80F) – so consider growing your greens in cooler east facing windows. If you really want to make the most of your natural light, you can read about 4 hacks to increase your natural light [coming soon].
Reading your plants
The ultimate test of your natural light will be your plant’s growth. You can tell very early if you are way off the mark – you’ll notice the seedlings stretching and becoming spindly. Beyond that it’s a bit harder to tell where you are in the “adequate to optimal” range, but if your growth is way slower than is listed on the seed packet, the plant would likely do better with more light. If you are unsure, we recommend trying radishes as a quick-growing, easy to read diagnostic [coming soon].
Setting up a grow light for year-round, fast-growing herbs
Grow lights can be a little intimidating – but they really shouldn’t be! There is a lot of marketing noise to cut through, but at the end of the day, a well designed grow light provides a 1:1 replacement for sunlight, looks nice in your home, and pays for itself. Plants love the consistency of grow lights, which helps your little space be as productive as possible.
We consider the grow light an essential tool of indoor gardening, so by familiarizing yourself through growing herbs – you’ll be ready to take on higher light plants – like peppers and tomatoes. The instructions below give practical instructions for our grow light, but if you’d like to have a deeper general understanding, check out the introduction to our grow light series.
Using a Grow Light Bar
Note: This section references Urban Leaf’s upcoming Grow Light Bar, due Spring 2021.
We have several grow light buying guides [coming soon] (for screw-in, clip on, bars, and free standing options) but if you’re using our Grow Light Bar then it’s quite simple to set up a leafy green grow area. The grow bar mimics a 6” x 12” patch of direct sunlight when placed 6 inches above a plant, so just match the timer to the plant’s “direct sunlight” hours.
Considerations with other grow lights
Grow lights come in all types of sizes, shapes, and technologies. For herbs, high powered lights (ie. Metal Halide or High Pressure Sodium) can put out too much way too much heat. LED’s can be great, but there is a wide range of light quality. Fluorescent grow lights run cooler and are perfectly suitable to grow herb, lettuce and greens. If you are interested in setting up a more complicated grow light system, we recommend understanding Daily Light Integral, correct setup and placement, and how many hours a day to leave them on [coming soon].