Vegetables have very high light needs – it’s likely that you’ll benefit from a grow light even if it’s just to supplement your sunshine. Fortunately, (unlike herbs and lettuce that we keep in a “perpetual spring”) veggies can have lights on for up to 16 hours a day, so the same grow lights will work just fine, you’ll just leave them on a bit longer. In this blog we’ll review the light needs for the different vegetables, how to assess your natural light, and how to set up a simple but effective grow light. If you’re just getting started, check out our overview of how to grow vegetables indoors.
How much light do vegetables need to grow?
The Total Amount Of Light Needed Varies By Plant
When they are just getting started, they need a decent amount of light to support their leafy growth. When they switch to growing vegetables, they need even more. It’s an energy intensive process for them and sufficient light as they are ripening helps develop their flavor. Some plants (like tomato) can be pushed along their development faster by receiving over 12 hours of light. The minimum and ideal hours of direct sunlight for vegetables are:
The Variety of the Vegetable Matters When It Comes To Lighting
You’d think that all tomatoes need the same amount of light – right? It’s not quite that simple. Some specialty varieties, like the ones we recommend, are actually more tolerant of the lower light levels typical of an indoor garden. While it’s not a fix all, you will have better luck choosing varieties that still grow well with slightly lower light needs.
Do I have enough sunlight to grow vegetables?
Probably not…. but you can still take advantage of the light you do have to get even better growth in combination with a grow light.
It’s Time to Consider Your Window Direction & Seasonality
Vegetables tend to be warmth loving, so will be happiest in a southern or western window given all options. If you have truly unobstructed, direct light coming through this window you’ll likely be able to grow vegetables in the spring through fall – but as winter sets in you will almost certainly benefit from a grow light.
Reading your plants: Are they happily lit?
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. You can always try lower light plants in the same space, like lettuce, to use as a point of reference.
Setting up a grow light for year-round vegetables
Grow lights can be a little intimidating – but they really shouldn’t be! There is alot 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 and it’s easy to put vegetables in their “optimal” range with lights. 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 Summer 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 Types of 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].