How much light do fruit trees need to grow?
The total amount of light needed for fruit
Growing fruit is an energy intensive process, and fruit trees have the highest light needs of any edible plant you can grow. In nature they are used to having a full view of the sky, so it’s unlikely that you will be able to provide enough natural light, unless you have an exceptionally bright window or sunroom. You’ll notice that many of the tropical fruits can actually handle moderate light – if you are in this range they’ll grow green but are unlikely to product fruit. Because fruit trees come from all over they have different day-length requirements to set fruit – most will appreciate getting over 12 hours a night, but a few (market in blue) need 12 hours of darkness to set fruit. The final column lists how long you should leave your grow light on to get fruit.
The minimum and ideal hours of direct sunlight for fruit plant are:
Believe it or not, the variety of the fruit matters!
The chart above provides useful generalizations, but light needs vary a bit by variety. While most trees are used to full sun – some evolved to understory conditions and can do OK with a little less. For citrus stay away from grapefruits and meyer lemons and instead go for Thai Limes, Finger Limes, and Thornless Key Limes, Owari Satsuma Tangerine, Bumper Satsuma Mandarin, Meiwa kumquat, ponderosa lemons, washington naval, ‘Flying dragon’ Bitter Orange or most Calamondins. For strawberries, alpine varieties are best.
Do I have enough sunlight to grow fruit?
Considering window direction & seasonality
Fruits are 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 get a little growth spring through fall – but as winter sets in you will almost certainly benefit from a grow light. If you do have bright outdoor space – your plant will most definitely appreciate spending the summer outside.
Reading your plants: Are they happily lit?
The ultimate test of your natural light will be your plant’s growth. The first sign will be that your plants isn’t growing much, if at all. If perfectly green leaves are falling off, it almost certainly is not getting enough 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 fruit
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 and can look nice in your home. 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 fruit plants in their “optimal” range with lights. The instructions below give practical instructions for two grow light recommendations, but if you’d like to have a deeper general understanding, check out the introduction to our grow light series.
Grow light setup: Spoiling your fruit with hours of sunshine
A powerful spotlight provides good lighting for a tree canopy. With either the DIY or High-end option below, you will want to set up the grow light 12 inches from the top of the canopy and leave it on for the “total light” hours per day (see chart above or the learn by plant section).
The DIY grow light option:
High-end grow light option:
The 40W Aspect Light ($200) is very sleek looking.
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].