How Much Sunlight Do Growing Vegetables Need?
How much sunlight do growing vegetables need is one of the most frequently asked questions, since not everyone who wants to grow a vegetable garden is blessed with an area that receives full sunlight all day long, or with an area large enough to allow the adequate separation of taller plants to keep them from shading shorter plants. Such an example would be corn or tomatoes; these taller plants tend to shade anything planted east of them. Large-leaved plants will also provide shade if planted too closely to other crops.
You may also have to take into consideration the existing trees, fences and architecture that can affect the amount of sunlight reaching certain areas of your vegetable garden. For example, some trees have a high, open canopy, allowing dappled sunlight to reach the garden during all times of the day. On the other hand, trees with a lower, denser canopy can mean your garden area is plunged into full shade for more than all but an hour or two a day, a situation impossible to grow almost any vegetables in. Sometimes it is a simple matter of trimming the lowest branches of the tree, in many cases improving the health and overall appearance of the tree, but also enabling more sunlight to reach your garden plot. In extreme cases, gardeners have been known to cut down the offending tree, using the stump to mount a birdbath or birdhouse, instead. It’s all a matter of priorities and what matters most to you. When it comes to existing architecture or a fence, the fix can often be as easy as applying a coat of white paint in order to reflect the sunlight and to help dispel some of the shade. You will also want to take your garden site into consideration when planning on planting trees or installing that new garden shed or privacy fence. These projects are often completed in the fall, after the active gardening season is over, but will directly affect your garden come spring.
So, for the purpose of describing shade or sunlight—it is not an exact science; it can depend on where you live. For instance, full sun in the northern part of the country can be 8 to 10 hours of direct sunlight per day. However, in the desert Southwest, full sunlight can mean at least 6 hours of morning sunlight, but almost full shade in the afternoon hours in the heat of the summer. For the purpose of this article, we will focus on the middle, in Zones 4 through 8, with any adjustments being made up or down in he amount of sunlight depending upon the area:
- Full Sun—at least 8 hours of direct sunlight per day
- Partial Sun—at least 6 hours of direct sunlight per day
- Partial Shade—at least 4 hours of direct sunlight per day
- Full Shade—less than 2 hours of direct sunlight per day. If your prospective garden area experiences this type of shade, we do not recommend planting vegetables
It will be necessary to observe your garden area throughout a sunny day as spring approaches, and to take a look every couple of hours or so, to determine the total hours of sunlight different areas of your garden will receive. An easier solution, one that doesn’t require your taking that walk out to the garden, and which is definitely more precise, is to use our SunCalc® Sunlight Calculator or Light Intensity Meter to accurately determine the amount of sunlight reaching any particular area of your yard.
As an easy-to-remember rule, leafy vegetables are the most adaptable to low light conditions, with root vegetables being the next in line and fruit-bearing vegetables requiring the greatest amount of sunlight. Most vegetables will grow in lower light conditions, except for fully shaded conditions, though their productivity could be adversely affected. When in doubt, err on the side of more sun.
As a solution to a garden site with less than desirable sunlight, consider planting your garden in two separate areas or think about planting your tomatoes and other fruit-bearing crops in containers on your sunny deck or patio. Bear in mind that you can also use shade-cloths to provide shade to overly sunny areas where you want to grow leafy vegetables.
As a guide to the amount of sunlight required for specific vegetable plants, you can use the following recommendations, making adjustments as needed for your particular situation:
Crops requiring at least 8 hours of direct sunlight per day (Full Sun):
- Asparagus (perennial)
- Brussels Sprouts
- Goji Berries (perennial)
- Rhubarb (perennial)
Crops requiring at least 6 hours but can grow with less than 8 hours of sunlight per day (Partial Sun):
- Collard Greens
- Rhubarb (perennial-can also grow in full sun)
- Swiss Chard
Crops requiring at least 4 hours of direct sunlight per day (Partial Shade—ideally midday sun):
- Asian Greens