Full Sun Definition
How Much Sun is Full Sun for Plants?
Learn what the exact definition of full sun is, and how to measure full sun in your landscape.
Whether you’re just starting out with gardening or trying to choose plants for a new project, you’ll often come across the term full sun. But what does it really mean? Understanding the exact definition of full sun is crucial for giving your plants the best chance to thrive. Let’s break it down and shed some light (pun intended 😉) on how much sun is full sun for plants, and what this term really means for your garden.
Full Sun Definition
Full sun is defined as 6 or more hours of direct, unfiltered sunlight per day. These hours don’t have to be consecutive, so your plant could get three hours of morning sun and three in the afternoon, and that would still count as full sun.
You are most likely to find full sun in south and west facing garden beds and in open, unobstructed landscapes where there are no trees, buildings, or other structures to cast shade. Other common full sun locations include the middle of a lawn, south-facing slopes, and alongside driveways. Land surrounding a newly built home typically receives full sun since it lacks mature trees and shrubs to create shade. Large patios, pool decks, and rooftop terraces that aren't shaded by other buildings tend to receive full sun as well.
It’s easy to assume that an area of your garden gets full sun, especially if it seems bright and open. However, sunlight can be deceptive, with amounts varying throughout the day and across the seasons. To ensure your plants thrive, it's essential to measure the actual amount of sunlight hitting the landscape. Keep reading to learn how simple it is to assess your garden's light conditions.
How to Measure Full Sun
Measuring full sun isn’t as complicated as it might sound. You don’t need any fancy equipment, just a bit of time and attention. Keep in mind that trees will leaf out from spring through fall and cast shade underneath, and there will also be extended daylight hours during the late spring and summer months.
Here’s a simple way to measure:
Pick a spot: Choose the area in your garden, yard, deck, or balcony where you want to measure the sunlight. You can use sticks or garden stakes to mark the area, if desired.
Observe the sunlight: Check how much direct sunlight the spot gets throughout the day. Start from when the sun rises and note what time the area gets sunlight and what time it becomes shaded.
Track the hours: Tally up how many hours the spot is in full sunlight. If it adds up to at least six hours (the definition of full sun for plants), you’ve got yourself a full sun spot!
Devices like sunlight meters aren't necessary, and can even be inaccurate due to factors like weather conditions and nearby reflective surfaces. If you want to use tech to help you visualize where and when the sun will hit specific areas of the garden, the Sun Seeker app can be helpful (and fun to play around with!). But really, you don’t need anything fancy to measure light levels. By simply observing your garden over the course of a day, you will gain a better understanding of the unique light conditions in your landscape.
Full Sun vs Partial Shade
So, what’s the difference between full sun and partial shade?
Full Sun: 6+ hours of direct sunlight per day
Partial Shade: 3-6 hours of direct sunlight per day.
Partial shade is also referred to as part shade.
Many plants that are labeled as requiring full sun can still grow in partial shade and survive. While these plants can manage in partial shade, they will not perform at their peak potential.
Can I Grow a Full Sun Plant in Partial Shade?
Full sun plants can survive in partial shade, but they won’t thrive and may quickly decline in health. When full sun plants don’t get their required amount of light, they often exhibit certain signs indicating they’re struggling:
Leggy Growth: Without enough light, plants stretch towards the light source, resulting in tall, thin stems with large spaces in between the leaves. This is referred to as “legginess” and can make the plant look sparse and weak.
Reduced Flowering: Flowering full sun plants rely on ample sunlight to produce their abundant flowers. In partial shade, plants will flower less because they lack the energy needed for robust bloom production.
Slow or Stunted Growth: Full sun plants will grow more slowly and may stop growing altogether if they don’t receive enough light. This can affect their overall health and appearance, and they will also become more susceptible to diseases and insect pests.
Paler Leaves: Insufficient sunlight can lead to less vibrant foliage and pale leaves.
When full sun is the only light level listed for a plant’s requirements, it’s best to give it the 6+ hours of direct sunlight per day it needs to be healthy, thriving, and looking its best.
What is Direct Sun?
Direct sun refers to the quality of light a plant receives. Direct sun is an intense, uninterrupted path of sunlight traveling directly from the sun to the plant, without any obstructions or filters.
Full sun refers to the quantity of direct sunlight a plant receives. Full sun is six or more hours of direct sunlight per day.