It doesn’t matter if you’re new to gardening or have been growing plants for decades. You already know that each plant has its own light requirements.
The determination of each plant’s light sensitivity includes many factors. The decision involves its place of origin and the environmental circumstances it has adapted to.
Before we discuss the light requirements for herbs, I should clarify that this is an extensive topic. There’s a lot of division between herbs concerning light sensitivity.
Don’t let this trouble you, though. We will go through the most critical elements of herbs and light. In the end, we will discuss some specific cases of herbs and their light requirements.
The Basics of Light Requirements for Herbs:
Every plant requires a certain amount of light per day to function normally. We usually don’t talk about the “amount of light” that a plant gets. Instead, we measure the hours of light it is exposed to.
Amount of Light: Full Sun, Partial Sun, and Full Shade
Full sun, partial sun, and full shade are the terms you should focus on the most. When we want to categorize herbs according to their light needs, we often use these words.
From the name, full sun indicates that the herb needs extended periods of light exposure. Full-sun herbs need at least six to eight hours of direct sunlight daily.
There is a wide variety of full-sun herbs, including sage, rosemary, and dill. Most of these plants are native to temperate and tropical regions. In these areas, the sun shines at high-intensity levels during the day.
It’s said that partial sun plants need four to six hours of direct sunlight exposure daily. We recognize those that require less than four hours of sun as partial or full shade.
We should note that these concepts aren’t strict; gardeners use them flexibly. Experts created these terms to make gardening easier for everyone, not to explain plants’ light needs.
Each herb can fall into one, two, or all of the above categories. In other words, a particular herb species may have the ability to flourish in both full sun and partial sun.
Other varieties of herbs may be able to survive on four hours of sunlight exposure daily. But they prefer six to eight hours instead.
Lemon balm, for instance, can stay alive in partial sun to full sun. It flourishes best when given at least six hours of sunlight per day, though.
To sum up, most plants are flexible about how much light they need. But you should ensure you’re getting the highest quality of herbs. For this reason, you should look at the optimal light needs of each herb, not just its light tolerance alone.
Another crucial point herb gardeners usually overlook is photoperiod. The photoperiod is particularly significant when growing your herbs indoors under artificial light.
Photoperiod generally indicates the sensitivity of plants toward the difference between day and night. It is an advanced way for them to detect the change in seasons.
Here’s an example. In the spring, days get longer, and nights become shorter (in the Northern Hemisphere). Some warm-weather-loving herbs will take advantage of this natural indicator to know when spring will arrive.
Generally, when herbs feel their sun exposure is longer or shorter (direct or indirect), they will move into the flowering phase.
With basil, mint, and other leafy herbs, this is troubling. Plants tend to end their life cycle when they finish their flowering phase. They also become stiffer and less flavorful.
Growing herbs under unregulated conditions makes it hard to control this aspect of their growth. In this case, the best thing you can do is wait for them to flower and then pinch off their buds.
But you can control your plants’ photoperiod if you grow herbs under artificial light. You can prevent them from blooming.
The photoperiod is less important than the total amount of light your plants get. In the end, this doesn’t affect your herbs’ survival chances at all.
What Could Possibly Go Wrong?
So, where do gardeners usually make mistakes when serving the light requirements of herbs?
Too Little Light:
Too little light is fatal for plants. Let’s say your full-sun plants only get four hours of direct sunlight daily. In that case, their leaves will start to turn yellow.
When your plants stop getting the ideal amount of light, they won’t be able to produce the necessary quantity of food. Lack of food for the plants means eventual weakness and probable death.
Many of the problems that gardeners face are due to a lack of light. So, don’t hesitate to give your herbs the amount of light they need and deserve.
Too Much Heat:
Plants can’t die from too much light, but they can from too much heat. Sunlight doesn’t consist of just bright, intense light but also heavy heat waves. Yes, plants need some warmth. But they can become upset by high-temperature light—especially for those that prefer shade and partial sun.
During the day, the sun’s heat gradually increases until sometime before sunset. In other words, the afternoon sun is much hotter than the morning sun.
Herbs getting excessive amounts of “warm” sunlight will become more prone to dehydration. The most obvious sign is that they will start to wilt. Then their leaves will slowly curl, turn yellow, and fall off.
That’s why gardening experts always tell people to expose their plants more to the morning sun than the afternoon sun.
Ideally, put your herbs where they can face the morning sun. Start when it rises until the afternoon. You can also buy LED or fluorescent grow lamps to prevent your herbs from receiving a lot of heat during the day.
Popular Herbs and Their Light Requirements:
Full Sun Herbs:
- Cilantro (Coriander): This herb can grow in full sun as well as partial and full shade. It grows best with at least six hours of sunlight daily. If the weather is too hot, avoid exposing it to the afternoon sun.
- Echinacea: Being a heavy-flowering plant, it’s not odd to find that echinacea loves the full sun.
- Borage: This is also a flexible plant that tolerates partial sun but prefers to grow in full sun.
- Fennel: This is an exclusively full-sun plant. Fennel should get at least six hours of sun daily.
- Sage: We know this herb as a sun-loving plant that tolerates drought rather well.
You can learn more about full sun herbs here!
Partial Sun Herbs:
- Parsley: This plant grows in partial to full sun. It’s preferable to grow it in the partial sun if the weather isn’t tolerant in your area.
- Mint: Mint can also grow in both full and partial sun, but I prefer to expose this plant to the sun only in the morning.
- Monarda (Bee Balm): Bee balm is a plant that grows best in partial sun, although it’s very flexible with light.
- Chervil: This plant cannot tolerate full sun in summer, so it’s usually grown in partial sun.
- Lovage: This herb can grow very tall if given the light it needs. It can tolerate partial to full sun.
You can learn more about partial sun herbs here!
Full or Partial Shade Herbs:
- Goldenseal: This herb grows naturally in the woods under trees, so it prefers full shade.
Discover how to grow goldenseal here!
- Gotu kola: This plant is more flexible with sunlight than goldenseal. But it grows naturally in shady conditions.
- Ginger: This plant can tolerate all amounts of sunlight. It grows best when given between two and four hours of direct sunlight daily.