Do Dahlias Like Full Sun, Partial Shade, or Fully Shaded Areas?
Trying to decide if you want to plant some dahlias, but want to know what their sun needs are before you do? Dahlias are some of the most popular flowers due to the many different varieties they produce. In this article, we examine if dahlias like full sun, partial shade, or if they can survive in full shade!
Dahlias are sure to delight gardeners far and wide, but they can be as mysterious as they are beautiful. These popular perennial flowers are grown all across the world, and there are over 50,000 different cultivars. This can lead to plenty of questions due to their differences, especially when it comes to how much sun they need.
If you’ve decided you’d like to grow some dahlias in your garden this season, you aren’t alone! It’s just a matter of where to put them. When it comes to the sun vs. shade debate, the answer isn’t entirely clear cut, due to how many varieties of dahlias there are.
Before we get to the details on the dahlia’s sun preferences, you’ll learn a little bit about the genus, and what hardiness zones they will live perennially. We’ll also cover some tips about dahlia placement, and where to put them so they get enough sun should you choose to grow them in containers. Let’s jump in!
The Short Answer
The short answer is that most dahlia cultivars prefer full sun, to partial sun. This means they need at least 6 to 8 hours per day in order to do well. Dahlias grow perennially in USDA Hardiness zones 8-11. However, if your temperatures routinely exceed triple digits (100°F or higher) then you’ll need to plan for some afternoon shade, when temps get their hottest.
Sun-Loving vs. Shade-Loving Plants
Most amateur and recreational gardeners carefully review and scrutinize the little sun icons on plant nursery labels. But, how many know what they mean? The terminology can even seem overwhelming to lifelong cultivators. The language encompasses a range of terms from full sun to part shade and everything in between.
A little extra context can go a long way in helping better understand your growing space and its climate. This will help you figure out how to produce a lush and thriving garden. Understanding the sun exposure labels usually found at nurseries is more about understanding how the light in your growing space relates to climate and heat.
Understanding Sun Exposure
When labels indicate that plants require full sun, they mean direct light equivalent to summer sun for six or more hours per day. This growing environment would likely resemble an open or prairie meadow environment in the natural world.
Plants that require part sun or part shade to grow will thrive in similar growing conditions with some key differences. Both part sun and part shade plants need three to six hours of sun per day. Plants labeled part-sun need exposure to direct sun during that time. In contrast, part shade plants need shielding from direct sunlight and should be in the shade during the hottest part of the day.
While this may seem overly complicated at first, these categories are about providing different amounts of protection from direct sun. Full shade plants need less than an hour of direct sunlight per day. Dense-shade plants love the dark the most, needing no direct sunlight.
When it comes to dahlias, they prefer full sun, in any environment that stays below 100°F. In environments that get hotter than that, they need partial shade. This means it’s best to provide them some shade for the hottest part of the afternoon.
Dahlias are favorite among gardeners worldwide. When it comes to determining if they are shade or sun-loving, the debate is split. A complete understanding of dahlias, how they grow, where they grow, and when they grow is hard to come by.
This is especially true due to the sheer number of dahlia cultivars you can grow. But understanding their native climates do provide us with at least some indication of what environments suit them best.
Climate and Geography
Dahlias are a species native to Central America, renowned for their large and beautiful flowers. These show-stopping flora can be over a foot wide and come in many colors, ranging from red to white to orange. As a species first grown by the Aztec peoples, dahlias are the national flower of Mexico. Dahlias bloom in late summer and early autumn.
From its native Central American origins, dahlias now span countries and continents worldwide. In the early 1500s, Spanish explorers brought dahlias back to Europe to the delight of many historic gardeners.
However, these gardeners encountered many of the same problems as their contemporary counterparts when attempting to grow the tuberous plant in the cooler, northern climate.
The dahlia plant slowly became more popular and was cultivated more broadly as a supposed starch source in Europe until the mid-1800s. By that time, dahlias had become a notorious garden favorite due to their bright and eye-catching flowers.
Part of the appeal of dahlias is their wide-ranging and diverse appearance. Dahlias can be classified by size, color, and form yielding thousands of possible hybrids and cultivars. The appearance of different varieties of the plants themselves is very similar.
Hoowever, the dahlia’s different flower types set them apart. Dahlias are categorized by the shape of their large and colorful flowers, which can be decorative, cactus-like, or even ball-shaped.
Ideal Growing Conditions
It is not uncommon to be confused about whether dahlias like sun or shade. The diverse array of dahlia types, combined with the plant’s Central American origins, make it a challenging species to understand its ideal planting location.
Understanding how the plant would naturally grow and what needs to be accounted for in different growing locations is the key to unlocking picturesque dahlias you can boast about. Planting them in locations they are not meant for can result in stunted blooms, or a dying plant.
Where Do Dahlias Grow Naturally?
Aside from Mexico, dahlias grow naturally in the neighboring mountainous regions of Guatemala and Colombia, which share Mexico’s warm climate. The dahlia plant thrives in oak and pine woodlands, demonstrating how it adapted over time to its native surroundings.
Adaptation was necessary for the plant to protect itself from losing moisture in the harsher conditions. It’s adapted to handle like dry heat and strong winds, that can affect the nations of Central America.
In What Soils Do Dahlias Grow Best?
Dahlias are like most plants in that they prefer soils that are loose, fertile, and well-drained. However, dahlias will not survive cold North American winters. It is generally best for gardeners to avoid planting tubers until the soil warms up in Spring and there is no risk of frost. Adding fertilizer, manure, or compost can help enrich the soil with nutrients. It is preferable to plant dahlias in an area where soil won’t become soggy or compact over time.
Soils are a critical factor in planting and growing dahlia tubers. Dahlia tubers love well-drained dirt. So, if you need to plant your dahlias in clay or heavy soil, try adding sand or peat to help with the drainage. Pre-packaged garden soil and mulch can potentially harm the tubers and prevent drainage. So, it’s best to avoid using them altogether.
Sun or Shade by Hardiness Zones
Knowing which hardiness zone you live in is a guiding resource in determining which plants will survive the winter in your area. Dahlias are winter hardy in zones 8-11. This means that the tubers will live if left in the ground during the winter months.
In the cooler, more northerly hardiness zones 3-7, dahlias can be grown as annuals. Or, the tubers can be dug up and removed from the ground at the first signs of killer frost.
In zones 8-11, dahlias will grow as herbaceous perennials similar to their native environment in Central America. Some gardeners in zones 6-7 may also be able to keep their tubers in the ground over winter. In these borderline zones, watch for the first killing frost and for the plant to die back in the autumn. At this point, you will want to protect the tubers from damage over winter by adding a layer of pine needles, straw, or mulch.
Once you understand your climate zone, considering which microclimates are present in your garden can help you pick the ideal planting location. The presence of a wall or other vegetation can create a warmer, more humid local environment. This should be accounted for when selecting your planting site.
Timing and Sun Exposure
The amount of sun exposure that dahlias need throughout the day depends on several factors. This includes whether or not they are potted, where you planted them, and where you live. For example, in Australia, exposing your dahlias to six hours of full-sun exposure would cause them to dry out, while six hours of full-sun exposure might be needed in a more northern European location.
It is best to plant dahlia tubers in the Spring, from mid-April to early June, depending on where you are located. Generally speaking, facing your Dhalias towards the morning sun is the best option, so they receive shade in the afternoon. The afternoon sun is often harsher and more intense. This is preferable for some species, but not dahlias, which prefer the gentler morning sun.
After first planting your tubers, it is important not to water them until the first shoots appear to prevent mold and root rot. Watering too early is a common problem amongst dahlia growers and should be avoided.
The soil should be loose, dry, and warm (55-60 degrees Fahrenheit) when the tubers are put in the ground. They shouldn’t be watered immediately unless you are living in an extremely arid and hot climate.
You should see shoots appear after four weeks. Then, you can start a regular watering routine as soon as they are more established.
Dahlias will still grow in areas that are more on the shady side, but the plants tend to be taller than those that get the morning sun and usually need staking. In the cool northern hemisphere, frost ends the dahlia growing season. For this reason, this perennial species is often planted and treated as an annual in most of the northern hemisphere.
Whether you are a dahlia fanatic or just a casual flower admirer, this eye-catching species comes in a diverse array of flowers with something for everyone. This species, native to Central America, is known to perplex even experts with its broad range of varieties and different growing conditions. Hopefully, this overview of dahlias’ sun and shade preferences has provided you with the knowledge to plant and grow any type of dahlia with confidence!