How Deep To Plant Dahlias ( Top 4 Things To Know )

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Planting Dahlias is relatively easy, although a lot of people tend to get it wrong. Usually, the most common mistake that people make while planting Dahlias is that they plant them too deep. While it would seem logical to plant the Dahlia tubers deeper, as they tend to be top heavy plants but if you do so the Dahlias might not even come up.

Dig a hole that is 4 to 6 inches (10 to 15 cm) deep. Place the dahlia tuber on its side, horizontally, with the growing eye facing upward. This is where the shoots will emerge. Once positioned, carefully refill the hole with soil, making sure to cover the tuber completely. Keep in mind that dahlias can grow quite large, so it’s essential to provide adequate spacing of 12 to 18 inches (30 to 46 cm) between each plant.

If you want to make planting your Dahlias as easy as possible then my personal recommendation is to use an auger drill bit for planting Click here to check it out on

Dahlias love to grow in a well draining soil, in fact, they perform much better in well draining soils than in clay soils. If you have set your mind to growing Dahlias in your garden then you are probably not going to be stopped from growing them even if you have clay soil. No matter if you are panting the Dahlia tubers in a well draining soil or in clay, make sure that the soil around the Dahlias is loose.

If you have clay soil, and you want to make it well draining, under no circumstances mix sand into the soil. As soon as it dries out it will be hard as a brick and it will be almost impossible to loosen it up again. If you have transplanted your Dahlias and they are wilting then check out my recent article for the most likely causes Dahlias Wilting After Transplant ( Top 5 Reasons ).

How Deep To Plant Dahlias

When planting dahlias, it’s important to consider the appropriate depth to ensure successful growth. Generally, dahlias should be planted with the tubers placed about 6-8 inches deep in the soil. The depth allows for good anchorage and stability while also providing sufficient coverage to protect the tubers from extreme weather conditions. It’s important to note that smaller or dwarf varieties may require slightly shallower planting depths, while larger or taller varieties may benefit from slightly deeper planting. Additionally, ensure that the soil is well-draining to prevent waterlogging, as excess moisture can lead to rot.

Plant The Dahlias In A 3-4 Inch Hole

Dahlias have to be planted in a shallow hole, of around 3-4 inches, in such a way that the main stem is at ground level. This way as soon as the Dahlia tubers sprout they will have access to sunlight and are less likely to get leggy. Dahlias tend to have relatively weak sprouts, the more soil they need to push through the harder they have to work for it. Oftentimes this means that Dahlias that are planted too deep will simply not have enough strength to push through the soil, and eventually, they will simply rot away.

While planting make sure that the tubers are covered by the soil, and the stems are right at the ground level. If the tubers are not completely covered then they might rot or dry out. Dahlias have a lot of pests that tend to eat them, for more information check out my recent article What Is Eating My Dahlias? ( Top 9 Dahlia Pests ).

Loosen Up The Soil Before Planting

Even if you do not have a well draining soil, you should still loosen it up. Dahlias do not have a strong root system, and they will have a really hard time penetrating the soil if it is not loosened up. Mike sure to dig a hole twice as big as the size of the Dahlia tubers, and loosen it up as well as you can. By doing this you will also limit the amount of water that will sit around the tubers, after heavy rain for example.

The looser the soil is the easier and the faster it will drain, although with time the loose soil will start to compact. If you are just about to plant your Dahlias then make sure to protect them from slugs and snails, for more info check out my recent article How To Protect Dahlias From Slugs And Snails ( Top 7 Effective Ways ).

Do Not Amend The Soil With Compost Or Fertilizers

Most people tend to add some compost or a slow release fertilizer to the soil before planting their Dahlias. On the surface, this might seem like a good idea but it really depends on the type of soil you have in your garden. If you have a well draining soil then do add a layer of compost, but if you have soil that is poorly draining, like clay for example, then you should not add compost to it. Compost tends to hold on to a lot of water, and clay soil does the same, having both of these in the soil can cause the Dahlia tubers to rot.

Slow release fertilizers, on the other hand, can burn or damage the roots or the Dahlia tubers. Although you can still feed your Dahlias but you should use a foliar fertilizer, this way you do not risk the tubers rotting or getting damaged by the fertilizer.

Avoid Stepping On The Soil After Planting

It is really common for stepping on the soil around any newly planted plants, although you should definitely avoid doing it with Dahlias. Dahlias have tubers, that can easily break or rupture, especially as they need to be planted relatively close to the surface. Once you step on the surrounding soil, the soil will not be able to absorb most of that pressure as there is not a lot of soil on top of the tubers.

Small tears or ruptures on the Dahlia tubers can develop into serious problems later down the line.

Key Takeaways

  • Dahlias should be planted as deep as the height of their tubers, in such a way that the stems of the tubers are at ground level. If your Dahlia tubers are 3-4 inches in height then dig a hole 3-4 inches deep and place the tubers with their stems facing upwards. If you plant your Dahlias way too deep then they will have a difficult time piercing the surface and if they do, the stems might be weak and leggy.
  • Make sure that the stem of the tubers is either at ground level or slightly sticking out of the soil.
  • If you plant the Dahlia tubers way too deep then they might not be able to come up.