Mulching Dahlias ( Top 7 Pros & Cons )

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People have been mulching their plants for a really long time, different mulches provide different benefits to plants, and this is the same case with Dahlias as well. For the most part, if you are mulching your Dahlias then you will definitely see better results on how they grow, although not all mulches are equal and some might even invite unwanted pests.

Mulching too early can lead to smothering of the plants or rotting of the tubers. To mulch your dahlias effectively, first remove any weeds around them and ensure they have been adequately watered. Once these steps are complete, apply a layer of mulch that is at least 2-3 inches thick. In areas where the plants may be exposed to extreme temperatures, it is advisable to use a thicker layer of mulch for added protection.

In nature as soon as there are some bare spots in the soil weeds will start to colonize it. The weeds in this case can be actually beneficial as they will penetrate the soil with their thick roots, which sooner or later will allow other plants to grow as well. For the most part, mulches are used to suppress weeds, although some weeds that spread with rhizomes will not be stopped even by a thick layer of mulch.

Certain types of mulches can be problematic for Dahlias, especially when it comes to slugs and snails as they will often simply live very comfortably under the mulch and come out to feed on the Dahlias during the evening. If you want to grow Dahlias in clay soil then check out my recent article Growing Dahlias In Clay Soil ( In 7 Easy Steps ).

Mulching Dahlias

Applying a layer of mulch around dahlias helps to conserve moisture, regulate soil temperature, suppress weed growth, and protect the tubers from fluctuations in temperature during the growing season. To mulch dahlias, wait until the soil has warmed up and the plants have started to grow. Apply a layer of organic mulch, such as straw, wood chips, or shredded leaves, around the base of the plants, taking care to avoid covering the stems or crowns. Aim for a mulch depth of about 2-3 inches. Mulching should be done after the soil has warmed to help retain moisture and prevent weed competition. Regularly check the moisture levels in the soil and adjust watering as needed, as mulch can also help to reduce water evaporation.

Stops Weeds From Growing

One of the main benefits of mulching Dahlias is that the mulch will stop weeds from growing. Although most plant seeds do not need any light to germinate, which is the same case with weeds as well, but once they germinate they will need some sunlight, if not they will simply die off. Even if you mulch your Dahlias you will still see the odd weed popping up, but you can easily pluck it out. Removing weeds from a mulched flower border will be a lot easier. If this is the first time you are planting Dahlias then check out my recent article How Deep To Plant Dahlias ( Top 4 Things To Know ).

Protect The Soil

If there are bare soil patches in your garden then plants will find it really difficult to grow in these areas after a while, mostly because the sun can actually bake these spots. Placing a thick layer of mulch on these bare soil patches will protect the soil from erosion and from the sun baking it. After a while, life will return to these bare patches and you will actually be able to grow plants in these spots as well.

If you place a thick layer of mulch around your Dahlias then the soil will be protected, this will allow the Dahlia roots to spread out a bit. As the Dahlia roots tend to be relatively weak they will need all the help they can get when it comes to penetrating the soil, all those bugs, worms, and microorganisms living under the mulch will aid them in doing so.

Protect The Dahlias Tubers During The Winter

If you live in zone 8 or above then you can keep your Dahlias in the ground even during the winter. However, it is still a good idea to protect them with a thick layer of mulch if the occasional frost comes. Just keep in mind that most mulches are extremely good at retaining water and even though your Dahlias will not freeze in the soil, they might simply rot away. You should probably avoid mulching the Dahlias during the winter if you have clay soil, as tuber rot can occur relatively easily.

Feed The Dahlias

If you use mulches that decompose relatively fast, like hay, straw, grass, and so on, then as these decompose their nutrients will be available for the Dahlias to absorb. Mulches that decay relatively slowly like wood chips for example will still provide the Dahlias with nutrients although only once they start to decay. You can actually skip fertilizing the Dahlias if you have provided them with a nice thick layer of fast decomposing mulch.

Mulches Can Attract Pests

Slugs and snails are one of the most problematic pests of Dahlias, they can simply eat these plants back to the tubers, which usually means that the tuber simply dies off. Mulches that decompose relatively fast like grass clippings, will attract pests like slugs and snails as they will eat dead and decomposing grass. If you want to mulch your Dahlias with grass clippings then it is extremely important to let the grass completely dry out before you use it as a mulch.

Slugs and snails are not attracted to dried out grass, so using them as mulch for your Dahlias is safe. If you want to know how to protect Dahlias against slugs and snails then check out my recent article How To Protect Dahlias From Slugs And Snails ( Top 7 Effective Ways ).

Mulches Can Rot Dahlia Tubers

While mulches do have a lot of benefits for Dahlias, but they can also kill off the tubers if the soil retains way too much water. As to how much water will the mulch and the soil retain depends mostly on what kind of soil you have, clay soil will hold a lot more water than sandy soil for example. In this case, it is better to make a thin layer of mulch around the Dahlias rather than a thick one, this way the water will still evaporate from the soil, although a lot slower.

Mulches Can Contain Herbicides

If you are using hay, straw, or grass mulches then there could be a chance that they will contain some herbicides. Usually, companies will spray herbicides in order to get rid of the weeds, thus making the mulch almost 100% hay, straw, or grass. These herbicides can last for years, if not decades in the mulches, and they will affect your plants. In the best case scenario if you use mulches that do contain herbicide then the most likely result will be that the Dahlias will be stunted.

In the worst case scenario, these herbicides will simply kill off the Dahlia tubers. In this case, you should use only your own grass clippings as mulch, and make sure never to use herbicides, this is the only way you can ensure that you do not contaminate your soil with herbicides.

Key Takeaways

  • Mulching Dahlias will protect the soil against erosion and from the soil drying out completely. In hardiness zones where you can overwinter your Dahlias in the soil, you should cover the tubers with a thick layer of mulch to protect them from the occasional frost. Mulches like leaves and grass clippings can also attract slugs and snails to the Dahlias, so only use them once they are completely dried out.
  • Avoid mulches that attract slugs and snails, like fresh grass clippings.
  • If you have clay soil then only use a thin layer of mulch for the Dahlias.