Dahlias grow the best in a well draining soil which is the exact opposite of clay soil. However, with some extra steps, you can actually get your Dahlias to grow relatively well in clay soil as well. As long as the clay soil isn’t compacted, your Dahlias should grow and even thrive.
If you have clay or heavy soil, make sure to loosen it thoroughly to improve drainage. Adding sand or peat can also help enhance drainage capabilities. It’s worth noting that dahlias are not fond of mulch or store-bought garden soil, as these products can potentially harm the tubers. Once the outdoor temperature of around 12-15°C (55-60°F), you’re ready to begin planting your dahlias.
A lot of people think that having clay soil is the worst, but it is far from it, clay soil is jam packed with nutrients, minerals, and a lot of microorganisms that actually benefit plants. Although clay soil has its cons as well, it can compact and dry out relatively easily. The advantages of having clay soil far outweigh the few cons that this type of soil has, and with a couple of steps, you can easily negate its cons.
One major risk of growing Dahlias in clay soil is tuber rot, either due to too much watering or because the tubers are sitting in the water, however, with some careful planning you can easily avoid these problems. If your Dahlias are growing in clay soil and tend to wilt fairly often then check out my recent article Wilting Dahlias ( Top 8 Reasons ).
Growing Dahlias In Clay Soil
Growing dahlias in clay soil can present some challenges, as clay soil tends to be heavy and compacted, making it difficult for water to drain properly. However, with proper care and preparation, it is still possible to have success with dahlias in clay soil. Start by improving the soil’s drainage and structure by adding organic matter such as compost or well-rotted manure. This helps to loosen the soil and improve its ability to hold water without becoming waterlogged. Prior to planting, work the organic matter into the clay soil to a depth of about 12 inches. It’s also beneficial to create raised beds or mounds to further improve drainage.
When planting dahlias, be sure to dig a hole that is wide and deep enough to accommodate the tuber, and incorporate some sand or perlite into the soil to aid drainage. Regularly monitor the moisture levels and adjust watering accordingly, being careful not to overwater. Additionally, mulching the soil surface with organic material can help retain moisture and regulate soil temperature.
Loosen Up The Clay Soil
Clay soil has to be loosened up before you plant your Dahlias, mostly because the Dahlias have relatively weak root systems that will have a really hard time penetrating the soil. If you skip this step then the roots of the Dahlias will most likely get root bound, which will only stress out the plant and stunt its growth. Simply get a shovel and start digging, and make sure to get rid of the weeds as well while you are at it.
Break Down The Clay Clumps
Depending on how moist or dry your clay soil is you will still find a lot of clumps while digging. You have to break up these clumps, into smaller pieces, or else they will obstruct the growth of the roots. Do not water the clay soil before breaking up the clumps, the dryer the clumps are the easier it is to break them up. If you do this with wet clay soil, then it will be impossible to break the clumps down and as soon as it dries it will become one massive clump. If pests are bothering your Dahlias then check out my recent article What Is Eating My Dahlias? ( Top 9 Dahlia Pests ).
Dig A Bigger Hole Then The Size Of The Dahlia Tubers
Make sure to dig a hole that is twice as deep and wide then the tubers are. This way the soil around the tubers will also be looser and the roots will have an easier time growing into the soil. The main reason why you have to dig the hole twice as deep as the size of the tubers is to avoid having the tubers sitting in water. Clay soil can hold a lot of water, and even slightly compacted clay soil can allow water to accumulate, which will rot the tubers if they are sitting in the water.
Plant The Dahlia Tubers At The Correct Depth
The correct depth for planting Dahlias is around the same depth as the size of the tubers, in such a way that the stems are at ground level. If you have dug the hole deeper than the size of the tubers, then fill it back up, to a point where the stems are actually at the ground level. Remember that the main reason why you need to dig the hole twice as deep as the size of the tubers is to fill it back up with loosened soil that will prevent water from pooling around the tubers. If you want more info about the correct depth of planting Dahlias then check out my recent article How Deep To Plant Dahlias ( Top 4 Things To Know ).
Mulch The Clay Soil
It is extremely important to mulch the area around your Dahlias, clay soil can dry out relatively fast, and as it dries out it can compact. Once the clay soil is dry enough that it actually cracks, it will be extremely hard to water the Dahlias properly. With that being said you should avoid using mulches that attract pests, like grass clippings for example. Pests like slugs and snails will be attracted both to the Dahlias and to the grass mulch as well, and they will eat the Dahlias.
In this case, you should use wood chips as mulch, it does an excellent job of protecting the soil from getting baked by the sun and it doesn’t attract unwanted pests. Avoid using wood bark, as it decays relatively fast and tends to clump up in clay soil way too easily.
Do Not Water The Newly Planted Dahlias
It is extremely important not to water your Dahlias after you have planted them. At this stage of their life, the Dahlia tubers will not be able to absorb any water as their roots have not formed yet. Watering them will only increase the risk of tuber rot. Once the tubers start to sprout it is a clear indication that they have woken up and they are not only sprouting but also growing roots, and this is when you can start watering them.
Just keep in mind that it can take even 3-5 weeks until Dahlias sprout, during this time you do not have to water them. If the occasional rain comes, then just don’t worry about it.
Water The Dahlias Growing In Clay Soil Less Frequently
As long as the clay soil is mulched you can cut back on watering your Dahlias significantly. Just put one of your fingers into the top inch of the soil and if it is still moist then you can skip watering the Dahlias that day. If the soil is dry then you can water them, just try to avoid overwatering the Dahlias. It is usually better to water plants more often with less water than rarely with more water if you have clay soil.
Key Takeaways
- To grow Dahlias in clay soil you have to loosen up and break down the large soil clumps. Make sure to dig a twice as deep hole as needed, this way the water will not pool around the Dahlia tubers. When planting the Dahlia tubers make sure that their stems are at ground level, this way they can easily sprout. Do not water the Dahlias right after planting, instead wait until they sprout and only then start watering them.
- Mulching clay soil will stop it from getting compacted and drying out.
- Loosening up the clay soil around the tubers will help their roots penetrate the soil easier.