Dahlias can provide beautiful colors to an outdoor area, as well as unique flower shapes that draw in the eye. This is why they are so popular for planting in gardens.
Although these plants are perennials (in warmer climates), meaning they grow back every year, there are some steps you will need to take prior to the frigid winter months if you want your delicate dahlias to continue thriving and producing blossoms year after year.
General Information
The gorgeous flowering plants known as dahlias originated in Central America and Mexico. These plants are technically perennials and are tuberous.
Although there are 40 different species of the dahlia plant, only six or so of them are used in personal gardens and sold at flower shops. These six species include the waterily, dinner plate dahlia, single, double, and peony-flowered.
The flower petals on dahlias range from red to yellow, white, and purple. These plants are great at growing in many kinds of soil.
Their flowers start to bloom in the late summer and continue doing so until the first good frost shocks them.
How to Overwinter Your Dahlias
Dahlia plants are tuberous rather than bulbs, so they have thin skin that is easily damaged in cold weather, putting them at higher risk of freezing and rotting throughout the winter.
The approach you use for overwintering your dahlias relies heavily on the climate in which you reside. If you live in an area where the ground freezes more than a few inches below the surface of the soil, it is a smart move to uproot your dahlias and store them somewhere until spring, at which time they can be replanted.
On the other hand, if you reside in a hotter area, such as Southern California or Texas, you should be able to leave your plants in the ground throughout the winter months.
However, in areas where the ground freezes, they need to be dug up and stored somewhere safe and cool throughout the winter season. This will be detailed within the information below.
Keep in mind that you should not dig up your dahlia tubers in the autumn, but rather, you should wait until the springtime to do so.
Leaving Them in Ground
If you do happen to live in a region where the ground does not freeze more than a few inches down, you can leave your dahlia plants in the ground all year. But, you can still dig them up and store them if you would like to ensure their survival.
When leaving your dahlias outside for the winter, there are a couple things you need to do to keep them safe.
First, either after the first good frost occurs or following November 15, you will need to cut your plants’ stalks to below ground level. This is known as dividing, and we will go into more detail regarding this step later in the article.
After chopping the stalks, you should place a plastic sheet over your dahlias, followed by an insulating material such as straw or even leaves. This should help the plants stay alive while the cold weather is wreaking havoc outside.
Digging Them up
When it comes to digging up your dahlias before winter, you will need to wait until the tubers have turned black or brown in color. If you dig the plants up too soon, it can result in your tubers remaining in a stage where they will not properly store over the winter months.
After you have dug up your tubers, you need to rinse them off to get the dirt off of them. You should let them dry in the air completely overnight before safely storing them.
Storing Your Plants
One of the best ways to store your dahlias over the winter months is by putting them into a crate or cardboard box with some slightly wet bedding. You can use various materials for the bedding, such as wood shavings, though many people prefer to utilize peat moss for storing their dahlia tubers.
You will also need about 10 sheets of newspaper or any other kind of comparable paper. You will use this to layer the bottom of the crate or box.
Following the newspaper, you will add a layer of your bedding material, and then you will add a layer of dahlia tubers. You can repeat this layering process until the container is filled to the top.
Your dahlia tubers are now ready to be stored away. They need to be kept in a temperature between 40 and 50 degrees Fahrenheit, so a refrigerator and cooler are ideal spots.
The tubers should be stored for at least three months outside of the growing seasons. However, ideally, you should examine your dahlias every month or so to make sure the bedding is not drying out too much and that the plants are not showing signs of rotting.
If the material seems quite dry, you can mist it down with a spray bottle filled with water. If you notice that your tubers are rotting, you should cut away the affected parts of the plants before it travels to other tubers in the container and affects them, too.
Dividing the Tubers
Once your dahlia tubers are about to be replanted, it is time for you to divide them. It is important to divide your dahlia plants every other year, at minimum.
You will know your dahlias are ready to divide once small roots start growing from them. Without these present, if you divide and replant your tubers, they will most likely never flower, which is why it is so important for you to wait until the right time to carry out this step.
There is a knife you can pick up from your local gardening supply store that is designed specially for dividing dahlias, but you can also utilize a sharp knife of any kind to get the dividing job done.
The next thing you will do is locate the eyes of your tubers, which is where the roots grow out from, as this is where you will cut the tubers. Look for a small pink bump near the base of the plant’s stem.
It may be difficult to notice them, in which case you can simply make your best judgment as to where they are, which should be in the middle of the plants’ stalks. Cut the stalks into quarters or halves down the center of the stalks.
After you have divided your dahlias, you can either plant them the following day, as long as the weather is dry and warm enough, or you can store them until the weather allows you to replant them. You may even need to wait a few weeks after dividing them to replant them if the weather is not cooperating, in which case you could always plant the tubers in pots before relocating them outside.
Once the conditions are ideal, you can finally replant your dahlias. The following section will go into detail in regards to doing this.
Replanting Your Tubers
When you are replanting your dahlias in the springtime, first make sure the soil you are putting them in is adequately fertilized and drains well. Also, if you want your dahlias to truly thrive, it is important to plant them in an area that gets full sunlight.
Do not put too much fertilizer that is high in nitrogen on the soil, or your dahlias will not produce as many flowers and be quite bushy with leaves instead. Mulch is not necessary around dahlias, as it will only block the sun from reaching them in totality, and it can attract slugs to the plants, which are unwanted visitors.
Finally, it should be noted that if you would like your dahlia plants to produce bigger flowers, one thing you can do is cut away the smaller buds found around the middle of the group of flowers.
This will redirect the plants’ nutrients to the larger flowers, in turn, making them even bigger. However, keep in mind that this will also lead to your plant producing fewer flowers, of course.
Final Thoughts
It might seem like a lot of work to get your dahlias stored over the winter months, but it is really just a lot of waiting around for the tubers to be ready for replanting, especially in colder climates.
The time it takes to overwinter dahlias is worth the money you will save using the same plants year after year. Each year that you dig up, store, divide, and replant your dahlias, the better you will get at it, and if you are a big gardener, you might even find that you love the process.
No matter what, once you see your dahlias from the year before producing beautiful new flowers in the spring, you will realize that the effort you put into storing and growing them was all worth it in the end. At that point, you can simply sit back and enjoy the colorful sights in your garden or yard.
Growing up with a mom who filled her home (inside and out) with all sorts of plants, Lisa got her start in gardening at a young age. Living now on her own with a home and yard full of plants (including an indoor greenhouse), she shares all the gardening tips she’s gained over the years.