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Past Articles Library | Tips for Growing Dahlias

When it comes to landscape design, there are two schools of thought. One is to plan your garden space so that you have different plants that bloom at different times so that you have something always flowering during the growing season. The second comes from the idea of planting something that will continuously bloom all throughout the growing season with little effort. The latter approach is the one that I prescribe to. It saves time and money but utilizing this technique also keeps your landscape looking the same from year to year but the choice is yours.

While you can change up your landscape design with dahlias, I am going to cover this lovely perennial as one that will be part of your landscape for years.

Believe it or not, there is a dahlia for you and your landscape needs. There are 42 species and many more cultivators that contain a rainbow of colors. The blooms can range from single to double flowers that can be as large as a dinner plate and as small as two inches. The foliage also provides you another layer of interest when it comes to your landscape design with unique texture but regardless of the different textures the leaves are always dark green.

Before you start to plant your first dahlias, keep in mind that they can remain in the ground in USDA Plant Hardiness Zones 7 through 10. If you do not mind a bit of work, you can really grow them anywhere as long as the growing requirements are met. In this case, you will need to dig up the tubers in the fall and store them. When the spring temperature warms up along with the soil, you will just need to replant them for the current year’s enjoyment.

Beyond plant hardiness zone requirements, dahlias require some room. Their mature height, depending on the type, can range from 1 to 6 feet and have a mature spread of 1 to 3 feet. They also require full sun and a soil that is well draining along with full of organic material. If you feel that your soil is not rich enough in organic matter, mix in well-seasoned compost as you prepare the garden space.

Once the garden space has been prepared, the next step is to mark the space with powdered milk according the space requirement for the species/cultivator you are planting. Next, pull out some tomato cages. Yes, I said tomato cages. At this point, you may be scratching your head. The reason for this is two-fold. First, the tomato cage will provide support for the dahlia. The second purpose is that the wires that make up the tomato cage provide you a surface by which to hang a plant tag that contains plant information, such as date, type, etc.

When using the tomato cage support system, make sure to push the legs of the cage firmly in the ground. Once that is done, dig the hole. This may seem a bit backwards but the point is to make sure that the tuber/plant is in the center of the support. Trying to work the cage around where you planted the tuber is too hard and you end up with some dahlias growing outside the tomato cage.

Now to answer the question about the hole for dahlias, this needs to be about 3 inches in depth. Once you have the hole dug, the next step is to look at the tuber. You will notice that there is an “eye” on the tuber. This “eye” or new bud needs to be facing up in the hole. After you have the tuber correctly situated in the hole, fill in with the removed soil carefully since many gardeners have knocked off the new bud on their tuber in the filling in step.

 Before moving on to the next hole and repeating the process, take the time to write your plant tag and attach to the tomato cage.

At this point, you may feel that you need to water in the tubers. Well, in this case, do not. During this time of the year, which in many areas mean the month of May, there should be enough moisture in the soil by which watering is not required.

In one to two weeks, you should see some little leaves begin to break ground.

When the leaves are 8 to 12 inches in height, pinch off the center stem. Why, you may wonder. The reason for this is that with a single stem the dahlia will produce one bloom. If you have more than one stem then you have several blooms. To encourage this type of growth, one must pinch the center stem so that it stops growing and the plant sends up other stems.

As your plant continues to grow, you will need to train your dahlia to stay inside the tomato cage. The easiest way of doing that is to wrap some garden twine around the outside of the cage. This not only aids in keeping the plant on the inside but it also adds another layer of support.

To get the most out of your dahlias, you will need to do two things. First, to encourage the largest blooms possible for your species/cultivator, you will need to pinch off the pea-sized buds that are on each side of the center flower. The second task you will need to perform is deadheading. This process called deadheading simply means that you remove any spent flowers. When it comes to the dahlia, this not only keeps the plant looking neat but also encourages the plant to produce more flowers.

If you added well-seasoned compost to your soil before planting your tubers, you will not need to fertilize but if you did not do this step you may need to feed your dahlias. The best fertilizer is bone meal. This should be done from June to October. When using bonemeal, always wear a mask to prevent you from inhaling the dust.

Love dahlias but do not have a landscape or space in your design for this perennial, do not worry low-growing and dwarf types grow well in containers. When using this approach though, there are a few things you need to keep in mind. First and foremost, while the planting medium is important the most critical aspect of this plant is that moisture can drain away from the tuber. In doing so, you need to make sure that the container has a drainage hole in bottom.

Once you have the proper container selected, clean and sterilize the pot. After it has dried, place drainage material in the bottom and fill the container with a well-draining soil that is high in organic material. Next, dig a shallow hole by which you will place your tuber. Unlike planting in the ground, you will barely cover the tuber. As the leaves and stem emerge, you can add more soil to cover the tuber more completely.

When it comes to plant diseases, if the environment is too wet you can expect to see fungal leaf spot, powdery mildew, and/or dahlia mosaic virus. Pests, on the other hand, can include aphids, spider mites, stem borers, and assorted caterpillars.


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Rotate Certain Crops

Avoid planting potatoes and tomatoes where they grew last year. They carry the same diseases, so it's best to rotate them.

You'll have much healthier plants, and more successful crops.

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