Lazy Girl’s Guide to Growing Dahlias

Dahlia flowers come in a rainbow of gorgeous colors, alluring gardeners and flower lovers alike with their beautiful blooms. They’re perfect for everything from wedding bouquets to everyday cut flower arrangements, and have even been used for their medicinal properties.

As a busy gardener, I love any sort of flower that gives back mounds of gorgeous flowers without a ton of work – and dahlias fit the bill! (Looking for more easy-to-grow options? Here are 19 of my favorite easy flowers!) In this guide, we’ll go over the important details you need to know about growing your own dahlia plants.

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What Are Dahlia Tubers?

First, let’s talk about dahlia tubers. When you go to grow dahlias, you’ll probably hear about tubers more than dahlia seeds. While you can plant dahlias from seed, many gardeners prefer to use tubers. 

Dahlia tubers are a starchy root from the plant that looks somewhat like a potato. Dahlia tubers come in all shapes and sizes, and can be anywhere from 1″ to 10″ long. Bigger tubers don’t necessarily produce larger plants. In fact, the size of the tuber doesn’t matter nearly as much as its health. In addition to being firm and rot free, each tuber should have at least one “eye” on it. 

Planting dahlia tubers is more reliable than starting from seed, and usually produces more flowers in the first year. The other benefit of tubers is that they pretty much produce a clone of the parent plant, where with seeds, the end result is a little bit more of a surprise. Tubers are usually more expensive than seeds, but they can produce better flowering plants that are also more reliable. 

Checking Your Tubers Before Planting 

Before you start planting, it’s a good idea to check your tubers over for rot. Good quality tubers will be firm and must have at least one eye each. If you’re unsure about the quality, either discard that tuber or mark it to keep an eye on it. 

Where to Purchase Dahlia Tubers and Seeds

Although you can get dahlias at most big box stores, I recommend shopping online or at your local garden center to find higher-quality tubers (or seeds). This will give you a higher success rate and less chance of disease. No matter which route you go, comb through your tubers before planting and remove any that don’t look healthy. 

Some of my favorite places to buy tubers and seeds include Kelly Welk from Ciderpress Lane and Flower People.

Types of Dahlias

​Dahlias come in all sorts of colors, shapes, and sizes! Here are some favorite types of dahlias you can look for.

• Single-flowered dahlias. These are daisy-like flowers that have a single ring of petals around a center disk.
• Decorative dahlias. These lush flowers have double blooms and no disks. They’re excellent for bouquets.
• Ball dahlias. ​Similar to decorative dahlias, ball dahlias are slightly larger, typically measuring about 3″-4″ across. 
• Cactus dahlias. ​These breathtaking flowers have pointy, ray florets.
• Double orchid dahlias. ​These flowers have fully double blooms with no disk and triangular centers. They look similar to orchids. 

The type and variety of dahlias you choose depends on your personal preference and how you want to use them. For example, do you want to make bouquets, or focus on showy garden plants? Do you want shorter plants for a border, or taller dahlias throughout your garden? Browse the options and choose one that stands out to you! 

When to Plant Dahlias

Plant dahlias in the ground in the mid to late spring, after all risk of frost has passed. For most zones, this is around late April or sometime in May. 

Some gardeners like to give dahlias a head start by planting indoors and keeping them under grow lights. You can start your dahlia tubers indoors about 6 weeks before your zone’s last frost date.

Dahlias have a long bloom time! Healthy plants will bloom from mid summer until the first frosts arrive.

Preparing Your Soil and Planting Your Dahlias

After all danger of frost has passed and your soil is at least 60°F, it’s planting time!

Choose a location that gets full sun and good drainage. Dahlias do not like to be soaking wet! In hot climates, you may need to provide some afternoon shade during the warm summer months. 

If you have the option of using raised garden beds with well-drained soil, this often provides the best results. However, you can definitely still grow beautiful flowers in an in-ground garden. You’ll just need to be a bit more vigilant to make sure your plants don’t receive too much water, especially in the early stages.

For healthy dahlia plants, make sure you have fertile soil. It’s a good idea to give your plants a boost by adding some compost, manure, or other organic matter to the top 2″ or so inches of your soil.

Once your soil is ready, it’s time to start planting dahlias! 

First, dig some holes that are 4″-6″ inches deep and 12″-18″ apart. Place a single tuber in each hole, with the eye facing up. Then, cover it up with soil. Don’t water them in. Then, don’t water until you see those first green shoots begin to pop up. 

After you plant your tubers, you can expect to see the beginnings of your dahlia plant start to pop out of the soil in about 2-4 weeks. Depending on the variety, you’ll typically see blooms around 90-100 days after planting. 

How to Water Dahlias

Dahlias need consistent water, but remember, they don’t like to be soaked! Too much water can easily rot your tubers and spoil your young plants. Keep in mind that you shouldn’t water until you begin to see some green growth coming out of the soil (you should see this within a month of planting your tubers).

A drip irrigation system is one of the best options for keeping your dahlias happy. 

For best results, water at the base of the plant in the early morning. This will allow your plants enough time to soak up the water before evening, which helps to prevent fungal issues.

Dahlia Care

Once the warm temperatures hit, you may be surprised at how quickly your dahlias grow! Keep watering constantly when the soil is dry. A couple of times per week may be sufficient depending on your soil and climate. 

When your dahlias reach about 12″ tall, give your plants a hard pinch or snip on the central stalk about 3″-4″ down (above a set of leaves is the best spot!). This will help the plant to direct its energy toward the lower branches, producing bushy plants with lots of blooms. 

As your plants begin to grow, you’ll want to support them with stakes to keep them upright and protect against strong winds. Metal or wooden stakes work well. Just position the stake near the plant and use some twine to tie the plant to the stake. You can also use tomato cages if you have just a few plants.

If you’re growing lots of dahlias, you may find it easier to use the corral method. This involves placing stakes every few feet down a row of plants, then winding twine through them to form a sort of “fence” that the dahlias can grow up through and use for support. 

Dahlias typically bloom starting in the mid summer, and they keep going throughout autumn, until hard frosts arrive. When your dahlias are blooming and open, harvest them in the early morning or in the evening. Dahlias tend to have a vase life of about 3-7 days. 

Overwintering Your Dahlia Tubers

After the hard frosts of fall, it’s time to switch gears to winter care. At the end of the growing season, you can dig up your tubers to save them for next year. Dahlias are also easy to divide. You can do this in the springtime, giving you even more dahlia tubers to plant or share.

Once your dahlias have turned black, cut them back, lift the plant up, and shake off the tubers. Then, store them in a cool, dark place where they have good airflow for the winter months. A basement or garage works well. 

Dahlias store well in crates, but a cardboard box can work, too. It’s a good idea to check on them every few weeks. This gives you a chance to turn them and pull out any rotten ones. 

In the springtime, you can divide up your dahlia tubers by using shears or a sharp knife to cut the tubers into pieces. Each piece needs to have an eye, body, neck, and crown in order to be viable. If you notice any tubers that are moist or show signs of disease, it’s best to just toss them.

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xoxo,

Kelly

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