How to Look After Dahlia Tubers

Table of Contents

1. Introduction
2. Getting to Know Your Dahlia Tubers
3. What to Do When Your Tubers Arrive
4. Timing Your Planting for Success
5. Selecting the Right Spot
6. How to Plant Your Tubers
7. Caring for Growing Dahlias
8. Harvesting and Deadheading
9. Preparing for Winter
10. Winter Storage Techniques
11. Multiplying Your Collection
12. Troubleshooting Common Issues
13. Conclusion
14. FAQ

Introduction

The arrival of dahlia season is one of the most exciting times for any gardener. There is a unique thrill in watching those first green shoots emerge from the soil, knowing that in just a few months, your garden will be filled with a spectacular display of color and form. Whether you are captivated by the massive, ruffled petals of a dinnerplate dahlia or the intricate, geometric patterns of a pompon variety, these plants bring a level of drama and joy that few other flowers can match.

At Longfield Gardens, we want to help you experience that success firsthand by simplifying the process of caring for your plants and exploring our PomPon Dahlia collection. While dahlias have a reputation for being high-maintenance, they are actually quite straightforward once you understand a few basic principles. This guide is designed for home gardeners who want to know exactly how to look after dahlia tubers from the moment they arrive in the mail until they are tucked away for their winter nap. If you want to explore even more choices, our dahlia collection is a great place to start. By following a few simple steps, you can ensure your dahlias grow strong, bloom prolifically, and return to your garden year after year.

Getting to Know Your Dahlia Tubers

Before you can provide the best care, it helps to understand what a dahlia tuber actually is. You can think of a tuber as a specialized underground storage unit. Much like a potato, the tuber holds all the energy, nutrients, and moisture the plant needs to get started in the spring. For a closer look at tuber anatomy, see Dahlia Tubers: What You Need to Know.

When you look at a dahlia tuber, you are looking for three main parts: the body, the neck, and the crown. The body is the fat, starchy part that stores the food. The neck is the narrow portion that connects the body to the crown. The crown is the area where the tuber meets the old stem of the previous year’s plant. This is the most important area because it is where the "eyes" are located. An eye is a small, slightly raised bump that will eventually sprout into a new plant.

It is helpful to remember that tubers come in all shapes and sizes. Some varieties produce long, slender tubers, while others produce short, round ones. The size of the tuber does not dictate the size of the flower. A tiny tuber the size of a AA battery can grow into a massive five-foot plant just as easily as a large one. As long as the tuber is firm and has a viable eye, it has everything it needs to thrive.

What to Do When Your Tubers Arrive

Receiving a package of dormant tubers is the first step toward a beautiful summer garden. When your order from us arrives, it is best to open the box immediately. This allows the tubers to breathe and helps you check their condition. For shipping timing and delivery details, see our Shipping Information.

If it is still too early to plant in your area, you can simply keep the tubers in the bags they arrived in. Most tubers are packed in a dry material like peat moss or wood shavings to help regulate moisture. Keep the bags in a cool, dark, and dry location, such as a basement or an unheated garage. The ideal temperature for storage is between 40°F and 50°F. It is important to avoid locations where the tubers might freeze, as freezing temperatures will damage the internal cells of the tuber.

If you notice a small amount of surface mold or condensation when you first open the bag, do not worry. This is quite common during transit. Simply leave the bag open for a day or two to let the excess moisture evaporate. If the tubers feel a bit soft or shriveled, they are likely just thirsty. You can give them a very light misting of water, but be careful not to make them wet, as "wet" can lead to "soft."

What to do next:

• Open your shipping box immediately upon delivery.
• Ensure the tubers are firm and the necks are intact.
• Store in a cool, dark place (40-50°F) until planting time.
• Keep the bags slightly open to allow for air circulation.

Timing Your Planting for Success

One of the most important rules for looking after dahlia tubers is to be patient with the weather. Dahlias are native to the warm climates of Mexico and Central America, which means they love heat and are very sensitive to cold. If you are unsure about your region, the Hardiness Zone Map can help you plan.

The best time to plant is when the soil has warmed up to about 60°F and the danger of frost has completely passed. A good rule of thumb is to plant your dahlias at the same time you would plant tomatoes or peppers in your vegetable garden. If you plant too early in cold, wet soil, the tubers will simply sit dormant, which increases the chance of rot. Waiting for the soil to warm up ensures that the tuber "wakes up" and starts growing immediately.

If you live in a region with a short growing season and want to get a head start, you can "start" your tubers indoors about four to six weeks before the last frost. Place the tubers in pots with slightly damp potting soil and keep them in a warm, bright spot. By the time the weather is warm enough to move them outside, you will already have established plants ready to take off.

Selecting the Right Spot

Dahlias are sun-worshippers. To get the most blooms and the strongest stems, you should choose a spot that receives at least six to eight hours of direct sunlight every day. In very hot climates, dahlias appreciate a little bit of afternoon shade to protect them from the most intense heat, but in most of the United States, full sun is the way to go. If you want to browse more forms and combinations, the Dahlia Collections page is a helpful place to look.

In addition to sun, dahlias need excellent drainage. "Drainage" is simply a measure of how quickly water moves through the soil. If your soil stays soggy for a long time after a rain, the tubers may struggle. If you have heavy clay soil, you can improve the drainage by adding organic matter like compost. Alternatively, planting in raised beds is a fantastic way to ensure your dahlia tubers stay happy and dry.

How to Plant Your Tubers

Once the soil is warm and the site is ready, planting is a quick and rewarding task. Follow these simple steps for the best results. For the biggest showy forms, browse our Big Blooms.

1. Dig the hole: Dig a hole about 4 to 6 inches deep.
2. Add support: If you are growing tall varieties, it is a great idea to place your stake in the hole before you put the tuber in. This prevents you from accidentally poking a hole through the tuber later in the season.
3. Position the tuber: Lay the tuber horizontally at the bottom of the hole. If you can see the eye or a sprout, point it toward the stake or upward.
4. Cover with soil: Fill the hole back in with soil. You do not need to pack it down firmly; a light touch is better for the emerging shoots.
5. Space them out: Give your plants room to breathe. Space smaller varieties about 12 to 18 inches apart, and larger varieties (like dinnerplate dahlias) about 2 feet apart.

The "No Water" Rule

This is perhaps the most important tip for early-season dahlia care. After you plant your tuber, do not water it until you see the first green shoots poking through the soil. There is usually enough natural moisture in the soil to get the tuber started. Watering a dormant tuber can lead to rot before the plant has a chance to develop roots. Once the plant is a few inches tall and has several sets of leaves, you can begin a regular watering schedule.

Key Takeaway: Patience is a virtue when planting dahlias. Waiting for warm soil and holding back on the watering can until shoots appear are the two easiest ways to ensure a healthy start.

Caring for Growing Dahlias

As your dahlias begin to grow, they will need a little bit of attention to help them reach their full potential. Looking after the plants during the summer months is mostly about providing consistent support and nutrition.

Watering Correctly

Dahlias are thirsty plants once they are actively growing and blooming. Instead of a light sprinkle every day, it is better to provide a deep watering two or three times a week. This encourages the roots to grow deeper into the soil, making the plant more resilient during hot spells.

Try to apply water at the base of the plant rather than over the leaves. Keeping the foliage dry helps prevent common issues like powdery mildew. If you have a large collection, a soaker hose or drip irrigation system can be a huge time-saver and is very effective for getting water right where the roots need it.

Feeding Your Plants

Because dahlias grow so much in a single season, they are "heavy feeders." This means they use a lot of nutrients from the soil. We recommend using a balanced fertilizer during the early stages of growth. Once the plants begin to form flower buds, you can switch to a fertilizer that is lower in nitrogen and higher in phosphorus and potassium (similar to a tomato or rose fertilizer). This encourages the plant to focus its energy on producing flowers rather than just more green leaves.

The Magic of Pinching

If you want a dahlia plant that is bushy and covered in flowers rather than one single tall stem, you should "pinch" your plants. When the plant is about 12 to 16 inches tall and has four sets of leaves, use your fingers or clean snips to remove the very top of the center stem. For more practical support, see How to Pinch and Stake Dahlias.

It might feel a little bit difficult to cut back a healthy plant, but this simple action tells the plant to stop growing upward and start branching out. This results in a sturdier plant and significantly more blooms throughout the season.

Providing Support

Many dahlias grow to be four or five feet tall, and their heavy flower heads can become quite weighted, especially after a rain. Staking is essential to keep them from flopping over. You can use wooden stakes, bamboo poles, or even sturdy tomato cages. As the plant grows, gently tie the stems to the support using soft twine or garden tape. Loop the twine loosely so you don't constrict the stem as it thickens.

Harvesting and Deadheading

One of the best ways to look after your dahlias is actually to cut the flowers! Dahlias are incredibly prolific, and the more you cut them, the more they will bloom. For more growing basics, see All About Dahlias.

Cutting for Bouquets

When cutting dahlias for the house, look for flowers that are almost fully open but still have firm petals in the center. Unlike roses or lilies, dahlias do not open much after they are cut. Harvest your blooms in the cool of the morning or evening and place the stems immediately into a bucket of clean, lukewarm water. This helps the flowers stay fresh for as long as possible.

Deadheading for More Blooms

If you prefer to leave the flowers in the garden, you should still practice "deadheading." This is the process of removing flowers as they begin to fade. If you leave the old flowers on the plant, it will start to produce seeds, which signals the plant to stop blooming. By removing the faded flowers, you encourage the plant to keep producing new buds all the way until the first frost.

When deadheading, it can sometimes be tricky to tell the difference between a new bud and a spent flower. New buds are usually round and firm, while spent flowers are more pointed or triangular. When you remove a faded flower, cut the stem back to the next set of leaves to keep the plant looking tidy.

What to do next:

• Pinch the center stem when the plant is 12 inches tall.
• Stake tall varieties early to prevent storm damage.
• Water deeply twice a week at the base of the plant.
• Cut flowers often to encourage more blooms.

Preparing for Winter

In most parts of the United States, dahlia tubers cannot survive the winter in the ground. Because they are tender perennials, they need to be "lifted" and stored indoors once the cold weather arrives. For a step-by-step storage walkthrough, see How to Store Dahlia Bulbs Over Winter.

The First Frost

You do not need to rush to dig up your dahlias at the first sign of autumn. In fact, it is better to wait until a killing frost has blackened the foliage. This frost tells the plant that it is time to go dormant. After the foliage turns brown or black, cut the stems back to about 4 to 6 inches above the ground.

Many gardeners like to wait about a week after the frost before digging. This short waiting period allows the tubers to "cure" slightly in the ground, which can make them more resilient during winter storage. However, you should make sure to dig them up before the ground actually freezes solid.

Lifting the Tubers

To lift the tubers, use a garden fork or a shovel to gently loosen the soil in a wide circle around the plant. You want to avoid piercing the tubers, so start digging about a foot away from the stem. Gently lift the entire clump out of the ground.

Shake off the excess soil and use your hose to wash the tubers clean. This makes it easier to inspect them for any damage. Once they are clean, let them dry in a shady, frost-free spot (like a garage or porch) for a day or two. This allows the outer skin to toughen up before they go into storage.

Winter Storage Techniques

The goal of winter storage is to keep the tubers dormant, cool, and just slightly moist so they do not completely dry out. There are several popular methods for looking after dahlia tubers over the winter, and the one you choose often depends on what supplies you have on hand.

Storage Media Method

The most common way to store tubers is to place them in a container filled with a packing material.

• Containers: You can use cardboard boxes, plastic bins (with the lids left slightly ajar), or even paper bags.
• Packing Material: Peat moss, vermiculite, coarse sand, or cedar wood shavings (like the kind used for pet bedding) all work well.
• The Process: Place a layer of material in the bottom of the box, lay the tubers in, and cover them completely with more material. This helps maintain a stable level of humidity around the tubers.

The Plastic Wrap Method

Some gardeners have great success by wrapping individual tubers in plastic kitchen wrap. This method involves dividing the clumps in the fall, cleaning and drying the individual tubers, and then wrapping them tightly. This creates a mini-greenhouse environment for each tuber and prevents moisture loss.

Where to Store

Regardless of the method, the storage location is the most important factor. You need a spot that stays consistently between 40°F and 50°F. A root cellar, a cool basement, or a crawl space is usually ideal. If the storage area is too warm, the tubers may start to sprout or shrivel. If it is too cold and they freeze, they will turn to mush.

Checking your tubers once a month during the winter is a great habit. If you see any soft spots or rot, remove the affected tuber immediately to prevent it from spreading. If the tubers look very shriveled, you can lightly mist the packing material with a bit of water.

Multiplying Your Collection

One of the most rewarding aspects of learning how to look after dahlia tubers is that they multiply! A single tuber planted in the spring will grow into a large clump of five to ten tubers by the fall. This means you can easily expand your garden or share the joy of dahlias with friends and neighbors. Our Dahlia Collections page makes it easy to find new favorites.

You can divide these clumps either in the fall after digging or in the spring before planting. If you are a beginner, many gardeners find it easier to divide in the spring because the "eyes" are more visible as they begin to swell. To divide, use a sharp, clean knife or garden snips to separate the tubers from the main stem. Remember the golden rule of dividing: each individual tuber must have a piece of the crown and at least one visible eye to grow into a new plant.

Troubleshooting Common Issues

While dahlias are generally healthy, you might encounter a few minor hurdles. The key to successful troubleshooting is to keep it simple.

• No Sprouts: If your tuber hasn't sprouted after three or four weeks, check the soil temperature. If it's too cold, they simply need more time. Also, ensure you haven't been overwatering the spot.
• Holes in Leaves: This is often the work of slugs or earwigs, especially when the plants are small. You can use simple barriers or organic baits to protect your young plants until they are large enough to withstand a little nibbling.
• Yellow Leaves: If the lower leaves are turning yellow, the plant might be getting too much water or not enough nutrients. Check the drainage and consider a light feeding.
• Powdery Mildew: This looks like a white dusting on the leaves. It usually happens in late summer when the air is humid. Improving air circulation by spacing plants properly and watering at the base can prevent this.

Conclusion

Caring for dahlias is a journey that follows the rhythm of the seasons. From the quiet anticipation of spring planting to the vibrant explosion of summer color and the careful storage of winter, each step is a rewarding part of the gardening experience. We at Longfield Gardens believe that anyone can grow these magnificent flowers with just a little bit of knowledge and a few simple tools. To shop our Dahlia Best Sellers, explore the collection.

By focusing on the basics—warm soil, proper support, and careful winter storage—you are setting yourself up for a garden that is the envy of the neighborhood. The effort you put into looking after your tubers is returned ten-fold in the form of armloads of beautiful, fresh-cut flowers.

• Wait for the warmth: Don't plant until the soil is 60°F and frost is gone.
• Hold the water: Avoid watering newly planted tubers until they sprout.
• Pinch for success: Snip the tops of 12-inch plants to get more blooms.
• Store with care: Keep lifted tubers cool (40-50°F) and slightly moist through winter.

Whether you are growing a single dahlia in a sunny pot or a whole field for cutting, the process is an invitation to slow down and enjoy the natural beauty of the garden. We are honored to be a part of your gardening journey and stand behind the quality of every tuber we ship.

FAQ

How do I know if my dahlia tuber is still alive?

A healthy dahlia tuber should feel firm to the touch, similar to a fresh potato. If the tuber is slightly shriveled but still firm, it is likely just dormant and will rehydrate once planted. However, if the tuber is mushy, smells bad, or feels completely hollow and dry like a cracker, it is no longer viable and should be discarded.

Can I leave my dahlia tubers in the ground over winter?

This depends on your USDA hardiness zone. If you live in Zone 8 or warmer, you can often leave dahlias in the ground if the soil is well-drained. Many gardeners in these areas apply a thick layer of mulch to protect the tubers from occasional cold snaps. In Zone 7 and colder, the ground usually freezes deep enough to kill the tubers, so lifting them is highly recommended. If you're not sure where you fall, the Hardiness Zone Map can help.

Why did my dahlia grow lots of leaves but no flowers?

This is usually caused by too much nitrogen in the soil. Nitrogen encourages lush, green foliage but can inhibit flower production. To encourage blooms, switch to a fertilizer higher in phosphorus and potassium. Also, ensure your dahlias are getting at least six to eight hours of direct sunlight, as too much shade can also lead to fewer flowers.

Do I have to divide my dahlia clumps every year?

You do not have to divide them every year, but it is a good idea to do so every two or three years. If the clump gets too large, the tubers in the center can become crowded, which may lead to smaller flowers or poor air circulation. Dividing the clumps keeps the plants vigorous and gives you more tubers to plant elsewhere.