Introduction
There is a unique kind of magic that happens in late summer when dahlias take center stage in the garden. From the massive, pillow-like blooms of dinnerplate varieties to the intricate, geometric petals of pompons, these flowers offer a rewarding experience for any gardener. At Longfield Gardens, we believe that anyone can grow these stunning perennials with just a little bit of practical knowledge.
Taking care of your dahlia tubers is the key to enjoying a season full of vibrant color and ensuring your plants return even stronger next year. Whether you are just receiving your first shipment of tubers or you are looking for tips on winter storage, this guide covers everything you need to know. We will walk through the entire lifecycle of dahlia care, from arrival and planting to summer maintenance and winter storage.
Growing dahlias is an achievable and joyful hobby that rewards your efforts with armloads of fresh-cut flowers. By following a few simple steps for tuber health, you can create a professional-looking flower garden right in your own backyard.
Understanding Your Dahlia Tubers
Before we dive into the daily care of these plants, it helps to understand what a dahlia tuber actually is. You can think of a tuber as a specialized storage tank. It is a starchy root that holds all the energy and water the plant needs to send up its first sprouts in the spring.
While they might look like modest brown potatoes, each tuber contains the blueprint for a spectacular floral display. A healthy tuber should feel firm to the touch, much like a fresh vegetable from the grocery store. It is normal for them to have some dirt on them or look a bit shriveled, but they should never feel mushy or soft.
The Anatomy of a Tuber
To take great care of your dahlias, you need to recognize three main parts of the tuber: the body, the neck, and the eye. The body is the thick, fleshy part that stores energy. The neck is the narrow portion that connects the body to the main stem. Finally, the eye is the small growth bud where the new sprout will emerge.
The eye is located on the "crown," which is the area where the tuber meets the old stem. It looks like a tiny, light-colored bump, similar to the eye on a potato. Without an eye, a tuber cannot produce a plant, even if the rest of the tuber is perfectly healthy. Protecting the neck is also vital, as a broken neck can prevent nutrients from reaching the eye.
Quality and Variety
At Longfield Gardens, we ensure that every tuber we ship is true to variety and arrives in prime condition for planting. You might notice that different varieties have differently shaped tubers. For example, a large decorative dahlia like 'Thomas Edison' might have a very different tuber shape than a smaller border variety.
Regardless of the size or shape, the care requirements remain the same. A small tuber can produce a plant just as large and vigorous as a big one, provided it has a healthy eye and receives the right care. The tuber’s primary job is to get the plant started until it develops its own root system to draw nutrients from the soil.
What to Do When Your Tubers Arrive
When your order from Longfield Gardens arrives, the first step is to open the box immediately. While we pack our tubers carefully to maintain the right moisture levels during transit, they are living things that appreciate a bit of fresh air once they reach their destination.
If you aren't ready to plant right away because the weather is still too cold, you can keep them in their original packaging. Simply open the top of the bag to allow for better air circulation. This prevents moisture from building up inside the bag, which helps the tubers stay dormant and healthy.
Short-Term Storage Before Planting
The best place to store your tubers before they go into the ground is a cool, dark, and dry location. A basement, a cool closet, or an unheated garage that stays above freezing is ideal. You want to aim for temperatures between 40°F and 50°F.
Check on your tubers once a week. If they look very shriveled, you can give them a very light misting of water, but be careful not to make the packing material wet. If you see a little bit of green growth starting to emerge from the eyes, don't worry. This is a sign that the plant is ready to grow and is a perfectly natural part of its lifecycle.
The "Waking Up" Process
Some gardeners like to "wake up" their tubers a few weeks before planting. You can do this by moving them to a slightly warmer spot with a bit more light. This encourages the eyes to begin sprouting, which can give you a head start once they are moved into the garden.
If you live in a region with a short growing season, you can also pot your tubers up indoors about four weeks before your last frost date. Use a standard potting mix and a container with good drainage. This allows the dahlia to develop a root system and a few inches of growth in a protected environment before moving outdoors.
Key Takeaway: Pre-Planting Care
- Open shipping boxes immediately to let the tubers breathe.
- Store in a cool, dark, frost-free area until planting time.
- Keep the packing material slightly dry to prevent rot.
- Potting up indoors can provide a head start in cooler climates.
Selecting the Right Spot in Your Garden
Taking care of dahlia tubers starts with choosing the right home for them. Dahlias have two main requirements: lots of sunlight and excellent drainage. "Drainage" is simply a way of describing how quickly water moves through the soil. If water sits in a puddle for hours after a rain, that spot may be too wet for dahlias.
Dahlias love the sun. To get the most blooms and the strongest stems, pick a spot that gets at least six to eight hours of direct sunlight every day. In very hot climates, they can benefit from a little bit of afternoon shade to protect the delicate petals, but full sun is generally the best rule of thumb.
Preparing the Soil
Good soil care is tuber care. Dahlias are "heavy feeders," meaning they use a lot of nutrients to produce those big, beautiful flowers. Before you plant, it is helpful to mix some compost or well-rotted manure into the soil. This improves the soil structure and provides a slow-release source of food for the growing plants.
If you have heavy clay soil, you might consider planting your dahlias in raised beds. Raised beds allow you to control the soil quality and ensure that excess water drains away quickly. This protects the tubers from sitting in cold, wet soil, which is the most common cause of problems in the early spring.
Spacing and Layout
It is tempting to plant your dahlias close together to create a dense wall of color, but they need room to breathe. Proper spacing ensures good air circulation, which helps keep the foliage healthy and makes it easier for you to access the plants for cutting and maintenance.
Most standard dahlias should be spaced about 18 to 24 inches apart. Smaller border varieties can be planted a bit closer, around 12 to 15 inches apart. When you give each plant enough space, the tubers have plenty of room to expand underground throughout the summer, creating a larger clump for you to enjoy next year.
Planting Your Dahlia Tubers
The most important rule for planting dahlias is to wait for the right timing. It can be tempting to get them in the ground as soon as the sun comes out in early spring, but dahlias are tropical plants at heart. They do not like cold soil or frost.
Wait to plant until the soil has warmed up to about 60°F and all danger of frost has passed. A good indicator is when you are ready to plant your tomatoes or peppers—that is usually the perfect time for dahlias, too. Planting in warm soil helps the tubers start growing immediately, whereas cold soil can cause them to sit dormant and potentially rot.
How Deep to Plant
Dig a hole that is about 4 to 6 inches deep. Place the tuber horizontally at the bottom of the hole with the eye (or the sprout) facing upward. If you aren't sure where the eye is, don't worry—simply lay the tuber flat, and the plant will figure out which way is up.
Backfill the hole with soil, but do not pack it down too tightly. You want the soil to be firm enough to support the tuber but loose enough for the new sprout to push through easily. There is no need to add fertilizer directly into the hole at this stage; the tuber already has all the energy it needs to get started.
The No-Water Rule
One of the most common mistakes in dahlia care happens right after planting. Unless your soil is bone-dry, you should avoid watering your dahlias until you see the first green shoots emerging from the ground.
The tuber has enough stored moisture to begin the growing process. Adding extra water before the plant has roots to absorb it can lead to rot. Once the plant is a few inches tall and has developed leaves, you can begin a regular watering schedule. This simple trick is one of the best ways to ensure your dahlias get off to a healthy start.
What to Do Next: Planting Steps
- Wait for soil temperatures to reach 60°F before planting.
- Dig a hole 4-6 inches deep and lay the tuber flat.
- Ensure the eye is pointing up if it is visible.
- Avoid watering until the first green leaves appear above the soil.
Summer Maintenance for Tuber Health
Once your dahlias are up and growing, the focus shifts to keeping the plants strong and productive. Healthy green growth above the ground usually indicates that the tubers are doing well below the surface. During the summer, your main tasks are watering, feeding, and providing support.
As the plants grow, the original tuber you planted will begin to grow "feeder roots." It will also start producing new tubers that will form a large clump by the end of the season. Consistent care during the summer ensures that these new tubers are high-quality and full of energy for next year.
Watering Correctly
Dahlias prefer deep, consistent watering rather than frequent light sprinkles. A good rule of thumb is to provide about one inch of water per week, either through rain or manual watering. In very hot or windy weather, they may need a bit more.
When you water, try to direct the flow at the base of the plant rather than over the leaves. This keeps the foliage dry and helps prevent common issues like powdery mildew. Using a soaker hose or drip irrigation is an excellent way to keep the roots hydrated while keeping the rest of the plant dry.
Fertilizing for Success
To support all those blooms, dahlias appreciate a little extra food. Start fertilizing once the plants are about a foot tall. Use a balanced, all-purpose fertilizer or one with a slightly lower nitrogen count. Too much nitrogen can lead to lots of green leaves but very few flowers.
Apply fertilizer every three to four weeks through mid-summer. Stop fertilizing by late August or early September. This encourages the plant to stop putting energy into new growth and start focusing on toughening up the tubers for their winter dormancy.
The Power of Pinching
Pinching sounds like it might hurt the plant, but it is actually one of the best things you can do for a dahlia. When the plant is about 12 to 16 inches tall and has four sets of leaves, snip off the very top of the center stem.
This tells the plant to stop growing one tall, lanky stalk and instead branch out from the sides. The result is a bushier plant with more stems and, most importantly, many more flowers. A well-pinched dahlia is also sturdier and less likely to fall over in a summer storm.
Staking and Supporting Your Plants
Because dahlias can grow quite tall—some reaching four or five feet—they need a little help staying upright. The heavy blooms and lush foliage can act like a sail in the wind, which can put a lot of stress on the tuber and the main stem.
It is best to put your stakes in the ground at the time of planting. This prevents you from accidentally driving a stake through the tuber later in the season. You can use wooden stakes, bamboo poles, or even sturdy tomato cages.
Individual Staking
For a few plants, tying each one to a single stake is very effective. As the plant grows, use soft twine or garden ties to gently secure the main stem to the stake every 12 inches. Be sure to leave a little bit of wiggle room in the ties so the stem can thicken as it matures without being strangled.
The Corral Method
If you have a row of dahlias, the "corral" method is a great time-saver. Drive sturdy stakes into the ground at the corners and every few feet along the row. Then, wrap twine around the outside of the stakes at various heights to create a supportive fence that keeps the plants from leaning out into the path.
End-of-Season Care: Lifting Your Tubers
In most parts of the United States, dahlias are not "hardy," meaning the tubers will not survive if the ground freezes. If you live in USDA zones 8 or warmer, you may be able to leave your tubers in the ground with a thick layer of mulch. If you're not sure, our USDA hardiness zone map can help. However, for most of us, taking care of dahlia tubers in the winter means digging them up and storing them indoors.
The process of digging up tubers is called "lifting." It is a rewarding end-of-season task that allows you to see how much your single tuber has multiplied over the summer.
When to Dig
Timing is everything when it comes to lifting dahlias. You want to leave the tubers in the ground as long as possible so they can complete their lifecycle. Wait until after the first hard frost has turned the foliage black or brown.
Once the frost hits, the plant sends a signal to the tubers to go into dormancy. It is usually best to wait about a week after this frost before you start digging. This short waiting period helps the "skin" on the tubers toughen up, which makes them easier to store without shriveling.
How to Lift Safely
Start by cutting the stalks down to about 4 to 6 inches above the ground. Use a garden fork rather than a shovel if possible. A fork is less likely to slice through the tubers. Start digging about a foot away from the stem and gently loosen the soil all the way around the plant.
Slowly pry the clump of tubers upward. Do not pull on the stem, as it can break off and damage the crown where the eyes are located. Once the clump is out of the ground, gently shake off the excess soil. You will likely find a large cluster of tubers where you originally planted just one!
Cleaning and Drying
Use a gentle stream of water from a garden hose to wash away the remaining soil. This makes it easier to inspect the tubers for any signs of damage or soft spots. Once they are clean, find a cool, dry place out of direct sunlight to let them dry for a day or two.
Do not leave them out for too long, or they will begin to shrivel. You just want the surface to be dry to the touch before they go into storage. This is also a great time to label your tubers using a permanent marker. You can write the variety name directly on the skin of the tuber so you know exactly what you are planting next spring.
Key Takeaway: Lifting Tubers
- Wait for a hard frost to turn foliage brown before digging.
- Use a garden fork to gently lift the clump from a foot away.
- Wash off the soil and let the tubers dry for 24-48 hours.
- Label each tuber or clump with its variety name.
Storing Dahlias for the Winter
Successful winter storage is the final step in taking care of dahlia tubers. The goal is to keep them in a "Goldilocks" environment: not too cold, not too warm, not too wet, and not too dry.
The ideal temperature for storage is between 38°F and 45°F. If the temperature drops below freezing, the tubers will turn to mush. If it stays above 50°F, they may start to sprout too early or dry out completely. A cool basement or an insulated garage is often the best spot.
Choosing a Storage Medium
To keep the tubers from drying out, most gardeners pack them in a material that holds just a tiny bit of moisture. Popular choices include:
- Pine shavings: The kind used for animal bedding is inexpensive and works very well.
- Vermiculite: A mineral that helps regulate moisture levels.
- Peat moss: Another classic choice, though it can be a bit dusty.
Place a layer of your chosen material in a cardboard box or a plastic bin. Lay the tubers or clumps inside so they aren't touching each other, and then cover them completely with more shavings or vermiculite. If you use plastic bins, be sure to leave the lid slightly cracked or drill small holes in the sides to allow for some air exchange.
Monthly Check-ins
Taking care of dahlia tubers doesn't stop once they are in the box. Set a reminder on your calendar to check on them once a month during the winter. This allows you to catch any potential issues before they spread.
If a tuber feels mushy or looks rotten, remove it from the box immediately and throw it away so it doesn't affect the healthy ones. If the tubers look very shriveled and dry, you can lightly mist the packing material with a spray bottle. You don't want it to be wet, just slightly less dry.
Dividing Tubers for More Plants
One of the most exciting things about dahlias is that they multiply. One tuber planted in the spring can result in a clump of 5 to 10 tubers by the fall. You can divide these clumps to create even more plants for your garden or to share with friends.
Many gardeners prefer to divide their tubers in the spring rather than the fall. In the spring, the "eyes" begin to swell and turn pink or green, making them much easier to see. Remember, each division must have at least one healthy eye, an intact neck, and a tuber body to be successful.
Tools for Dividing
Use a clean, sharp pair of garden snips or a small knife to separate the tubers from the main clump. Be careful to cut through the crown so that the eye remains attached to the tuber. It takes a little practice, but once you get the hang of it, you will have more dahlias than you know what to do with!
If you make a cut that exposes the white "flesh" of the tuber, you can let it sit out for a few hours to "callus" over before planting. This creates a dry scab that protects the tuber from soil-borne bacteria.
Common Tuber Challenges
While dahlias are generally very easy to grow, you might encounter a few minor hurdles. Most of these are easily solved with the right approach.
Tubers Not Sprouting
If you've planted your tubers and nothing has happened after three or four weeks, don't panic. Some varieties are just "slow starters." As long as the soil is warm and you haven't overwatered, they are likely just taking their time. You can gently move a bit of soil away to check for growth, but be careful not to snap off any tender sprouts.
Slugs and Snails
In the early spring, when the sprouts are just an inch or two tall, slugs and snails can be a nuisance. They love the tender green growth. To protect your dahlias, you can use organic slug bait or simply keep the area around the plants clear of debris where slugs like to hide. Once the plants are about a foot tall, they are usually tough enough that slugs are no longer a concern.
Signs of Rot
If a plant suddenly wilts or the stem feels soft at the base, it may be a sign of tuber rot caused by too much water. The best way to handle this is to ensure your soil has good drainage before you plant. If you do lose a plant, don't be discouraged. Even expert gardeners lose a tuber now and then due to unexpected weather or soil conditions. Simply try a different spot next year or add more compost to improve your drainage.
Conclusion
Learning how to take care of dahlia tubers is a journey that brings more beauty to your garden every year. From the first moment you open your shipment from us to the quiet winter months when your tubers are resting, each step is a simple part of a rewarding process. By focusing on the basics—sunlight, drainage, and proper storage—you can enjoy these spectacular blooms season after season.
Gardening is about more than just the results; it is about the joy of watching something grow from a humble tuber into a floral masterpiece. We are here to support you with quality plants and the practical advice you need to succeed.
The best time to start planning your dahlia garden is right now. Browse our dahlia collections and find the colors and shapes that inspire you.
Decorative dahlias are a great place to start, and we look forward to helping you grow your most beautiful garden yet!
Final Thoughts on Dahlia Care
- Start with high-quality tubers from a trusted source.
- Respect the weather; wait for warmth before planting.
- Focus on deep watering and consistent support during the summer.
- Store tubers in a cool, dry place to ensure they return next year.
FAQ
How long can dahlia tubers stay out of the ground?
Dahlia tubers can stay out of the ground for several months if they are kept in a cool, dark place. Most gardeners lift them in late autumn and store them until the following spring, which is usually a period of four to six months. The key is to keep them dormant and prevent them from drying out completely during this time.
Can I leave my dahlia tubers in the ground all winter?
Whether you can leave tubers in the ground depends on your USDA hardiness zone. In zones 8 and warmer, dahlias can often survive the winter if the soil is well-drained and you apply a thick layer of mulch to protect them from light frosts. In zones 7 and colder, the ground usually freezes deep enough to kill the tubers, so they must be lifted and stored indoors.
Do dahlia tubers need to be washed before storage?
Washing dahlia tubers is not strictly necessary, but it is highly recommended. Cleaning off the soil makes it much easier to see the "eyes" and to check for signs of rot or damage. It also helps prevent soil-borne diseases from being carried into your storage containers, which keeps your collection healthier throughout the winter.
Why are my dahlia tubers shriveling in storage?
Shriveling usually means the humidity in your storage area is too low or your packing material is too dry. Dahlia tubers are mostly water, and they naturally lose some moisture over time. If they look like prunes, you can lightly mist the shavings or peat moss with water to help them rehydrate, but be careful not to make them soggy.
