Introduction
There is nothing quite like the excitement of seeing the first dahlia buds open in mid-summer. These spectacular flowers, known for their incredible variety of colors and intricate shapes, are a highlight for any home gardener. Whether you are holding your very first shipment of tubers or looking for ways to preserve your favorite varieties for next year, knowing exactly what to do with dahlia bulbs is the key to a vibrant, blooming yard.
At Longfield Gardens, we want to make sure your experience with these summer-blooming favorites is as rewarding as possible. Dahlias are remarkably resilient plants that offer an abundance of cut flowers from July all the way until the first frost. While they may seem a bit more involved than a typical tulip or daffodil, the process is straightforward when broken down into simple, seasonal steps.
This guide will walk you through the entire lifecycle of a dahlia, from the moment your package arrives to the final steps of winter storage. We will cover the best practices for planting, the secrets to getting more blooms all summer long, and how to safely overwinter your tubers so you can enjoy them year after year.
By focusing on a few essential basics—like timing, drainage, and proper storage—you can enjoy a professional-level flower garden right in your own backyard.
What to Do When Your Dahlia Bulbs Arrive
When your order from Longfield Gardens arrives, the first thing to do is open the box immediately. While our tubers are packed carefully to stay healthy during transit, they are living plants that appreciate fresh air. If you aren't ready to plant them because the weather is still too cold, a few simple steps will keep them in peak condition.
Inspect and Store
Take the tubers out of the shipping box and check them over. Healthy dahlia tubers (which are technically tuberous roots, though often called bulbs) should feel firm, much like a potato. It is normal for them to have some loose skin or even a bit of surface dust. If you see a small sprout beginning to emerge from the "eye" or the neck of the tuber, that is a great sign! It means the plant is ready to grow.
If you need to wait more than a few days to plant, store the tubers in a cool, dry, and dark place. A garage or a basement that stays between 40°F and 50°F is ideal. Keep them in the wood shavings or breathable bags they arrived in to help maintain a consistent moisture level. Avoid the refrigerator, as it is often too humid and cold, and stay away from uninsulated sheds where the temperature might drop below freezing.
Preparing for Planting
A common question for beginners is whether to soak dahlia tubers before planting. While some gardeners like to "pre-sprout" their dahlias in pots indoors to get a head start on the season, soaking the tubers in water is generally unnecessary and can actually lead to rot if they stay submerged too long. If the tubers look slightly shriveled, you can place them in a tray of lightly dampened potting soil for a few days to plump them up before they go into the ground.
What to do next: Unboxing
- Open your package immediately upon delivery.
- Check tubers for firmness.
- Store in a cool, dark spot if the ground is still cold.
- Keep tubers in their original packing material to prevent drying out.
Planting Your Dahlias for Success
Getting your dahlias off to a strong start depends more on timing than any special gardening tricks. Because dahlias are native to the warm climates of Mexico and Central America, they have no tolerance for frost and prefer soil that has had a chance to warm up in the spring sun.
Wait for the Right Temperature
The biggest secret to dahlia success is patience. It is tempting to get them in the ground on the first sunny day of April, but dahlia tubers planted in cold, wet soil are prone to rotting before they ever sprout. We recommend waiting until the soil temperature reaches about 60°F. A good rule of thumb for most regions is to plant your dahlias at the same time you would plant tomatoes or peppers. Ensure all danger of frost has passed in your specific hardiness zone.
Choose the Perfect Spot
Dahlias are sun-worshippers. To get those large, dinnerplate-sized blooms and sturdy stems, they need at least six to eight hours of direct sunlight every day. If they are planted in too much shade, the plants will become "leggy" as they stretch for the light, and they will produce far fewer flowers.
Drainage is the other non-negotiable factor. Dahlias need "well-draining soil," which simply means the water should move through the soil quickly rather than sitting in puddles. If your garden has heavy clay soil, you can improve the drainage by adding organic matter like compost or planting in raised beds.
Depth and Spacing
When you are ready to plant, dig a hole about 4 to 6 inches deep. Lay the tuber horizontally in the hole with any visible sprouts or "eyes" pointing upward. If you are planting multiple dahlias, give them plenty of room to breathe.
- Large varieties (like 'Cafe au Lait' or 'Kelvin Floodlight') should be spaced about 18 to 24 inches apart.
- Smaller border dahlias can be spaced 12 inches apart.
Proper spacing ensures good air circulation, which helps keep the foliage healthy and prevents common garden issues like powdery mildew later in the summer.
The First Watering Rule
Here is a counter-intuitive tip: do not water your dahlias immediately after planting. The tuber has enough stored energy and moisture to start growing on its own. Adding too much water before the plant has developed a root system can cause the tuber to rot. Wait until you see the first green sprouts poking through the soil before you begin a regular watering schedule.
Key Takeaway: Planting Basics "The best way to ensure dahlia success is to wait for warm soil and a sunny spot. Once you see green growth, you can begin regular care, but let the tuber do the initial work in the warm, dry earth first."
Caring for Dahlias During the Growing Season
Once your dahlias have sprouted and are about 12 inches tall, they enter a period of rapid growth. This is the time to transition from "planting mode" to "maintenance mode." With a few simple tasks, you can transform a single stem into a bushy, flower-filled masterpiece.
To Pinch or Not to Pinch
If you want more flowers, you should "pinch" your dahlias. When the plant is about 12 to 16 inches tall and has four sets of leaves, use your fingers or a clean pair of snips to remove the very top of the center stem. This might feel like you are hurting the plant, but it actually signals the dahlia to send its energy to the side buds. This results in a bushier plant with many more flowering stems rather than one tall, lanky stalk.
Staking and Support
Dahlias are prolific bloomers, and the weight of the flowers—especially after a rainstorm—can be heavy enough to snap the stems. It is much easier to set up support early in the season than to try and fix a fallen plant later.
- For large varieties, drive a sturdy wooden or metal stake into the ground at planting time to avoid poking the tuber later.
- As the plant grows, loosely tie the main stem to the stake using soft garden twine or strips of fabric.
- For smaller varieties or mass plantings, "tomato cages" or horizontal netting can also work well.
Watering and Feeding
Once the plants are established, they appreciate consistent moisture. Aim for a deep watering two or three times a week rather than a light sprinkle every day. This encourages the roots to grow deeper into the soil, making the plant more drought-tolerant.
Dahlias are "heavy feeders," meaning they use a lot of nutrients to produce their spectacular show. A low-nitrogen fertilizer (often labeled for blooms or roses) applied every few weeks can help sustain the flower production. Avoid high-nitrogen fertilizers late in the season, as this can encourage too much green leaf growth at the expense of flowers and may make the tubers harder to store over the winter.
Deadheading for More Blooms
To keep the color coming until autumn, you must deadhead your dahlias. This simply means cutting off the faded flowers before they have a chance to form seeds. When you remove a spent bloom, cut the stem back to a point just above where the next set of flower buds is forming. This tells the plant to keep blooming rather than focusing its energy on seed production.
What to do next: Summer Care
- Pinch the center stem when the plant is 12 inches tall.
- Provide sturdy stakes for tall varieties.
- Water deeply twice a week.
- Deadhead faded flowers every few days to encourage new buds.
What to Do with Dahlia Bulbs in the Fall
In most parts of the United States (Zones 3 through 7), dahlia tubers cannot survive the winter in the ground. If you live in a region where the ground freezes, you will need to dig them up and store them indoors. This is an exciting part of the process because dahlia tubers multiply! One tuber planted in the spring will often turn into a large clump of five to ten tubers by October.
The Signal to Dig
Don't rush to dig your dahlias as soon as the weather turns chilly. They need the cooling temperatures of autumn to signal the tubers to go dormant and toughen up for storage. The best time to dig is right after the first "killing frost." This is the frost that turns the green foliage black or brown.
Once the frost hits, cut the stalks down, leaving about 4 to 6 inches of stem above the ground. This "handle" makes it easier to lift the clump. Many gardeners like to leave the tubers in the ground for about a week after cutting them back. This short rest period helps the "eyes" (the growth points) become more visible and allows the skin of the tubers to cure.
Lifting the Tubers
Dahlia tubers are brittle and can snap easily, so be gentle. Use a garden fork rather than a shovel, as a fork is less likely to slice through the tubers. Start digging about 12 inches away from the center stem to ensure you don't accidentally strike the clump. Gently pry upward from all sides until the clump lifts easily from the earth.
Cleaning and Drying
Once the tubers are out of the ground, shake off the excess soil. If you have heavy clay soil, you may want to gently rinse the clumps with a garden hose. If your soil is sandy, you can simply brush the dirt off once it dries.
After cleaning, turn the clumps upside down to drain any water that might be trapped in the hollow stems. Let them air dry in a frost-free, shaded area (like a garage) for one to three days. You want the surface to be dry to the touch, but you don't want the tubers to shrivel up like raisins.
Key Takeaway: Harvesting Success "Waiting for the first frost is the natural way to tell your dahlias it is time to sleep. Lifting them carefully and allowing them to dry ensures they enter storage healthy and ready for next spring."
Winter Storage Methods
The goal of winter storage is to keep the tubers in a "Goldilocks" environment: not so cold that they freeze, and not so warm or dry that they shrivel up. At our trial garden at Longfield Gardens, we have found that a few different methods work well depending on your home's humidity.
The Best Storage Environment
The ideal temperature for storing dahlia tubers is between 40°F and 50°F. If the temperature stays in this range, the tubers will remain dormant.
- Basements, crawl spaces, and insulated garages are usually the best spots.
- Avoid attic spaces, which can get too hot, or unheated sheds where the temperature fluctuates too much.
Packing Your Tubers
You can store the clumps whole or divide them before storage. For beginners, storing the whole clump is often easier.
- Choose a container: Use cardboard boxes, plastic bins with loose-fitting lids, or paper bags.
- Use packing material: Surround the tubers with slightly damp (but not wet) material like vermiculite, peat moss, or wood shavings. This helps regulate the moisture.
- Check them periodically: Once a month, take a peek at your tubers. If they look shrivelled, lightly mist the packing material with water. If you see any soft spots or signs of rot, remove the affected tuber immediately to prevent it from spreading to the others.
For more detailed guidance, see these dahlia tuber storage tips.
Dividing Tubers
If you want to increase your flower count for next year, you can divide your dahlia clumps. Each division must have a piece of the "crown" (the part where the tuber meets the stem) and at least one "eye." The eyes look like tiny bumps or pimples and are the spots where next year's growth will emerge. Use a clean, sharp knife and sterilize it with a quick dip in a 10% bleach solution between clumps to prevent the spread of garden diseases.
What to do next: Winter Storage
- Find a dark spot that stays between 40°F and 50°F.
- Pack tubers in boxes with wood shavings or vermiculite.
- Set a reminder to check for moisture once a month.
- Discard any tubers that feel mushy or soft.
Growing Dahlias in Containers
If you have limited garden space or want to bring a splash of color to your patio, dahlias do wonderfully in pots. When deciding what to do with dahlia bulbs in a container setting, the rules are very similar to in-ground planting, with a few small adjustments.
For additional help, see this guide to planting dahlias in containers.
Selecting the Right Pot
Choose a container that is large enough to support a full-grown plant. For mid-sized dahlias, a 3-to-5-gallon pot is usually sufficient. Make sure the pot has plenty of drainage holes. Since pots dry out faster than the ground, you will need to water your container dahlias more frequently—sometimes every day during the heat of the summer.
Potting Soil and Support
Use a high-quality potting mix rather than garden soil, which is too heavy for containers. Because the plant is in a confined space, it will need regular liquid fertilizer to keep producing flowers. You can also use a tomato cage inserted directly into the pot to keep the plant upright.
When the season ends, you can simply move the entire pot into a frost-free area for the winter. Let the soil dry out completely, and the tubers will rest comfortably inside the pot until spring.
Troubleshooting Common Questions
Gardening is a learning process, and dahlias sometimes present little puzzles. If your plant isn't blooming as much as you'd like, check the sunlight. Even an extra hour of shade can significantly reduce the number of flowers. If the foliage looks great but there are no buds, you might be using a fertilizer with too much nitrogen. Switch to a "bloom booster" formula with more phosphorus and potassium.
If you find that your tubers have shriveled significantly during winter storage, don't give up on them yet. Many times, a slightly shriveled tuber will "wake up" once it hits warm, moist soil in the spring. As long as the neck and the eye area are firm, the plant likely has enough energy to start growing.
We stand behind the quality of our plants at Longfield Gardens. Our 100% quality guarantee means we ensure your items arrive in prime condition and are true to their variety. If you follow these simple steps for planting and care, you are well on your way to a season filled with incredible color.
Conclusion
Caring for dahlias is one of the most rewarding journeys a gardener can take. From the moment you unbox your tubers in the spring to the quiet satisfaction of tucking them away for the winter, every step brings you closer to a more beautiful home landscape. By mastering the basics of warm-soil planting, summer pinching, and careful winter storage, you can enjoy these spectacular blooms for many years to come.
- Wait for the warmth: Don't plant until the soil is 60°F and the danger of frost is gone.
- Sun and drainage: Give your dahlias at least 6 hours of sun and soil that doesn't stay soggy.
- Pinch for more: Removing the top of the stem in early summer leads to more flowers.
- Store safely: Dig after the first frost and keep tubers in a cool, dry place over winter.
"Dahlias are more than just flowers; they are a season-long celebration of color. With a little bit of care and the right timing, anyone can grow a world-class dahlia garden."
Whether you are dreaming of giant dinnerplate blooms or delicate border varieties, we are here to help you succeed. Your next step is to choose a sunny spot in your garden and prepare for a summer full of beauty.
FAQ
How deep should I plant dahlia bulbs?
You should plant dahlia tubers about 4 to 6 inches deep in well-draining soil. Place the tuber horizontally in the hole with the "eye" or any visible sprouts pointing upward. Do not water the soil until you see the first green shoots appear above ground to prevent the tuber from rotting.
For more information, read this guide on how to plant dahlia tubers.
Can I leave my dahlia bulbs in the ground over winter?
In USDA zones 8 through 11, dahlias can often survive the winter in the ground if the soil stays well-drained and the area is mulched heavily. However, in zones 3 through 7, where the ground freezes, you must dig up the tubers after the first frost and store them in a frost-free location to keep them alive.
Why are my dahlias not blooming?
The most common reasons dahlias fail to bloom are insufficient sunlight and improper fertilization. Dahlias need at least 6 to 8 hours of direct sun daily. Additionally, using a fertilizer too high in nitrogen can promote lush green leaves but very few flowers; try switching to a phosphorus-rich "bloom" fertilizer.
For additional ideas, see these tips for managing dahlias for maximum blooms.
When is the best time to divide dahlia tubers?
You can divide dahlia clumps either in the fall after digging them up or in the spring before planting. Many gardeners find it easier to divide them in the spring because the "eyes" (growth points) are more swollen and easier to see. Always ensure each division has a piece of the crown and at least one viable eye.
