Introduction
The arrival of a package filled with dahlia tubers is one of the most exciting moments in a gardener’s spring. These humble, potato-like roots hold the potential for some of the most spectacular displays in the floral world, ranging from tiny pompons to massive dinnerplate blooms. At Longfield Gardens, we want to help you make the most of every tuber so your garden stays vibrant from midsummer through the very first frost of autumn.
Knowing what to do with dahlia bulbs—which are technically called tubers—is the key to a rewarding growing experience. Whether you have just received your first shipment or you are looking for tips on how to save your favorite varieties for next year, the process is straightforward and manageable. This guide will walk you through every stage of the dahlia life cycle, from unboxing and planting to mid-season care and winter storage. For a broader overview, see our Planning Guide for Dahlias.
Managing dahlias throughout the year is a simple cycle of matching the plant’s needs to your local climate and timing.
Receiving Your Dahlias in the Spring
When your order arrives from us, the first thing to do is open the box immediately. Dahlias are living plants in a state of rest, and they need fresh air after their journey. We ship our tubers at the right time for your USDA hardiness zone so they arrive roughly two weeks before the ideal planting time in your area. For help finding yours, see our Hardiness Zone Map.
Inspecting Your Tubers
Take the tubers out of the shipping material and give them a quick look. A healthy dahlia tuber should feel firm, similar to a fresh potato. It is normal for them to have some minor surface shriveling or a bit of loose peat moss clinging to them. They come in many shapes and sizes depending on the variety. Some may be long and thin, while others are short and round. For a closer look at dahlia structure, see Dahlia Tubers: What You Need to Know.
Do not worry if you don't see green sprouts right away. Many dahlias stay "sleepy" until they feel the warmth of the soil. As long as the tuber is firm and the "neck" (the narrow part connecting the tuber to the stem) is intact, it is ready to grow. If you notice any soft, mushy spots, our guarantee covers quality concerns when you contact us promptly.
Temporary Storage Before Planting
If your garden soil is still too cold or wet to plant, you can easily store your tubers for a few weeks. Keep them in a cool, dry, and dark place where the temperature stays between 40°F and 50°F. An unheated basement or a cool closet works well. Keep them in the breathable packaging they arrived in, such as a paper bag or a box with wood shavings, to prevent them from drying out completely or getting too much moisture.
What to do next:
- Open your shipping box immediately upon arrival.
- Check each tuber for firmness and intact necks.
- Keep them in a cool, dark place until planting day.
- Avoid the refrigerator, as it is often too cold and humid.
When and How to Plant Your Dahlias
Timing is everything when it comes to dahlias. These are tropical plants native to Mexico, so they love warmth and cannot tolerate frost. One of the most common mistakes is planting them too early when the soil is still cold and damp.
The Importance of Soil Temperature
Wait to plant your dahlia tubers until the soil temperature reaches at least 60°F. A simple way to tell if it is time is to check if your local garden center has started selling tomatoes and peppers for outdoor planting. If it is warm enough for a tomato, it is warm enough for a dahlia. For more planting timing details, see When Can You Plant Dahlia Bulbs?.
Planting in cold, wet soil can cause the tuber to rot before it ever has a chance to sprout. If you want a head start, you can "start" your dahlias indoors in pots 4–6 weeks before the last frost. Place them in a warm, sunny window or under grow lights, then move them to the garden once the weather is consistently warm.
Planting Depth and Spacing
Choose a spot that receives at least six to eight hours of direct sunlight. Dahlias are heavy feeders and drinkers, so they need plenty of energy from the sun to produce those famous blooms.
- Dig a hole: Create a hole about 4 to 6 inches deep.
- Place the tuber: Lay the tuber horizontally in the hole. If there is a visible sprout or "eye," point it upward, but don't worry if you can't find it—the plant will find its way to the surface.
- Space them out: Give your dahlias room to breathe. Small border dahlias can be 12 inches apart, while large dinnerplate varieties need at least 18 to 24 inches of space.
- Cover with soil: Fill the hole back in with soil.
- Hold the water: This is a "simple gardening rule" for dahlias: do not water the tubers immediately after planting unless your soil is bone-dry. The tuber has enough stored energy and moisture to start growing. Wait until you see the first green shoots poking through the soil before you begin a regular watering schedule.
Mid-Season Care and Maintenance
Once your dahlias are up and growing, they are relatively low-maintenance, but a few simple tasks will drastically improve the number of flowers you get.
Pinching for More Blooms
When your dahlia plant is about 12 inches tall and has four sets of leaves, it is time to "pinch" it. This might feel like you are hurting the plant, but it is actually very helpful. Use your fingers or a clean pair of snips to remove the very top of the center stem. If you want a refresher on the technique, see How to Pinch and Stake Dahlias.
This signals the plant to stop growing one tall, lanky stalk and start growing multiple side branches. More branches mean more flowers and a sturdier, bushier plant that is less likely to fall over in the wind.
Watering and Fertilizing
Dahlias are thirsty plants once they are established. "Water correctly, not constantly" is our guide here. Check the soil; if the top inch is dry, give them a deep soak. In the heat of the summer, this might mean watering two or three times a week. For more season-long care tips, see 8 Tips for Growing Better Dahlias.
Because they grow so fast and produce so many flowers, dahlias benefit from regular feeding. Use a fertilizer that is lower in nitrogen and higher in phosphorus and potassium (the second and third numbers on the label). Too much nitrogen will give you lots of green leaves but very few flowers. A "bloom booster" type fertilizer applied every 3 to 4 weeks will keep the colors vivid and the stems strong.
Supporting Tall Varieties
Many dahlias can grow 4 to 5 feet tall, and their heavy flower heads can act like sails in a breeze. It is much easier to provide support early than to try and fix a flopped plant later. For a big-blooming example, browse Dahlia Dinnerplate High Summer Mix - Bulk Offer. Place a sturdy stake—like a bamboo pole or a wooden stake—into the ground at the time of planting to avoid hitting the tuber later. As the plant grows, gently tie the main stem to the stake using soft garden twine or strips of fabric.
Key Takeaway: Pinching your dahlias when they are a foot tall is the easiest way to double your flower count and create a fuller, healthier plant.
What to Do When the Season Ends
In many parts of the United States, dahlia tubers must be dug up and stored indoors for the winter. If you live in USDA zones 8 through 11, you may be able to leave them in the ground with a thick layer of mulch. However, for those in zones 3 through 7, the tubers will freeze and turn to mush if left outdoors.
The Frost Signal
The best time to dig up your dahlia bulbs is after the first hard frost. You will know it has happened because your beautiful green plants will turn black or dark brown overnight. While it looks sad, this is actually a helpful signal. The cold snap tells the plant to send all its remaining energy down into the tubers for winter storage. For a step-by-step walkthrough, see How to Lift and Store Dahlia Bulbs.
Curing Tubers in the Ground
After the frost hits, cut the stalks down to about 4 to 6 inches above the ground. If your schedule allows, leave the tubers in the soil for another 7 to 10 days. This "curing" period helps the skin of the tubers toughen up, which makes them much more resistant to rotting or shriveling while they are in storage. If heavy rain or a deep ground freeze is predicted, you can dig them sooner.
How to Dig and Clean Dahlia Tubers
Digging dahlias requires a bit of patience and a gentle hand. Think of it as an archaeological dig rather than heavy construction.
Lifting the Clumps Gently
The tubers grow in a clump around the base of the stem. Over the summer, that single tuber you planted may have turned into a clump of five, ten, or even twenty new tubers.
- Use a pitchfork: A garden fork is better than a shovel because it is less likely to slice through the tubers.
- Start wide: Insert your fork into the soil about 12 inches away from the stem on all sides. Gently pry upward to loosen the soil.
- Lift by the base: Once the soil is loose, reach under the clump and lift it out. Avoid pulling hard on the "stem handle," as this can break the fragile necks of the tubers.
Washing and Preparing for Storage
Once the clump is out of the ground, shake off the big clods of dirt. Some gardeners prefer to wash their tubers with a garden hose to see the "eyes" and check for any damage. Others prefer to leave some soil on, as it provides a bit of natural protection.
If you do wash them, let them dry thoroughly in a protected area (like a garage or porch) for 24 to 48 hours. They should be dry to the touch before they go into a box. If they are tucked away while wet, they are very likely to rot.
Overwintering: Storing Your Tubers for Success
The goal of winter storage is to keep the tubers in a "Goldilocks" environment: not too cold (or they freeze), not too warm (or they grow or rot), and not too dry (or they shrivel).
Choosing the Right Storage Medium
You want to pack your tubers in a material that regulates moisture. At Longfield Gardens, we recommend using one of the following:
- Vermiculite: Excellent for moisture control.
- Pine shavings: The kind used for animal bedding is inexpensive and works well.
- Peat moss: Just make sure it is slightly damp, not soaking wet.
Place a layer of your chosen medium in a cardboard box or a plastic bin with holes for ventilation. Lay the tubers in the box so they are not touching each other, then cover them with more material.
Temperature and Humidity Goals
The ideal storage temperature is between 40°F and 50°F. A basement, a root cellar, or a cool crawl space is usually perfect. If you store them in a garage, make sure the temperature doesn't drop below freezing. A single night of freezing temperatures can kill an entire collection of tubers.
Dividing Now vs. Spring
You can divide your dahlia clumps into individual tubers in the fall, or you can wait until spring. Many beginners find it easier to wait until spring because the "eyes" (the small bumps that become new sprouts) are much easier to see. If you divide in the fall, you save space, but you must be very careful to ensure each piece has a part of the original stem crown where the eyes are located.
What to do next:
- Cut back stalks to 4-6 inches after the first frost.
- Wait one week for skins to toughen.
- Dig carefully with a fork, starting 12 inches from the stem.
- Store in a ventilated box with pine shavings at 40-50°F.
Troubleshooting: Identifying Healthy Tubers
It is a good idea to check on your stored tubers once a month during the winter. This allows you to catch any issues before they spread.
Rot vs. Normal Discoloration
If you pick up a tuber and it feels like a soft sponge or oozes liquid, it has rotted. Remove it immediately and throw it in the trash (not the compost) so the rot doesn't spread to healthy tubers. If you see a small spot of mold on the surface, you can often wipe it off and increase the airflow in your storage box.
Dealing with Shriveled Tubers
If your tubers look like wrinkled raisins, they are losing too much moisture. This usually happens if the storage area is too dry or the packing material is too airy. You can fix this by lightly misting the packing material with a spray bottle of water. You don't want it wet, just "barely damp" to the touch. Healthy tubers have a surprising ability to plump back up once they are planted in moist soil.
Identifying the Eye
If you are unsure if a tuber is viable, look for the eye. The eye is a small, rounded bud located on the "crown" (where the tuber meets the stem). This is where all the new growth comes from. If a tuber breaks off and doesn't have a piece of the crown attached, it will not grow, even if the tuber itself looks perfect. These are often called "blind" tubers.
Conclusion
Dahlias are some of the most rewarding flowers you can grow, offering a spectacular return on your investment of time and care. By following these simple steps—waiting for warm soil in the spring, pinching back for more blooms in the summer, and providing a cool, dry home in the winter—you can enjoy these stunning plants year after year. If you love trying different forms and colors, take a look at the Dahlia Assorted Sunlit Jewel Collection.
At Longfield Gardens, we are proud to provide the high-quality tubers and practical advice you need to succeed. Gardening should be an enjoyable journey, and with dahlias, every season brings a new opportunity to see something beautiful bloom in your yard. For help with order timing, see our Shipping Information.
- Patience pays off: Wait for 60°F soil before planting.
- Support your plants: Stake tall varieties early to prevent wind damage.
- Stay observant: Check your stored tubers monthly to ensure they stay firm and healthy.
The most important step you can take next is to mark your calendar for your local "average last frost date." Once you know that date, you can plan your planting schedule and get ready for a summer filled with color. If you prefer a more classic look, the Dahlia Dinnerplate Summer Lovin Collection is another great place to start.
"Dahlias are not just flowers; they are a seasonal highlight that rewards a little bit of care with an abundance of beauty."
FAQ
Can I leave my dahlia tubers in the ground all winter?
This depends entirely on your location. If you live in USDA zones 8 or warmer, you can usually leave them in the ground if the soil has excellent drainage and you apply a thick layer of mulch. In zones 7 and colder, the ground usually freezes deep enough to kill the tubers, so they must be dug up and stored indoors to survive.
Why didn't my dahlias bloom this year?
The most common reasons for a lack of blooms are too much nitrogen fertilizer (which grows leaves instead of flowers), not enough sunlight, or planting too late in the season. Ensure your dahlias get at least 6–8 hours of sun and use a fertilizer higher in phosphorus. Also, make sure you are "deadheading," which means cutting off faded flowers to encourage the plant to make new ones.
Do I need to soak dahlia tubers before planting?
No, you should not soak dahlia tubers. Unlike some other bulbs or corms, dahlia tubers are very prone to rotting if they get too wet before they start growing. They contain plenty of moisture to get started. Simply plant them in warm soil and wait for the green shoots to appear before you start watering regularly.
How big should a dahlia tuber be to grow a healthy plant?
Size is not the most important factor for a dahlia tuber. As long as the tuber is about the size of a AA or AAA battery and has an "eye" at the crown, it has enough energy to produce a full-sized, healthy plant. Some varieties naturally produce very small tubers, while others produce large, chunky ones, but both will grow into beautiful plants.
