Introduction
There is nothing quite like the sight of a dahlia in full bloom. These spectacular flowers are the crown jewels of the summer and autumn garden, offering a variety of colors and shapes that few other plants can match. Whether you are dreaming of massive "dinnerplate" blooms the size of a volleyball or cheerful border varieties that brighten up a walkway, the journey begins with a humble bare root tuber.
At Longfield Gardens, we believe that growing these stunning perennials should be an enjoyable and rewarding experience for every gardener. While their intricate petals might look intimidating, dahlias are actually quite straightforward to grow once you understand their basic needs. This guide will walk you through everything you need to know about planting bare root dahlias, from choosing the right spot to the simple steps that ensure a season full of flowers.
By focusing on a few essential rules regarding soil temperature, planting depth, and early-season care, you can transform a dormant tuber into a flourishing plant. Our goal is to provide you with the practical support and clear instructions needed to make your dahlia garden a success.
Understanding Bare Root Dahlias
When you receive a dahlia in its dormant state, it is often referred to as a "bare root" or a tuber. These tubers are thickened, underground stems that store the energy the plant needs to grow. They look somewhat like a cluster of elongated potatoes or carrots joined together at a central point.
Success with dahlias begins with understanding the anatomy of the tuber. There are three main parts to look for: the individual tubers (the fleshy "fingers"), the neck (the narrow part connecting the tuber to the center), and the crown (the top part where the previous year's stem was attached). The most important feature is the "eye." The eye is a small bump or bud located on the crown, and this is where the new growth will emerge.
We work with trusted growers in major bulb-growing regions like Holland to ensure that the tubers we ship are healthy and ready to grow. While some tubers may arrive with visible green sprouts, many will still be dormant. This is perfectly normal. As long as the tuber is firm and the neck is intact, it has everything it needs to produce a beautiful plant.
Choosing the Best Location
Matching the right plant to the right place is one of the most important steps in gardening. Dahlias have specific preferences for light and soil that will determine how well they perform throughout the season.
Prioritizing Sunlight
Dahlias are sun-loving plants. For the best results and the most abundant blooms, choose a location that receives at least six to eight hours of direct sunlight every day. While they can grow in partial shade, you may find that the stems become "leggy" as they stretch toward the light, and the number of flowers will be significantly lower.
In particularly hot climates, such as the southern United States, dahlias appreciate a little bit of afternoon shade. The intense midday sun can sometimes stress the plants, so a spot that gets bright morning light and some protection during the hottest part of the day is often ideal.
The Importance of Drainage
Drainage is how fast water leaves the soil, and for dahlias, it is the "quiet winner" of gardening success. These plants love consistent moisture once they are growing, but their dormant tubers are very sensitive to rot if they sit in cold, soggy soil.
If you have heavy clay soil that stays wet for a long time after a rain, you may want to consider planting your dahlias in raised beds or large containers. Another option is to amend the soil with compost to help improve the structure and allow water to move through more freely. A simple way to check your drainage is to dig a hole and fill it with water; if it takes more than an hour to empty, your soil is likely too heavy for dahlias without some modification.
Space to Breathe
Dahlias need good air circulation to stay healthy. Crowding your plants too closely can lead to issues with powdery mildew or other foliage problems later in the summer. When planning your garden, consider the mature size of the variety you have chosen. Large dinnerplate dahlias will need significantly more room than compact border varieties.
Key Takeaway: Choose a sunny spot with excellent drainage. If your soil stays soggy, use raised beds or containers to keep the tubers safe from rot.
When to Plant Your Dahlias
Timing is more important than any gardening "trick" or "hack." Because dahlias are native to the warm climates of Mexico and Central America, they have no tolerance for frost and do not like cold soil.
Soil Temperature Matters
The most common reason for a dahlia tuber failing to sprout is being planted too early in cold, wet soil. You should wait to plant your bare root dahlias until the soil has warmed up to about 60°F. For most gardeners, this is around the same time you would plant tomatoes or peppers in the garden.
Using a simple soil thermometer is a great way to take the guesswork out of the process. If you don't have one, a good rule of thumb is to wait until the danger of spring frost has completely passed. It is always better to wait an extra week for the soil to warm up than to risk the health of your tubers by planting too early.
Hardiness Zones and Shipping
At Longfield Gardens, we ship our tubers based on your USDA hardiness zone. We aim to have them arrive about two weeks before the ideal planting time for your specific region. This gives you time to prepare your garden beds while ensuring the tubers aren't sitting in storage for too long. See the shipping information for additional details.
If your tubers arrive and the ground is still frozen or too cold, keep them in a cool, dark, and dry place like a basement or garage. Leave them in the packaging they arrived in to prevent them from drying out completely. Do not store them in a refrigerator or anywhere they might freeze.
Preparing the Soil
Taking a few minutes to prepare your soil before planting will pay dividends all summer long. Dahlias are heavy feeders because they grow so quickly and produce so many flowers.
Amending with Organic Matter
We recommend mixing a few inches of compost or well-rotted manure into the top 8 to 12 inches of your soil. This adds essential nutrients and improves the soil's ability to hold the right amount of moisture. If you are using a fertilizer, look for one that is lower in nitrogen and higher in phosphorus and potassium. Too much nitrogen can result in lots of green leaves but very few flowers.
Soil Texture
Dahlias prefer loose, friable soil. If your soil is compacted, spend some time loosening it with a garden fork or spade. This makes it easier for the dahlia's root system to expand and for the new shoots to break through the surface.
Step-by-Step Planting Guide
Once the soil is warm and prepared, it is time to get your bare root dahlias into the ground. Follow these simple steps for the best results. For another detailed walkthrough, see this step-by-step guide to planting dahlia bulbs outdoors.
1. Dig the Hole
Dig a hole that is approximately 4 to 6 inches deep. The width of the hole should be large enough to accommodate the tuber without bending or breaking the individual "fingers." If you are planting a variety that will require a stake for support, it is helpful to drive the stake into the ground now. This prevents you from accidentally puncturing the tuber if you try to add a stake later in the season.
2. Place the Tuber
Lay the tuber horizontally in the bottom of the hole. If you can see an "eye" or a small sprout, make sure it is facing upward. If you can't tell which side is the top, don't worry—the plant is smart enough to find its way to the surface. Just lay it flat in the hole.
3. Spacing Your Plants
The amount of space between your plants depends on the variety:
- Large Varieties (Dinnerplate and Decorative): Space these 18 to 24 inches apart.
- Medium Varieties (Cactus and Ball): Space these 12 to 18 inches apart.
- Small Varieties (Border and Mignon): These can be spaced 10 to 12 inches apart.
Proper spacing ensures that each plant has enough light and airflow to thrive. It also makes it easier for you to navigate the garden for deadheading and harvesting flowers.
4. Cover and Label
Fill the hole back in with the soil you removed. Gently firm the soil with your hands to remove any large air pockets, but do not pack it down tightly. Finally, add a label with the variety name. It is easy to forget which dahlia is which before they bloom, and a label will help you keep track of your favorites for next year.
What to Do Next:
- Confirm your local frost-free date before starting.
- Prepare the soil with compost.
- Dig holes 4–6 inches deep.
- Place tubers horizontally with the eye facing up.
- Label each variety clearly.
The Watering Rule: Less is More
One of the most important rules for planting bare root dahlias is to not water them immediately after planting. This advice often surprises new gardeners, as we are usually taught to "water in" new plants.
Because the tuber is currently dormant, it does not have a root system to absorb water. Adding water to the soil before the plant has started growing can lead to the tuber rotting. There is usually enough natural moisture in the soil to sustain the tuber until it wakes up.
You should wait to start watering regularly until you see the first green shoots emerging from the soil. This usually takes two to four weeks, depending on the weather. Once the plant is about 6 inches tall and has several sets of leaves, you can begin a regular watering schedule. At that point, the goal is to water deeply and then let the soil dry out slightly before watering again.
Support and Staking
Many dahlia varieties, especially the taller ones, produce heavy blooms on stems that can be somewhat brittle. To keep your plants from toppling over in a summer rainstorm or high wind, providing support is essential.
When to Stake
As mentioned earlier, the best time to install a stake is at the time of planting. This is much easier on you and the plant. You can use sturdy wooden stakes, bamboo poles, or even metal "T-posts" for very large dahlias.
How to Tie
As the plant grows, use soft garden twine or strips of fabric to gently tie the main stem to the stake every 12 to 18 inches. Avoid tying it too tightly, as the stem will continue to thicken as the plant matures. A "figure-eight" loop is often the best method, as it provides support while allowing the stem some room to move.
For border dahlias or shorter varieties, you may not need individual stakes. Instead, a simple tomato cage or a low decorative fence can provide enough support to keep the plant upright.
Starting Dahlias Indoors
If you live in a region with a short growing season, you might want to give your dahlias a head start by potting them up indoors about four to six weeks before the last frost.
The Potting Process
Choose a container that is at least 2 gallons in size and has good drainage holes. Use a high-quality, well-draining potting mix. Plant the tuber about 2 inches deep in the pot. Just like in the garden, do not overwater. A light misting or a very small amount of water to settle the soil is all you need until you see growth.
Light and Warmth
Keep the pots in a warm spot (around 65–70°F) with plenty of light. A sunny windowsill or a spot under grow lights works well. Once the weather has warmed up and the risk of frost is gone, you can "harden off" the plants by gradually exposing them to outdoor conditions over a week before transplanting them into the garden.
Aftercare: Pinching for More Flowers
Once your dahlias are established and growing well, there is one simple technique that will dramatically increase the number of flowers you get: pinching.
The "Easy Win" of Pinching
When your dahlia plant is about 12 inches tall and has four to five sets of leaves, use your thumb and forefinger (or a clean pair of snips) to remove the very top of the center stem. It may feel a bit strange to cut off the top of a healthy plant, but this is an "easy win" for any dahlia grower.
Pinching signals the plant to stop putting all its energy into one tall main stem and instead start growing lateral branches. This results in a bushier, stronger plant with many more flowering stems. If you skip this step, you will still get flowers, but the plant will likely be taller, thinner, and produce fewer blooms overall.
Encouraging Realistic Expectations
Gardening is a partnership with nature, and results can vary based on factors beyond our control. While following these steps will give you a great foundation, remember that weather, microclimates, and soil health all play a role in how your dahlias perform.
Some varieties may take longer to wake up than others. If you don't see green shoots after three weeks, don't panic. Gently brush away a little bit of soil to check the tuber. If it is still firm, it is simply taking its time. If a particular spot in your garden doesn't seem to be working, observe the light and drainage and consider making a change next season. One change at a time is the best way to troubleshoot and learn what your specific garden needs. For additional site-selection guidance, read where dahlias should be planted for the best blooms.
Protecting Your Plants
Dahlias are generally robust, but they do have a few fans in the animal and insect world.
Pests and Visitors
Slugs and snails are often the biggest threat to young dahlia shoots. They love the tender new growth that emerges in late spring. Using a pet-safe slug bait or creating a barrier can help protect your plants during this vulnerable stage.
Dahlias can be toxic if ingested by pets or livestock. It is always a good idea to check toxicity levels and keep tubers and plants out of reach of curious dogs or cats. If you have deer or rabbits in your area, you may find that they occasionally nibble on the foliage. While dahlias aren't their first choice, a hungry deer will eat almost anything. Using a repellent or a small fence can help keep them away.
Maintaining Your Dahlias
Once the blooming season begins, usually in mid-to-late summer, your main job is to enjoy the show and keep the plants tidy. If you are growing flowers for bouquets, explore this bulk dahlia mix for cutting gardens.
Deadheading
The more you cut dahlias, the more they bloom. To keep the plant producing new flowers, you must remove the old ones as they fade. This process is called deadheading. When a flower starts to lose its petals or the center begins to look brown, follow the stem down to where it meets a set of leaves and make a clean cut.
Deep Watering
During the heat of the summer, your dahlias will appreciate a deep watering once or twice a week. It is better to water deeply and less frequently than to give them a light sprinkle every day. This encourages the roots to grow deep into the soil, making the plant more resilient to drought. Aim the water at the base of the plant rather than over the leaves to help prevent foliage diseases.
Conclusion
Planting bare root dahlias is a wonderful way to bring color and excitement to your summer garden. By starting with high-quality tubers from Longfield Gardens and following the basic rules of timing, depth, and drainage, you are setting yourself up for a successful and beautiful season. These plants are incredibly rewarding, and once you see those first blooms unfurl, you'll understand why so many gardeners fall in love with them. Browse assorted dahlia collections to find a combination that suits your garden.
- Wait for the soil to reach 60°F before planting.
- Select a sunny spot with excellent drainage.
- Don't water until you see the first green shoots.
- Pinch your plants when they are 12 inches tall for more blooms.
- Deadhead regularly to keep the flowers coming until frost.
If you ever run into a problem or have a question, our responsive customer service team is here to help. We stand behind our quality with a 100% guarantee, and we want to ensure you have everything you need to create a more beautiful yard. The next step is simply to choose your favorite colors and get ready for a spectacular summer.
"Dahlias are proof that a little patience and a few simple steps can lead to a garden filled with extraordinary beauty."
FAQ
Should I soak dahlia tubers before planting?
Soaking is not necessary for dahlia tubers and can actually increase the risk of rot. Unlike some other bulbs or corms, dahlia tubers contain enough moisture to begin growing on their own once they are placed in warm soil. It is best to plant them dry and let them wake up naturally as the soil temperature rises.
Why hasn't my dahlia sprouted yet?
The most common reason for slow sprouting is cool soil. Dahlias are very sensitive to temperature and may stay dormant until the ground is consistently warm. If it has been more than four weeks, you can gently move a small amount of soil to check the tuber; if it is firm and has a small sprout or "eye," it is healthy and just needs more time.
How deep should I plant my dahlia tubers?
The ideal depth for planting dahlia tubers is 4 to 6 inches. This depth protects the tuber from temperature fluctuations and provides a stable base for the stems to grow. If you plant them too shallow, the plant may struggle to stay upright; if you plant them too deep, the shoots may have difficulty reaching the surface.
Can I grow dahlias in containers?
Yes, dahlias grow very well in containers, provided the pots are large enough. For medium to large varieties, choose a container that holds at least 5 to 7 gallons of soil and has excellent drainage. Smaller border varieties can thrive in 2- or 3-gallon pots. Use a high-quality potting mix and be prepared to water more frequently than you would for dahlias planted in the ground. For additional planting ideas, browse the dahlia collection.
