Introduction
There is a unique sense of excitement that comes with the arrival of spring. As the soil warms and the days grow longer, we begin to imagine the vibrant colors and lush textures that will soon fill our yards. Planting spring-planted summer-blooming bulbs like dahlias and gladiolus is one of the most rewarding ways to ensure your garden is a showstopper from midsummer through the first frost.
At Longfield Gardens, we want to help you make the most of every square foot of your growing space with our dahlia collections. This guide is designed for home gardeners who want to understand the simple steps needed to grow stunning blooms. Whether you are looking to fill your flower beds with color or grow enough stems for endless indoor bouquets, these two plants are the perfect choice for a successful season.
We will cover everything from selecting the right spot and preparing your soil to the specific techniques for planting and harvesting. By focusing on a few basic principles, you can enjoy a professional-looking garden with minimal stress. Growing these beautiful flowers is an achievable joy for gardeners of every skill level.
Why Dahlias and Gladiolus Belong in Your Garden
Dahlias and gladiolus are the workhorses of the summer garden. They offer a level of variety and productivity that few other plants can match. While they are often grouped together as "summer bulbs," they each bring a different architectural element to your landscape.
Dahlias are known for their incredible diversity. They come in almost every color imaginable and range in size from tiny pompons to massive dinnerplate varieties that can be larger than a dinner plate. Their bushy growth habit makes them excellent for filling gaps in perennial borders or creating a dedicated spring-planted bulbs for cut flowers collection. Because they bloom more the more you cut them, they provide a constant supply of flowers for your home.
Gladiolus, on the other hand, provide much-needed vertical interest. Their tall, sword-like leaves and elegant flower spikes stand out in any setting. They are often used in the back of a flower bed to provide a colorful backdrop or planted in rows for easy harvesting. Because they take up very little horizontal space, they are easy to tuck into existing gardens.
When you grow both, you get the best of both worlds: the voluminous, intricate shapes of dahlias and the stately, architectural height of gladiolus. Together, they create a balanced and visually interesting garden that feels full and intentional.
Getting the Timing Right
Success with dahlias and gladiolus starts with understanding when to put them in the ground. Because these are "tender" plants, they do not like the cold. Waiting for the right conditions is the most important thing you can do to ensure they get off to a strong start.
Watching the Soil Temperature
Many gardeners use the calendar to decide when to plant, but the soil temperature is a much more reliable guide. If you are unsure where your climate falls, check the Hardiness Zone Map. Both dahlias and gladiolus thrive when the soil is warm—ideally around 60°F. If you plant them when the soil is still cold and wet, the tubers and corms may sit idle or struggle to develop roots.
A simple rule of thumb is to plant your dahlias and gladiolus at the same time you would plant your tomatoes or peppers. In most regions, this is a few weeks after the last expected spring frost. When the trees are leafing out and the grass is growing vigorously, your garden is usually ready for these summer stars.
The Benefits of Pre-Sprouting
If you live in a region with a short growing season, you might feel like you are racing against the first frost of autumn. To get a head start, you can "pre-sprout" your tubers and corms indoors about four to six weeks before your outdoor planting date.
To pre-sprout dahlias, place the dahlia tubers in a shallow tray filled with slightly damp potting soil or peat moss. Keep them in a warm, bright spot. You will soon see "eyes" (small bumps) or green shoots beginning to emerge from the neck of the tuber. For gladiolus, you can simply place the corms in a bright, warm area to encourage the central sprout to begin growing.
Starting them indoors allows the plants to develop a root system and a little bit of top growth before they even hit the garden. This can result in flowers appearing two to three weeks earlier than if they were planted directly in the ground.
Key Takeaway: Always wait until the danger of frost has passed and the soil is warm before planting outdoors. If you want earlier blooms, starting your plants indoors for a few weeks is a simple way to jumpstart the season.
Choosing and Preparing the Perfect Spot
Both dahlias and gladiolus have a few non-negotiable needs: sun and drainage. How to Prepare Soil for Planting can help you get those two factors right.
Sun Exposure
These plants are true sun-lovers. To produce those big, beautiful blooms and strong stems, they need at least six to eight hours of direct sunlight every day. If they are planted in too much shade, the stems may become "leggy" or weak as they reach for the light, and you will see fewer flowers.
When choosing a spot, observe your yard throughout the day. Areas that get full morning and early afternoon sun are usually the most productive. If you have a very hot climate, a little bit of late-afternoon shade can actually be helpful to keep the blooms from fading too quickly, but direct sun for the majority of the day remains the goal.
Soil Drainage
"Drainage" simply refers to how quickly water moves through your soil. Dahlias and gladiolus do not like to have "wet feet." Soil that stays soggy for a long time after a rain can prevent oxygen from reaching the roots.
If your soil is heavy clay, you can improve it by adding organic matter like compost or well-rotted leaves. This helps create a looser structure that allows water to drain away while still holding onto the moisture the plants need. If you have very sandy soil, compost helps here too by giving the soil more substance to hold onto nutrients.
Space to Breathe
Air circulation is an often-overlooked part of garden health. When plants are crowded too closely together, humidity can get trapped between the leaves. Giving your plants enough room helps keep the foliage dry and healthy.
- Dahlias: Space larger varieties about 18 to 24 inches apart. Smaller, border-type dahlias can be spaced 12 to 15 inches apart.
- Gladiolus: These can be planted more closely, usually 4 to 6 inches apart, which allows you to fit a lot of color into a small area.
How to Plant Dahlia Tubers
Dahlias grow from tubers, which look a bit like a bunch of brown carrots. While they may look unassuming when they arrive, they hold all the energy needed to grow a large, lush plant.
Identifying the Tuber Parts
Before planting, it helps to know what you are looking at. A viable dahlia tuber has three main parts:
- The Body: The thick part that stores food and energy.
- The Neck: The narrow part that connects the body to the crown.
- The Eye: The small growing point located on the crown (right where the neck meets the old stem). This is where the new sprout will come from.
Planting Depth and Direction
Dig a hole about 4 to 6 inches deep. Place the dahlia tuber horizontally in the bottom of the hole with the "eye" or sprout facing upward. This horizontal placement allows the roots to spread out easily and provides a stable base for the plant as it grows.
Once the tuber is in place, cover it with soil. At this stage, you do not need to water them immediately unless the soil is exceptionally dry. Waiting until you see the first green shoots emerge from the soil is a safe way to ensure the tuber doesn't get too much moisture before it has roots to drink it.
Supporting Tall Varieties
If you are planting tall dahlia varieties (those that grow 3 feet or higher), it is best to put a stake in the ground at the time of planting. This prevents you from accidentally poking a hole through the tuber later in the season. Staking provides the support these heavy-blooming plants need to withstand wind and rain.
What to do next:
- Check your soil temperature to ensure it's at least 60°F.
- Clear the area of weeds and mix in some compost.
- Dig holes 4–6 inches deep and space them according to the variety size.
- Lay tubers flat with the eye facing up and cover with soil.
How to Plant Gladiolus Corms
Gladiolus grow from corms, which are rounded, slightly flattened structures. For a deeper overview, see All About Gladiolus. They are incredibly easy to plant and are perfect for filling in small gaps in your landscape.
Successive Planting for Continuous Blooms
The "simple rule" for gladiolus is that they bloom once per corm. Each spike of flowers lasts for about two weeks. If you plant all your corms on the same day, you will have a massive explosion of color all at once, and then the show will be over.
To keep the color going all summer, use "successive planting." Spring Planted Flower Bulk Buys can help if you want enough corms for repeat plantings. Plant a handful of corms every 10 to 14 days starting in late spring and continuing through early July. This staggers the bloom times so that as one group of flowers finishes, the next group is just beginning to open. This technique is the best way to ensure you have fresh glads for your vases for months.
Planting Depth and Spacing
Gladiolus should be planted about 4 inches deep. A good tip for height is to plant them slightly deeper in sandy soil (up to 6 inches) to help the tall stems stay upright without needing stakes.
Place the corms in the hole with the pointed side facing up and the flat side (where the roots will grow) facing down. You can plant them in rows, or for a more natural look, plant them in small clusters of 7 to 10 corms. This creates a "bouquet" effect in the garden.
Grouping for Impact
While a single gladiolus spike is beautiful, they look much better when planted in groups. Because the foliage is vertical and thin, individual plants can look a bit sparse. By grouping them, you create a solid block of color that has much more visual impact from a distance.
Essential Care for Summer Success
Once your dahlias and gladiolus are in the ground and growing, they don't require much work, but a little consistent care will go a long way in maximizing their performance.
Watering Correctly
The goal with watering is to provide deep, consistent moisture rather than frequent, shallow sprinkles. Deep watering encourages the roots to grow further down into the soil, which makes the plants more resilient during hot, dry spells.
Once your plants are about 6 inches tall, they will begin to need more water. Aim to give them about an inch of water per week, either from rain or your hose. If the weather is particularly hot, you may need to water more frequently. Using a layer of mulch, such as shredded bark or clean straw, around the base of the plants helps keep the soil cool and prevents moisture from evaporating too quickly.
Fertilizing for Blooms
Dahlias, in particular, are "heavy feeders." For a broader look at their growth habits, see All About Dahlias. This means they use a lot of nutrients to produce their large flowers and foliage. We recommend using a balanced fertilizer or one specifically formulated for flowers (look for a lower first number on the package, which represents nitrogen, and higher middle and last numbers for phosphorus and potassium).
Start fertilizing once the plants are well-established and continue every 3 to 4 weeks through midsummer. This provides the "fuel" the plants need to keep producing new buds. Avoid over-fertilizing with high-nitrogen products late in the season, as this can lead to lots of green leaves but very few flowers.
Deadheading and Grooming
"Deadheading" is the simple act of removing faded flowers. For dahlias, this is essential. When you remove an old flower, the plant stops putting energy into making seeds and redirects that energy into producing more blooms. To deadhead properly, follow the flower stem down to where it meets the main stalk or the next set of leaves and snip it off there.
For gladiolus, once the entire spike has finished blooming, you can cut the stalk down near the base. Leave the green leaves intact, as they will continue to photosynthesize and store energy in the corm for next year.
Harvesting for Beautiful Bouquets
One of the greatest joys of growing dahlias and gladiolus is bringing them inside. Both are legendary cut flowers with a long vase life, provided you harvest them at the right time.
When to Cut Dahlias
Dahlias are different from many other flowers because they do not continue to open much once they are cut. If you cut a dahlia bud while it is still tight, it will likely stay that way in the vase.
Wait until the flower is almost fully open. Look at the back of the flower head; the petals should be firm and not starting to wilt or turn brown. Harvest them in the cool of the morning when the plants are most hydrated. Immediately place the stems into a bucket of clean, room-temperature water.
When to Cut Gladiolus
Gladiolus should be harvested when the very first blossom at the bottom of the spike begins to open or show color. The rest of the buds on the spike will open progressively over the next week while in the vase.
This "bottom-up" blooming habit is what makes gladiolus so wonderful for arrangements. It gives you a changing display every day. As the lower flowers fade, you can simply pinch them off to keep the spike looking fresh as the upper buds open.
Vase Care Tips
To get the longest life out of your flowers:
- Use a clean vase. Bacteria are the enemy of cut flowers.
- Strip any leaves that will sit below the water line. Leaves in the water will rot and shorten the life of the blooms.
- Change the water every two days.
- Give the stems a fresh "angled" snip every time you change the water to help them continue to drink efficiently.
End of Season Care
As the summer winds down and the first frost approaches, your dahlias and gladiolus will begin to fade. Depending on where you live, you have a few choices for how to handle the end of the season.
Understanding Your Zone
In warmer climates (USDA zones 8 and above), dahlia tubers and gladiolus corms can often stay in the ground year-round. A thick layer of mulch can help protect them from occasional cold snaps.
In colder regions (zones 7 and below), these plants are treated as annuals, or they must be "lifted" and stored for the winter. Many gardeners enjoy the process of digging them up to save their favorite varieties for the following year. At Longfield Gardens, we ship our bulbs based on your specific planting zone, so they arrive right when your soil is ready. See our Shipping Information for details.
How to Lift and Store
If you choose to save your tubers and corms:
- Wait for Frost: Let the first light frost kill the foliage. This sends a signal to the plant to go dormant.
- Cut Back: Cut the stems down to about 2 to 4 inches above the ground.
- Dig Carefully: Use a garden fork to gently lift the tubers or corms from the soil, being careful not to bruise or cut them.
- Dry: Let them air dry in a cool, frost-free place for a few days.
- Store: Place them in a box with peat moss, vermiculite, or wood shavings. Store the box in a cool, dark, and dry place (like a basement or crawl space) where temperatures stay between 40°F and 50°F.
If you prefer a low-maintenance approach, you can simply treat them as annuals. Many gardeners find it easier to start fresh with new varieties each spring, allowing them to experiment with different colors and shapes every year.
Key Takeaway: Whether you save your bulbs or plant new ones each year, the cycle of the garden is a rewarding process. The effort you put into fall care or spring planning ensures another season of beauty.
Designing with Dahlias and Gladiolus
Creating a visually stunning garden is easier when you think about how these plants work together. You don't need a professional landscape design to have a garden that looks balanced and beautiful.
Layering for Height
Use the natural height of gladiolus to your advantage. Because they are tall and narrow, they are perfect for the "back row" of a garden bed. They create a wall of color that frames the plants in front of them.
Dahlias, with their bushier habit, are great for the "middle" layer. They hide the base of the gladiolus stems and provide a dense mound of foliage and flowers. If you are growing smaller border dahlias, place those at the very front to create a colorful edge.
Color Combinations
Don't be afraid to experiment with color. You can create a harmonious look by sticking to a specific palette—for example, mixing various shades of pink, purple, and white. This creates a calm, elegant feel.
Alternatively, for a high-energy garden, go for high contrast. Pair bright yellow dahlias with deep purple gladiolus, or orange and red tones for a fiery late-summer display. Because we offer a wide variety of colors, you can easily find the perfect match for your personal style at Shop Spring-Planted Bulbs By Color.
Texture and Filler
While dahlias and gladiolus are the stars, adding some filler plants can make your garden feel complete. Airy plants like baby's breath or the delicate foliage of cosmos can soften the bold look of large dahlia blooms. These "companions" help bridge the gap between different plant types and make your flower arrangements look more professional.
Summary of Success
Gardening should be a source of relaxation and pride. By following these simple steps, you can grow a garden that brings joy to you and your neighbors.
- Wait for Warmth: Don't rush the season. Warm soil is the key to healthy growth.
- Sun and Water: Give them the light they crave and deep, consistent moisture.
- Succession Planting: Stagger your gladiolus for months of flowers.
- Harvest Often: The more you cut, the more they bloom.
At Longfield Gardens, we take pride in providing high-quality tubers and corms that are ready to thrive in your yard. We want your gardening experience to be as successful as possible, which is why we stand behind the quality of everything we ship with our 100% Quality Guarantee.
Conclusion
Growing dahlia and gladiolus bulbs is one of the most satisfying projects a gardener can undertake. From the first sprout to the final frost, these plants offer a spectacular return on a small investment of time and care. By focusing on the basics—right plant, right place, and proper timing—you can transform your outdoor space into a vibrant sanctuary.
- Choose a sunny spot with good drainage.
- Plant at the right depth and give plants room to grow.
- Enjoy the process of harvesting and arranging your own home-grown flowers.
The best way to learn is to get your hands in the dirt. We invite you to explore the many colors and varieties available and start planning your most beautiful summer garden yet.
"A garden filled with dahlias and gladiolus is a testament to the beauty of the summer season. These simple-to-grow plants prove that spectacular results are within reach for every gardener."
FAQ
Do I need to soak my dahlia tubers before planting?
Soaking is generally not necessary for dahlia tubers. While some gardeners like to give shriveled tubers a quick 20-minute dip in room-temperature water, most tubers have plenty of stored moisture to begin growing once they are in warm, damp soil. Over-soaking can sometimes lead to rot, so it is usually best to simply plant them directly into prepared ground.
Why are my gladiolus leaning over?
Gladiolus stems are tall and can become top-heavy when they are in full bloom. If they are leaning, it may be because they weren't planted deeply enough or they are in a spot with high wind. To prevent this, plant corms 4 to 6 inches deep and consider planting them in tight groups so they can support each other. You can also use small bamboo stakes for individual stems if needed.
When should I stop fertilizing my dahlias?
It is a good idea to stop fertilizing your dahlias by late August or early September. As the days shorten and the weather cools, the plant begins to shift its energy from flower production to strengthening the tuber for dormancy. Continuing to add high-nitrogen fertilizer late in the season can result in "soft" growth that is more susceptible to frost damage and doesn't store as well over winter.
Can I grow dahlias and gladiolus in containers?
Yes, both plants do very well in containers. For dahlias, choose a large pot (at least 12–15 inches in diameter) and use a high-quality potting mix. Low-growing or "border" dahlia varieties are usually the best choice for pots. For gladiolus, you can plant 7 to 10 corms in a large container to create a stunning vertical accent. How to Grow Gladiolus Bulbs in Containers has a simple step-by-step guide. Ensure your containers have drainage holes, as these plants do not like sitting in standing water.
