Few flowers deliver quite as much drama as dahlias. Their blooms range from neat little pompons to enormous dinner-plate flowers, with colors spanning creamy white, buttery yellow, coral, pink, orange, red, burgundy, lavender, and nearly black.
Even better, dahlias don’t give you just one brief show. With good care and regular flower picking, healthy plants can bloom from midsummer until frost finally brings the season to an end.
Despite their extravagant appearance, dahlias aren’t especially difficult to grow. Give them plenty of sun, fertile well-drained soil, consistent moisture once they’re actively growing, and support for taller varieties. Then keep cutting or deadheading the flowers to encourage the plants to produce more.
The one complication is winter. Dahlias are frost-tender plants grown from tubers, so gardeners in cold climates generally need to lift and store those tubers or treat the plants as annuals.
Here’s how to grow dahlias from planting time through the final flowers of fall.
🌸 Get to Know Dahlias
Dahlias are native to Mexico and Central America and belong to the daisy family, Asteraceae.
The diversity found among cultivated dahlias is extraordinary. Some varieties stay compact enough for containers, while others grow several feet tall and carry flowers almost as large as dinner plates.
Flower forms include decorative, cactus, semi-cactus, ball, pompon, anemone-flowered, collarette, waterlily, and single dahlias, among others.
That variety means there is a dahlia for almost any sunny garden. Compact plants work beautifully near the front of a border or in pots, while tall varieties can become spectacular background plants or dedicated cut-flower crops.
Before planting, check the expected mature height of your variety. A 20-inch bedding dahlia and a towering dinner-plate type require very different amounts of space and support.
☀️ Choose a Sunny Location
Dahlias flower best with plenty of sunlight.
Choose a position that receives at least six hours of direct sun on most days. In areas with extremely hot summers, some protection from the most intense late-afternoon sun can be useful, but deep shade usually produces weaker growth and fewer flowers.
Air circulation matters too.
Avoid squeezing dahlias tightly between large plants where their foliage remains crowded and damp. Good spacing helps leaves dry after rain and makes it easier to inspect plants for pests or disease.
Taller dahlias also appreciate some shelter from strong winds. Large flowers become heavy, particularly after rainfall, and exposed plants can snap or lean without adequate support.
🌱 Give Dahlias Rich, Well-Drained Soil
Dahlias like fertile soil that retains some moisture while still draining freely.
Waterlogged ground is a problem because the fleshy tubers can rot when they remain saturated for long periods.
Before planting, improve poor soil with finished compost or other well-decomposed organic matter. If your soil is extremely heavy and stays wet for long periods, raised beds may provide better drainage.
At the other extreme, very sandy soil can dry quickly during hot weather. Organic matter and mulch can help it retain moisture more consistently.
Good soil preparation is worth the effort because a vigorous dahlia may spend months growing, flowering, and producing new tubers underground.
📅 When Should You Plant Dahlia Tubers?
The most important rule is simple: don’t rush them into cold, wet soil.
Dahlias are frost-sensitive. Wait until the danger of frost has passed and the soil has begun warming before planting dormant tubers outdoors.
Gardeners who want an earlier start can pot tubers indoors several weeks beforehand. Keep the pots in a bright, frost-free location and water sparingly until active growth begins.
Before moving indoor-grown dahlias permanently outside, gradually acclimate them to outdoor sunlight, wind, and temperature changes.
Your local frost dates are more useful than a fixed national planting date. A gardener in a warm southern climate may be planting long before someone in the northern United States can safely put dahlias outside.
🥔 How to Plant Dahlia Tubers
A dahlia tuber clump can look a little intimidating the first time you see one.
The swollen tubers are attached to a central crown, and new shoots emerge from eyes around that crown rather than randomly along each tuber.
Place the tuber cluster with the crown and any visible shoots or eyes facing upward. The tubers themselves can lie horizontally beneath the soil.
Planting depth varies with the size of the variety and local recommendations, so follow the directions supplied with your tubers. The crown generally sits only several inches below the finished soil level rather than being buried extremely deeply.
Space plants according to mature size. Compact dahlias can grow closer together, while large varieties may need roughly two feet or more between plants.
If your dahlia will need a stake, install it at planting time. Driving a stake through the ground later creates a real possibility of spearing the tubers underneath.
💧 Don’t Overwater Newly Planted Tubers
This is one of the easiest dahlia mistakes to make.
A freshly planted dormant tuber doesn’t need the same amount of water as a vigorously growing plant in July.
If the soil is already reasonably moist, avoid continually watering before shoots appear. A dormant tuber sitting in cold, saturated soil is vulnerable to rot.
Once new growth emerges and the plant begins developing leaves, gradually increase watering.
By summer, an established dahlia with a large canopy and numerous flower buds can use a considerable amount of moisture. The watering strategy therefore changes as the plant grows.
🌿 Water Deeply Once Plants Are Growing
Once dahlias are actively growing, aim for reasonably consistent soil moisture.
Deep watering is generally more useful than frequent shallow sprinkling because it encourages moisture to reach the root zone.
How often you need to water depends on rainfall, temperature, soil type, plant size, and whether the dahlias are growing in containers or in the ground.
Use the soil as your guide rather than following a rigid calendar.
During hot, dry periods, check plants regularly. Dahlias that remain drought-stressed may slow flower production.
Mulching can help stabilize soil moisture and reduce evaporation, but keep mulch from being piled directly against the stems.
🌱 Pinch Young Dahlias for Bushier Plants
It can feel completely wrong to cut the top from a healthy young dahlia.
But pinching can encourage a fuller plant with more flowering stems.
Once a young dahlia has developed several sets of leaves and is growing strongly, removing the central growing tip encourages buds lower on the stem to develop into side branches.
Instead of producing one dominant central stem, the plant becomes bushier.
Those additional branches can ultimately produce additional flowers.
Pinching isn’t essential for every dahlia. Compact varieties may naturally branch well without much intervention, while gardeners growing large exhibition flowers may use very different pruning techniques.
For ordinary garden and cut-flower dahlias, however, one early pinch can create a sturdy, productive plant.
🪵 Stake Tall Dahlias Early
A mature dahlia can become surprisingly heavy.
Tall stems support dense foliage and multiple blooms, and one summer thunderstorm can flatten a plant that looked perfectly stable the day before.
Install strong stakes before the plant becomes large.
As stems grow, loosely secure them with soft garden ties. Don’t cinch the material tightly against the stem; leave room for growth and movement.
Another option is to surround several dahlias with stakes and create a supportive framework using garden twine.
Compact bedding dahlias may need no support at all, while enormous dinner-plate varieties deserve something substantial.
Waiting until a plant is leaning across its neighbor is much harder than supporting it early.
✂️ Deadhead Regularly for More Flowers
If you want dahlias to keep blooming, don’t allow every faded flower to remain on the plant.
Once a bloom finishes, the plant begins directing energy toward seed production. Removing spent flowers encourages it to continue producing new buds.
Cut the faded stem back to a healthy leaf joint rather than simply snapping off the flower head.
Dahlias can occasionally make deadheading confusing because an unopened bud and a spent flower can look similar once the petals have disappeared.
Look at the shape.
Fresh buds tend to be rounded, while spent flower heads become more pointed and irregular.
Checking the plants once or twice a week during peak flowering keeps deadheading manageable.
💐 Cutting Dahlias for Bouquets Encourages More Blooms
One of the pleasures of growing dahlias is that you shouldn’t feel guilty about cutting them.
Regular harvesting encourages plants to continue flowering in much the same way as deadheading.
Cut stems with clean, sharp pruners and take a reasonably long stem rather than clipping the bloom immediately beneath the flower. Cutting farther down encourages the plant to branch from lower leaf nodes.
Dahlias should generally be harvested when the flower is fully or almost fully open because closed dahlia buds do not continue opening particularly well after cutting.
For the longest vase life, choose fresh flowers whose outer petals are still firm rather than blooms already beginning to fade at the back.
A garden filled with dahlias can supply bouquets for weeks without looking empty for long.
🌺 Feed for Flowers, Not Just Leaves
Dahlias grow vigorously and appreciate fertile soil, but excessive nitrogen can produce an impressive amount of leafy growth with disappointing flowering.
If your soil is already rich, heavy feeding may not be necessary early in the season.
Once plants begin forming buds and flowering, a fertilizer intended to support flowering plants can be used according to label directions if additional nutrients are needed.
More fertilizer is not automatically better.
Plants receiving excessive nitrogen may grow tall, lush, and green while devoting less energy to flowers.
If you’re unsure what your garden soil actually needs, a soil test is more useful than guessing.
🌾 Mulch Around Dahlias in Summer
Once the soil has warmed and the plants are established, a layer of organic mulch can make summer care much easier.
Mulch helps slow moisture loss, suppress weeds, and protect the soil surface during hot weather.
Shredded leaves, compost, fine bark, or another locally appropriate organic mulch can work well.
Leave a little open space around the stems rather than piling material directly against them.
Mulch doesn’t eliminate the need to water, but it can make moisture levels much more consistent during hot, dry spells.
🐛 Watch for Slugs and Snails
Tender young dahlia shoots can be irresistible to slugs and snails.
Damage can be particularly discouraging early in the season because an emerging plant may lose a large portion of its foliage overnight.
Inspect plants regularly as they emerge.
Reducing hiding places immediately around vulnerable plants, hand-picking pests where practical, and using an appropriate management strategy for your garden can all help.
Once dahlias become larger and tougher, early-season chewing may become less threatening, although flowers and foliage can still attract various pests.
🕷️ Look for Aphids, Mites and Other Pests
Aphids may gather on tender new growth, while spider mites can become troublesome during hot, dry weather.
Earwigs, caterpillars, and other insects may occasionally damage leaves or flowers as well.
Before treating anything, identify the pest.
A garden naturally contains insects, and many of them are beneficial predators or harmless visitors. Routine spraying can eliminate the very insects helping keep pest populations under control.
If you notice fine stippling, discoloration, or webbing, inspect the undersides of leaves carefully. Our guide to getting rid of spider mites on plants explains the telltale signs of mite feeding.
Early detection makes nearly every pest problem easier to manage.
🐝 Choose Open Dahlias for Pollinators
Not every dahlia offers the same value to bees and other pollinators.
Highly double varieties can have so many layers of petals that their pollen and nectar are difficult for insects to reach.
Single and other open-centered dahlias provide much easier access.
You don’t need to give up spectacular double dahlias if you love them. Instead, consider growing some open-centered varieties alongside them and combining dahlias with other pollinator-friendly flowers.
A diverse flower bed containing plants that bloom at different times is generally more useful to bees than relying on a single species.
Our World Bee Day guide to making a garden more bee-friendly has more ideas for providing flowers and habitat throughout the growing season.
🪴 Can You Grow Dahlias in Containers?
Yes, particularly smaller varieties.
Choose a generously sized container with excellent drainage. Dahlias grow quickly and need enough soil volume to support their roots and help prevent the pot from drying out constantly.
Compact cultivars are easiest, although larger dahlias can be grown in substantial containers if you’re willing to provide strong support and attentive watering.
Container plants usually dry faster than dahlias growing in the ground, so check moisture frequently during hot weather.
They may also require more regular feeding because repeated watering washes nutrients from the potting mix.
Never let the container sit continually in standing water.
🌼 What If Your Dahlia Isn’t Blooming?
A healthy-looking dahlia covered in leaves but producing few flowers often provides clues about what’s wrong.
Start with sunlight. Plants growing in too much shade may stretch toward the light and bloom poorly.
Next consider fertilizer. Too much nitrogen encourages leafy growth at the expense of flowering.
Water stress can also reduce bloom production. Dahlias growing in very dry soil may stop producing flowers as vigorously.
Finally, remember timing. Depending on when they were planted and your climate, dahlias may not reach peak flowering until later in summer.
Give them good conditions and a little patience.
Many dahlias are at their most spectacular when other parts of the garden are already beginning to look tired.
🌧️ Protect Dahlias From Storm Damage
Big dahlias and summer thunderstorms can be a bad combination.
Rain collects on large blooms, making already heavy flower heads even heavier. Wind then pushes against tall, leafy stems.
Good staking is your first defense.
After a storm, inspect plants for broken or partially snapped stems. Remove severely damaged growth cleanly with sharp pruners.
Check ties and supports as the plants grow. A stake that seemed enormous in June can almost disappear inside a mature dahlia by August.
Keeping plants properly supported throughout the season preserves more flowers and prevents the entire clump from collapsing onto neighboring plants.
🌺 How to Get the Biggest Dahlia Flowers
Most gardeners want lots of flowers.
But if your goal is a smaller number of exceptionally large blooms, you can use a technique called disbudding.
When a flowering stem develops one main bud accompanied by smaller side buds, remove the side buds while they’re still small. That directs more of the plant’s resources toward the remaining central flower.
The tradeoff is obvious: fewer flowers, but potentially larger individual blooms.
This is particularly useful for giant decorative and dinner-plate dahlias.
If you prefer an abundant cottage-garden look or lots of stems for bouquets, you may decide that more medium-sized flowers are better than a few enormous ones.
Neither method is wrong.
🍂 What Happens to Dahlias After Frost?
Dahlias will continue blooming until cold weather ends the show.
The first substantial frost typically blackens and collapses the foliage.
In warm climates where the ground doesn’t freeze and winter soil remains suitable, gardeners may be able to leave tubers in place. A protective layer of mulch can provide additional insulation where winters are mild.
In colder regions, the safer approach is to dig the tubers and store them somewhere protected from freezing.
Winter survival isn’t only about temperature. Cold, waterlogged soil can rot tubers as well, which is why even gardeners in relatively mild climates sometimes prefer to lift them.
🥔 How to Dig Dahlia Tubers for Winter
After frost has killed the top growth, cut the stems back while leaving a short portion attached to help you locate and handle the clump.
Use a garden fork or spade and begin digging well away from the stem.
Dahlia tubers can spread farther than you expect, and plunging a shovel directly beside the stalk is an excellent way to slice through them.
Gently lift the entire clump.
Remove loose soil without aggressively snapping the tubers apart.
Allow the clump to dry sufficiently before storage, following a method appropriate to your climate and storage conditions.
Label each variety before everything becomes a pile of nearly identical brown tubers.
You may believe you’ll remember which is which in spring.
You probably won’t.
❄️ How to Store Dahlia Tubers
The goal of winter storage is to keep tubers cool, frost-free, and neither excessively wet nor completely dried out.
Exact storage methods vary because homes, basements, garages, and climates differ enormously.
Some gardeners pack tubers in slightly moisture-retentive materials, while others store intact clumps in breathable boxes or crates.
Whichever method you use, check the tubers occasionally through winter.
Remove anything that has developed extensive rot before it spreads to neighboring tubers. If tubers are becoming extremely shriveled, your storage environment may be too dry.
The perfect system may require a little experimentation with the conditions available in your home.
🔪 When Should You Divide Dahlia Tubers?
A healthy dahlia can produce a much larger tuber clump by the end of the season.
Eventually, that clump can be divided to produce more plants.
Each viable division needs part of the crown containing at least one eye along with an attached healthy tuber. A detached tuber without an eye won’t produce a new dahlia.
Some gardeners divide in fall before storage. Others prefer spring, when emerging eyes can be easier to identify.
Use clean, sharp tools and discard tubers that are badly damaged, rotting, or diseased.
Dividing is one of the reasons a modest dahlia collection has a habit of becoming a large one surprisingly quickly.
🌻 Dahlias Are Made for Late Summer
Dahlias require a little more attention than plants you can put in the ground and forget.
They may need staking. They appreciate regular watering. Spent flowers need removing, and gardeners in cold climates have to decide what to do with the tubers every fall.
But the reward is difficult to beat.
Just as many early-summer flowers begin fading, dahlias are gaining momentum. By late summer and early fall, a well-grown plant can be covered in buds and blooms.
Cut an armful for the house and more appear.
Deadhead the faded ones and the next buds are already waiting.
Then keep going until frost finally decides the season is over.
Give dahlias sunshine, good drainage, consistent care, and permission to bloom freely, and they’ll repay you with some of the most spectacular flowers in the summer garden.
🔗 Related Articles
- June Gardening Checklist: What to Plant, Prune & Do This Month
- World Bee Day: 10 Ways to Make Your Garden More Bee-Friendly
- How to Grow Zinnias: Planting, Care & Tips for More Blooms
- Hydrangea Care: How to Grow, Prune & Keep Hydrangeas Blooming
📚 Sources & Further Reading
- Royal Horticultural Society — How to Grow Dahlias
- Royal Horticultural Society — Dahlias
- Illinois Extension — Plant of the Week: Dahlias
- Illinois Extension — Tender Bulbs Make for Summer Delights
- Illinois Extension — Planting Bulbs
- Penn State Extension — Pruning Herbaceous Plants
- Penn State Extension — Supporting Herbaceous Plants in a Flower Garden
