Learn how to grow dahlias at home — from planting tubers in spring to storing them for winter — with step-by-step guidance on varieties, care, and getting the most spectacular blooms.
If any single flower can transform an ordinary backyard into something truly extraordinary, it’s the dahlia. From the size of a dinner plate to the delicacy of a pompon, from pure white to deepest burgundy to sunrise-streaked bicolors — dahlias offer more variety, more drama, and more color impact than virtually any other flower a home gardener can grow.
And despite their spectacular appearance, dahlias are genuinely beginner-friendly plants. They are not difficult to grow — they simply need a few specific conditions to perform at their best.
At Outz News Garden, Maria Walker loves dahlias for their unrivaled late-season color impact just as spring and summer annuals begin to fade. This complete guide walks you through everything — variety selection, tuber planting, staking, watering, pinching for more blooms, and storing tubers through winter. For a complementary late-season color combination, see our guide to low-maintenance perennial flowers that pair beautifully with dahlias.
Understanding Dahlia Types
According to the University of Minnesota Extension, when digging dahlias and other tender tubers, always loosen soil on all sides of the plant before lifting the clump to avoid cutting or skinning the fleshy roots — wounds create entry points for disease that cause rotting during storage. According to Penn State Extension, dahlias are easy-to-grow plants that yield bountiful, beautiful blooms from midsummer to the first frost, with many shapes and riotous colors that can brighten gardens, borders, and even patio containers.
Dahlias are classified by both flower form and size. Here are the most important categories for home gardeners:
By Flower Form
- Decorative dahlias — the classic “dinner plate” dahlia; large, fully double blooms with broad, flat petals. The most dramatic dahlia form. Varieties like Cafe au Lait (blush/cream), Thomas Edison (deep purple), and Labyrinth (orange/pink) are popular choices.
- Ball dahlias — perfectly spherical, fully double blooms; smaller than decorative types but incredibly long-lasting as cut flowers. Jowey Mirella and Cornel are outstanding varieties.
- Pompon dahlias — even smaller spheres than ball dahlias; prolific producers of petite, perfectly round flowers. Very long-lasting cut flowers.
- Cactus dahlias — petals are rolled into narrow tubes, creating a spiky, dramatic appearance. Hamari Accord and Nuit d’Ete are outstanding varieties.
- Waterlily dahlias — flat, open blooms with broad petals that resemble a water lily. Cameo and Gerrie Hoek are beautiful varieties.
- Collarette dahlias — outer ring of petals surrounds an inner “collar” of shorter petals; charming, slightly informal look loved by pollinators.
By Size
- Giant (AA) — flowers over 10 inches across; the iconic “dinner plate” dahlias
- Large (A) — 8 to 10 inches
- Medium (B) — 6 to 8 inches
- Small (BB) — 4 to 6 inches
- Miniature (M) — under 4 inches; most productive, excellent for cutting
- Pompon — under 2 inches; extremely prolific
Step 1 — Choosing a Site for Dahlias
Penn State Extension emphasizes that dahlias require three fundamentals: full sun, water, and fertilizer. Getting the site right before planting determines everything that follows.
- Full sun — 6 to 8 hours minimum: dahlias bloom most prolifically in full sun. In partial shade, they produce fewer and smaller blooms with taller, weaker stems. Morning sun is especially valuable for drying overnight dew.
- Well-draining soil: dahlias cannot tolerate waterlogged conditions — tubers rot rapidly in standing water. Raised beds are excellent for dahlia growing in heavy soils.
- Soil pH 6.0 to 7.0: slightly acidic to neutral. Rich, loamy soil amended with compost produces the best results.
- Shelter from wind: tall dahlia varieties reach 4 to 6 feet and are vulnerable to wind damage. Siting near a fence or hedge provides wind protection without excessive shade.
Step 2 — Planting Dahlia Tubers
When to Plant
Penn State Extension notes that dahlias have tender tuberous roots — plant in spring after danger of frost has passed. In most regions this means planting from late April through mid-May, when soil temperature has reached at least 60°F. Cold soil causes tubers to sit dormant without growing and increases their susceptibility to rot.
University of Maryland Extension confirms that summer annual bulbs including dahlias can be planted once frost danger has passed and conditions are genuinely warm.
Planting Steps
- Prepare the soil: loosen to 12 to 15 inches deep and incorporate 3 to 4 inches of compost. Dahlias are heavy feeders that reward rich soil preparation.
- Dig the planting hole: create a hole 6 to 8 inches deep and wide enough to accommodate the tuber horizontally.
- Place the tuber correctly: lay the tuber on its side with the “eye” (growing bud) facing upward. The eye is found where the tuber joins the old stalk from the previous season. No eye = no plant.
- Set the depth: cover tubers with 2 to 3 inches of soil. Don’t cover too deeply in cool soils — deeper planting in cold conditions delays emergence and increases rot risk.
- Do not water until shoots emerge: this is the most important planting tip. Watering immediately after planting tubers in cool spring soil creates the conditions for rot before shoots have emerged. Wait to water until you see the first green growth breaking the soil surface — typically 2 to 4 weeks.
- Space properly: miniature varieties need 18 to 24 inches; medium and large varieties need 24 to 36 inches. Proper spacing is critical for air circulation and disease prevention.
Step 3 — Staking Dahlias
Penn State Extension notes that staking is important to prevent taller dahlia varieties from being toppled by strong wind. All but the smallest compact varieties need support.
- Install stakes at planting time — driving stakes near established plants risks piercing tubers
- Use sturdy stakes — 4 to 6 foot bamboo or metal stakes for medium and large varieties; giant varieties may need even taller support
- Tie loosely as the plant grows — use soft garden twine in a figure-eight pattern between stake and stem, leaving room for stem growth
- Cage or multiple stakes for giant varieties — very large dahlias develop heavy, multi-stemmed structures that need substantial support
Step 4 — Pinching for More Blooms
Pinching is the single most effective technique for transforming a single-stemmed dahlia into a bushy, prolific flowering plant that produces 3 to 5 times more blooms than an unpinched plant.
When your dahlia reaches 12 to 16 inches tall with 3 to 4 sets of leaves, pinch out the growing tip — the very top of the main stem — with clean scissors or your fingers. This redirects the plant’s energy from a single central stem into multiple side branches, each of which will produce flowers. The result is a fuller, more compact plant with dramatically more blooms across the season.
Step 5 — Watering and Fertilizing
Watering
- Water deeply once or twice per week during the growing season — approximately 1 inch per week
- Increase watering during hot weather and when plants are actively flowering
- Always water at the base — wet foliage promotes powdery mildew
- Mulch around plants to conserve moisture and regulate soil temperature
Fertilizing
- At planting: balanced slow-release fertilizer incorporated into the planting hole
- Monthly through the season: low-nitrogen fertilizer (higher phosphorus and potassium) encourages more flowers rather than excessive foliage. Avoid high-nitrogen fertilizers — they produce lush, vegetative plants with fewer blooms.
- Stop fertilizing 6 weeks before first frost — to allow the plant to naturally harden before digging
Step 6 — Deadheading for Continuous Bloom
Dahlias bloom continuously from midsummer through the first frost — but only if spent flowers are removed promptly. Deadheading redirects the plant’s energy from seed production back into flower production, extending the bloom season by weeks.
Cut spent blooms back to the first set of leaves below the faded flower. At the same time, check for and remove any small, undeveloped side buds near the main bloom — known as “disbranching” — which channels energy into fewer, larger flowers on cutting-garden varieties.
Step 7 — Digging and Storing Tubers for Winter
Penn State Extension notes that dahlias have tender tuberous roots that should be dug out every year after a hard frost and divided before being planted again in the spring.
- When to dig: after the first hard frost blackens the foliage — typically in October or November. Don’t dig too early; the plant is still storing energy in the tubers until frost.
- How to dig: cut stems to 6 inches above ground. Insert a garden fork 12 inches from the stem and lever upward gently to lift the tuber clump without breaking. Brush off excess soil.
- Cure the tubers: allow tubers to dry in a warm, ventilated location for 2 to 3 days. Do not leave outdoors overnight where temperatures could freeze them.
- Store properly: pack in boxes of slightly moist peat moss, vermiculite, or coconut coir. Store at 40 to 50°F in a dark, frost-free location — an unheated basement or garage works well.
- Divide before storage or at spring planting: clumps should be cut into sections with a sharp knife, ensuring each division contains at least one eye (growing bud). Eyes are found where the tuber joins the old stalk.
Quick-Reference Dahlia Growing Tips
- Plant after last frost when soil reaches 60°F — cold soil delays emergence and promotes rot
- Do not water until shoots emerge — most important planting tip for preventing tuber rot
- Install stakes at planting time — before driving stakes near mature tubers
- Pinch at 12 to 16 inches — triples or quadruples bloom production
- Deadhead consistently — extends bloom from midsummer all the way to frost
- Dig after first hard frost and store properly — protects your tuber investment for next season
- Start with small to medium ball or pompon varieties — easier to manage and highly productive for beginners
Learning how to grow dahlias opens the door to some of the most spectacular flower gardening available to home gardeners. Few plants offer the color range, the bloom size variety, the cutting garden productivity, and the sheer late-season impact of a well-grown dahlia planting in full bloom from August through October.
Start with two or three tubers in a sunny, well-draining spot. Stake them early, pinch them at 12 inches, and deadhead faithfully through the season. By September, you’ll be cutting armfuls of extraordinary flowers from your own garden — and planning a much larger dahlia planting for next year.
Share your dahlia photos in the comments — there’s no flower more photogenic! And for a complete guide to storing dahlias and other tender bulbs through winter, revisit our fall garden cleanup guide.
👉 Read Next: Spring Flower Garden — The Best Flowers to Plant and How to Grow Them
Maria Walker is a certified horticulturist and gardening specialist with over 15 years of hands-on experience in plant care, garden design, and sustainable growing practices.
She holds a Bachelor’s degree in Horticulture Science and a Master’s degree in Sustainable Agriculture — and has spent her career helping people of all skill levels create beautiful, thriving gardens.
Maria launched Outz News Garden with one simple mission: to make gardening accessible and inspiring for everyone, from first-time planters to seasoned green thumbs.