PLANTING &
GROWING
DAHLIAS
Dahlias are native to the mountainous regions of Mexico and Central America, where they were cultivated for ornamental and medicinal use. Introduced to Europe in the late 18th century, they quickly gained popularity for their vivid colors and wide range of flower forms, leading breeders to develop thousands of cultivars. Today, dahlias are valued for their diversity, with blooms ranging from compact pompons to expansive dinnerplate flowers, displaying petals in everything from soft pastels to bold color combinations. Their long blooming season and strong visual presence continue to secure their place among the most popular ornamental flowers.
Timing: Plant outdoors only after all danger of frost has passed and nighttime temperatures remain consistently above freezing.
Soil temperature: Wait until soil temperatures reach at least 60°F to encourage strong sprouting and reduce tuber rot.
Typical window: Late April through May in cooler climates, and March through early April in warmer regions.
Important note: Tubers lacking eyes will never sprout, even if they appear firm, plump, and disease-free.
PLANTING TIME
Exposure: Provide at least six to eight hours of direct sunlight daily for strong stems and abundant flowering. Morning sun with light afternoon shade improves performance in regions with intense summer heat.
Air circulation: Open planting areas with good airflow help prevent powdery mildew and other fungal diseases.
Soil type: Loose, fertile, well-drained soil prevents tuber decay during wet periods. Incorporate compost, leaf mold, or aged manure to improve drainage, fertility, and soil structure.
SITE & SOIL
Before emergence: Keep soil mostly dry after planting, as excessive moisture before sprouting frequently causes tuber rot.
After emergence: Water deeply two to three times per week once shoots appear and active growth begins.
Best practice: Apply water at soil level to minimize foliage wetness and reduce disease risk.
WATERING
Depth: Plant tubers six to eight inches deep to anchor tall plants and protect developing roots.
Orientation: Lay tubers horizontally with the eye facing upward to encourage straight, even shoot emergence.
Spacing: Space plants twelve to thirty-six inches apart depending on mature variety size and airflow requirements.
Important note: Deeper planting improves stability, reduces wind damage, and helps prevent top-heavy plants from snapping later in the season.
PLANTING DEPTH & SPACING
Fertilizer type: Use low-nitrogen formulations such as 5-10-10 or 10-20-20 that emphasize phosphorus and potassium to promote flowering rather than excessive foliage.
Frequency: Feed plants every three to four weeks from early summer until early September.
Mulch Timing: Mulch only after soil has warmed and plants are well established.
Why: Mulching conserves moisture, suppresses weeds, moderates soil temperature, and protects shallow feeder roots.
FERTILIZER & MULCH
Installation: Install stakes or cages at planting time to avoid damaging developing tubers later in the season.
Height: Tall varieties typically require four- to six-foot supports for adequate wind protection.
Benefit: Proper support prevents stem breakage, lodging, and flower damage during summer storms.
STAKING & SUPPORT
Pinching: Remove the central growing tip when plants reach twelve to sixteen inches tall. Pinching encourages branching, sturdier stems, and significantly increased flower production.
Deadheading: Remove spent blooms promptly to redirect energy toward continuous bud development.
Bloom Maintenance: Regular cutting and deadheading significantly extends bloom duration and stem production.
Cutting flowers: Harvest blooms early in the morning or evening when stems are fully hydrated. Cut flowers when buds are three-quarters open.
Note: Bloom size, stem length, and color intensity often improve as the season progresses.
PRUNING & BLOOM CARE
After frost: Allow frost to blacken foliage naturally before lifting tubers from the ground, then cut stems back to four to six inches once foliage has collapsed. Dig carefully with a fork to avoid breaking fragile necks and crowns.
Storage: Store tubers between 40–50°F in a frost-free, dark, well-ventilated location with moist peat moss, vermiculite, or wood shavings to prevent dehydration. Inspect monthly and remove any tubers showing rot or mold.
Dividing: Divide tubers in spring shortly before planting for easiest eye identification. Each division must include at least one viable eye attached to the crown.
DIGGING, STORING & DIVIDING TUBERS
GARDEN TOURS • OREGON
Swan Island
Dahlias
Swan Island Dahlias showcases expansive fields filled with thousands of blooming dahlias in every color and form, set within a working flower farm environment that offers sweeping views, seasonal displays, and a vibrant late-summer destination for garden enthusiasts and photographers.
Dahlia Flower Forms
Dahlias display an impressive range of flower forms. From small, tightly patterned blooms to large, fully layered blossoms, these forms create varied visual effects in the garden. This diversity allows dahlias to suit many planting styles, providing bold focal points, soft texture, and abundant color in borders, cutting gardens, and seasonal displays.
