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Dahlia Growing Guide

Dahlias are one of the most rewarding flowers you can grow—abundant blooms, incredible color, and a steady supply of cut flowers from mid-summer through frost. With a little care upfront, they’ll give back all season long.

Getting Started – Light + Soil

Dahlias thrive in full sun (at least 6–8 hours daily) and rich, well-draining soil. They’re heavy feeders, so adding compost or organic matter before planting will set them up for success. Poor drainage can cause tubers to rot, so raised beds or mounded rows work beautifully.

When to Plant

Wait until after your last frost and the soil has warmed. In cooler climates like Wisconsin, this is typically late spring.

Dahlias are not frost-tolerant, so planting too early can set them back.

How to Plant

  • Plant tubers 4–6 inches deep
  • Lay them on their side with the “eye” facing up
  • Space plants about 10–12 inches apart
  • Cover with soil and hold off on watering right away

Sprouts can take anywhere from 2–6 weeks to appear, so patience is key.

Watering

Less is more in the beginning.

  • Do not water immediately after planting
  • Wait until you see green growth above the soil
  • Once plants are established (about 12–18”), water deeply about 1 inch per week
  • Increase watering during hot, dry stretches

Overwatering early on is one of the most common mistakes.

Supporting Your Plants

Dahlias grow quickly and can get top-heavy once they start blooming.

  • Stake plants early to avoid damaging roots later
  • Tie stems as they grow to keep them upright and protected from wind

Harvesting Blooms

For the longest-lasting flowers:

  • Cut in the early morning or evening
  • Harvest when blooms are almost fully open (they won’t open much after cutting)
  • Use clean, sharp snips and cut at an angle
  • Refresh water and re-trim stems regularly

With proper care, cut dahlias typically last 3–5 days in a vase.

Keep Them Blooming

The more you cut, the more they produce.

Regular harvesting encourages your plants to send out new blooms all season long—making dahlias one of the best cut flowers you can grow.

End of Season Care

After the first frost, plants will die back. At that point you can:

  • Dig up tubers
  • Let them dry
  • Store them in a cool, dry place over winter

Replant the following spring to grow your collection year after year.