Dahlia care guide

Welcome to the Funtail Farm dahlia care guide, your go-to resource for growing beautiful dahlias in New Zealand. We share simple, effective tips to ensure your dahlias thrive from planting to bloom. Let's get your garden flourishing!

Simple tips for thriving dahlias

Growing stunning dahlias doesn't have to be complicated. Here are our top three super simple tips to get you started and ensure your dahlias flourish:

1. Getting started: storage & timing

  • Arrival care: If you're not ready to plant immediately, store your tubers in a cool, dark, dry place like a garage or basement. Keep the bag open so they can breathe.
  • The golden rule: Do not plant outdoors until the risk of frost has completely passed. In New Zealand, Labour Day (late October) is the traditional "safe" time to plant.
  • Soil temperature: Dahlias only start producing roots when the soil temperature reaches about 15°C.

Planting your tubers

Proper planting is the foundation for healthy dahlia growth. Follow these steps for successful establishment:

  • Location: Choose a spot that receives at least 6–8 hours of direct sunlight each day.
  • Soil preparation: Dahlias adore rich, well-draining soil. If your soil is heavy clay, amend it generously with compost or well-rotted manure to improve drainage and fertility.
  • The planting hole: Dig a hole 5–10cm deep. Lay the tuber horizontally with the "eye" (the small growing point) facing upward.
  • Spacing: Space tubers 30–50cm apart. This allows for good airflow and ample room for growth, preventing overcrowding.

Common dahlia problems & solutions

Even with the best care, dahlias can face challenges. Here are the most common issues and how to fix them:

1. Slugs, snails, and earwigs (the midnight snackers)

The problem: You go to bed with beautiful green shoots and wake up to ragged, holy leaves—or worse, the entire shoot is eaten down to the ground.

The fix:

  • For slugs/snails: Scatter organic iron phosphate bait (like Sluggo) around the base of the plants as soon as they sprout.
  • For earwigs: Place upside-down small flower pots filled with damp shredded newspaper or straw near the plants. Earwigs hide inside overnight, and you can dump them into a bucket of soapy water in the morning.

2. Powdery mildew

The problem: Late in the summer season, a fuzzy white or gray coating spreads across the leaves, causing them to crisp up and die early.

The fix:

  • Airflow is key: Space your dahlias properly (at least 2–3 feet apart) and strip the lower leaves off the bottom 12 inches of the plant once it gets bushy.
  • Water wisely: Always water at the base of the plant rather than overhead to keep the foliage dry.
  • Treatment: Spray early with a mild fungicide if powdery mildew appears.