Planting Dahlia Tubers

Spacing

Depends on tuber size:

  • Small tubers: 12 inches apart

  • Medium tubers: 18 inches apart

  • Large tubers: 24 inches apart

  • Clumps: 24 inches apart or more

Preparing the Hole

  • Dig a hole 6 inches deep, OR dig a continuous trench 6 inches deep along a row

  • Add a small handful of organic compost and a teaspoon or so of organic amendment (organic Bulb-Tone)

  • Mix compost and Bulb-Tone into the soil before planting

Placing the Tuber

  • Place the tuber with the eye facing up

  • Ensure the eyes are positioned so that all tubers face the same direction and plants grow evenly and spacing remains consistent

If the Tuber Has Sprouted

  • If the eye has already sprouted, that is perfectly fine

  • Plant the tuber so the tip of the growth remains above the soil line

Long Sprouts

  • If the sprout is long, trim it, as it may otherwise break. Leave an inch or so of growth

  • Ideally allow the cut to heal for a day before planting

  • If a sprout breaks, don’t worry — the plant will grow again, it will just take longer

Covering the Tuber

  • Cover up the hole with soil

  • Do not pack the soil down

Irrigation

Before Growth

  • Set up drip irrigation before planting if you have drip

  • Also set up overhead irrigation

  • Do not water immediately after planting, especially if rain is expected

  • Wait to water until visible growth appears

Early Growth

Use overhead irrigation until plants become too tall for water to get through the leaves.

If there is no rain:

  • Water once per week

  • Up to 30 minutes per session

  • Avoid overwatering — tubers can rot and turn to mush

Established Plants

Once plants are growing well:

  • Water 1–2 times per week, depending on heat and dryness

  • Approximately 30 minutes per session

Soil should be moist but never soggy.

Plant Care

Pinching

When the first flower bud forms in the center, pinch it out.

This encourages branching and more blooms.
(It’s hard, but do it!)

Pruning

Remove lower leaves as plants grow to improve airflow and plant health.

Pest Management

Gently hand-pick Japanese beetles DAILY and remove them from the plants. Don't be shy… they will damage your blooms. Drop them in a jar of warm soapy water.

Support 

Dahlias can grow quite tall and produce heavy blooms, so providing support keeps stems straight, prevents breakage in wind or rain, and makes harvesting flowers easier. There are several common support methods, and the best one depends on how many plants you have, spacing, and how intensively you grow them.

1. T-Post and Twine System (Best for Rows)

2. Horizontal Netting (Hortonova ) - This is what we use on the farm (see below)

3. Individual Stakes (Best for Small Gardens)

4. Tomato Cages (Best for Large Decorative Dahlias)

For more details on supporting your dahlias you can peek online using any of the keywords above.

Veggies to Table Support Netting - how we support the dahlias that we grow here on the farm in 30' rows

Bed Preparation

We plant our dahlias in 30-inch beds with two rows per bed.

Install T-posts before planting:

  • Place posts 10 feet apart

  • Posts should face each other across the bed exactly 30 inches apart

  • Ensure all posts run in the same direction, with the eyes facing the outside the bed

Install one layer of Hortonova netting:

  • Position netting approximately 2 feet above the ground

  • Attach securely to the T-posts

  • Make sure the netting is tight. This is key to the success of supporting the plants

Of Note: Use one continuous 100-foot piece of netting, do not skimp. This is not the place for it. Do not use multiple small sections.