Dahlia Growing Guide

Dahlias are not hard, but they are not completely hands-off either. Treat them right, and they will absolutely show off for you.

Rooted Cuttings (Beginner Friendly Walkthrough)

Cuttings require a bit more attention than tubers, but they reward you with earlier blooms. Yes, cuttings will produce tubers.

Think of them like teenagers instead of babies. They can fend for themselves, but they still need guidance.

Step-by-step:

1. Harden off first
   Gradually introduce them to outdoor conditions over several days. Do not just toss them outside and hope for the best.
2. Plant after last frost
   Cold soil and tender cuttings do not mix well.
3. Planting
   • DO NOT peel the rooting cubes off!  This will void all warranty, and could severely damage your cutting
   • Plant in well-drained soil
   • Water in thoroughly
   • Ideal timing is a cloudy or rainy day, which helps reduce transplant shock
4. Group planting (recommended)
   Plant cuttings together so you can water, fertilize, and manage them consistently.

5. Fertilizing schedule

   • Day 0: Plant and water well
   • Day 2–3: Fertilize at 50% strength
   • Week 2: 50% again
   • Week 3: Move to 100% strength
   • Then: Every other week for about 2 months
   • After that: Monthly through August
   • September: Final feeding at 50%

   We use Vigor, but any balanced liquid fertilizer will work.

6. Pinching (very important)
   Once the plant reaches about 10 inches tall, pinch it back.
   It feels wrong, but it encourages branching and more blooms.
7. Deadheading
   Remove spent blooms. This helps redirect energy into tuber production.

Sun and Placement

• Minimum of 6 hours of sunlight per day, 8 is ideal
• In warmer climates, afternoon shade is beneficial
• White varieties especially benefit from shade to prevent browning or sunburn

Planting Tubers

• Plant 4–6 inches deep in well-drained soil
• A useful method is to dig a 6-inch hole, plant at 4 inches, and leave a shallow depression
  • This acts as a watering basin
  • Keeps water near the plant instead of feeding surrounding weeds
• Ideal soil pH is around 6.5

Feeding Dahlias

Dahlias are heavy feeders early in the season and should be fertilized regularly through summer. Stop fertilizing in September.  We feed our tubers monthly, June-September.

They are also foliar feeders, meaning they can absorb nutrients through their leaves. Liquid fertilizers can be applied as sprays if needed.

Water and Drainage

Dahlias need consistent moisture but do not tolerate sitting in water.

In winter, excess moisture is often more damaging than cold. Poor drainage can lead to rot.

Overwintering

Leaving in the ground

• Cut stalks after frost
• Add 4–6 inches of compost
• Consider covering to limit excess winter moisture

Digging and storing

• Cut stalks to 6–9 inches after frost or around November 1
• Dig 2 weeks later
• Allow tubers to dry before storage
• Store in a cool, dark location that does not freeze
• Use peat moss, vermiculite, or potting soil to maintain humidity

Pacific Northwest Timing (Oregon)

• Around April 1: Move stored tubers to a warm, dark place to encourage sprouting
• Around May 1: Inspect and discard damaged or rotting tubers
• Mid-May to June 1: Plant outdoors

For earlier blooms, start tubers in pots and protect from frost before transplanting.

Dahlias typically take 90 to 120 days to bloom and will continue until frost.

Soil Testing

The best fertilizer decision starts with a soil test.

A soil test identifies what nutrients are needed and what should not be added.

Without a test, it is generally safe to assume nitrogen is low, especially in regions with heavy winter rainfall like the Pacific Northwest. Nitrogen and magnesium are often the primary deficiencies early in the season.

Common Amendments

• Ammonium Sulfate (21-0-0)
  Fast-acting nitrogen with added sulfur. Leaches quickly.
• Urea (42-0-0)
  High nitrogen content. Efficient and fast acting.
• Epsom Salt (Magnesium Sulfate)
  Provides magnesium, which supports nitrogen uptake. Use sparingly.
• Bone Meal
  Adds phosphorus and calcium. Use only if a deficiency is confirmed.
• Gypsum
  Adds calcium and sulfur without significantly changing soil pH.
• Dolomite Lime
  Adds calcium and magnesium and raises soil pH.
• Manure
  Adds nitrogen, phosphorus, and potassium. Can lead to phosphorus buildup over time.
• Blood Meal
  Fast-release nitrogen source.
• Feather Meal
  Slow-release nitrogen source.
• Elemental Sulfur
  Lowers soil pH and supports plant health.
• Dried Molasses
  Supports microbial activity and overall soil health.

A Practical Note

Blood meal, feather meal, and bone meal can attract dogs, squirrels, and other animals. If something starts digging in your garden, this is often the reason.

Bottom Line

• Start with good soil
• Add nitrogen if you are not soil testing
• Avoid overcomplicating the process
• Focus on consistency

You are not growing tubers for appearance. They spend the season underground doing their job.

You are growing blooms. Focus on what shows up above ground.