Intermediate Dahlia Growing: Form Classifications & Advanced Culture

Understanding Dahlia Classifications

The American Dahlia Society (ADS) classification system organizes the vast dahlia world into manageable categories based on form, size, and color. Understanding this system helps you select the right dahlias for your purposes and communicate accurately about varieties.

The ADS Classification System

Classification Code Format

Each dahlia receives a code like: FD-LT-DR

• First letters: Form (FD = Formal Decorative)
• Second letters: Size (LT = Large)
• Last letters: Color (DR = Dark Red)

Form Classifications

Decorative Types

Formal Decorative (FD):

• Flat petals evenly and regularly placed
• Petals may recurve toward stem
• Closed center
• Classic dahlia appearance

Informal Decorative (ID):

• Generally flat petals
• Irregular arrangement
• May be slightly rolled
• More relaxed appearance

Cactus Types

Straight Cactus (ST):

• Narrow at base
• Straight, rolled petals
• Reflex toward stem
• Points evenly in all directions

Semi-Cactus (SC):

• Broad at base
• Rolled for half length
• Straight or slightly incurved
• Popular for exhibition

Incurved Cactus (IC):

• Rolled for most of length
• Curve upward toward bloom face
• Creates domed appearance
• Dramatic texture

Laciniated (LC):

• Split petal tips
• Twisted or curled splits
• Fringed appearance
• Unique texture

Spherical Types

Ball (BA):

• Ball-shaped or slightly flattened
• Involute (rolled inward) petals
• Spiral arrangement
• Size: 3.5+ inches

Miniature Ball (MB):

• Same form as Ball
• Size: 2-3.5 inches
• More compact

Pompon (P):

• Nearly spherical
• Tightly quilled petals
• Size: under 2 inches
• Perfect for cutting

Other Forms

Stellar (S):

• Long, narrow petals
• Pointed tips
• Space between ray florets
• Star-like appearance

Waterlily (WL):

• Closed center
• Broad, flat petals
• Slightly incurved
• Depth less than half diameter
• Resembles water lily

Collarette (CO):

• Single row of outer petals
• Inner collar of smaller petals
• Open center with disc
• Often contrasting colors

Orchid (O):

• Single row of petals
• Petals rolled for 2/3 length
• Open center
• Graceful form

Peony (PE):

• Open center
• 2-5 rows of petals
• May have smaller petals near center
• Loose, informal appearance

Anemone (AN):

• One or more rows of ray florets
• Dense group of tubular disc florets
• Pincushion center
• Distinctive appearance

Single (S):

• One row of petals
• Open center
• Simple beauty
• Great for pollinators

Mignon Single (MS):

• Single form
• Plants under 18 inches
• Compact habit

Novelty (NX):

• Forms not fitting other categories
• Unique characteristics

Size Classifications

Color Classifications

Advanced Cultural Techniques

Pinching Strategy

Basic Pinch: When main stem reaches 12-16 inches:

1. Identify top pair of leaves
2. Remove growing tip above them
3. Creates two new growing points
4. Results in bushier plant

Double Pinch (for more stems):

1. First pinch as above
2. When new shoots are 8-12 inches, pinch again
3. Creates 4+ growing points
4. Delays flowering but increases stems

When NOT to Pinch:

• Very late plantings
• Pompon varieties (self-branching)
• If you want earliest possible blooms

Disbudding for Exhibition

Terminal Disbudding:

1. Identify terminal (center) bud
2. Remove all side buds
3. Allows all energy to one bloom
4. Creates largest possible flower

Timing:

• Remove side buds when pea-sized
• Work gently to avoid damage
• Check every few days

Staking Methods

Individual Stakes:

• One stake per plant
• Tie at 12-18 inch intervals
• Use soft ties (twine, foam)
• Most common method

Corral System:

• Stakes around bed perimeter
• String between stakes
• Plants grow through string layers
• Good for mass plantings

Tomato Cages:

• Work for compact varieties
• Install at planting
• No tying needed
• Limited for tall types

Tuber Division

When to Divide

• Spring before planting (recommended)
• Fall after digging (also works)
• Never divide in storage

Anatomy Understanding

Division Steps

1. Wash clump - Remove all soil
2. Identify eyes - May need to wait for visibility
3. Plan cuts - Each division needs eye + tuber
4. Cut carefully - Use sharp, clean knife
5. Label immediately - Before you forget variety
6. Allow to callus - Dry cuts for 1-2 days
7. Store or plant - Based on timing

Encouraging Eye Visibility

If eyes aren't visible:

• Place clump in warmth (70°F)
• Mist occasionally
• Wait 1-2 weeks
• Eyes will swell and green

Cutting Technique

• Cut through crown, not tuber
• Each piece needs portion of crown with eye
• Tuber neck must be intact
• One eye per division is sufficient

Season Extension

Early Season

Indoor Starting:

• Start 4-6 weeks before last frost
• Use pots in warm location (65-70°F)
• Provide light once sprouted
• Harden off before transplanting

Soil Warming:

• Black plastic mulch
• Raised beds
• Southern exposure

Late Season

Frost Protection:

• Cover with sheets/blankets on cold nights
• Remove covering during day
• Can extend season several weeks

Variety Selection:

• Choose early-blooming varieties
• 'Bishop' series starts early
• Many pompons are early

Container Growing

Container Size

• Minimum 12 inches diameter
• Larger for big varieties
• Good drainage essential

Best Varieties for Containers

• Gallery series (compact)
• Mystic series (dark foliage)
• Topmix series
• Most pompons
• Single and collarette types

Container Care

• Water more frequently
• Fertilize regularly but lightly
• May need daily watering in heat
• Stake if needed

Pest and Disease Management

Integrated Approach

Cultural Controls:

• Good air circulation
• Avoid overhead watering
• Remove plant debris
• Rotate planting areas

Monitoring:

• Check plants regularly
• Scout undersides of leaves
• Early detection is key
• Know what's normal

Common Issues

Earwigs:

• Night-feeding pests
• Chew petals and leaves
• Trap with rolled newspaper
• Debris removal helps

Thrips:

• Tiny insects on flowers
• Cause streaking, distortion
• Blue sticky traps monitor
• Water spray helps

Two-Spotted Spider Mites:

• Worse in hot, dry weather
• Bronzing of lower leaves
• Strong water spray
• Increase humidity

Disease Prevention

Powdery Mildew:

• Spacing for air flow
• Avoid evening watering
• Sulfur sprays preventive
• Remove affected leaves

Botrytis (Gray Mold):

• Worse in humid conditions
• Remove spent flowers
• Good air circulation
• Fungicides if needed

Viral Diseases:

• Mosaic, ringspot
• No cure—remove plants
• Control insect vectors
• Use clean tools

Cut Flower Production

Maximizing Stems

Pinching:

• Essential for stem count
• Each pinch doubles stems

Feeding:

• Regular fertilization
• Balanced nutrition
• Avoid excess nitrogen

Harvest Stage

For Longest Vase Life:

• 3/4 to fully open
• Petals firm, not limp
• Cut in morning
• Check back of flower

Too Early:

• Buds may not open
• Poor color development

Too Late:

• Short vase life
• Petals drop quickly

Conditioning

1. Cut stems at angle
2. Strip lower leaves
3. Place in warm water
4. Add floral preservative
5. Cool for several hours
6. Recut before arranging

Understanding the classification system and advanced techniques transforms dahlia growing from simple gardening to an art form. Whether growing for exhibition, cutting, or garden display, these skills enable you to maximize your dahlias' potential.