Basics of Forced Flowering Perennials Royal D. Heins Oro Farms

What information do you need when someone wants to buy perennials from you? Green or in flower Space availability and when Acceptable input costs Pot size Facility availability

Equipment needed to produce perennials Heated greenhouse Long-day lighting Photosynthetic lighting Short-day environment Cooler Late source of plants

Plant material options Small, immature seedling or URC Mature seedling/vegetative plug Mature cooled plug Bareroot clump uncooled Bareroot clump cooled

Let’s talk about perennials, then come back and identify the best plants for the situations

1 st Year Subsequent Years Emergence DormancyFlowering Vernalization Winter FallSummer Long Days Spring Winter Spring / Summer Seed Germination DormancyJuvenile Growth Maturity Vernalization Fall Short Days Cooler temps. Herbaceous perennial life cycle

Flowering Mechanisms Juvenile plant Mature plant Flower Warm temps. Flower Cold required Warm temps. Cold required required Long days Flower Warm temps. required Long days Flower Warm temps.

Horticultural Perennial Flowering Schedules SummerFallWinterSpringSummer FallWinterSpringSummer Plant Grow to Flower VernalizeGrow to Flower PlantBulk PlantBulk In the field

Plant Material from Plugs Plant to finish pot Force to Flower Bulking Vernalization Seed Vernalization Bulking Germination Force to Flower Plant JuvenilityJuvenility Vegetative Cutting Vernalization Bulking Rooting Force to Flower Plant

Plant Material from Bareroot Clumps PropaguleSeedRooted Cutting or Division Bulk during summer Force to flower Plant to field Dig from field Vernalize in cooler Plant during winter or early spring Plant to finish pot Bulk Vernalize Force to flower

Keys to Success Mature plants Proper plant size Proper cold treatment Proper photoperiod Proper timing Adequate light

Keys to Success Mature plants – plants not juvenile

Juvenility – Usually refers to seed-propagated plants – This is a period where plants will not flower even if given appropriate environments – A plant must reach maturity to flower

Not by the size of the plug tray in which it was produced… How Can You Tell if an Herbaceous Perennial is Mature?

___________________________________________________ How Can You Tell if an Herbaceous Perennial is Mature? Plant leaf number is the key.

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Plug size by itself does not provide the answer. But, older plants in larger plug trays have a higher potential to be mature.

___________________________________________________ Age Requirements for Flowering Common Herbaceous Perennials Aquilegia Columbine Some species require at least 15 leaves to flower consistently Aster alpinus Alpine aster Plants require at least 15 leaves to flower consistently Astilbe arendsii Astilbe Plants with five to six leaves flowered very inconsistently Coreopsis ‘Sunray’ Tickseed Juvenile phase ends with about 16 leaves Echinacea purpurea Coneflower Plants with four leaves flower Euphorbia epithymoides Cushion spurge Plants with six to eight leaves failed to flower Goniolimon tatarica Statice Plants with 10 to 14 leaves failed to flower Heuchera sanguinea Coral bells Plants require 16 leaves to flower consistently Physostegia virginiana Obedient plant Plants require at least 10 leaves to flower consistently Veronica spicata ‘Blue’ Speedwell Plants with six to eight leaves will flower Plant nameCommon name Age requirements

Lack of flowering may be caused by juvenility or lack of adequate vernalization

Keys to Success Mature plants Proper plant size

___________________________________________________ Considerations Container size for finished product Planting date (time to bulk before flower induction)

Horticultural Perennial Flowering Schedules SummerFallWinterSpringSummer FallWinterSpringSummer Plant Grow to Flower VernalizeGrow to Flower PlantBulk PlantBulk In the field

___________________________________________________ Available Plant Sizes Plug trays – 512-cell – 288-cell – 128-cell – 72-cell – 50-cell – 36-cell 2-1/4 inch pots Field grown, bare-root divisions or clumps Previous year Current year

___________________________________________________ Starting Material Influences Flowering percentage (if plant has a juvenile phase) Plant size at flowering Flower number Time to flower

___________________________________________________ Starting Plant Sizes

___________________________________________________ Influence of Starting Size on Subsequent Flowering of Plants

___________________________________________________ Starting Material Disease free

Artemisia ‘Silver Mound’

Echinacea

___________________________________________________ Starting Material Disease free Uniform development

Phlox paniculata

Aquilegia

___________________________________________________ Starting Material Disease free Uniform development Multiple eyes (buds)

Multiple buds produce a full pot

More lateral buds will yield more shoots to fill the pot

___________________________________________________ Points to Remember Determine final container size Select starting material that is an appropriate size based on the planting date The larger the starting plant material and the earlier the plant is potted, the larger the finish plant

___________________________________________________ Points to Remember To produce large plants – Bulk small plants before flower induction – Plant multiple small plugs into one large pot – Start with large plant material with multiple shoots

Keys to Success Mature plants Proper plant size Proper cold treatment

Flowering Mechanisms Juvenile plant Mature plant Flower Warm temps. Flower Cold required Warm temps. Cold required required Long days Flower Warm temps. required Long days Flower Warm temps.

___________________________________________________ Responses to Cold Treatment Cold treatment not recommended

___________________________________________________ Cold Treatment Not Recommended

___________________________________________________ Cold Treatment Not Recommended

___________________________________________________ Responses to Cold Treatment Cold treatment not recommended No response to cold treatment

___________________________________________________ No Response to Cold Treatment No cold15-weeks cold

___________________________________________________ Responses to Cold Treatment Cold treatment not recommended No response to cold treatment Cold treatment beneficial – Increased flowering percentage – Decreased time to flower – Increased flower number – Improve flower uniformity

___________________________________________________ Cold Treatment Beneficial No cold15-weeks cold

___________________________________________________ Responses to Cold Treatment Cold treatment not recommended No response to cold treatment Cold treatment beneficial Cold treatment required

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Delivering Cold Treatment Cool seedlings or cuttings in the plug tray – Plants that are mature, not juvenile Pot in larger container, grow until mature and then place in a cooler or cold greenhouse – Species with a juvenile phase – Plants that do not have the minimum recommended number of leaves

___________________________________________________ Delivering Cold Treatment In a cooler – Nine-hour photoperiod – Lights delivering about 50 footcandles In a greenhouse Under a thermal blanket outdoors Purchase plugs that have been cooled

Plant appearance after cooling can be “ugly”

Keys to Success Mature plants Proper plant size Proper cold treatment Proper photoperiod

1 st Year Subsequent Years Emergence DormancyFlowering Vernalization Winter FallSummer Long Days Spring Winter Spring / Summer Seed Germination DormancyJuvenile Growth Maturity Vernalization Fall Short Days Cooler temps. Herbaceous perennial life cycle

___________________________________________________ Types of Photoperiod Responses Day-neutral plants (DNP) Short-day plants (SDP) Long-day plants (LDP)

___________________________________________________ Perennials in Northern Climates DNP = no response to long days (generally only after cold) Facultative LDP = long days beneficial Obligate LDP = long days required

___________________________________________________ Day-Neutral Plant

___________________________________________________ Facultative Long-Day Plant

___________________________________________________ Obligate Long-Day Plant

Obligate long-day plant

Rudbeckia showing short day growth habit

Echinacea with short day growth habit

Echinacea growing with LD

___________________________________________________ Points to Remember Night interruption or day-extension lighting is more effective than predawn lighting for inducing flowering For rapid and uniform flowering, night interruption should be four hours long with lights on the entire four hours In most perennials, provide at least 10 footcandles to induce flowering

___________________________________________________ Points to Remember Standard mum lighting is adequate to induce flowering in many perennial species Cool white fluorescent, high pressure sodium or metal halide lights are also effective and will result in more compact plants for some plant species

QUESTIONS?