Invasive Plants from aInvasive Plants from aHorticultural PerspectiveHorticultural Perspective

Mike Schnelle, OSUMike Schnelle, OSU

Please speak up as you have Please speak up as you have thoughts/questions during thoughts/questions during presentationpresentation

Origins of Plant Origins of Plant MaterialsMaterials

Both native and non-native plants Both native and non-native plants have value in the garden and have value in the garden and landscapelandscape

Both native and non-native plants Both native and non-native plants have pest resistance, not just have pest resistance, not just nativesnatives

Both will be discussed todayBoth will be discussed today

Start With Native PlantsStart With Native Plants

Growers and consumers could spend a Growers and consumers could spend a lifetime just working with plants from lifetime just working with plants from the Lower 48. However, many the Lower 48. However, many ornamental characteristics and ornamental characteristics and ““lookslooks”” cannot be satisfied by our natives alone.cannot be satisfied by our natives alone.

So when aesthetics and ornamental So when aesthetics and ornamental attributes are factored in, it is hard to attributes are factored in, it is hard to overlook plants from other countries.overlook plants from other countries.

Mexican PlumMexican Plum(Prunus mexicana)(Prunus mexicana)

12-1512-15’’ tree native to Mexico and much of tree native to Mexico and much of U.S. including KansasU.S. including Kansas

Grow for spring white flowers and sheer Grow for spring white flowers and sheer toughness of the treetoughness of the tree

Heavy, wet soils will send this species into Heavy, wet soils will send this species into a mortality spiral – OKC Bombing Memoriala mortality spiral – OKC Bombing Memorial

Some yellow fall color, attractive summer Some yellow fall color, attractive summer fruitsfruits

Seed propagationSeed propagation

Mexican PlumMexican Plum(Prunus mexicana)(Prunus mexicana)

Prunus mexicanaPrunus mexicana

Despite the name, Mexican plum IS Despite the name, Mexican plum IS native to many southern and central native to many southern and central U.S. statesU.S. states

Serviceberry (Amelanchier)Serviceberry (Amelanchier)

Greatly underutilized group Greatly underutilized group of plants for Oklahoma and of plants for Oklahoma and Southern locationsSouthern locations

Better known and used Better known and used north of usnorth of us

White flowers in springWhite flowers in spring Pest-free summer foliagePest-free summer foliage Yellow-orange-red fall colorYellow-orange-red fall color Showy edible fruits range Showy edible fruits range

from red-purple-blackfrom red-purple-black Growth habit varies from Growth habit varies from

shrub to treeshrub to tree Many native to U.S.Many native to U.S. A crabapple alternativeA crabapple alternative

Serviceberry (Amelanchier)Serviceberry (Amelanchier)

Non- native plantsNon- native plants

Appropriate when researched and Appropriate when researched and used responsiblyused responsibly

Pest advantage?Pest advantage? Traits not found in U.S. Traits not found in U.S.

Unsupervised ReproductionUnsupervised Reproduction Happens with natives or exoticsHappens with natives or exotics

Arguments Against Non-Arguments Against Non-NativesNatives

May not serve as host plants for May not serve as host plants for pollinatorspollinators

May not be a significant food source May not be a significant food source for native faunafor native fauna

May reproduce without human May reproduce without human interventionintervention

OtherOther

Invasive PlantsInvasive Plants

A cultivated plant that under certain A cultivated plant that under certain conditions will reproduce, unassisted by conditions will reproduce, unassisted by people, and ultimately displace native flora people, and ultimately displace native flora and occasionally native faunaand occasionally native fauna

No longer should we consider only exotic or No longer should we consider only exotic or introduced plants to be the only candidates. introduced plants to be the only candidates. Natives in some instances could be invasive Natives in some instances could be invasive when moved out of their original U.S. range., when moved out of their original U.S. range., Eastern redcedar for example.Eastern redcedar for example.

ChallengesChallenges

Most horticulturists want to continue to Most horticulturists want to continue to have the right to RESPONSIBLY introduce have the right to RESPONSIBLY introduce and grow plants of origins outside the U.S.and grow plants of origins outside the U.S.

Invasive plants are a hot topic among Invasive plants are a hot topic among diverse professionals.diverse professionals.

Horticulturists have different training Horticulturists have different training backgrounds and backgrounds and ““ornamental motivesornamental motives”” than do ecologists for example.than do ecologists for example.

Communication and rational discussion Communication and rational discussion amongst various disciplines is paramount in amongst various disciplines is paramount in coming to agreements that all can live with.coming to agreements that all can live with.

Widespread Condemnation of Widespread Condemnation of PlantsPlants

Because of the sheer size of the U.S., it Because of the sheer size of the U.S., it is not logical nor appropriate to is not logical nor appropriate to condemn any one species for cultivation condemn any one species for cultivation anywhere in the continental U.S.anywhere in the continental U.S.

It is questionable whether any species It is questionable whether any species exists that would prove problematic in exists that would prove problematic in all 48/49 states (Hawaii is the all 48/49 states (Hawaii is the exception). exception).

Ornamentals that Bear FruitOrnamentals that Bear Fruit

Strong movement underway to discourage Strong movement underway to discourage many female or otherwise fruiting plants many female or otherwise fruiting plants in the landscapein the landscape

The notion that a fruit-bearing plant will The notion that a fruit-bearing plant will automatically be weedy IS NOT accurateautomatically be weedy IS NOT accurate

Plants have to be screened/observed on Plants have to be screened/observed on an individual basis to determine their an individual basis to determine their propensity to reproduce rampantly outside propensity to reproduce rampantly outside their intended area. their intended area.

TamarixTamarix

PyrusPyrus

Ligustrum sinense Ligustrum sinense ‘‘WimbeiWimbei’’(Chinese dwarf privet)(Chinese dwarf privet)

This cultivar (also found as This cultivar (also found as ‘‘WimbishWimbish’’) has ) has been around for quite some time. been around for quite some time. However, it has taken me years to realize However, it has taken me years to realize its value in the landscape!its value in the landscape!

Its diminutive size (4-7Its diminutive size (4-7’’), short internodes, ), short internodes, variability from plant to plant really make variability from plant to plant really make for an exciting shrub, or extremely small for an exciting shrub, or extremely small ““treetree”” in the landscape. in the landscape.

Chinese dwarf privetChinese dwarf privet

MimosaMimosa

LantanaLantana

In the lower 48, this species is In the lower 48, this species is normally harmless to the environment.normally harmless to the environment.

Most breeders are working on fruitless Most breeders are working on fruitless types more for the reason of toxicity types more for the reason of toxicity than for weedinessthan for weediness

However, if we lived in Hawaii, for However, if we lived in Hawaii, for example, lantana could be a major example, lantana could be a major issueissue

Breeding for SterilityBreeding for Sterility

Breeding for sterility, non-fruiting Breeding for sterility, non-fruiting plant, should be encouraged plant, should be encouraged however when flowers are the however when flowers are the primary focus and the resulting fruits primary focus and the resulting fruits are known to be problematic.are known to be problematic.

Buddleia, for example, is currently Buddleia, for example, is currently being worked with to develop sterile being worked with to develop sterile new selectionsnew selections

Euonymus alataEuonymus alata

Has reseeded in Eastern forestHas reseeded in Eastern forest Remains essentially innocuous to our Remains essentially innocuous to our

environment here in Oklahoma environment here in Oklahoma

Ironwood (Parrotia persica)Ironwood (Parrotia persica)

Parrotia persicaParrotia persica

One of many exciting plants, from One of many exciting plants, from the Middle East, that so far are not the Middle East, that so far are not proving to be invasive!proving to be invasive!

What About Our Native What About Our Native Plants?Plants?

Eastern redcedar and others are Eastern redcedar and others are beyond the scope of todaybeyond the scope of today’’s s presentation. However, some experts presentation. However, some experts have issues with this indigenous have issues with this indigenous conifer and others. Osage orange, conifer and others. Osage orange, hackberry and other natives are now hackberry and other natives are now being watched largely because setting being watched largely because setting fires has been discouragedfires has been discouraged

Commonly Grown Oklahoma Commonly Grown Oklahoma Ornamentals That are Being Ornamentals That are Being

Scrutinized Scrutinized Sawtooth oak (Quercus acutisiima)Sawtooth oak (Quercus acutisiima) Russian olive (Elaeagnus angustifolia)Russian olive (Elaeagnus angustifolia) Autumn olive (Elaeagnus umbellata)Autumn olive (Elaeagnus umbellata) Privet (Ligustrum ssp.) – all of them!Privet (Ligustrum ssp.) – all of them! Japanese barberry (Berberis thunbergii)Japanese barberry (Berberis thunbergii) Japanese spirea (Spiraea japonica)Japanese spirea (Spiraea japonica) Chinese/Japanese wisteria (W. Chinese/Japanese wisteria (W.

sinensis/floribunda)sinensis/floribunda) Asian bittersweet (Celastrus orbiculatus)Asian bittersweet (Celastrus orbiculatus) Wintercreeper (Euonymus fortunei)_Wintercreeper (Euonymus fortunei)_

Barberry a Problem in Barberry a Problem in New EnglandNew England

Again, most fruiting non-natives in Again, most fruiting non-natives in OK are not problematicOK are not problematic

More More ““BadBad”” Plants Plants

Periwinkle (Vinca minor)Periwinkle (Vinca minor) Porcelain berry (Ampelopsis Porcelain berry (Ampelopsis

brevipedunculata)brevipedunculata) Japanese akebia (Akebia) Japanese akebia (Akebia) Ajuga (Ajuga reptans)Ajuga (Ajuga reptans) Saltcedar (Tamarix spp.)Saltcedar (Tamarix spp.) Beach vitex (Vitex rotundifolia)Beach vitex (Vitex rotundifolia) Many more as well as grasses and Many more as well as grasses and

aquatics not discussed today!aquatics not discussed today!

Possible SolutionsPossible Solutions

Horticulturists must implement screening Horticulturists must implement screening processes before introducing new plants to processes before introducing new plants to the market. This would demonstrate our the market. This would demonstrate our concern for the environment and in some concern for the environment and in some cases squelch a small no. of plants from cases squelch a small no. of plants from ever becoming widespread.ever becoming widespread.

There may come a time when growers There may come a time when growers may want to consider voluntary stop sales may want to consider voluntary stop sales on a few species. This has already on a few species. This has already transpired on the West Coast. For transpired on the West Coast. For example, some people are no longer example, some people are no longer growing/selling Hedera helix (English ivy). growing/selling Hedera helix (English ivy).

Proposed Code of EthicsProposed Code of Ethics

Do no harm to plant diversity and natural areasDo no harm to plant diversity and natural areas Perform risk assessments for introductionsPerform risk assessments for introductions Remove invasives from plant collectionsRemove invasives from plant collections Control invasives in natural areasControl invasives in natural areas Develop noninvasive and native alternative plant Develop noninvasive and native alternative plant

materialmaterial Do not distribute plants and seeds that will be Do not distribute plants and seeds that will be

invasive elsewhereinvasive elsewhere Educate the publicEducate the public Become partners with conservation organizationsBecome partners with conservation organizations

Drought/Heat/ColdDrought/Heat/Cold

Up until about two years ago, many of us Up until about two years ago, many of us considered a number of our considered a number of our ““staplestaple”” landscape plants to be essentially bullet-landscape plants to be essentially bullet-proof. However, given extreme drought, proof. However, given extreme drought, few record-cold nights and also record few record-cold nights and also record heat, some of these heat, some of these ““bulletbullet’’proofproof”” plants did plants did indeed succumb or were badly damaged indeed succumb or were badly damaged beyond aesthetically acceptable levels. beyond aesthetically acceptable levels. Many of the best survivors are exotics!Many of the best survivors are exotics!

Native vs. ExoticNative vs. Exotic

It is interesting to note that many of It is interesting to note that many of our affected plants were/are native our affected plants were/are native to the U.S. and often including the to the U.S. and often including the State of Oklahoma. Still, even with State of Oklahoma. Still, even with their native origins we have all been their native origins we have all been reminded that all living organisms reminded that all living organisms have limits to what they can survive! have limits to what they can survive!

One of the Few Unscathed One of the Few Unscathed Species from 2011-2012Species from 2011-2012

VitexVitex(Vitex spp.)(Vitex spp.)

Genus as a whole taken for grantedGenus as a whole taken for granted White, pink, purple or blue flowers on White, pink, purple or blue flowers on

long spikes (for most spp.)long spikes (for most spp.) Marijuana-like foliageMarijuana-like foliage Can grow to be a tree sometimes to Can grow to be a tree sometimes to

2020’’ Normally winters will take it back Normally winters will take it back

down down

VitexVitex

Aralia elata Aralia elata ‘‘VariegataVariegata’’

Variegated araliaVariegated aralia

Has been scorned by most because it Has been scorned by most because it is coarse and considered too is coarse and considered too overwhelming with itoverwhelming with it’’s color patternss color patterns

Should be used more – see Should be used more – see Lendonwood Gardens or Sunshine Lendonwood Gardens or Sunshine Nursery for specimens to viewNursery for specimens to view

Aralia spinosaAralia spinosa(Devil(Devil’’s walkingstick/Hercules s walkingstick/Hercules

club)club) Native Aralia sometimes Native Aralia sometimes

goes unnoticedgoes unnoticed Large shrub – often a small Large shrub – often a small

tree to 20tree to 20’’++ Tropical looking leaves, Tropical looking leaves,

white creamy flowers, white creamy flowers, club-like stems great for club-like stems great for winter interest, purple winter interest, purple black fruitsblack fruits

Not a plant for the timidNot a plant for the timid II’’ve grown weary of ve grown weary of

people rejecting this genus people rejecting this genus solely based on the solely based on the presence of thornspresence of thorns

Staghorn sumac (Rhus Staghorn sumac (Rhus typhina)typhina)

Tiger Eyes sumacTiger Eyes sumac

Rhus typhina Tiger EyesRhus typhina Tiger Eyes

DonDon’’t Lose Sight of Sheer t Lose Sight of Sheer Size of U.S.Size of U.S.

Put Popular Articles Into Put Popular Articles Into PerspectivePerspective

Prioritizing InvasivesPrioritizing Invasives

Work could be done between Work could be done between ornamentals industry and OkIPC to ornamentals industry and OkIPC to rank rank ““biggestbiggest”” offenders in order to offenders in order to have a realistic starting point.have a realistic starting point.

Plants of ConcernPlants of Concern

Ornamental pears (Pyrus spp.)Ornamental pears (Pyrus spp.) Privet (Ligustrum spp.)Privet (Ligustrum spp.) Honeysuckle (Lonicera spp.)Honeysuckle (Lonicera spp.) Tamarix (Tamarix spp.)Tamarix (Tamarix spp.) Russian olive (Elaeagnus Russian olive (Elaeagnus

angustifolia)angustifolia) OtherOther

Species of Less ConcernSpecies of Less Concern

Paper mulberry (Broussenetia Paper mulberry (Broussenetia papyrifera)papyrifera)

Mimosa (Albizia julibrissin)Mimosa (Albizia julibrissin) Common mullein (Verbascum spp.)Common mullein (Verbascum spp.) Siberian elm (Ulmus pumila)Siberian elm (Ulmus pumila) OtherOther

Planned Planned ““TalksTalks”” are are Underway for 2013Underway for 2013

I am hopeful that a representative of I am hopeful that a representative of OkIPC will come to an ONLA board OkIPC will come to an ONLA board meeting yet this year to begin a meeting yet this year to begin a dialogue.dialogue.

SummarySummary

1) All of us desire the same end result 1) All of us desire the same end result in leaving the land as good or better in leaving the land as good or better than what we inherited. However, than what we inherited. However, our approaches to doing so will differ.our approaches to doing so will differ.

2) Many horticulturists will always 2) Many horticulturists will always desire to grow non-native plant desire to grow non-native plant materials in a responsible fashion of materials in a responsible fashion of course.course.

Summary (continued)Summary (continued) 3) Plantspeople must continue to educate 3) Plantspeople must continue to educate

themselves about alternative plant themselves about alternative plant materials, when warranted, that are safer to materials, when warranted, that are safer to the environment, i.e. male selections, the environment, i.e. male selections, triploids, etc.triploids, etc.

4) Solving or at least mitigating the 4) Solving or at least mitigating the invasives dilemma will necessitate a invasives dilemma will necessitate a multidisciplinary approach meaning that multidisciplinary approach meaning that horticulturists, ecologists, botanists, etc. horticulturists, ecologists, botanists, etc. come to the table and begin discussionscome to the table and begin discussions

Summary (continued)Summary (continued)

5) 5) ““TalksTalks”” will occur yet this year will occur yet this year between OkIPC and the Oklahoma between OkIPC and the Oklahoma Nursery and Landscape Association Nursery and Landscape Association (ONLA). This is a step in the right (ONLA). This is a step in the right direction.direction.

6) In the end, concessions and 6) In the end, concessions and compromise will be required from all compromise will be required from all parties involved.parties involved.

Thanks for Your AttentionThanks for Your Attention

Questions?Questions?