Climate Matching Map
| Attachment | Size |
|---|---|
| climatematch-vitex_agnuscastus-united_states___nevada-20261025.pdf (1.39 MB) | 1.39 MB |
1. Question 1
Yes
1
Very High
This species is native to both Southern Europe and Asia. It has become naturalized in North, Central and South America, the Caribbean, Hawaii and Southeastern United States in areas such as limestone outcrops and dry creek beds. It has been assumed that it might dominate in a riparian habitat as well.
CABI, Invasive Species Compendium. 2021. “Vitex Agnus-Castus (chaste Tree)”. https://www.cabi.org/isc/datasheet/56520$\#$tosummaryOfInvasiveness.
2. Question 2
Yes
2
High
According to the climate matching map, it has become naturalized In areas similar to Clark County in Southern Nevada such as Western/Central Texas and parts of Southern California, New Mexico, and Arizona that all have a subtropical desert climate.
No references cited.
3. Question 3
Yes
2
Low
It is listed in the Invasive Plant Atlas of the United States (Invasive Plant Atlas of the United States, 2018). It is noted as being invasive by Oregon, California, Cuba, Texas, and Georgia (CABI, 2021). It is not, however, on an official prohibited list for either state or federal lists. It is mentioned that this plant has the characteristics that make it capable of becoming invasive. These characteristics include surviving and growing in a variety of soil types, drought tolerant, disease and pest tolerant, and readily produces copious amounts of fertile seeds Invasive Plant Atlas of the United States, 2018).
“Lilac Chastetree Vitex Agnus-Castus L”. 2018. https://www.invasiveplantatlas.org/subject.html?sub=14022.
CABI, Invasive Species Compendium. 2021. “Vitex Agnus-Castus (chaste Tree)”. https://www.cabi.org/isc/datasheet/56520$\#$tosummaryOfInvasiveness.
4. Question 4
Yes
3
Low
California and Texas has noted this species as being invasive (CABI, 2021). There are similar climates in parts of these states to Southern Nevada according to the climate matching map. This might suggest that this plant could potentially become invasive in Southern Nevada only. It is noted that this species has the potential to become invasive in areas that have milder winters where it can survive the cold (Invasive Plant Atlas of the United States, 2018). This also indicates that it might have the potential to become invasive in Southern Nevada.
CABI, Invasive Species Compendium. 2021. “Vitex Agnus-Castus (chaste Tree)”. https://www.cabi.org/isc/datasheet/56520$\#$tosummaryOfInvasiveness.
“Lilac Chastetree Vitex Agnus-Castus L”. 2018. https://www.invasiveplantatlas.org/subject.html?sub=14022.
5. Question 5
No
0
Very Low
There are other species of same genus that are invasive in other climates that do not match the climate of concern. Vitex rotundifolia is found typically in sandy coastal areas in Japan, eastern Asia, Southeast Asia and India and along the shorelines in a large number of Pacific islands. This does not match Vitex agnus-castus, which typically grown in desert ecosystems that are much drier and more saline.
“Lilac Chastetree Vitex Agnus-Castus L”. 2018. https://www.invasiveplantatlas.org/subject.html?sub=14022.
6. Question 6
No
0
Medium
According to the climate map, this species is found predominantly found in climates that match Western Asia's Mediterranean region. This ecozone in Western Asia is mostly subtropical desert and subtropical steppe. This does not match most of Nevada's climate, but it does match the climate in Southern Nevada. For this reason, it is believed it has the potential to become invasive in only Southern Nevada.
“Native Plant Alternatives to Vitex Agnus-Castus (Chaste Tree)”. 2023. https://www.gardenia.net/guide/native-plant-alternatives-to-vitex-agnus….
7. Question 7
Yes
1
Very High
This species has the ability to displace native plants and dominate native plant communities. It produces a large numbers of seeds, has high seedling recruitment rates, and may form dense monospecific thickets in plant communities.
CABI, Invasive Species Compendium. 2021. “Vitex Agnus-Castus (chaste Tree)”. https://www.cabi.org/isc/datasheet/56520$\#$tosummaryOfInvasiveness.
8. Question 8
No
0
Medium
It is rated that this species does not promote or change fire changes in a natural ecosystem (PIER, 2011). However, it is also suggested that it might induce higher seed germination following a fire (Travlos, 2007). This could suggest that this species could establish quickly following a disturbance such as a fire and outcompete native plants for resources.
No references cited.
9. Question 9
No
0
Very Low
There is no evidence at this time that this species impacts grazing systems or poses a health risk to humans or animals/fish.
No references cited.
10. Question 10
Yes
1
High
This species has the potential to quickly take over native habitats and forms dense thickets effectively displacing native plant and animal species from the native ecosystem (CABI, 2021) (Gardenia.net, 2023). It is noted in the Central Texas Invasive Plants source that it takes over native habitats especially near water (Austin Invasive Management, 2013). This could block or slow animals, livestock or humans from accessing or crossing over the water.
CABI, Invasive Species Compendium. 2021. “Vitex Agnus-Castus (chaste Tree)”. https://www.cabi.org/isc/datasheet/56520$\#$tosummaryOfInvasiveness.
“Native Plant Alternatives to Vitex Agnus-Castus (Chaste Tree)”. 2023. https://www.gardenia.net/guide/native-plant-alternatives-to-vitex-agnus….
“Central Texas Invasive Plants”. 2013. https://www.austintexas.gov/sites/default/files/files/Watershed/invasiv….
11. Question 11
No
0
Low
This plant reproduces primarily by seeds. In a nursery environment, new plants can form from pruning stems, but no information has been found about this species spreading vegetatively on its own in nature.
Zasada, John C., and C. S. Schopmeyer. 2023. “Vitex Agnus-Castus L. Lilac Chastetree”. www.fs.usda.gov/nsl/Wpsm/Vitex.pdf.
12. Question 12
No
0
Low
There is some information that suggests detached branches that are replanted are capable of producing new plants from fibrious roots that form, but it is unclear if this would occur on its own in nature without the assistance of a person.
Myers, Vanessa Richins. 2022. “How to Grow and Care for Chaste Tree (Vitex)”. https://www.thespruce.com/chaste-tree-growing-profile-3269206.
13. Question 13
Yes
1
High
Chaste tree readily produces high numbers of fertile seeds per plant into the surrounding soil. This indicates that the species commonly produces viable seeds.
CABI
CABI
“Lilac Chastetree Vitex Agnus-Castus L”. 2018. https://www.invasiveplantatlas.org/subject.html?sub=14022.
14. Question 14
Yes
1
Medium
There is no data that states exactly how many seeds the plant produces each year. Several sources claim a single plant produces a high number of seeds each year and those seeds have the ability to germinate readily (Gardenia.net, 2023). One study about a closely related plant in the same genus, Vitex rotundifolia, found 2,730 fruits per square meter on average on one plant (Glenn, 2009). The plant fruits are drupes, which contain up to 4 seeds per fruit.
“Native Plant Alternatives to Vitex Agnus-Castus (Chaste Tree)”. 2023. https://www.gardenia.net/guide/native-plant-alternatives-to-vitex-agnus….
Glenn, Gerry Moore Steve. 2009. “NEW YORK NON-NATIVE PLANT INVASIVENESS RANKING FORM”. https://nyis.info/wp-content/uploads/2018/01/bf8f1_Vitex.rotundifolia.N….
15. Question 15
Yes
1
High
This plant has a high seedling recruitment rate, which means that many of the seeds are being germinated from the previous season (CABI, 2021). There is no stated environmental requirement for this to happen. This is probably due to the fact that this plant is extremely tolerant of several factors such as soil type, drought, and pests. Sources claim it commonly germinates fertile seeds readily into the soil, suggesting there is significant germination of seeds the next growing season (Gardenia.net) (Invasive Plant Atlas of the United States, 2018).
CABI, Invasive Species Compendium. 2021. “Vitex Agnus-Castus (chaste Tree)”. https://www.cabi.org/isc/datasheet/56520$\#$tosummaryOfInvasiveness.
“Native Plant Alternatives to Vitex Agnus-Castus (Chaste Tree)”. 2023. https://www.gardenia.net/guide/native-plant-alternatives-to-vitex-agnus….
“Lilac Chastetree Vitex Agnus-Castus L”. 2018. https://www.invasiveplantatlas.org/subject.html?sub=14022.
16. Question 16
Yes
1
Low
This plant produces seed crops almost every year under nursery conditions. It isn't made clear by literature how often this plant produces viable seeds in a natural setting that is not influenced by people. It is suggested that it can sprout germinated seeds within 2-3 weeks of planting if conditions are warm enough. It is also noted that this plant can act as a woody species or a herbaceous species depending on the environmental conditions.
“Chaste Tree (Vitex Agnus-Castus)”. 2023. https://www.floralencounters.com/Seeds/seed_detail.jsp?grow=plants\&productid=1194.
17. Question 17
Yes
1
Medium
Some sources suggest the blooming period can occur from May through September which may indicate the seed production can occur for longer than 3 months each year (White, 2013). Other sources state flowering only occurs for about one month in the year (Texas Master Gardener, 2023), so the flowering period may depend on the ecosystem and resources available.
No references cited.
18. Question 18
Yes
1
Low
This species is visited by pollinators (Hawkins & Robacker, 2019), but it is not made clear in the literature that it has a morphological adaptation that allows propagules to be transported long distance or that the fruits are eaten or transported by animals such as birds or mammals. However, multiple sources claim that small birds enjoy eating the seed heads that this species produces (Dial, 2014) (Wetherbee, 2022) (Smith, 2022) (UF/IFAS, 2021). It is possible that these seeds might be dropped by these birds a long distance away from the parent plant.
Hawkins, Susan M., and Carol D. Robacker. (2019) 2019. “Attractiveness of Species of Vitex (Chastetree) to Pollinators”. Journal of Environmental Horticulture 37. doi:https://doi.org/10.24266/0738-2898-37.1.24.
Dial, Mary T. 2014. “An Avian Sanctuary How to Attract Birds to a Winter Garden”. https://columbiametro.com/article/an-avian-sanctuary/.
Wetherbee, Kris. 2022. “Drought Resistant Trees and Plants to Grow for Birds”. https://www.birdsandblooms.com/birding/attracting-birds/plants-and-tree….
Smith, Barbara H. 2022. “CHASTETREE”. https://hgic.clemson.edu/factsheet/chastetree/.
“Chastetree”. 2021. https://gardeningsolutions.ifas.ufl.edu/plants/trees-and-shrubs/trees/c….
19. Question 19
No
0
Very Low
There is no literature that explains wind or water as being a way of spreading its propagules. This species is found typically in areas that do not have a lot of bodies of flowing water. The berries found on chastetree do not appear to be light enough or seem adapted to spread long distances by wind as they are round and dense.
Dial, Mary T. 2014. “An Avian Sanctuary How to Attract Birds to a Winter Garden”. https://columbiametro.com/article/an-avian-sanctuary/.
20. Question 20
No
0
Very Low
There is no information that indicates the seeds spread by equipment, vehicles, shoes, boats or clothing/shoes. The seed heads do not have any barbs on them that cling to surfaces, animal hair, or clothing.
No references cited.
Evaluation Notes
ClimateMatch version 2.0 map link & pdf added after PRE was ported over to new PRE site. The updated climate model did not appear to signifcantly change the answer to questions 2,4, or 6. 10/24/2026 JB
Total PRE Score
16
20
54
