CPC Best Plant Conservation Practices
to Support Species Survival in the Wild
Horticulture
Maintaining Rare Plants in Cultivation in the Nursery and on the Grounds
Joyce Maschinski 
Lesley Randall 
Johnny Randall 
Jessica DeYoung 
Ashley Clayton 
Stacy Kinsell 
Talia Portner 
Jessica Stephens 
Michael Hagen 
US Endangered Polystichum calderonense is extremely rare in the wild. Luckily Fairchild Tropical Botanic Garden successfully propagated plants.
Key Messages for Maintaining Rare Plants in Cultivation in the Nursery and on the Grounds
“By far, the chemical used most frequently in the nursery that causes the most damage is water. Too much water on plants encourages damping-off, root disease, fungus gnats, moss and liverwort growth, excessive leaching of mineral nutrients and potential groundwater contamination, and foliar diseases such as Botrytis blight….Too little water on plants may cause damage to root systems through salt damage or desiccation, allowing entry points for root disease pests. Plants under severe moisture stress have lower resistance to stresses associated with heat, cold, and wind.”
-Landis et al. 2009
In General
Understand target species watering needs. Water judiciously and appropriately.
Rare plant species commonly grow in rare soils. Mimicking the soil texture and composition may be necessary to grow the rare species successfully.
Maintain genetic diversity of all forms rather than artificially selecting the most beautiful or the most fecund.
- This may mean that some genotypes are not suitable for display to the public.
If the species is accessible to the public, safeguard it against theft.
- This may be particularly important for cactus, succulents, orchids, palms, and cycads.
If the species is cold sensitive, protect from freezing temperatures either by covering or moving indoors.
Specific to Nursery
Understand the conditions within your nursery and match the target plant needs to the microsite conditions of light and water within the nursery.
If the conditions required of the target species are not available in the existing nursery, it is possible to create small areas to accommodate plant needs.
- Using additional lighting or plastic to change light or humidity in small spaces for the target species.
- Cold frames may be appropriate for overwintering some species or for providing extra protection during variable spring conditions. They can provide slightly warmer or more humid conditions than outdoor ambient conditions.
When moving plants from the nursery to outdoors, acclimatize gradually.
When you are in the fortunate situation that you have more plants than you need to maintain a conservation collection at your facility, share with other botanical gardens or use the material in a carefully planned reintroduction.
- See CPC Best Practices Section “Preparing the Rare Plant Reintroduction”
Questions to Ask about Your Nursery Conditions
Nursery spaces can provide controlled environments for endangered plants." Photo credit: Fairchild Tropical Botanic Garden
- Where are the temperature pockets within the nursery – places slightly cooler or warmer?
- How do conditions change in the nursery across seasons?
- Is there a best time of year for germination in your greenhouse?
- Are there recurring pest problems that need to be addressed?
On the Grounds
Prior to planting on the grounds, conduct research about the species’ natural history, cultivation and history in your garden’s collection.
- Seek information about the species’ natural habitat.
- See “Questions to Ask about How to Select the Best Location for Planting a Rare Species in a Botanical Garden.”
Understand factors needed for proper maintenance of the species. Use the following resources:
- Native Plant Network Propagation Protocol Database
- Nursery Manual for Native Plants (Dumroese et al. 2009)
- Hawaiian Native Plant Propagation Database
- International Plant Propagators Society
- Plant Propagation of California Natives
Develop and maintain a Cultivation Management Plan.
- Decide the best microclimate match (bioclimatic zone) for placing the species on display.
- Determine what the species’ irrigation needs are.
- When placing the plant into a garden display plot, be conscious of how it will alter present and future conditions of surrounding plants.
- Allow enough space for future growth.
- Map the accession planting so that all personnel working on the grounds understand the importance of the target species.
- See Example of Rare Plant Cultivation Management Plan
Questions to Ask About How to Select the Best Location for Planting a Rare Species in a Botanical Garden
Matilija poppy
- What are conditions in the natural habitat? (soils, light conditions, water)
- Will the plant grow and shade others around it over time?
- Is the plant appropriate for public contact or does it require a backdrop setting far from visitors?
Determine what is required for the species to reproduce and what factors limit reproduction.
- In some cases, you may want to control reproduction, while in other cases you may wish to encourage open pollination.
- Understand the breeding system of the species to guide reproduction plan.
- If hand-pollination is required, develop a technique to bag individual flowers or inflorescences with clear labeling of paternal pollen contributor. (Kearns and Inouye 1993)
- Understand the pollinators of your species and promote IPM that supports pollinator health.
If the destination of the offspring is reintroduction to the wild, several actions are warranted:
- Maintain populations distinctly to avoid hybridization See CPC Best Practices Sections, “Maintaining a Conservation Collection” and “Using the Conservation Collection for Reintroductions and Other Purposes.”
- Be prepared to collect propagules, assign a staff member to track the phenology and schedule time for seed or propagule collection into his/her work plan.
- Label offspring from maternal lines separately. Follow institution accession policy. This may mean that F1 generation propagules receive a new accession number.
Learn the invasive species in your area, watch for them in your garden plots, and remove them promptly once detected.
Be observant. Record observations systematically and on a routine schedule.