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Plant Profile

Lakela's Mint (Dicerandra immaculata var. immaculata)

Global Rank: G1 - Critically Imperiled
Legal Status: Federally Endangered
Family: Lamiaceae
State: FL
Nature Serve ID: 159688
Lifeform: Forb/herb
Date Inducted in National Collection: 04/04/1991

Description:

Lakela's mint is a small, fragrant, perennial shrub that was listed in 1985 as federally threatened. It faces a high risk of extinction because so much of its habitat has been lost and its populations are so fragmented. This species is known from only one wild population (USFWS 1999). Dicerandra immaculata can be differentiated from others in the Dicerandra genus by its lavender-rose colored flower that has no spots on it. As it grows, it forms small mats or domes of ascending to spreading or sprawling branches. The main leaves are horizontal or pointing upwards, while those with flower clusters sometimes point downward that appear in September through November (USFWS 1999). Its anthers have tiny spurs, while its stamens extend beyond the flower. Both the stems and leaves have a strong mint odor that is unique to the species (Bok Tower Gardens, unpublished data).

Where is Lakela's Mint (Dicerandra immaculata var. immaculata) located in the wild?

Habitat:

This endangered taxon is restricted to sand scrub habitats found along the Atlantic Coastal Ridge in ancient dunes formed along former ocean shorelines in Indian River and St. Lucie Counties. These soils consist of highly drained, infertile sands (USFWS 1991). Dicerandra immaculata has been observed growing in both yellow and white sands, and does best in light shade or clearings in the scrub. It is a gap specialist, and requires open canopy and sand gaps for persistence and recruitment (Richardson et al. 2013). These bare areas were historically maintained by wind action and fires (USFWS 1999). Other species found in this coastal scrub include sand pine, sand live, myrtle and live oaks, scrub hickory, cabbage palm, hog plum, and tough Bumelia along with some epiphytic species (USFWS 1991).

Distribution:

The range of D. immaculata is very small, being confined to a area one-half mile wide by three miles long in southern Indian River and northern St. Lucie Counties. It persists in five of its historical sites that are part of one metapopulation. An experimental population was introduced into Hobe Sound National Wildlife Refuge in Martin County in 1991 and 1992 (Race 1994), and a new population was introduced in St. Lucie County from 2002-2009 by Bok Tower Gardens.

States & Provinces:

Lakela's Mint can be found in Florida

Which CPC Partners conserve Lakela's Mint (Dicerandra immaculata var. immaculata)?

Bok Tower Gardens

Conservation Actions

Tina Stanley

05/11/2023

According to a March 2023 extract of the Florida Plant Rescue Database, Bok Tower Gardens holds 21 accessions of Dicerandra immaculata totalling approximately 230442 seeds.

Cheryl Peterson

04/05/2023

Lakela’s Mint (Dicerandra immaculata var. immaculata) is a short-lived, woody shrub that grows only within a narrow three-mile stretch of Scrub habitat of the Atlantic Coastal Ridge in the Indian River and St. Lucie Counties in Florida. From one larger meta-population spanning this range, the species has been reduced to only five small and vulnerable subpopulations. Plants likely historically numbered in the tens of thousands, but fewer than 3,000 plants may currently exist. Populations continue to decline due to decreasing habitat quality. It is thought that seed viability in the wild is not retained for longer than six months. Therefore, seed preservation in long-term, cold storage is important to preserve existing genetic diversity and provide source material for augmentations. Dried seed pods from 50 maternal parent plants were collected from throughout one population in January and brought back to Bok Tower Gardens for cleaning, counting, sorting, drying to 25% RH. Half the seeds from each parent were sent to NLGRP for cryogenic storage.

Cheryl Peterson

03/28/2022

Lakela’s Mint (Dicerandra immaculata var. immaculata) is a short-lived, woody shrub that grows only within narrow coastal dunes along roughly a three-mile stretch at the Indian River and St. Lucie County border in Florida, and is found nowhere else in the world. The species has been reduced to only five small and vulnerable populations due to development of privately-owned sites and lack of land management at protected sites. Plants within just those five natural populations likely historically numbered in the tens of thousands, but fewer than 4,000 plants may currently exist. For this project, seeds from the largest natural remaining population were collected from 50 maternal parents. A maximum of four nutlets can be produced per seed pod. For this collection there was an average of 1.60 seeds produced per pod, which is average for collections in past years. Dissections showed that 5% of the seeds were intact, which is higher than the typical 1-3% observed previously for this species.

Center for Plant Conservation

08/18/2021

In 2021, CPC contracted the Bok Tower Gardens to recollect seed from a population currently held in long term orthodox seed storage as part of an IMLS-funded seed longevity experiment. The National Laboratory for Genetic Resources Preservation will evaluate how germination tested viability and RNA Integrity of seed lots decline over time in storage.?

10/17/2020

Living plants are important to maintain in an ex situ collection to provide source material of cuttings for introduction and augmentation efforts. Seeds do not retain viability in storage for more than two years, except in -20C or cryogenic temperatures.

10/17/2020

Currently, Lakela's mint is known from a single meta population that is scattered across five of its historical sites. Bok Tower Gardens has introduced three additional populations on protected land This species also occurs at two sites in Hobe Sound National Wildlife Refuge, where it was introduced in 1991 and 1992. (USFWS 1999)

10/17/2020

Lakela's Mint is a gap specialist (Richardson et al. 2013). The non-native honey bee is by far the most frequent pollinator, but may negatively impact population dynamics because of its foraging behavior compared to native bees (Richardson et al. 2015). Models of climate change impacts suggest a dramatic decrease in plant number and that increased population size and improved habitat will be vital to prevent extinction (Peterson 2016). Lakela's Mint has an essential oil profile that is unique to it. and the species is tetraploid (Richardson and Peterson 2017).

10/17/2020

10/17/2020

A study conducted by researchers at Bok Tower Gardens revealed that Lakela's Mint is a facultative outcrosser: producing higher seed set when it is pollinated by insects than when it reproduces asexually. This study also found that honey bees (Apis mellifera), a non native pollinator, are the most frequent visitor of Lakela mint flowers. Honey bees visit nearly all plants regardless of size. In contrast, native pollinators such as Bombus impatiens prefers to visit flowers on shorter plants (Richardson et al. 2016).

Katie Heineman

09/25/2017

A study conducted by researchers at Bok Tower Gardens revealed that Lakela's Mint is a facultative outcrosser: producing higher seed set when it is pollinated by insects than when it reproduces asexually. This study also found that honey bees (Apis mellifera), a non native pollinator, are the most frequent visitor of Lakela mint flowers. Honey bees visit nearly all plants regardless of size. In contrast, native pollinators such as Bombus impatiens prefers to visit flowers on shorter plants (Richardson et al. 2016).

Nature Serve Biotics

05/02/2017

A narrow endemic, known only from St. Lucie and Indian River counties, Florida. The Florida Natural Areas Inventory's database contains 4 occurrence records. Suitable habitat is rapidly being lost to development.

C.L. Peterson

01/01/2010

Commercial and residential development. Lack of sufficient land management. Reduced native pollinators. Fungal disease. Hybridization with other mints is a serious issue when propagation and collection is not regulated.

C.L. Peterson

01/01/2010

C.L. Peterson

01/01/2010

C.L. Peterson

01/01/2010

St. Lucie County and Indian River County work to manage Scrub habitat for Lakela's Mint through mechanical treatment and volunteer work days to remove overgrowth and exotics. Fire is recommended but hard to perform in the urban settings (Peterson 2017)

C.L. Peterson

01/01/2010

Purchase and protect privately owned sites. Control off-road-vehicle traffic. Manage habitat. Keep species out of the nursery trade to prevent hybridization. Encourage native pollinators. Use occasional fire to open up habitat. (FNAI 2000)

Philip Gonsiska

01/01/2010