Annual Pennyroyal


Hedeoma acinoides has appeared in abundance after the inch of rain this past weekend.  

Blooming for a short time in the spring it is a delightful miniature spring annual.  Only an inch or three high, in these pictures, it has created delightful little patches that look like miniature forests.

Plant identification books such as Marshall Enquist’s Wildflowers of Texas say it can be up to 8 inches.  Common in the rocky limestones of the hill country this member of the Lamiaceae or mint family has a minty smell if you crush the leaves a little.

This is not the only member of the family Lamiaceae to be called Pennyroyal, several other genera have this common name. In Culpeppers Herbal the pennyroyal he refers to grows in damp areas and flowers at the end of August.


Breaking the winter fast


Blanco crab apple at Selah Bamberger Ranch

It’s been a curiously cold winter here in Texas, while elsewhere in the country has been inundated by unrelenting snow storms.  Still the first Spring trees are beginning to flower and the crab apples have been blooming for almost three weeks despite the weather alternating between freezing temperatures as low as 28F and highs near the 80’s.  Here the Blanco crabapple (Malus ioensis var. texana), an endemic species of the Texas Hill Country, is blooming next to a tributary of Miller Creek on the Bamberger ranch.  This splendid tree is a member of the Rosaceae family and, as it’s genus (Malus) suggests related to the domesticated apple.  The characters that place this plant in the Rosaceae family are best seen in its flowers.  The blooms are actinomorphic, meaning they are radially symmetrical.  They have five petals, as can be seen in the adjacent close up, and five sepals.  The flowers have both male and female parts, making them hermaphroditic, and many stamens arranged in whorls.  Three stigma and styles (slightly greenish structures at the center of the flower) are evident in this photograph


Close up of the Crab apple flower by Abe Halbreich

disappearing into the top of the ovary that will ultimately become the apple once the flowers have been pollinated.  The base of the flower, calyx (sepals), corolla (petals) and androecium (filaments of the stamens) essentially fuse to form a hypanthium enclosing the ovary.  According to the Ladybird Johnson site, this species is particularly important to a variety of native bees.  Naturally the bitter fruit that appear later in the summer are food for a variety of animals.  As a harbinger of spring and warmer weather it brightens the dry, cold landscape and it’s bright fresh blooms easily draw the eye against the brown palette of the grasses and olive green cedars.


Lake Madrone at the Bamberger Ranch in February 2014

Texas Mountain Laurel – Sophora secundiflora

OLYMPUS DIGITAL CAMERASpring is springing up quickly after our warmish winter.  The mountain laurels have been blooming for over a month now and are slowly beginning to fade.  Their bumpy seed pods, containing poisonous seeds, are appearing from the delicate purple-blue blooms that still fill the night with heady scent.  I thought it might be fun to take a closer look at these flowers since this species is a member of the Fabaceae, one of the largest and most cosmopolitan of all plant groups. Just about anywhere in the world you will find examples of the pea family.  They could be evergreen, deciduous, climbers, herbaceous plants or trees.  Specifically, Texas Mountain Laurel is a beautiful evergreen multi-trunked trees that is part of the sub-family Faboideae.  This is the group of Fabaceae that we typically recognize as “pea”. OLYMPUS DIGITAL CAMERA The other two subfamilies are Mimosoidae and Caesalpiniodae.


Half flower diagram of Texas Mountain Laurel

So what is a “classic” pea flower. It has a floral structure where the petals are arranged into banner, wings and keel.


Stigma, style and ovary of the Texas mountain laurel

The banner is one large petal with two wing petals enclosing two keel petals.  The keel closes around the 10 stamens  and the ovary that will later develop into the pod if the flower is pollinated.  Two curious features of the flower are the widening of the filaments at the base (filaments support the anther forming the stamen) and a protrusion on the lower side of the keel petal which seem to help the petals stay closed over the stamens and stigma.


10 stamens clustered tightly around the gynoecium

What’s green in January? #1

Thibam2s past Sunday I took a drive out into the hill country. I was visiting one of my favorite places – the Bamberger Ranch.  While there are green trees (Live oaks – Quercus fusiformis and cedars – Juniperus asheii) scattered through the landscape there were many without any leaves.  bam1Yet they still had what appeared to be balls of greenness high up in their canopy.OLYMPUS DIGITAL CAMERA  These apparently innocuous tufts of green are actually parasites (mistletoe –Phoradenron tomentosum) with their haustoria deep in the xylem and phloem of the plant they draw out the nutrients from the very heart of each branchOLYMPUS DIGITAL CAMERA.  The leafy parts seen here are growing out of a small Spanish Oak (Quercus texana).  The texture of the leaves is leathery and quite tough.  What is not seen here are the tiny white berries that the birds love to eat.  We are perhaps more familiar with the idea of red berries on mistletoe since that is what is found on the european mistletoe Viscum album.  When the berries pass through the gut of the bird they become goeey and the bird has to wipe its bottom on a branch to remove the dropping.  In this way the berry becomes attached to the next victim, commonly Cedar elms (Ulmus crassifolia) or hackberry (Celtis laevigata), and the haustoria (specially adapted roots) can grow into the bark and a new plant is infected.  Amazingly haustoria can extend deep into the plant.  After removing an infected branch from a Spanish oak I traced haustoria up to 2 yards inside the vessels of the plant! OLYMPUS DIGITAL CAMERA I do wonder if trees are more prone to infection with all the droughts we have been having.  I seem to be noticing it more and more each winter and infected trees seem to have more infestations.  Do plants typically have resistance to parasites and that is weakend by drought?

Fall Color

cedar elm (Ulmus crassifolia)

cedar elm (Ulmus crassifolia)

While many parts of the country have begun their winter, here in Texas we are still enjoying the balmy days of Autumn.  While our fall color isn’t perhaps as dramatic as some places in the country we still have some lovely yellows and reds set against the backdrop of the evergreen cedar. (Juniperus ashei).  Cedar elms are tall stately trees that can be found on their own or hidden within the forest.  This year their small winged fruits covered the ground in September and October as their yellow golden leaves are doing now.


Bur oak (Quercus macrocarpa)

Another source for hints of gold on the hillside is the Bur Oak.  The leaves of this oak are enormous as are their beautiful acorns that have caps with dramatic “burrs” surrounding them.  A beautiful tree in a park setting this wonderful tree is now dropping its leaves, that are the size of a childs shoe, making a crunchy brown flooring for park goers to enjoy in the fall light.


Spanish Oak (Quercus buckleyi or texana)

Oaks are also a source of dramatic reds seen along roads and on hillsides. The Spanish Oak belongs to the group of Oaks known as the Red Oaks and doesn’t disappoint. The identification of this fast growing species can be tricky as it has much in common with the Shumard Oak (Quercus shumardii) and Southern Red Oak (Quercus falcata). Another source of deep red is from a slightly small tree, the flame leaf sumac (Rhus lanceolata). This wonderful plant specimen changes from a vibrant green in the spring to a deep red in the fall. It candelabra like inflorescences of tiny cream flowers resulting in reddish seeds which marks the beginning of the change in late September/October. Their color emphasized by the late fall light they optimize winter metaphor of burning the old and opening ways for new beginnings.


Flora vacations #1

Looking down into Cape Town from the top of Table Mountain, Lions head off to the left

Since it’s the time of year to get together with family, I thought I would post a “holiday”post about the flora of my home town – Cape Town.  The Cape Floristic region is world-renowned for its unique and fascinating flora.

Pincushion (Leucospermum conocarpodendron) framing the walk up to the mountain

Pincushion (Leucospermum conocarpodendron) framing the walk up to the mountain

Elegia capensis – Restionaceae

A Mediterranean ecosystem that is frequently compared to that of California, Australia and, of course the Mediterranean, it has its own set of unique species that are adapted to its acid soils and winter rainfall.  It is indeed so special, with 8200 species in an area 1/3 the size of Britain, that in 2004 it was declared a World Heritage Site.  One of the gems in the crown is Kirstenbosch gardens.  Situated on the back slopes of Table Mountain this garden displays many of the unique and beautiful species found in Fynbos and in other flora of South Africa.  Many of these species are popular, not only locally, but around the world and have been developed for horticulture.  As a site with multiple uses, providing access to mountain walks, acting as a music and art venue, Kirstenbosch is popular with locals and tourists alike.When walking on Table Mountain there are many extraordinary plants to see.  Families that are common in Fynbos and relatively rare globally are Proteaceae,

Mimetes hirtus

Helichrysum vestitum (Asteraceae)

and Restionaceae.  Unique genera of the Proteaceae, such as Grevillea sp., are also found in Australia.

Ubiquitous families like the daisies (Asteraceae) are well represented too.  Pictured here is an example of the group known as “Everlastings”, the ray florets of this group have a papery texture and dry very well making them popular with florists.

Disa uniflora

Herschelia graminifolia – blue disa

Even the more delicate gems of the plant world can be found here.  It is quite possible that climbing on the mountain in summer or winter you might come across members of the family Orchidaceae.    Many of the species such as Disa uniflora are well-known by enthusiasts around the world and bred with great care.

Everlastings and Leucodendron sp. on the mountains of the Cape Peninsula

The diversity of species and form is connected to the dynamic patchwork of soil, water and light conditions that are found in the mountains and plains of the region.   Trees of the temperate forests line the Kloofs, while grasses and shrubs vie for space on sandy flats, and a successional array of bulbs, forbs and shrubs are to be found all over the micro climates of the mountains.

Evidence of fire on the Cape Peninsula mountains

But all the species that are found in this dynamic landscape have to be able to cope with fire. Fire is a transformative element in the landscape patchwork and plants are able to survive by employing different strategies.  Some plants produce myriads of seeds holding them in protective structures until the fire has passed.  The fire stimulates the release of seed of these serotinous individuals and the smoke of the fire stimulates seed germination.  Another strategy is to protect the meristematic buds beneath the surface of the soil and resprout after fire., taking advantage of a nutrient rich environment with few competitors.

It is interesting that many of the remarkable species of this landscape have been developed for horticulture and utilized around the world in gardens.  In agriculture species, such as corn or the apple, have not appeared desirable at first and have been worked for centuries to obtain the suite of appealing characters that we now enjoy.  It makes me wonder what inconspicuous species lie in wait in the many different flora around the world, waiting for some creative enthusiast to spot their inherent beauty and potential.

The Devil is in the Details

Through the process of photosynthesis, plants are mediators in the environment.  From our perspective plants provide us with oxygen and form the basis of our food chain by making sugars.  From a plants perspective we, and all other aerobic life forms, are the basis of their food chain – the carbon dioxide suppliers.  Linking soil and air plants combine elements of mineral and sunlight to build the substances of their bodies.  Just like us, plants require minerals.  They obtain macro and micro nutrients, such as iron, sulfur, calcium, and magnesium from the soil.  But some are able to survive conditions where there are toxic substances present.  It is not news that plants can survive a wide range of conditions, frequently occupying very specific ecological niches.  Our relatively new investigations are into how some plants are not only able to survive toxic conditions but can ameliorate them and can be employed as mediators in their clean up.  This is an exciting development as it offers and sustainable and comparatively non-invasive way of effectively dealing with challenging contaminated sites (Mench et al 2009).

What toxic conditions are these you ask?  You can easily imagine a mine dump or contaminated effluent situation, fairly commonly described in the literature.  In these cases metals such as cadmium, lead, cobalt, copper, mercury, chromium, nickel, selenium and zinc are of great concern with regards to the food chain (Branzini et al 2012).  Greater consideration is being given to compounds known as xenobiotics that are accumulating in the environment and food chains.  The majority of these toxic situations are as a result of human activities (Mench et al 2009).

But how do plants cope with these conditions?  Where do they put the substances that they are absorbing? Studies have looked at the mechanisms that plants employ when taking up these substances, as well as their genetics.  Plants sequester the toxic compounds in vacuoles and cell walls, and they may also produce exudates through stems and leaves (Azzarello et al 2012).  There are papers on genetically modified plants being utilized to clean up environments (Vangronsveld et al 2009) and on locating native species that facilitate restoration of landscapes (Salas-Luevano 2009).  As one would expect even those plants able to cope with challenging conditions have their limits.  Work with Pauwlonia tomentosa indicates inhibited growth and leaf production which, at the cellular level, is connected to damage to the chloroplast (Azzarello et al 2012).  Sesbania virgata is remarkable, being able to germinate and grow in certain toxic conditions, but it does become challenged when there is more than one toxic element (Branzini et al 2012).  Like P. tomentosa, S. virgata appears to concentrate the metals taken up in the roots, limiting translocation to the stems and leaves.

Basically there are three strategies that can be employed in
phytoremediation: phytostabilization, phytoextraction and phytodegradation.  Each strategy requires different characteristics of the plants that might be selected (Vangronsveld et al.  2009).    Hyperaccumulators that take up the elements and translocate them to shoots and leaves are useful candidates for phytoextraction.  In some cases the material is harvested and can be remined or utilized in other ways (for examples Salix sp. grown on toxic sites and harvested).  Of course the concern is that the toxin not enter the food chain as a result of phytoremediation.  Native species are prominent candidates in situations that would benefit from phytodegradation.  Here the microbial relationships that the native species have with bacteria and fungi create optimal conditions in the rhizosphere to transform toxins that might enter groundwater (Mench et al 2009).  This is particularly effective in the restoration of land affected by xenobiotics.

Where do we find these plants? Are there naturally occurring suites of species that prefer these toxic conditions?  It seems that there are many plants that can utilize trace elements that are present at toxic levels, and some, for example the metallophytes, actually prefer these conditions.  There are specific taxons that have been utilized repeatedly, in particular the Poaceae and Fabaceae, the genera Salix sp.  and Populus sp.  (Vangronsveld et al, 2009; Mench et al 2009).  But the unique nature of each contaminant situation and the individuality of species means that there is great scope for research.  In particular we need a greater understanding of relationship: contaminant and soil conditions, plant and soil, plant and contaminant.  The nuances prevalent in each environment ensure that we need to broaden our understanding of the mechanisms plant species utilize in these conditions.  We have some generalizations to guide us, for instance hyperaccumulators appear to have high levels of transpiration, plants that work best in phytodegradation have extensive root systems and of course the species has to tolerate the toxic conditions.  But just because a plant forms mycorrhizal relationships does not necessarily mean it can be employed in phytoremediation.  And this results in a situation that fascinates me: the interaction of the social, economic and the academic.

The details of the leaf cell in a hyperaccumulator is the business of a biochemist or maybe microbiologist, but it is the landscape designer or land manager who is desperately seeking a list of species that can be utilized.  A piece of land needs to be restored or treated because of potential health or environmental dangers, but someone has to pay for the plan and intervention (and the research behind it).  And so we begin to arrive at some practical questions: would it be alright to utilize an introduced, invasive species known to remove toxins from the landscape if the work on native species is not done?  What is the cost of looking for a possible native species?  Is it possible to create a field test, or relatively rapid test, to locate local species that could be utilized in land reclamation and restoration projects?


Azzarello E., Pandolfi C., Giordano C., Rossi M., Mugnai S., Mancuso S., 2012.  Ultramorphological and physiological modifications induced by high zinc levels in Paulownia tomentosa.  Environmental and experimental Botany 81: 11-17

Branzini A, Gonzalez R, Zubillaga M, 2012.  Absorption and translocation of copper, zinc and chromium by Sesbania virgata.  Journal of Environmental Management.  102: 50-54

Mench M, Schwitzguebel J.P, Schroeder P, Bert V, Gawronki S, Gupta S,   2009.  Assessment of succeful experiments and limitations of phytotechnologies: contaminant uptake, detoxification and sequestration, and consequences for food safety.   Environmental Science Pollution Research.  16:876-900.

Salas-Luevano M. A,  Mazanares-Acuna E, Letechipia-de Leon C, Vega-Carrillo H. R,  2009.  Tolerant and Hyperaccumulators Authochthonous Plant Species from Mine Tailing Disposal Sites.  Asian Journal of Experimental Science.  23.  27-32.

Vangronsveld J, Herzig R, Weyens N, Boulet J, Adriaensen K, Ruttens A, Thewys T, Vassilev A, Meers E, Nehnevajova E, van der Lelie D, Mench M,  2009.  Phytoremediation of contaminated soils and groundwater: lessons from the field.  Environmental Science Pollutation Research.  16:  765-794.