The diversity of the ‘star’ flowers – Asteraceae

Black foot daisy (Melapodium leucanthum) – Tribe Heliantheae

Firewheel (Gaillardia pulchella) – Tribe Helenieae

A humble daisy is the characteristic member of this cosmopolitan group.  You can imagine that a plant family with members spread across the globe might well have species occupying a range of niches.  The vast diversity is taxonomically captured by dividing the family up into sub families and tribes.

The tribes that you might be the most familiar with are the Heliantheae and Helenieae (the classic daisy form), the Cynareae (artichokes and thistles)

Texas thistle (Cirsium texanum)

, Astereae (which has Golden rod and the fleabanes as members)

Prairie fleabane (Erigeron modestus) – Tribe Asteraeae

and the ubiquitous Chicorieae (dandelions and chicory).

Colorado dandelion

While most asters (or composites) are herbaceous perennial, biennials or annuals there are also shrubs and vines.  The complexity of this group extends to its taxonomy and you may see frequent name changes.  In fact you might see the family referred to as Compositae!  This name is in reference to the classic head inflorescence of the family.The flowers (disc florets) are typically collected together and surrounded by what are termed ray florets.  You might be tempted to call them petals but they are in fact a different type of flower to the others on the head.  In the image to the left you can see (from outside to center)the large yellow ray florets, the  yellow stigmas (female parts) of individual flowers and the brown anthers (male parts) in the center disc florets.

The curiously square bracts of Nerve- ray (Tetragonotheca texana – Tribe Heliantheae)

Below the inflorescence are bracts that you might mistake for sepals (if you viewed the whole daisy as a flower).  The bracts of different species are quite different and might even be sticky or spiky!

Brownish bracts of Navajo tea ( Thelesperma simplicifolium – Tribe Heliantheae)

Helianthus maximiliani

Ratibida columnaris

Here we have a classic example in the case of the sunflower – Maximilian sunflower to be exact (Helianthus maximiliani – Tribe Heliantheae).  A variation on this capitulum inflorescence is Ratibida columnifera (also in tribe Heliantheae) where the platform of tiny flowers are proud of the bronze or yellow ray florets.

The multiple inflorescences of Poverty weed

Of course Nature never obeys our taxonomic rules so there are other members of the family that do not have the classic daisy flower.  Poverty weed (Baccharis neglecta – Tribe Astereae), for instance, does not conform to the usual idea of a “daisy”.  A tall shrub, it grows well in disturbed areas and is very difficult to remove!  In fall it becomes very attractive covered with multiple inflorescences.  It’s overall silvery appearance earns it a place in the landscape.  Come spring I will be wondering how to get rid of it again!

Blue mist flower (Eupatorium coelestinum – Tribe Eupatorieae)

You can see that the inflorescence of poverty weed lacks the ray florets common in other tribes.

They are also much reduced or absent in the Eupatorieae.  Blue mist flower (seen here with friend) (Eupatorium coelestinum) is a beautiful summer flowering example of this tribe.  There is a wealth of hardy Asteraceae species that can be utilized for different effects in the landscape.  They are a global family well worth exploring.

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Green Roofs

Greening the neighborhood one roof at a time.

hortitude

 

The idea of green living is popular right now, and what better place to start than in the garden? Saving energy, reducing impact, and reusing materials are all part of going green. Ironically, one of the most intriguing places to put your new environmental awareness into practice may not be in the garden, but above it.

The idea of a living roof is not new. In Scandinavia, people have been building roofs with sod since the Middle Ages. And you’ve probably heard of the Hanging Gardens of Babylon? Of course, modern life and building practices bring new needs, and planted roofs continue to offer many benefits. Making a roof “green” extends the life of the roof, reduces water runoff and reduces energy costs (especially for cooling) up to 40%.

Plants absorb sunlight, whose energy would otherwise go into heating a roof’s surface. The evapo-transpiration of plant leaves also helps…

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Contrasts in Texture

Image

We might be very familiar with the red poppy (Papaver rhoeas), a European native Imagecommon in disturbed areas, or even the yellow Californian poppy (Escholzia californica), native to the USA.  But we might not be so quick to recognize the prickly body of the White Prickly poppy (Argemone albiflora).Image  This Texas native is a survivor, preferring to grow in disturbed and nutrient poor conditions.  It can be seen on the roadside in many southern states and has a rose-pink variant in Southern Texas.  An annual or biennial, it has delicate paper white flowers beloved by bees and butterflies but shunned by deer and cows.  Probably because it is very prickly and toxic.  It produces copius quantities of seeds and would possibly be a good candidate for restoration in very disturbed sites where people would not necessarily pass to close by.  Given it’s deep root system I wonder if it would also be a candidate for phytoremediation?

Lepidopteran Surprises!

It was a spring for caterpillars, butterflies and moths in Texas.  But I was still surprised when I was walking to my car in May and saw clumps of caterpillars on the evergreen sumac in the parking lot.  Much to the joy of colleagues and students we watched the caterpillars devouring great sections of leaves.  What made it even more interesting was that while some of the caterpillars stayed in a tight group others had wondered off by themselves a little and would arch their backs if you peered too closely.

Curious, I contacted the LBJ Wildflower center and they put me in touch with a volunteer who was an expert in these matters.  Several emails later the caterpillar was identified as Datana perspicua or spotted Datana.  It turns out that they are the only species that uses Evergreen Sumac (Rhus virens) as a host plant and then they go underground before emerging again as an adult!

Things are never quite what they seem

Nothing should be taken for granted.  Out at the Bamberger Ranch last in February we were treated to early wildflowers.  Over the past three years I have been out to this private ranch at the same time and we seldom have any flowers to look at.  This year, a mild winter and regular spring rains have filled rivers and encouraged early flowering of several different species.  Colleen Gardner, executive director, told us that from September 2010 to September 2011 they had had approximately 4 in of rain.  Since then they have had approximately 6 in and it is still coming!

And so the flowers bloom.  One in particular caught my eye – Puccoon or Lithospermum incisum.  This perennial is found in the majority of the states in disturbed and open areas near woodland.  In some states it is endangered or even eradicated!  The plant pictured here was on the side of a path at the base of a steep limestone hill.  It appears that plants that are found from Kansas south are typically smaller than those found to the North (Govoni 1975).  Flower form and vegetative characteristics vary greatly, independent of one another and depending on environmental characteristics.  Generally wetter conditions produce bigger plants.  The flowers are not always obvious as they are sometimes hidden by leaves.

The very beautiful but relatively scentless flowers can be seen from March to May in Texas and into July in other states.  Surprisingly these pretty flowers are mostly sterile!  Later in Spring and Summer puccoon plants will produce hidden flowers that will self-fertilize without opening.  This type of flower is said to be cleistogamous.  This condition is not as rare as you might think.  The genus Viola sp.  and many grasses utilize this reproductive mode.  Some species are known to use it in response to damage or environmental stress.  The opposite of cleistogamous is chasmogamous which describes flowers that open before fertilization and are usually cross pollinated.  Interestingly annuals are frequently cleistogamous (or self-pollinating) and perennials are cross-pollinated.  Whatever the breeding system is the literature suggests that annuals are more succesful than perennials at setting viable seed (85% in annuals and 50% in perennials – Wiens 1984).  So I am left with three questions:  Firstly why does Pucoon bother to have such beautiful flowers? Secondly, what is the genetic make up of this curious species and Is there a way to grow this flower horticulturally so that it could take the place of Pansies or other spring bedding plants?

References

Harris and Harris.  2001.  Plant Identification terminology

Enquist.  1987.  Wildflowers of the Texas Hill Country

Wiens.  1984.  Ovule survivorship, brood size, life history, breeding systems,and reproductive  success in plants.  Oecologia. Volume 64, Number 1, 47-53

Govoni.  1975. Evidence for Divergence in Lithospermum incisum Lehm. in the Western Great Plains.

Taxon   Vol. 24, No. 4.  431-441

Botany For Design

My love for plants and landscapes originated in my childhood in Africa. 

A traditional Botannical training introduced me to the wealth of plant diversity and the idea that plants have an important and specific function in the environment.    Their place in the landscape,  stems from what they are able to do, physiology, and how they interact with the landscape, ecology.  This blog is a complement to a course in landscape design where we explore aspects of eco-physiology and taxonomy relevant to landscape design.

Using the local flora of Central Texas, the goal is to connect science, application and aesthetics in order to promote the creation of ecologically intelligent landscapes in our increasingly urban world.