Purple Shamrock!

Purple Shamrock is formally known as oxalis triangularis.  It is endemic to Brazil.  Historically it was grown as a house plant in the United States but has moved into the yard very well in Texas.  It works best in zones 8a–11, preferably in light shade.  THIS IS A TRUE DROUGHT RESISTANT PLANT!  GREAT NEWS FOR TEXAS.
The purple shamrock (or sometimes referred to as a black shamrock) and as pictured below does very well in full sun!  It is pictured in April, May and June here.   You are able to watch the gold lantana expand and eventually cover the shamrock as the summer progresses.
Purple_Shamrock_Texas_Lee_Ann_Torrans
Black Shamrock is of the same family.

Velvet Oxalis regnellii or Black Shamrock is the darkest of the Purple Shamrocks.  Velvet runs a close second.

Purple Shamrock Lantana and Red Yucca

Purple Shamrock Lantana and Red Yucca

Purple Shamrock – Oxalis regnellii atropurpurea.  In Texas purple shamrock blooms on St. Patrick’s day.  This gives you a good idea of when it is at its peak in Texas! As you can see in the June image above, purple shamrock has stopped blooming but it’s leaves have become more profuse!  Purple shamrock is grown for its leaves and not its blooms, though the blooms are very sweet.
Purple Shamrock Mixed with Annuals
I stopped using yellow lantana many years ago.  For the most part it acts as a perennial in Texas, but that allows its root structure to become so established that it grows too large August onward becoming unwieldy for my eye.  It’s a good and easy perennial, to be sure.  Perhaps I just became bored with it.  I don’t use it.  But if you are just starting out and want a quick, easy impact, go for it!  Clearly, the lantana is on its way to taking over the purple shamrock — and perhaps that is good.  It will allow the purple shamrock to go dormant.
Purple Shamrock Mixed with Annuals
Purple shamrock mixed with Holly Fern.  Purple Shamrock and Holly Fern Read more about ferns in Texas here.

Purple Shamrock in April in Dallas Landscape Design

Purple Shamrock in April in Dallas Landscape Design

More Purple Shamrock!

Purple shamrock with miniature pink crape myrtle makes a lovely combination.
  Purple Shamrock with Dwarf Pink Crape Myrtle
Miniature Pink Crape Myrtle:  More Here
Pink Miniature Crape Myrtle
Purple Shamrock in Texas
Relatively little care is required during the growing season. Water strongly the first two years while they become established. Once the shamrock goes dormant, you will observe leaf drop, trim the vegetation down.  In Texas you cannot always stop watering Purple Shamrock because of its proximity to other plants.  However, ideally, during the dormancy period let it wilt and lose leaves.
Purple Shamrock, Spreading Yew and Japanese Maple.
Purple shamrock, spreading yew and Japanese Maple.
Propagation and Purple Shamrock:  Purple Shamrock grows from tiny bulbs the size of your thumbnail.  Propagation is by bulb division.  Purple Shamrock (like all bulbs) experiences a dormancy period on a regular basis.At the end of the dormancy period, the bulbs can be unearthed, side bulbs can be cut and replanted.
Purple Shamrock Perennial
Above Purple Shamrock nestles amongst the rocks.
Purple Shamrock
During the day you will see the Purple Shamrock leaves stand up and pay attention and wilt in the evening.  The leaves of the Purple Shamrock respond to light levels, opening in high ambient light (in the day) and closing at low light levels (at night). This movement is powered by changes in turgor pressure in cells at the base of the leaf. It is an example of photonasty.  See cool video below of this process.
Purple Shamrock with Holly Fern in Perennial Shade Garden Setting.

Silver  Shamrock  –  Lavender Shamrock – Mahogany Shamrock

Purple is not the only color!  Try these sweet shamrocks as well.
Silver shamrock
Silver Shamrock
Lavender Shamrock
Lavender Shamrock
Mahogany Shamrock
Mahogany Shamrock
Purple Shamrock and Pets:  Known to be poisonous to cats and dogs.
This is one reason to consider Purple Heart rather than Purple Shamrock.  See Purple Heart below.
Shade Garden Perennial Purple Shamrock with Holly Ferns.
Wood Ferns and Purple Shamrock
  Purple Shamrock and Purple Japanese Maple with Hostas
  Purple Shamrock in Perennial Bed
A perfect situation for purple shamrock is morning sun!  But that’s a perfect situation for most plants in Texas.  Dappled shade works. However, with lots of water it will survive in full sun. LOTS OF WATER. Fundamentally, this is a bulb about the size of your thumbnail.  Consequently, it will go semi-dormant in Texas several times a year.  They are just ‘resting’.
  Purple Shamrock in Perennial Bed - May Images
  Purple Perennials Mixed with Annuals
  Lee-Ann-Torrans-Purple-Shamrock
 Purple shamrock tucked in with annuals is a great idea in the first years while the shamrock is becoming established.  You will be watering and fertilizing your annuals and the shamrock will benefit as well.  In a few years the purple shamrock will become stronger and more established and you will require fewer annuals.
  Purple Shamrock mixed with annuals while they become established.
Purple Shamrock Summary:  I love this precious little plant.  Every year in the fall I dig it up, separate it, and tuck it around the garden near the border in the shade.That’s coral bells Palace Purple Heuchera beside the purple shamrock.  I have never had long term luck with coral bells.  I treat them like an annual but perhaps someone else might do better.  THey are very popular at the plant stores.

 Purple Shamrock and Purple Heart

Purple Heart is another perennial that works better in full sun.  Purple Heart is a more compact and reliably broader leafed version of Purple Wandering Jew.
Purple Heart and Hydrangeas
Purple Heart is slightly more elevated than Purple Shamrock.

Purple Shield for the Perennial Shade Garden

Perennial Shade Garden Texas
Purple Persian Shield makes a strong statement.  Here you see it combines with traditional Purple Wandering Jew.  See more on this Perfect Perennial Shade Garden Here.
Because Purple Shamrock can be harmful to pets many are electing to use Purple Persian shield or Purple Heart.
Purple Heart and Purple Shamrock
Purple Persian Shield
Purple Shamrock Time-Lapse from Harry Tajchman on Vimeo.