Christmas Cactus

The bright red fruits of Tasajillo are present at holiday time, giving 
it an alternate common name of Christmas Cactus.

While many people are familiar with the tropical, non-native species of Christmas Cactus (Schlumbergera sp.) often sold as houseplants, not all are aware that we have a native Christmas Cactus (Cylindropuntia leptocaulis) here in Texas.   Our Christmas Cactus, also called Tasajillo, Pencil Cactus, Christmas Cholla, and Desert Christmas Cactus, is a true cactus much more adapted to our types of soils and climate. Common in the central and western parts of Texas, this plant’s species name, leptocaulis, means ‘slender-stemmed’, and it is a very good descriptor of its form.

Unlike many other cactus species, the flower of our native Christmas
Cactus is small, at only one half-inch across.

Upright, shrub-like, with many branches made up of slender, cylindrical jointed segments, this 2 to 5 foot tall plant is most often found growing in sandy or bottomland soils, having a trunk or main stem up to 4 inches in diameter with thicket-forming stems that exhibit various shades of green and feature a solid, woody internal core.  While occasionally spineless, it typically has very slender, 1-inch grayish-white spines grouped with much tinier spines, along each stem.  Botanists now think that two forms grow in Texas, a ‘long-spine’ form and a ‘short-spine’ form. Its leaves are very small, often not even noticed before they fall early in the growing season.  Small, pale, yellow-green flowers appear at irregular intervals in April/May and July/August, opening in late afternoon or evening.  But the true color display occurs in December, when its fruits turn conspicuously bright red and seemingly cover the plant like it has been festooned for the holiday season.

Christmas Cactus, short-spined growth form.

Christmas Cactus can grow from seed, but it is much more likely to spread by cloning.  The jointed stems can easily detach without harming the rest of the plant, and they are dotted with areoles, a structural feature of cacti that contain buds. All a stem needs to do is come in contact with the right soil, and it can take root and grow a whole new plant.

Christmas Cactus, long-spined growth form.

While the Christmas Cactus can be a nuisance if it develops in the wrong areas, it can also provide desirable value to wildlife and to humans.  Growing best under the protection of other vegetation, it offers dense cover for a variety of nesting birds and provides a good food source for white-tailed deer, bobwhite, wild turkey, most bird species, and many small mammals.  In West Texas, this plant is a larval host plant for the beautiful Staghorn Cholla Moth. From a human perspective, Christmas Cactus has a good ornamental value in a mostly xeric landscape, as it stands out in the bleak winter landscape, adorned with red fruit when most other vegetation is bare.

Staghorn Cholla Moth

Several sources describe the fruits of the Christmas Cactus as edible, even intoxicating.  But they are so small, and the spines so troublesome, that the plant usually yields only a sporadic nibble to the curious human. Nevertheless, native tribes made it part of their traditional diet, noting that the fruits, also called tunas, are vaguely sweet with a taste similar to the fruit of a prickly pear cactus.

Take the time to get to know our native Christmas Cactus and consider adding it to your wildscape.  You will easily learn to fall in love with its prickly nature, especially at Christmas time!

Frost Flowers

Blooming from August to November, Frostweed provides late season nectar
and a unique surprise at the first frost.

Accompanying the crunching of fallen leaves and the rattling of seed pods drying in the breeze is the arrival of the first frost.  This marks the seasonal change from our relatively warm autumn to the cooler days of a mild central Texas winter.  How does frost, this sparkling layer that sometimes covers the fall landscape, form? 

When the temperature of the air reaches a point where the water vapor in it can condense out into water, it is called the dew point.  The frost point is when the dew point falls below freezing, and rather than producing dew, it creates frost.  Consisting of tiny, spike-like crystal structures called spicules that grow out from a solid surface, frost generally forms on surfaces that are colder than the surrounding air.  Even the size of the crystals can vary, depending upon the amount of time they took to grow, the relative changes in temperature, and the amount of water vapor available. 

A frost flower.

Cold air is denser than warm air, so quite often lower areas become colder on calm nights due to differences in elevation.  Known as surface temperature inversion, this phenomenon forms ‘frost pockets’ or areas where frost forms first, due to cold air trapped against the ground.  It is here, in these areas, that you can find a rare and wonderful spectacle of nature called ‘frost flowers.’

While many plants can be damaged or killed by freezing temperatures or frost, this varies by the type of plant and tissue exposed to these conditions.  In central Texas, there is a common plant called Frostweed (Verbesina virginica), which is found in low-lying areas near streams, creeks, canyon bottoms, and in dappled shade at woodland edges. 

Bordered Patch

Silvery Checkerspot

Much of the year, Frostweed goes unnoticed while it grows 5 to 8 feet tall and leafy, the top of each stalk crowned by a cluster of small white flowers.  Its stalks are oddly square-like, with fleshy green flanges. Frostweed begins to bloom in the August heat, and continues until first frost, well into the fall.  These flowers provide late-season nectar for many insects, including bees, beetles, flies, wasps, and even migrating hummingbirds and Monarch butterflies.  It is also a host plant for Silvery Checkerspot and Bordered Patch butterflies.

A patch of frost flowers.

With the first frost, however, the water contained in each Frostweed plant stem expands, causing the stems to crack.  Via capillary action, more water is drawn through the cracks, freezes when it hits the cold air, and forms long curls of ice like petals of a flower, ribbons, or other delicate, abstract sculptures.  Most often, they consist of longitudinal bands of fine ice threads at right angles to the stem.  These delicate flowers of the frost are fleeting in nature, and can only be found in early morning, as the rising temperature quickly melts them away. 

A prime example of crystallofolia.

Only a few species of plants exhibit this unique phenomenon, which has been called ‘crystallofolia’ by Bob Harmes at the University of Texas, from the Latin crystallus or ‘ice’ and folium or ‘leaf’.  Much is left to be discovered reading the purpose of this process, but further research by Dr. James Carter at Illinois State University has concluded that the ice formation often far exceeds the amount of moisture locally available within the plant’s stem, so it must be augmented by water drawn up from the roots.

Delicate curls can form when more plant moisture is available.

On the surface, fall may seem as if nature is shutting down for the winter, but take the time for a second look and you just might be surprised.  The first frost of the season is another intriguing part of the ongoing cycle of life and renewal for our native plants and animals.