Abies balsamea 'Nana'

Abies balsamea 'Nana'

Friday, February 14, 2014

My Favorite Plant...This Week: Schlumbergera x buckleyi

My favorite plant this week, or at least today, is Schlumbergera x buckleyi, the Christmas cactus. My plant seems not to have read any of the descriptions saying that this rain forest epiphyte is supposed to bloom around Christmas, but it never has shown much interest in reading. Frankly I approve of it's decision to bloom nearer to the end of winter, especially since North Carolina, along with most of the rest of North America, has had a rather harsh time of it this season. The end of winter is when I really start to get antsy and desperate for flowers and new growth.

I propagated my Christmas cactus from a very large specimen donated to my university's horticulture department along with several colors of Thanksgiving cacti and some hoyas by a woman who could no longer care for them due to deteriorating health. My heart goes out to people like these who must give up what they love because their minds or bodies are no longer able to care for them.

My Christmas, I mean Valentine's Day, cactus must have known February would bring some miserable weather. It's kept me in happy suspense through January and is now bursting with color just when I need it most.
Christmas cacti, and their close relatives, Thanksgiving cacti, are easy-care house plants. Keep them out of direct afternoon sunlight by growing them in an east-facing or a shaded south or west facing window. They don't need a lot of water, though they will need more than your typical desert cacti. They are from rain forests, after all. Let the soil surface dry between waterings for most of the year. In winter it is recommended to water only enough to keep the stems firm. The potting mix should be well draining, as these are epiphytes, growing on tree branches in their native haunts, but most any soilless potting mix should do. I have noticed that certain "miraculous" potting mixes have changed their formulas in recent years to increase water-holding capacity. This is great for outdoor containers in the heat of summer, but for most houseplants I would recommend adding extra perlite, vermiculite, pumice, or some other coarse material to increase drainage and prevent the mix from becoming too compacted. A well-drained mix and a relatively small pot will help keep your forest cacti happy and prevent it from drowning in the advent of over-zealous watering (more of a problem for helicopter plant parents like me than for most people).

In what is turning into typical fashion, being the annoying know-it-all that I am, I'd like to share a few distinguishing characteristics about the Christmas cactus. Many people are not aware that what is typically sold in stores around the Christmas holiday is not the true "Christmas" cactus. They are almost always cultivars or hybrids of Schlumbergera truncata, which is traditionally known as the Thanksgiving cactus. Of course, Schlumbergera x buckleyi is itself a hybrid between S. x russeliana and S. truncata, so what difference is there, really?

Stem shape
The cultivars and hybrids of Schlumbergera truncata classified as "Thanksgiving" cacti have points on their stem segments, or phylloclades, and tend to be more upright or spreading.  The true Christmas cactus, Schlumbergera x buckleyi, has scalloped edges on rather pendulous stems.

Bloom shape
When in flower, Christmas and Thanksgiving cacti are easily differentiated by their blooms. The flowers of Christmas cacti point straight out from the end of the stem (which usually hangs down) and are radially symmetric (actinomorphic), like a daisy. Thanksgiving cacti are a little kinkier, having a distinct bend in the ovary that causes the flower to point out horizontally. The petals also flair up and back, making the flower zygomorphic (meaning a line can be drawn down it to make two mirror halves).

Bloom time
Ironically, the least reliable distinction between the two groups is also the one that lead to their common names. Thanksgiving cacti are supposed to bloom around Thanksgiving, while Christmas cacti typically bloom around Christmas, right? Did you catch those key words, "supposed to" and "typically?" Really this just means that Thanksgiving cacti bloom a few weeks earlier than Christmas cacti, but the actual bloom time is dependent on temperature and day length. Bloom time can be manipulated by controlling day length and temperature to produce flowers almost any time of year. Thanksgiving cacti require a shorter period of cool temperatures and/or short days/long nights to initiate bloom, thus they have become the favored holiday cactus in the trade. In the home, these plants need to be kept in a place where they will not receive artificial light in Fall as the days get shorter, like a spare bedroom you don't need to get into frequently after dark in the fall. If the plants are exposed to light after the sun goes down (or after your grow-lights are turned off for the night), most of the developing flower buds will abort and fall off. You'll still get a few flowers, but not mass flush of blooms that you see in stores. Cool temperatures in the 50-60 degree Fahrenheit range also helps, but is not critical.

Of course, further hybridization of Schlumbergera has resulted in more intermediary types between Thanksgiving and Christmas cacti, blurring the distinctions in stem shape, bloom shape, and bloom time, but at least this gives you a better guess as to what you are actually buying (or the ID of that plant that's been passed down from Grandma, a traditional method of receiving holiday cacti). Luckily, newer cultivars are also easier to rebloom than older selections, being less dependent on that careful control of light I discussed above.

The following two pictures are of Thanksgiving cacti. Note that the flowers are held horizontally, with the petals on the bottom reflexed to lie flat along the rest of the flower and the rest of the petals pointing straight up. You can also see the points on the stem segments, typically four per segment.

The blooms of Thanksgiving cacti always remind me of some sort of exotic bird with wings thrown back and up.

Take a look at the bud above the open flower. This shows particularly well the bend at the base of a Thanksgiving cactus flower.

 The following pictures are of Christmas cacti. Technically it's all the same plant, as the last three pictures are of my plant, which was grown from cuttings taken from the plant in the first picture. What I really wish these photos captured is the complex blend of colors in the flowers. They have an almost iridescent quality in sunlight. They start out pink touched with some fantastic shade of red (carmine, vermilion, I don't know), and as they age a purple sheen develops, like oil on water. You can actually see a little of the red shades in some of these photos, but the purple oil slick is indiscernible from the base pink color. It seems to blend in, making the pink a little more purplish than it really is.
This is the original plant from which I took cuttings to propagate my own Christmas cactus. The scallop-edged stems of this venerable old specimen had become completely pendulous, like a small succulent weeping willow. As you can see, the flower hangs straight down. The color is much better developed in this flower, growing with ample light in a greenhouse. 


The blooms on my plant, grown in a house, have less red and almost none of that illusive, possibly hallucinatory purple sheen, but aren't they lovely just the same?

Because my plant is growing indoors with light coming primarily from one side, I've noticed that the flowers aren't as perfectly actinomorphic as they were on the original plant growing in the greenhouse. They seem to want to bend a little towards the light. You can see the radial symmetry a little better in the recently opened flower in the top left corner.

This flower, still opening, shows the red shades a little better, I think. 

And so ends another protracted post. Maybe I should change my name to the Obnoxious Plant Geek. Or I'll just start doing Wordless Wednesdays so people can enjoy some nice pictures without me rambling in their heads. ;)

My Favorite Plant This Week is hosted by Loree, of Danger Garden fame. You can see her favorite this week by clicking here

Until next time...

2 comments:

  1. Love it! And it's really rather apt that it be blooming those fabulous flowers on Valentines Day.

    I once shared an office with a lady who had a trio of Christmas cactus on her desk. The old terra cotta pots were half empty of soil and the poor things looked half dead. Yet every year they'd bloom their crazy heads off for a couple of weeks.

    ReplyDelete
    Replies
    1. Just goes to show how tough these plants are. They would actually make great office plants, since they don't need much light and in an office people are gone for the night so they can get their needed dark period to bloom.

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