Asparagus Fern or Bridal Creeper
This month’s plant is a South Africa native that has become naturalized in Southern California where there has the potential to become an extremely troubling weed species. It is already considered so in some localities in Southern California, New Zealand and Australia. It had become a major infestation in the oak grove near Lupine Point in the Los Osos Elfin Forest until it was successfully removed after much effort.
The problem with its eradication is obvious from looking at the cluster of corms that form just under ground. If left to multiply, this corm mat forms an extensive, impenetrable mat just below the soil surface that prevents other plant roots from getting to the nutrients they require. A second problem with the corm cluster is that if one just goes out and attempts to pull them up or cut them down, the corms just send up new shoots. One would have to repeat the removal process until the corms have been starved to death. That would be a long arduous process.
The fast and extensive stem and leaf growth is also a problem. It allows the asparagus fern to cover existing plants so well that sunlight can’t get to them.
I asked Bonnie to draw the plant with flower buds only because plants currently available to us are at that stage. I suspect that, if deadlines weren’t a consideration, a plant with fully open flowers might have been found since its blooming period is from December through April. But more importantly, this species’ vegetative state is so distinctive that the smallish, nondescript flowers are often overlooked anyway.
A word of warning, written descriptions of this plant in many books are totally deceptive. First, what looks like leaves are in fact flattened stems, which botanists often term cladodes. Unfortunately I also ran across several other technical terms for them.
How does one know they are “flattened stems” and not what they actually look like – “leaves.” All vascular plants have the same leaf-stem morphology. First the stem is divided into alternating nodes where the leaves are attached and internodes where there are no leaves. The exterior nodal structure includes the leaf and a bud found in the upper angle between the leaf base and the stem. When the bud germinates it produces a new stem which then can produce more leaves. This means that a given portion of stem produces a leaf only once or leaves are produced only during the first year of that particular stem’s life.
Remember, buds produce new stems only. So a reexamination of Bonnie’s drawing shows the green flattened stems (cladodes) arising from the angle of a small grayish scale. That scale is all there is to the true leaf. Using flattened stems for leaves is considered an adaptation to drought conditions.
As an example of how confusing this can be, look at the identification keys in the New Jepson Manual. The keys from group to family to genus to species all assume that you know that the leaves are those tiny, insignificant, hardly visible scales under the things that everyone but a botanists would assume where leaves but aren’t.
Bonnie has drawn a couple of flower buds coming from the axil of leaf whose bud grew into the cladode. Examine the node again very carefully. You will note that there are actually three scales visible. The largest one is the leaf and the two smaller ones just visible are the bracts (leaves associated with flowers) whose buds germinated to produce the flowers. Botanists consider flowers to be highly modified leafy branches. Why they think this must be the subject for another time. Oh yes, that means this plant must produce 3 leaves and buds per node. Two of them only develop when that node produces flowers, otherwise they would be invisible.
The plant has a number of common names as might be expected of a plant used by humans. Its primary use is in floral arranging. Its thin stem and abundant dark green cladodes together give it a kind of filmy or ferny appearance which explains the “asparagus fern” name.
Its long use in bridal bouquets explains its African bridal creeper, bridal-veil creeper, or merely bridal creeper names. Other names that I’ve seen include Gnarboola, Smilax or Smilax asparagus. The last two names should be forgotten as they indicate it is related to the genus, Smilax, which it is not. I assume Gnarboola is its name in its native Southern Africa. The genus, Asparagus, belongs to a group of monocots that produce flowers with a perianth of six sterile elements that are more commonly called sepals and petals.
This genus’ flowers have 3 greenish-white sepals and 3 identical greenish white petals. When sepals and petals are identical except for position (sepals are always the outer whorl and petals interior to the sepals) botanists use the term “tepals.” There is a large assembly of tepal plants including the lilies, amaryllis, tulips, onions, and garden asparagus. The list could go on and on. The problem with this group is that all their flowers are built on the same plan and whenever this happens taxonomist often can’t agree on family or even ordinal boundaries. For example, a search on my library and internet finds this genus placed in the lily family (Liliaceae – order Liliales) or the Asparagus family (Asparagaceae – Asparagales). Added to this the current distinction between these orders has to do with different DNA sequences and unique chemical constituents found in their seed coats, neither of which are hardly field characters. For the record, the new Jepson Manual puts this plant in the Asparagales and the Asparagaceae.