(Editor's Note: This article was originally published on April 19, 2009. Your comments are welcome, but please be aware that authors of previously published articles may not be able to respond to your questions.)
I am constantly trying to organize my plants and plant photos in categories that make sense and perhaps easy for me to look them up when I want to see them again. This sounds easier than it turns out to be. Do you put plants that look alike together... or ones that are related to each other together... or ones that have similar life strategies together? At first I decided to put plants in categories based on their relationships (e.g., Agavaceae with other Agavaceaes, palms with palms etc.). Soon I realized some of these related plants were simply so different that few plants in my collection could have much in common with each other. So since I have group plants in type/style categories (e.g., succulents with succulents, and trees with trees, no matter if they are related or not). This would mean sometimes splitting up obviously related plants, like my Oxalis gigantea, a drought-tolerant succulent, from my other Oxalis, which are anything but. While doing all this shuffling about of plants and lists, I was struck by how many plants were closely related but seem as unrelated as plants could get. So just for fun, I decided to write an article about it.
Oxyalis gigantea shots Oxalis triangularis
Cyphostemma juttae and edible grapes: both of these are in the family Vitaceae and I have both growing in the yard. But other than them both making grape-like fruits, they have little obvious in relation that I can tell. One is a vining, water-loving, edible-fruit bearing plant with thin, somewhat edible leaves that seem to abhor the summer heat in the Los Angeles valley. The other is a succulent, toxic stump with large rubbery leaves and toxic berries that loves the heat and tends to rot with too much water. Both are deciduous plants, and admittedly there are several vining Cyphostemma species (my Cyphostemma juttae is not one of those, though).
Cyphostemma juttae shots: old plants, close up of toxic fruits and winter leafless look
Grapes growing in my yard
Star Jasmine and Adenium: I had a lot of Star Jasmine (Trachelospermum jasmenoides) and it is a powerful smelling vine (in just the right ‘doses' it is a wonderful scent, but sometimes it smells like cat urine!) This plant is an aggressive, thin stemmed vining non-succulent ornamental. I unfortunately killed mine by not watering it enough. Adenium (I have obesum) is a thick, succulent-stemmed plant with extreme cold-sensitivity and amazing drought-tolerance. The two plants look about as opposite as the Cyphostemma and fruiting grape, but they are indeed related (in the family Apocynaceae). My guess is they share some floral characteristics, since nothing else about them is similar.
Adenium obesum in pot Adenium obesum flower (photo Xenomorf) Mature plant in nature (photo albleroy)
Star Jasmine photos: left and right by Thaumaturgist; Middle photo is plant in my yard grown specifically to eventually cover this ugly telephone pole support
Periwinkle and Pachypodium: I don't have any Periwinkles (Vinca or Catharanthus species) in my yard anymore (another loss due to lack of irrigation), but I do have many of their relatives, the Pachypodiums, growing about the yard. These two are also opposites in the Apocynaceae spectrum, one a small, creeping, delicate flowering color plant, and the other being a succulent, trunking, spiny-stemmed, drought hardy desert plant.
Periwinkles (Vincus and Catharanthus sp.); both photos by htop
Pachypodium lamerei Pachypodiums for sale in nursery Pachypodium lamerei flowers (photo RWhiz)
Osteospermum (Cape Daisy) and Senecio haworthii: These two members of the large family of Asteraceae (daisies) are too different to notice any obvious relationship, though I understand they have some similar floral characteristics.
Cape Daisies: Osteospermum 'Nasinga Purple' (photo Happenstance); Osteosperma 'Side Show Purple' (photo by Kell)
Poinsettia and Euphorbia obesa: These two members are even of the same genus (Euphorbia), yet they hardly look like they could be related. One is a popular Christmas color plant while the other is a succulent sphere. But if you cut into them, you will see they both bleed a white latex-like, noxious sap. And their flowers have obvious similarities. These are just two extremes in this large, interesting family. Below are a few more Euphorbia 'extremes'
Euphorbia pulcherrimas (Poinsettias)- trees in Southern California; bracht and flower close up (photo by careyjane); white-bracht form as a tree (photo by ginger 749)
Euphorbia obesa photos
A few more seemingly unrelated Euphorbias: Euphorbia tirucali Sticks of Fire; Euphorbi ingens 'drooping form'; Euphorbia antisyphilitica
Lithops and Trichodiadema: These are two plants at the opposite end of the physical spectrum of this South African family of desert growers, the Aizoaceae (aka Mesembs, after their old family name). I find they are not only dissimilar in appearance in every way, but also in their ease of care (one I kill by just looking at them wrong and the other is one of the easiest plants in the yard.) But both are drought tolerant and have similar flower parts.
Lithops in my garden (most gone now). Middle photo also shows an Argryoderma (another Mesemb). As a group these are called living stones
Trichodiadema bulbosums- Mesembs, too, but hardly 'living stones'...
Bowiea and Hyacinths: Here are two about as dissimilar as possible. Both are bulbs, but one is an above ground bulb with a thin, succulent vining light green thread coming from it which eventually forms a mass of green hair. The other is an underground bulb with leaves and brilliantly colored flowers; that they are related at all still amazes me.
Bowiea volubilis vining Bowiea shot of vines and flowers
Hyacinths in my yard (Hyacinthus orientalis)
Adenia fruticosum and Passion Vine: Adenia fruticosum is another cold sensitive succulent with a thick green trunk and small green leaves (during a short part of the year). The Passion Vines (both are members of Passifloraceae) have no succulent properties whatsoever and are rampant, aggressive vines with huge, brilliant and amazingly complex flowers, as well as edible fruits.
Adenia fruticosa and flower (second photo CactusJordi)
Passion vine, Passiflora coerula (photo by rylaff) Passion flowers in my yard
Passiflora coerula fruit in my yard another shot of my vine Passion fruit (photo by Thaumaturgist)
I have a lot of cacti in my collection and some just don't seem like they should be related to others. For example, here are a few of the cacti that just don't look anything alike, yet all are cacti.
Seemingly unrelated plants (all cacti): Browningii hertlingia; Ariocarpi; Unknown cristate cactus (Echinopsis?)
Disocactus Gymnocalycium Leuchtenbergeri (all cacti in my yard)
More cacti in my yard: Mammillaria elongata 'brain'; Pereskia grandiflora (leafy plant in background); Rhipsalis species
Schlumbergera (Christmas cactus) Opuntia microdasys 'Funny Bunny' Zig Zag Cactus
But one group of plants I am having the most trouble getting my head around is the family Xanthorrhoeaceae. That is about has hard to say as it is to spell. I actually have a Xanthorrhoea in my yard. It is a genus of Australian grass trees that are very slow growing, but some eventually grow into magnificent trunking plants topped with a huge head of long, arching, stiff grass-like leaves (see photo below). I have no problem with Xanthorrhoeas being in the family Xanthorrhoeaceae--makes sense to me. If I tried to imagine another plant in that same family I might be tempted to say Mexican Grass tree (Dasylirion species), but it turns out those are not even closely related. It is the other members of this unusual family of grass trees from down under that I am having trouble with. If anyone knows me, they know I am an aloe nut, and have been collecting and growing aloes for about a dozen years. It seems about every year aloes get put in a different family. At one time they were in the family Liliaceae with the lilies. That didn't make a lot of sense to me, but I didn't question it much since that is such a huge family with thousands of plants in it. Then it was moved to its own family, Aloaceae. Then it was moved to another name I found hard to spell and pronounce, Asphodelaceae. Just when I was learning this family name and how to pronounce it, it seemed Aloes were being moved back to Aloaceae. (Can't these scientists make up their minds??) Then, on my last attempt to clear things up I visited England's Royal Botanical site that some consider the be all and end all for arguments like this; that was when I discovered it was in the same family as the Xanthorrhoeas. I can think of few plant groups that look so unrelated as these two, though I suppose the overall flower shape of some aloes could be said to resemble those of the Xanthorrhoeas. But then I looked at the third major group making up this family- the Hemerocallis, or Daylilies. Yikes! This is a group of plants I bet most readers of this article are far more familiar with than I am, but they sure seem unlikely plants to be paired up with African rosette succulents and Australian grass trees. It's almost as though Xanthorrhoeaceae is being used as a dumping ground for plants that just don't seem to have a good home, taxonomically speaking, so the taxonomists plopped them all in this remote family near the end of the alphabet, hoping no one would notice. I know that's not really the case, but it sure seems hard to understand sometimes why this is related to that.
Xanthorrhoeas quadrangularis and pressii
Various Aloe species in my yard (except middle photo right above- from private garden in southern California)
Various Hemercaullis (Daylily) cultivars: 'Indian Giver' (photo by fearneyhough); 'Kwanza Gold' ; 'Shaka Zulu' (photos by Calif_Sue)
How could all these plants be related? Anyone?