5.10.18

Cycads: Life in the Slow Lane


 



Gardening is an endeavor that can teach us many things about life. Surely one of the obvious lessons is patience: patience to make garden designs become a reality, patience to nurture plants and watch them thrive. Patience is needed when setbacks occur from pests or disease or truly damaging weather events like cold snaps or hurricanes. Unless our gardens are composed of annuals that quickly cycle through blooming and replacement, we learn patience from watching our plants grow in time into beautiful specimens.

 

Cycads, seed-bearing plants that are frequently mistaken for palms or ferns, are perhaps the ultimate slowpokes in our gardens. They are members of three very closely related families whose nearest relatives are conifers, such as pines, and the Ginkgo, an ancient tree species widely planted in northern landscapes. In books and films, cycads are popularly portrayed as primitive plants that were grazed upon by dinosaurs. The origins of the cycads reach far back in geologic time to the dinosaur period and beyond, but the origins of present-day species are much more recent. Today, cycads are considered relic survivors found in the New World, Africa, Asia, and Australia. Some cycad species are amongst the rarest of plants, with populations that are scattered and highly localized, sometimes to a single hill or mountain. Nevertheless, within their native ranges, certain cycad populations can number in the hundreds of thousands or even millions of individuals. 



Cycads are magnificent garden plants that live on a timescale that can humble us short-lived humans. They often grow slowly, take a while to reach maturity, and have lifespans that can stretch through centuries. Unfortunately, many cycad species numbers are dwindling or threatened with extinction. Human-caused habitat alteration and loss are the great dangers posed to their survival. Changing climate that increases the occurrences of drought and intense fires also plays a part. Due to rarity, slow maturation, and difficulties in propagation, certain species have come under intense illegal collecting pressure, pushing them to the point of disappearance in the wild. Ongoing Cycad conservation efforts focus on research and increasing both the numbers and sustainability of wild populations. An additional benefit of all this attention is that valuable horticultural knowledge has become available to gardeners who are interested in growing cycads.

 

The fascinating reproductive strategies of cycads could easily be the subject of a dedicated lengthy blog post. Cycads bear cones on separate male and female plants; sometimes odors and heat are generated within the cones  to attract specific insect pollinators, required to produce viable seeds. When habitat pressures eliminate wild pollinators, or when the number of adult plants of reproductive age falls below a certain density to maintain pollinator populations, the cycad population can become functionally extinct. If the unfortunate species is only found in a single location, it's game over. In cultivation, however, male pollen can be stored and female cones can be hand pollinated. Some cycads produce offsets that can be detached and rooted to produce more plants.  

 

Probably the best known cycad is the Sago, Cycas revoluta, originating in Southern Japan and its offshore islands, but now popular worldwide, even as a houseplant.  Many desirable cycads originate in South Africa, growing in places that are drier and have lower humidity than Florida. There are still many species, however,  that do well in South Florida. Some make superb xeriscape specimens, while others will thrive in irrigated garden settings. Of course, many cycads from Summer- rainfall regions of Africa and Asia as well as from areas of Mexico, Central and South America and Australia are suited to South Florida gardens. Our state even has its own native cycad, Coontie, a quite adaptable species.

 
A severe threat to the numerous species in the genus Cycas is the Aulacaspis Scale, Aulacaspis yatsumatsui. originally native to Southeastern Asia. The insect has been inadvertently introduced into various locations around the world, where it has no natural predators. In Guam and other Western Pacific islands it has virtually eliminated the native Cycas micronesica. It is a serious horticultural pest in Florida, where its presence has essentially ended the cultivation of Cycas without constant vigilance and treatment of infested plants. 

 

No comments:

Post a Comment