When is a tree not a tree? When it is a palm tree!
Despite appearances and name, the biology of palm trees is sufficiently different from its woody counterparts.
Interior plantscapers seeking to establish palm trees indoors should be familiar with these differences if their palms are to thrive.
The Arecaceae, or palm family, is a family of perennial flowering plants, including over 183 genera and 2364 species of climbing, shrubby, stemless and treelike plants1.
Palms may be single stemmed or multi-stemmed (clustering) as a result of branching from axillary buds low on the stem.
Single-stemmed palms commonly used indoors include:
🌿 The Kentia Palm (Howea forsteriana)
🌿 Majesty Palm (Ravenea rivularis)
🌿 Mexican Cotton Fan Palm (Washingtonia robusta)
🌿 Dwarf Date Palm (Phoenix roebelenii)
🌿 Christmas Palm (Adonidia merrillii)
🌿 Chinese Fan Palm (Livistona chinensis)
Clustering, i.e. multi-stemmed, palms commonly used indoors include:
🌿 The Fishtail Palm (Caryota mitis)
🌿 Golden Cane Palm (Dypsis lutescens)
🌿 Rhapis Palm (Rhapis excelsa)
🌿 Bamboo Palm (Chamaedorea erumpens)
🌿Parlor Palm (Chamaedorea elegans) is mostly single stemmed.
Smaller palms like the Parlor Palm may be used in dish gardens, miniature gardens, fairy gardens, terraria, or as desktop or floor plants, or even in green walls.
However, larger palms are commonly used indoors as focal points in atria, gardens, floor plants, or for event hire.
Despite the treelike appearance of larger palms, the palm family belong to the division (clade) of the flowering plants (angiosperms) known as the monocotyledons (or monocots).
Most monocot families consist of herbaceous plants such as grasses or lilies. Yet palms can grow to quite sizable heights and even resemble those woody trees and shrubs belonging to the dicotyledon division.
Palms may be described as arborescent (treelike) monocots.
University of Florida has produced an excellent extension guide entitled Ornamental Palm Horticulture, in which the authors demonstrate the differences between woody dicots and members of the palm family2.
Woody plants possess a specialized layer of cells called the vascular cambium which is formed between the water-conducting tissue (xylem) and the carbohydrate-conducting tissue (phloem).
The vascular cambium produces new xylem toward the inside of the stem, and new phloem toward the outside. However, no vascular cambium exists in palm or most other monocots. Instead, the xylem and phloem occur in bundles scattered throughout the internal tissue of the stem, with little or no regenerative ability.
Palms are essentially devoid of the secondary growth experienced by dicots which can be seen in those woody species in cross-section as growth rings.
The University of Florida claim that once a palm stem achieves its maximum diameter, not one single additional vascular bundle will be added to the internal tissue of the stem. Palms are unable to repair their vascular bundles if damage is received to the stem. Hence, it is impossible to graft one part of a palm to another.
The authors of Ornamental Palm Horticulture claim that the future of a palm stem rides upon the continued health of a single actively growing apical meristem within the bud with little or no ability to regenerate itself.
They say that if the apical meristem is killed, the entire palm (if single-stemmed) or an individual palm stem (if clustered) is doomed to eventual death. Another interesting fact about palm trees is that they complete their increase in stem diameter before elongating, with some palms not developing a conspicuous aerial trunk for several years.
During this establishment phase, the palm is particularly sensitive to less-than-optimal environmental conditions.
Nutrient deficiencies?
Retired American interior plantscaper and IPA Honorary Member, Kathy Fediw claims that palms are notorious for developing nutrient deficiency problems because their vascular system is scattered, i.e. discontinuous.
Fediw claims that this makes it harder for palms to take up nutrients form the soil compared to plants with a ringlike (continuous) vascular system3 and highly recommends a closely monitored fertilisation program for palms, including a complete fertiliser.
On the other hand, the authors of University of Florida’s Ornamental Palm Horticulture claim that transport of water and nutrients throughout the palm’s leaf canopy is efficient due to the numerous vascular bundles throughout the trunk
NB. The University of Florida has produced an excellent summary of nutrient deficiencies in palms that interior plantscapers would find useful:
Nutrition and Fertilization of Palms in Containers https://edis.ifas.ufl.edu/publication/EP262
When is a ‘palm’ not a palm?!
The Ponytail Palm (Beaucarnea recurvata) is a member of the Asparagus family (Asparagaceae). While it is not a true palm, it is an arborescent monocot.
The Sago Palm (Cycas revoluta) is not a palm or arborescent monocot.
This species belongs to the Cycadaceae, a family of dioecious gymnosperms bearing male and female cones on separate plants.
Your recommendations?
What tips can you give to fellow interior plantscapers to keep their palms looking good?
Share your stories and photos on the Interior Plantscape Association’s Facebook page https://www.facebook.com/interiorplantscapeassociation or tag LinkedIn www.linkedin.com @Interior Plantscape Association of Australia.
Further reading – ‘Advancing the use of trees indoors’
If you would like to know more about designing, constructing and maintaining an interior plantscape featuring advanced trees, read IPA’s article ‘Advancing the use of trees indoors’, in the September 2021 issue of Hort Journal Australia. www.hortjournal.com.au
In this article Chay King, Director of Kings Landscapes and a Level 8 arborist were interviewed. Chay regularly supplies advanced trees to interior plantscapers, including IPA member Advance Plants Qld.
Written by:
Gabrielle Stannus / Inwardout Studio
IPA Committee Member
References
1 Gomez-Navarro, C, Jaramillo, C, Herrera, F, Wing SL & Callejas, R 2009, ‘Palms (Arecaceae) from a Paleocene rainforest of northern Colombia’, American Journal of Botany, Vol. 96, iss. 7, pp. 1300-1312, (page 1300 cites Govaerts & Dransfield, 2005 ; Dransfield et al., 2008)
2 Broschat, TK, Meerow, AW & Elliott, ML 2017, Ornamental Palm Horticulture, 2nd edition, Chapter 1, ‘Palm biology in relation to horticulture’, University of Florida, IFAS Extension
3 Fediw, K 2015, The Manual of Interior Plantscaping: A guide to design, installation, and maintenance, Timber Press, Portland, Oregon (pp. 186-187)
Images
- Kentia Palm (Howea forsteriana) installed in the Westfield Chermside Shopping Centre in Brisbane (Image: Kings’ Landscapes)
- The Parlor Palm is perhaps one of the most popular plants for use indoors (Bachelot Pierre J-P 2015,’Chamaedorea elegans Mart. dans la serre du Botanischer Garten de Berlin-Dahlem’, 27 June 2013 (CC BY-SA 3.0))
- Generalised palm morphology (Image: A. W. Meerow, University of Florida/IFAS Extension)
- Comparison of a palm (A) and an oak (B) stem in cross section, with detail of a single palm vascular bundle (C). In palms there is no vascular cambium, and there are no growth rings. Vascular bundles are scattered throughout the central cylinder, usually in greater density at the periphery, and last the life of the palm. The epidermis and cortex are often referred to as “pseudobark.” (Image: Broschat, TK, Meerow, AW & Elliott, ML 2017, p.7)
- Beaucarnea recurvata is an arborescent monocot, but not a true palm (Image: Conrado 2005, ‘Pataelefante’, 1 February 2005 (CC BY-SA 3.0))
- The Sago Palm (Cycas revoluta) is a dioecious gymnosperm and not a palm! (Image: Wikizoli 2015, ‘Palm trees in the Botanical Garden in Cluj’, 28 June 2015 (CC BY-SA 4.0))