Tag Archives: Angiosperms

Angiosperm buds

Angiosperms (flowering trees) are more predictable in terms of their buds, because in addition to the terminal bud/s, in most cases a bud is also developed below a leaf petiole (stalk), and when that leaf falls off, the new bud grows from that position, known as the leaf axil (hence it’s known as an axillary bud). Therefore the bud pattern is equivalent to the leaf pattern or phyllotaxy.

It’s important to understand whether your tree has compound leaves, which have multiple leaflets.ref These leaves only have one true petiole and at the base of this is where the lateral/axillary bud will form. No buds will form in the leaflet stems. See the below diagram.


Variables in the phyllotaxy include the number of leaves per node and whether they spiral around the stem or not. According to an article in Natureref, at the shoot tip itself, the ‘golden angle’ is observed between leaves: 137.5° – in the article the researcher finds that this angle minimises the energetic investment of creating divergent leaf positions (in the creation of vascular tissue to supply the leaves). After the stem elongates, leaves start to spiral according to the Fibonnaci rule, whereby common leaf spiral angles are 1/2, 1/3, 2/5, 3/8 and 5/13. For example a 3/8 would mean the angle between leaves is 3/8 of 360o, or 135o. This means it takes 8 spirals before a leaf is in the same position on the stem (although now vertically separated).


As can be seen above with only one leaf per node the arrangement simply spirals at different angles. With more than one leaf per node a similar principle applies but each pattern spirals (eg. both leaves in a two leaf per node spiral at the same angle). Multiple leaves at the same node is also called a whorl (common in gymnosperms).

So you should be able to predict where buds will develop on your angiosperm trees by simply looking at the leaf arrangement, and if it’s winter and your tree is deciduous, by the branch arrangement. What these buds will turn out to be – short shoots with flowers, vegetative shoots or flowers, is not as easy to understand but some pointers are here: Bud types – reproductive & vegetative.

Tree in Seattle Japanese garden

The kingdom Plantae and where trees fit in

Life on earth is classified into different categories and the process of doing this is the science of taxonomy. There is a lot of interesting history associated with biological taxonomy but my goal with this post is to show where trees fit into the taxonomy of life. Plant taxonomy is governed by the International Code of Nomenclature for algae, fungi and plants. They define the ranking of taxonomy as kingdom, division or phylum, class, order, family, genus, and species.


As of 2015 there are seven kingdoms – Animalia, Plantae, Fungi, Bacteria, Chromista, Protozoa and Archaearef – viruses aren’t considered living so they have their own separate grouping.

Trees fall into the kingdom Plantae, which comprises “all organisms possessing plastids with double envelopes that are free in the cytoplasm”.ref Which must be one of the most brain-exploding definitions of plants you will ever read! What it means is that members of the kingdom Plantae are dependent on chloroplasts, organelles with the green pigment chlorophyll, which can photosynthesise, AND these chloroplasts have specific morphology and location. The reason there is this qualifier is because the kingdom Chlorista, which includes some algae, also has chloroplasts, although they are different to those in Plantae.

Anyway even though ‘tree is only a way of being a plant‘, it’s not as far as we know a way of being a chlorista, so we will focus on Plantae for this post.

(Bear with me on this next bit – to drill down yourself you can refer to this site). Plantae is broken into 8 phylla, one of which is Tracheophytaref (plants which have a vascular system); within Tracheophyta are 8 classes, including:

  1. Cycadopsida includes cycads & palms (not so relevant for bonsai)
  2. Ginkgoopsida includes only one member – the ginkgo
  3. Gnetopsida includes nothing we care about from a bonsai point of view (Gnetum, Welwitschia, and Ephedra)
  4. Liliopsida – also known as the monocots, includes lillies & bamboo (not bonsai relevant unless you’re into bamboo)
  5. Lycopodiopsida – club mosses (not for bonsai)
  6. Magnoliopsida – also called the dicots or angiosperms – includes all the flowering plants, including many trees we use for bonsai
  7. Pinopsida – also known as conifers, again, a favourite of bonsai enthusiasts.
  8. Polypodyopsida – leptosporangiate ferns (maybe an accent plant, but not a bonsai)

Angiosperms evolved a lot later than gymnosperms – their last living ancestor was no earlier than 140–250 million years ago, whereas their joint ancestor with gymnosperms was 310–350 million years ago.ref They evolved to produce flowers which could be pollinated by insectsref, and to have lower reproductive costs overallref, making angiosperms the most successful plant family today. There are 444k angiosperm species entries in the Global Biodiversity Information Facility databaseref, which constitutes 74% of the total species in the database. You can see them all here.

Pinophytes are a bit easier to get your head around as the only surviving order within it is Pinales. Pinales contains all the conifers in six families (along with some extinct families and species which I haven’t listed):

  1. Araucariaceae (including monkey puzzles and the Wollemi pine)
  2. Cupressaceae (including cypress, juniper, redwood)
  3. Pinaceae (including pines, cedar, spruce, hemlock & fir)
  4. Podocarpaceae (mainly southern hemisphere evergreens including Buddhist Pine) and Phyllocladaceae (celery pines)
  5. Sciadopityaceae (Japanese umbrella pine is the only member in this family)
  6. Taxaceae (yews) including Cephalotaxaceae (plum yew)

Here’s a useful chart which was created on genetic analysis of 64 protein-coding genes to determine the position of dawn redwood relative to other conifers (you can see it there in the Cupressaceae family) :


Quite often trees are moved from one classification to another, specially once their DNA has been sequenced and this has been very much the case in angiosperms – an updated classification is created by the Angiosperm Phylogeny Group every few years. Here is a summary of the most recent changes made in 2016.

What is a Tree?

Roland Ennos gives an excellent explanation of the evolution of trees and their differences in his book Trees: A complete guide to their biology and structure and most of the below comes from Chapter 1 of his book. But the simple version comes from Colin Tudge: “‘Tree’ is not a distinct category, like ‘dog’ or ‘horse’. It is just a way of being a plant.”

A botanical definition for ‘tree’ is ‘any plant with a self-supporting, perennial (living for more than one year) woody stem’. The main way that trees become self-supporting is through a process known as secondary growth, where a layer of stem cells around the outside of the stem divides to produce xylem tissue on the inside and phloem tissue on the outside. The xylem transports water but also gives structural strength to the tree, and this annual growth is responsible for trunk thickening.

From a biological taxonomy point of view, the tree form exists in several classes and families within the Tracheophyta phyllum, which is the phyllum within the Plantae kingdom containing all vascular plants (that is, plants with conducting vessels for water and phloem). You can read more about this in: The kingdom Plantae and where trees fit in.

The angiosperms (flowering plants), as the latest evolving and most successful class have some differences from other trees which is relevant to bonsai-ists. These differences include:

  • Angiosperms have specialised water transport vessels in their xylem which allows them to move more water more quickly than non-angiosperms (leaving these species more subject to embolisms and less drought-proof).
  • Their leaves are a lot more variable in terms of size and shape, and are often deciduous (there are a few deciduous species in non-angiosperm families but these are a minority – including Ginkgo, Dawn redwood and Swamp cypress). Deciduousness means that these trees do not need to create frostproof leaves, so they can take different, more productive forms (such as large leaves with high photosynthetic capability).
  • Even so, leaves of evergreeen angiosperms are still more productive than those of their counterparts in other families – possibly because their more efficient water transport allows for more transpiration and so larger leaves with more stomata (hence more photosynthesis).ref
  • Angiosperms produce ‘tension wood’ in response to gravity – if they detect a displaced stem they react by creating wood on the upper side of the stem to pull it back up again. Conifers do the opposite – they produce compression wood on the underside of a stem to change its position.ref

The next question you might want to ask is what is a bonsai?