Category Archives: Leaves

This category is for listing plants for which the leaves are the useful part. Some plants have many useful parts; So this may be combined with other categories where the plants have multiple useful parts.

Structure and Parts of a Leaf

No seriously! It’s more complex than you might imagine, and having a common language really helps when talking about the parts of a leaf.

For the avoidance of doubt, leaf refers to both the flat type that you imagine, and the needles and scales found on some evergreens. This is not a complete reference, just the parts that I find most useful.

You’d better get comfortable, this is a long post…

Simple Parts of a Leaf

Parts of a leaf diagram

This is a simplified, generalisation. There are, of course, exceptions and variations. The leaf Blade, attaches to the stem of the plant with it’s Petiole. Quite often you will find a Stipule at the base of the petiole, which is like a miniature leaf arrangement. Within the leaf, there will be at least one strengthening midrib, and veins running from it. The leaf receives water and returns sugars through these.

Identification Categories

When it comes to identifying plants by their leaves, there are a number of areas to consider:

  1. The arrangement of the leaves on the stem.
  2. Simple vs Compound Leaves.
  3. Characteristics of the petiole.
  4. Veins.

1. Arrangement

The arrangement of the leaves on the stem can provide vital clues to the identification of a plant. Indeed, for some plants, it’s even in the name. For example, Opposite-leaved, Golden Saxifrage.

These are the main arrangements you may encounter:

  • Opposite – Two leaves from the same point at each point or node on the stem, growing in opposite directions.
  • Alternate – One leaf attached at each point or node on the stem, each successive leaf growing in opposite directions.
  • Basal – Arising from the base of the stem.
  • Cauline – Arising from the Aerial stem.
  • Whorled or Verticillate – Three or more leaves from the same point or node.
  • Rosulate – The leaves form a rosette.
  • Distichous – Leaves are attached in two rows. They can be either opposite or alternate in arrangement.

As a stem grows, leaves tend to grow in the optimum position for collecting light. This can result in leaves forming a helical pattern around the stem.

2. Simple vs Compound Leaves

So, a leaf is a leaf, right? Well, not exactly. There are simple leaves, and leaves which are made up of leaflets. In deciduous trees, for example, the part which detaches itself from the tree in Autumn (Fall) is a leaf. So in Oak trees, that’s a simple Oak leaf, whereas in Ash trees, it’s a compound leaf with multiple leaflets (see images below).

A simple leaf may be deeply lobed, but as long as gaps do not reach the midrib, it is still a simple leaf. Each leaflet of a compound leaf may have it’s own Petiolule (equivalent of a Petiole) and Stipule (Stipel).

Types of Compound Leaf

  • Palmately Compound – Leaflets radiate from the end of the Petiole, like the fingers of a hand e.g. Horse Chestnut
  • Pinnately Compound – Leaflets are arranged along the main or mid-vein.
    • Odd Pinnate – With a terminal leaflet e.g. Ash.
    • Even Pinnate – Without a terminal leaflet e.g. Mahogany.
  • Bipinnately Compound – The leaves are twice divided. The leaf has a main vein, and further secondary veins on which the leaflets are attached e.g. Silk Tree.
  • Trifoliate – A pinnate leaf with just three leaflets e.g. Clover.

3. Characteristics of the Petiole

Leaves with a stalk (petiole) are said to be petiolate. Those without a stalk, which join straight to the branch are said to be sessile.

Where the blade of a leaf partially surrounds the stem, it is said to be clasping or decurrent. Where the blade completely surrounds the stem they are called perfoliate.

The stipule, where present, is a leaf-like appendage on each side at the base of the petiole. Stipules may remain (such as on roses) or be shed as the leaf expands, leaving scars; Known as stipulations.

4. Veins

Veins, occasionally referred to as nerves, extend into the leaf via the petiole and transport nutrients and water between the leaf and the stem. They also play a mechanical role in supporting the leaf structure. Branching from the main vein are secondary veins, and there can be many more branchings, sometimes leading to a net-like structure.

Leaf Shape Terminology


Image Name Description
 Auriculate  Having ear-shaped appendages near the petiole e.g. Arum Maculatum
 Cordate  Heart-shaped, with the petiole or stem attached to the notch.
 Deltoid  Shaped like Greek letter Delta, triangular, stem attaches to side.
 Digitate  With finger-like lobes, similar to palmate.
 Elliptic  Oval, with a short or no point.
 Hastate  Spear-shaped: Pointed, with barbs, shaped like a spear point, with flaring pointed lobes at the base.
 Lanceolate  Long, wider in the middle, shaped like a lance tip.
 Linear  Long and very narrow like a blade of grass.
 Lobed  Being divided by clefts, may be pinnately lobed or palmately lobed.
 Obcordate  Heart-shaped, stem attaches at the tapering end.
 Oblique  Asymmetrical leaf base, with one side lower than the other.
 Oblong  Having an elongated form with slightly parallel sides, roughly rectangular.
 Obovate  Teardrop-shaped, stem attaches to the tapering end; reversed ovate.
 Ovate  Oval, egg-shaped, with a tapering point and the widest portion near the petiole.
 Palmate  Palm-shaped, i.e. with lobes or leaflets stemming from the leaf base.
 Perfiolate  With the leaf blade surrounding the stem such that the stem appears to pass through the leaf.

Leaf Edge Terminology


 Entire  Even; with a smooth margin; without toothing.
 Ciliate  Fringed with hairs.
 Crenate  Wavy-toothed; dentate with rounded teeth.
 Lobate  Indented, with the indentations not reaching the center.
 Serrate  Saw-toothed; with asymmetrical teeth pointing forward.
 Doubly-Serrate  Each tooth bearing smaller teeth.


Source: Wikipedia, Paul Kirtley at

Getting confident with the Apiaceae family, Hemlock – Conium maculatum

The Apiaceae family, formerly Umbellifers, also known as the carrot family, is the one that scares me the most. The simple reason is that whilst there are many edible species in the family, there are also a few deadly ones; And the worst part is that they look very similar. Hemlock, deadly, not only looks very similar to Cow Parsley, for example, but also grows right in the same spot! I mean, really!

Can you identify which Apiaceaes are in this picture?

Anyway, since my last outing, I’m feeling a lot more confident. The main reason is that whilst I’m still not 100% sure about positively identifying the edibles, I’m now 100% confident to identify Hemlock itself.

Hemlock Identification

How did I get there? Following the advice of my peers, and using multiple points of reference. As you can see from the picture above, looking at the leaves can narrow it down to maybe 5 of the Apiaceaes, but that’s not enough.

Warning – Please, please, please don’t take this as a definitive source. You really must be 100% sure for yourself, or you’re playing Russian roulette with herbs.


The first clue that clinched it for me, was the purple spotting. Hemlock sometimes has purple spotting on the stems, like the photo below. Cow Parsley can also have purple on the stems, but with Cow Parsley the purple is like a wash of colour. On Hemlock it’s like someone flicked a purple ink-pen at it.


The second clue, was the cross-section and shape of the stems. Hemlock has a circular, hairless stem, which is hollow. Cow Parsley has a ridged stem (similar to celery), minute hairs, and has much thicker walls to the hollow stem.

The leaf stems are a little different. Hemlock leaf stems are also circular and hollow, whereas Cow Parsley leaf stems are solid and a ‘V’ shape; Or, I prefer to think of it as 3 sided, where one of those sides has a groove in it to channel rain water.


The final thing that clinched it for me, was the smell. Cow Parsley smells like, well, Parsley. It’s generally considered that Hemlock has a really unappealing smell. When I first smelt it, I thought it was actually quite nice – If I smelt that as a men’s cologne, I’d be quite happy with it, but hold on; Would I want to put it in my mouth smelling like that? Oh god, no! That would be awful. There we go then.

Retrospective learnings

Of course, now that I have a 100% positive identification, I can look back at the plant and think about what else I notice. For example, compared to Cow Parsley, it’s quite a dark glossy green (NOTE: Plants’ colour can vary regionally as well as with age). The leaves’ “toothing” continues right to the end, whereas in Cow Parsley, the notches become less prominent toward the end. Also, I think that where the veins in the leaves cause an indentation and fold on the top of the leaf, it seems to be more pronounced in Hemlock.

It’s all about familiarity and confidence. I’ll be taking the time to smell and look at Hemlock every time I come across it, so recognising it becomes second nature. If you’re into foraging, I recommend you do the same, and never forget “If in doubt, leave it out”.

Scary Warning

And scary with good reason. I didn’t pick Cow Parsley as a comparison by random. They grow together and look similar. If you were in any doubt about just how poisonous Hemlock could be, lets start with the fact that there’s no cure for Hemlock poisoning. The poison causes muscle weakness, then paralysis from your toes upwards. Eventually, paralysis of the lungs and/or heart causes death.

Scared? You should be. I’m not scared now that I’m confident that I could easily identify Hemlock, but I will remain wary forever. I hope that you will too, and stay safe.