PTYXIS, (Botany) noun, pronunciation: Tik'-sis. – the way an individual leaf is folded within a bud, how an immature leaf is creased and bent upon itself within a bud.
I have always loved spring as plants unfurl new leaves. It's happening now in my garden, in the Demonstration gardens and in every place that has plants growing, whether they are wanted greenery or weeds. I have enjoyed the different shapes and colors of the new leafage but I didn't know there was a term to define the intricate folding of new leaves before they appear and expand. As with all Botany subjects, diving deeply into any horticultural term reveals a complex, evolutionary study designed to categorize the myriad growing habits and leaf forms of millions of plants.
Generally, Ptyxis has two major categories:
Leaves that are bent or folded in the bud:
1. Reclinate Ptyxis: Example: Loquat, Rhododendron. New leaf tips are folded toward the leaf base.
2. Plicate Ptyxis: Example: Palms, deciduous trees like maples. The nascent leaves are folded like a fan on vein lines
3. Conduplicate Ptyxis: Example: Magnolia. The leaf is folded in half length-wise like a V.
4. Crumpled Ptyxis: Example: Cabbage. New leaves are covered by older leaves, wrinkling the new leaves more and more in the cramped space.
Leaves that are rolled up and emerge by unfurling:
5. Circinate Ptyxis: Example: Ferns. New fern fronds are tightly wound spirals in the center of the fern. Each slowly rolls upward from the bottom to the top. This new growth is also called a fiddlehead. This careful unrolling allows the base of the frond to strengthen as the “basal lump” is exposed to light and begins photosynthesis. By rolling from the bottom up the tender tip of the frond is protected from weather and hungry animal eaters.
6. Involute Ptyxis: Example: Lotus, Sago Palm. A new leaf on a lotus is held as two tight wound tubes rolled toward the mid-vein. As the leaf emerges (vernation) the tubes remain wound up until the full diameter is reached and then they slowly unfurl.
7. Convolute Ptyxis: Example: Hosta, Canna Lilies. New leaves are held in a roll like paper towels. When the plant emerges in the spring it looks like a cone. As it gets taller the first leaf begins to unroll, then a little taller, then the second leaf, etc. If the deer or snails eat the tip of the new cone, each and every leaf that unfurls will have a bite out of it.
8. Revolute Ptyxis: Example: Oaks, Ilex, Primrose. The leaf margins curl toward the backside of the leaf. In newly emerged leaves it is easiest to see. In new primrose leaves the revolute shape is prominent, looking like tubes until fully unfurled.
I just wandered my yard for a bit. The Japanese maples are beginning to flush out, each unfolding like they have been stored carefully in a Space Bag. No ironing needed as they flatten themselves out as they grow. The boxwood is showing new growth that is V-shaped – conduplicate. I'll cut an iceberg lettuce head in quarters for dinner to see the crumpled ptyxis. I have many ferns beginning to unfurl new fiddleheads – circinate ptyxis. I found some newly emerged leaves on my primroses and they certainly are revolute. My hosta are just showing a tiny bit of their cone shaped emergence. Better protect them from the snails. The sago palms are not ready to start their new growth. It's too cold but I am very familiar with the involute leaves that emerge like rolled tubes and then stretch to great lengths with their pokey veined leaflets. It is interesting that once mature the leaf shape is called revoluted as the leaflets curve down from the midrib. The only plant type I don't own is one with reclinate ptyxis. Guess I have to go to the nursery!
Author - Master Gardener