Dichotomous key (VII.d) - The world of internodes cont'd (Adornment)

Adornment - thorny parts

A twig at its most basic form, is rather helpless against predators. Fortunately, trees do not leave them unaided. For example, sap can contain a range of chemical defenses (like the toxic orange sap of staghorn sumac) - this is particularly prominent later in spring when the sap gets, as they say in the sugaring world, buddy; I've written about that previously. Many plants, however, have figured out clever solutions by remolding different parts to serve a more spiky purpose; we only have a scant few trees in our area that have these spikes along their stems - though there are a number of delightfully delicious plants that have thorns (e.g. raspberry, blackberry, roses). These sharp projections derive from three different parts of the plant, the stem, leaves, or epidermis. Also good to remember that the terms below are botanical terms and are vernacularly often used interchangeably.

Chickadee flies from buckthorn branch

Spines are projections that form from the stem of the tree, arising from buds. In buckthorn, as shown above, they form at the tips of branches, or rather these spines are the tips of the branch. Hawthorn has very prevalent spines, as do honey locust and osage orange.

Thorns are modified stipules or leaves. The sharp projects on barberry and black locust, for example, are thorns. Above are the paired thorns of black locust, or pointed ears of Marrowzodufia Blugly the Dwarf, as you'll remember from my posting on bud scars.

Multi-flora rose thorn

Blackberry thorn with a scar just above it from where another thorn fell off

Prickles derive from the epidermis and are not vascularized (hence the can be popped off quite easily). Roses, raspberries, and blackberries all have prickles. Tracing the stem of a blackberry, rose, or raspberry, it is easy to find a number of scars dotting the stem from where thorns have fallen (or been ripped) off.

Tendril anchoring a grape vine to another twig. 

Showing adhesive pads on the ends of Virginia creeper

Adornment - clasping parts

Since vines put very little investment into their stem for structural support, and therefore need some mechanism by which they can cling to other objects as they wend their way up to the top of the canopy. Grape vines and Virginia creeper (both in the grape family, Vitaceae), have tendrils, which are highly specialized anatomical features for vining, originating from the stem. Virginia creeper, which is in the grape family Vitaceae, even has adhesive pads at the tips of the tendrils. 

Zoomed in view of a sharp and grippy bud of a bittersweet vine

Bittersweet climbing a sugar maple sapling

Tumurous growth of a sugar maple in response to a bittersweet vine

Other vines, like hardy kiwis and oriental bittersweet, accomplish this task with pointy buds that anchor the vine as it spirals and wraps around a substrate, often strangling and killing its unwilling host over several years. The constricting force around the stem of the tree being strangled cuts of circulation in new conductive tissue, effectively cutting off the host's supply chain. We also have a number of perennial herbaceous vines that encircle the substrate as they climb up it (e.g. deadly nightshade, morning glory, bindweeds, hops).

Poison ivy vine attached to white pine trunk. Image is from August 2012

Poison ivy vines have thousands of root hairs that anchor the stem to a surface. No other vine in our woods have this. This paper provides a good synthesis of different strategies of vining plants and unanswered questions concerning vines.

Jewelweed & Poison Ivy

What: I got poison ivy (Toxicodendron radicans), at least I think I did, this year for the first time ever. I know I've been exposed to it numerous times before so I was disappointed that I might have finally reacted. This year I thought I'd try what Eric Garza (http://path2resilience.com/) had mentioned to me a few years ago: nibbling a bit of the leaves to build up immunity. I started small, with a bit no bigger than my pinky nail. I waited a couple of days without reaction and nothing happened so I ate another one of the small leaves. That was two days ago and I'm still here. I'll try one more small leaf this year and see if I react to the plant again.

An old timey journal says that anything alkaline (or basic) will temporarily alleviate symptoms but does not grant long-term immunity to poison ivy (Dr WF Dieffenbach's "Treatment of Ivy Poisoning" in Southern California Practitioner v.29). The author describes his experience developing a strong adverse response to poison ivy, finding out about auto-lacto therapy (drinking milk of an animal that had grazed on the toxin), and testing the treatment with success. He fed a cow grass and poison ivy then consumed a pint a day for two days. That year he developed no further rashes. In following years he developed a rash again, indicating that immunity is not permanent and follow-up treatments are required. Admittedly the article is quaint in its anecdotalness (it was published in 1917), but warrants a closer look at treatments for ivy poisoning. **It is appropriate to note here that the plural of anecdote is not data. Also pertinent is that I'm not an apothecary, healer, or medical professional and I only recommend doing this after doing your own research/asking the plant itself.

Ecological notes: Centennial Woods is filled with poison ivy, as are most places that are wet, but well drained, and rich, but not excessively so. As is convenient with mugwort growing near poison oak out west (mugwort can be used as a poultice to treat the itchiness caused by urushiol in poison oak), here in New England jewelweed (Impatiens capensis and I. pallida) almost always grows near poison ivy (but the reverse is not true as poison ivy is much less common).

Where: The photos are from Centennial Woods. Below are a couple of look-alikes, at least in the early stages. On the left is sarsaparilla, which has 3-5 leaflets, doesn't have a woody stem, and splits into three branchlets. On the right Virginia creeper (Parthenocissus quinquefolia), which has suction like discs on the ends of their tendrils and five, not three leaflets.

Warning: While I've seen catbirds eat poison ivy berries with gusty, people should never eat older leaves or berries and definitely don't burn poison ivy. If you do try eating young leaves or milk from goats be extremely cautious. Only try exceedingly small amounts at first. And most importantly, do your own research. I'm quoting stuff that I found that proves what I want to believe, I'm sure there's a thousand other anecdotal sources out there that contradict what I've written.

Other notes: Poison ivy is in the same genus as other toxic plants like Poison sumac (T. vernix), poison oak (T. diversiloba out west and T. pubescens out east). The genus is in the Cashew family, Anacardiaceae, which also includes staghorn sumac (delicious) and, not surprisingly, cashews. Members of Toxicodendron are occasionally placed in Rhus, the same genus as staghorn sumac.