Friday, June 9, 2017

Pretty Yellowtops

Senecio pinnatifolius var. pinnatifolius 
(Senecio lautus subsp dissectifolius)

Keep an eye out for these attractive local wildflowers, on roadsides and in paddocks. Short-lived perennials, they make very good garden plants. They grow easily from seed, and are worth it both for their colour, and their potential to attract butterflies.

They are  very frost and drought hardy, needing no watering once established, and flower from early spring to Autumn, with strong flushes in both those seasons. This would be an excellent waterwise species to use in our district as a bedding annual.

There are a number of Australian yellowtop species. This is the common one around Toowoomba. It’s an upright little perennial, about 30cm high and broad, with a slightly woody stem. It can be scraggly in dry paddocks, but in good garden soil has fairly dense mid-green foliage and makes a neat round shape. Most of its wispy leaves are very finely divided, to the point where no part of the leaf is more than about 1mm wide.

Do they Poison the Horses?

Many good native plants are less appreciated than they deserve, because they have an unfair reputation for deadliness to livestock.

Yes, all Senecio species do contain poisons, and eating too much of them will kill stock. However, the CSIRO book which is the best authority on the subject ("Australia's poisonous Plants, Fungi and Cyanobacteria" by Ross McKenzie) states that “no confirmed poisoning cases (by this Senecio species) are recorded in Australia” . There are two reasons. One is that no single plant contains much of the poison, and a bit of a munch does the animals no more harm than we suffer when we eat plants with similar poison levels such as mint, basil, or parsley. The other is that animals don’t like the taste, and won’t eat it if anything more palatable is available.

It is probable that most of the reports of “seneciosis” in Australia are old stories (which would be why they are not "confirmed") from the days when droving was common. Starving mobs would find themselves following routes that had already been used many times in the season. Previous mobs had eaten out everything worth eating. Deaths occurred. In fact, Senecios may or may not have been the actual cause of the problem, but are the ones most likely to be blamed just because they are so bright and conspicuous. The ability to diagnose just which plant was poisoning the stock has come a long way since then.

We see situations similar to those over-used old stock routes nowadays in  horse paddocks just west of Toowoomba, where overgrazing leaves nothing but the unpalatable and poisonous plants. With most of the competition removed, the paddocks can be taken over by wall-to-wall yellowtops. These are an indication of the owner's style of pasture management, not a sign that the yellowtops are poised to take over the world.  Fortunately, those horses are not depending on what grows in the ground for their feed. So long as they are well fed in other ways, the Senecio is not a danger to them because they really don't want to eat it.

In normal healthy local pasture, native yellowtops are dotted about amongst the other pasture plants. The photo above was taken on a local cattle property where livestock have grazed for more than a century and a half, apparently taking no harm from them.

But don’t Grow Madagascar Fireweed.
Senecio madagascariensis

This is a non-Australian plant that has become a major weed in Australia. It is just beginning to creep into our district from the east. It has been in the Lockyer valley for some time, and is now found in the Ravensbourne area.

Madagascar Fireweed is an aggressive coloniser, definitely a threat to stock because of its high level of invasiveness, and its tendency to out-compete native pasture plants. This could happen simply because it seeds more vigorously (up to six generations a year compared with one generation a year for our local Senecio species.)

Unfortunately, alarmist attitudes to all fireweeds can do more harm than good. Some landholders remove all of the local Senecios, just on principle.

Obviously care is needed with plants in yards or wherever alternative feed is not on offer, but otherwise it is probably best to leave the native plant in place. It saves unnecessary work and expense, and a side benefit is that property owners who are familiar with the local species will find it easy to pick the difference between it and the Madagascar fireweed, should an infestation occur. This difference is difficult to describe or show in a photo, but anyone seeing the interloper in the flesh would immediately notice that it is not their familiar plant. I just has a different look about it. A bit more upright. More of the leaves lance-shaped and only a minority deeply dissected (it’s strongly the other way round with the local Senecio pinnatifolius). Bigger seeds in those fluffy seedheads.

A further clue, if you are not sure, can be to count the involucral bracts. These are the long narrow green bits, pointy at one end (with a little brown dot on the point), which together form the involucre.

For me, essential equipment is: a pin (so I don’t lose my place); another pin (to point with); and a good pair of reading glasses. Senecio madagascariensis has 19-21 (usually 20-21) of these bracts. S. pinnatifolius var pinnatifolius usually has 13, though it sometimes has more. If the flowers on your plant have fewer than 19 bracts,  this confirms what you probably already knew from looking at the foliage - that it is the native species.

So. It's important not to grow Madagascar fireweed - but it's also important not to go overboard, exterminating perfectly good native plants on suspicion. Quite apart from being pretty wildflowers, an ornament to our landscape, they are also (like every component of any natural environment), an important part of the web of life. Some insects depend heavily upon them. Birds depend on the insects, and so on. We should never tear wantonly at the fabric of our local web.

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