Mugwort, Artemesia vulgaris.
It's a lovely plant, an old hearth herb. Burns with a white scented smoke, and is nowadays 'contra-indicated'
it used (still is in some countries) to be added to smoking mixtures.
It's the dried fluff used in Japanese incense, and the flower buds are traditionally used to flavour drinks or fatty meat.
It's a clear out insects type smoke, billowing white from dried leaves. It's not so much a spark catcher as a smouldering herb, but if tubed in birch bark and blown through it will flame.
It's a common weed around roadsides here, but I grow a plant in the garden so I have a 'clean' one. It growns over two metres high in the garden. It transplants fine from roots.
Peel the leaf fronds from the stems and dry somewhere shaded and airy. I tie them into little bunches to do this and they last very well indeed.
cheers,
M