Chemical gardens are inorganic, plant-like
structures that self-organize in certain
precipitation reactions. They typically form
within minutes when metal salts (here MnCl2) are placed into aqueous solutions containing anions such as silicate. The main building blocks of chemical gardens are hollow macrotubes with an outer layer of silica and an inner layer of metal hydroxide. Earlier studies identified three tube morphologies that occur depending on the density difference between the inner and outer solution. Here we report a fourth type of growth regime that produces tubes with (i) small outer diameter (50-100 µm), (ii) thin walls (about 7 µm), (iii) smooth wall texture, and (iv) very fast growth speeds. The latter reach values of up to 1 cm/s, which is about 100 times faster than for conventional structures. Furthermore, the growth of these novel structures often occurs around the tubes' mid-section, whereas conventional chemical gardens always grow at the tube tip (i.e. distant from the seed crystal). All velocity data are obtained from the three dimensional measurements that typically rely on high-speed cameras.