Avocado

The avocado is not hardy. Bring the tub indoors as soon as nights are permanently below about 10 °C (in Germany, Austria and Switzerland usually mid to late October) and put it in the brightest possible spot at a south-facing window. Overwinter it cool at about 10 to 15 °C, water only sparingly when the top layer of soil has dried out, and do not feed again until it starts growing in spring.

In gardens in Germany, Austria and Switzerland, the avocado is grown almost exclusively as a container or houseplant, because it does not tolerate frost. Three methods are suitable. Sowing from the stone is the simplest method for a decorative houseplant: take the fresh stone of a ripe avocado, wash it and push three toothpicks into its sides so that about a third of it hangs in a glass of water, broad end down. Change the water every few days. After a few weeks roots and a first shoot form; once the shoot is 15–20 cm long, pot it on into nutrient-rich, well-drained compost. Important: a plant raised this way does not come true, as a rule never fruits indoors and serves purely as a decorative plant. Cuttings (for the more experienced) give a genetic clone of the parent plant. In spring, cut a semi-ripe shoot about 20–30 cm long with several leaf bases, directly below a leaf node. Remove the lower leaves and cut large leaves in half so that the still rootless cutting loses less water. Put it into moist, loose substrate and cover the pot with a clear dome or a plastic bag for high humidity. A bright, warm spot at 20–25 °C is ideal. The rooting rate is low and rarely succeeds for beginners; after 6–8 weeks, new leaves indicate that roots have formed. Grafting is the only method for a true-to-variety, fruiting avocado, and a grafted plant also bears fruit much earlier than one grown from a stone or cutting. First raise a strong seedling as a rootstock. Graft in spring, when the plant is growing actively and the bark separates easily from the wood, with scion and rootstock as close in thickness as possible. Make all cuts cleanly with sterile tools and bind the graft union airtight with grafting tape. Success depends on the cambium layers (the green ring directly under the bark) of both parts meeting exactly, and it depends heavily on practice. Demanding for hobby gardeners, but doable.