I recently planted three Genoa fig trees, which are only about 30 cm high. I've found that they are developing brown spots on the leaves, which spread and eventually the leaf curls up and falls off. Can you please tell me what this is and how I cure it?
It sounds like fig rust. This article will help:
https://www.gardeningknowhow.com/edible/fruits/figs/figs-disease-rust.htm
Does this have an influence on the pollination of the fruit?
Some (not many) varieties of fig do need 2 trees so that cross pollination can happen in order to get fruit. Most figs though are fine as a solo plant. Smyrna varieties need male and females, but this is not a variety commonly found in homes.
How do I start a fig tree if I do not buy it at a nursery? Can I use a pit? How would one grow shallots? Can I grow then in a small garden or a pot of some sort?
It is not recommended to start a fig tree from seed. Purchasing them at your local gardening center or propagating them is the better choice. Fig trees root easily and are easy to propagate through cuttings. These articles should help: https://www.gardeningknowhow.com/edible/fruits/figs/how-to-grow-figs.htm
https://www.gardeningknowhow.com/edible/vegetables/shallot/tips-for-growing-shallots.htm
I have two fig trees that were bought last year. They were 3 and 5 feet tall, with good leaves/fruit. In fall the trees were transplanted into bigger pots and stored in my garage (live in Toronto). I did water them once a month during the winter season and put them out last month in April. I did use fruit fertilizer sticks on both plants, but see that they show leaf buds but have not opened for days. The tree looks totally bare, the stems look brown, and the soil is watered with a wet look. My question is whether there is too little water or too much. Do I try to prune it? Please give me some idea as to what is wrong.
It's hard to tell, as over watering usually results in yellow leaves. Without any foliage, it's more difficult to diagnose. Under watering usually results in dry, brown leaves. It could just be slow to start. Give it a couple more weeks. As long as the stems are alive, it should regrow.
Here are some articles that you may find helpful: https://www.gardeningknowhow.com/edible/fruits/figs/how-to-grow-figs.htm
https://www.gardeningknowhow.com/edible/fruits/figs/pruning-fig-trees.htm
How big a pot needed for growing fig?
It is hard to say how big a pot you will need as it depends on how big the fig you have is. If it is a baby, say under 3 feet tall, you will only need a 12-18 inch container. If it is larger than this, you will want a container that is at least 2 inches larger than the rootball is wide.
Regular potting soil will be fine for figs in containers.
Last summer, in late July, I purchased a small 4' to 5' fig tree. I planted and watered regularly. The tree looked healthy. Now this spring there is absolutely no sign of growth and the tree trunk and branches appear to have orange, yellowish spots up and down the trunk. The base of the trunk also appears to have an outer layer of bark coming off. Will any treatment help it at this point? We live in western Washington state, but the nursery where we bought it said this fig tree thrived in the area.
It sounds like the plant may have had fig rust. This articles will help:
https://www.gardeningknowhow.com/plant-problems/environmental/how-to-tell-if-a-plant-is-dead-and-how-to-recover-an-almost-dead-plant.htm
After I unwrapped my fig trees from the winter, they were gone! Nothing left. I live in NY state and they were well wrapped.
It was a very cold winter this year, and they may have died. But figs can grow back from the roots if the roots survived. Check the roots to see if they are still healthy. If they are, give the tree some time to sprout. You may find this article helpful: https://www.gardeningknowhow.com/plant-problems/environmental/how-to-tell-if-a-plant-is-dead-and-how-to-recover-an-almost-dead-plant.htm