I have been away for weeks and when I got home, the weather had turned very cold. My leeks are now frozen in the ground. Are they a complete loss?
They may not be yet, but if you do not get them out of the ground soon, they will be. Harvest them as soon as you can.
When planting onions and leeks, do each of the stalks have to be planted individually? They each came with about 20 stalks and in one bundle with all of the roots grown together.
These articles will help: https://www.gardeningknowhow.com/edible/vegetables/onion/find-how-to-grow-onions-in-your-garden.htm
I would like to know how to prevent rust from the leaves of leeks; and if there are signs of rust, is there a cure?
Should I remove the seeds from leek plants? And when do you harvest chard?
These articles will help: https://www.gardeningknowhow.com/edible/vegetables/leeks/how-to-grow-leeks-and-tips-for-harvesting-leeks.htm
What part of the leek is edible/usable?
Here is an article that you may find helpful: https://www.gardeningknowhow.com/edible/vegetables/leeks/how-to-grow-leeks-and-tips-for-harvesting-leeks.htm
All of it. I chop it up like green onion and fry with other vegetables.
My leeks have started to bolt. Why, and what do I do? I'm growing vegetables for the first time.
This article should help: https://www.gardeningknowhow.com/edible/vegetables/leeks/leeks-bolting.htm
Can leeks be harvested and frozen?
They can be frozen, but they will not be as pretty when they are thawed. If you plan on cooking with them, this is not a problem, as the heat of the cooking process would leave them looking like this anyway.