Now that my plant is budding, how long do I keep it in the basement? Also, I have a humidity tray beneath the plant, but have discontinued watering. Should I resume watering?
If it is budding, you can bring it up into the light and resume normal care.
I have some of a 'christmas' cactus that is at least 50 yrs old that always used to flower at 'easter' in vivid pink coloured blooms - like fuschias. However for several years now the flowers have come after xmas usually in jan or feb. It is quite neglected but this years flowers have come through in a 'yellow' colour with a vivid pink stamen!
Light and temperature can sometimes cause a Christmas cactus to change color, though normally that is from a less dominate color, like white, to a more dominate color, like pink. It can also happen if you get a genetic mutation, also known as a sport but that would occur on only a single stem.
It sounds like yours, since it was blooming one color and is now blooming another, something has changed with the light and temperature and this is causing the flowers to change as well.
I understand February is the best time to repot Christmas cactus. I have two old and two new plants that I would like to combine in one pot. Do I use all new soil or the existing plus some new? Will they all four grow happily together?
As long as the pot is big enough, they will be fine together. You can use both the existing soil and new soil.
I had the chance to cross a yellow Christmas cactus with a lavender one, and it made seeds. I would love to know what is the best way to sprout the seeds? I have been growing plants for many years. But I really want to have success in germinating these seeds, with the hopes of a new color of Christmas cactus.
Near the end of this article, there are directions for growing the seeds:
https://aggie-horticulture.tamu.edu/plantanswers/publications/cactus/growingcactus/index.html
I have three Christmas Cactus plants that always bloom at Christmas time. Why are two of my plants blooming now?
They bloom more on a schedule based on dormancy, water and light than time of year. It sounds like they were possibly inadvertently put into a dormant state (this can happen if the plant is left unwatered for a period of time) and received the required amount of dark hours at that same time. When normal care resumed, the Christmas cactus went into blooming stage.
I overwatered my Christmas cactus. I took it out of the dirt and some of the pieces were real rotted. I cut off the rotted part and I am now going to let them sit out for a few days. Do you think I can save my plant?
It has root rot. It is hard to say how well it will recover. This article will help:
https://www.gardeningknowhow.com/plant-problems/disease/treating-root-rot-gardening-tips-for-housplants.htm
I would get some starts from the plant, just in case it does not make it. This article will help with that:
https://www.gardeningknowhow.com/ornamental/cacti-succulents/christmas-cactus/how-to-propagate-and-plant-christmas-cactus.htm
I came across one sight that said you could plant cacti and succulents together. I wondered whether a Christmas cactus and snake plant could be planted together, or is it too much of a stretch putting them both in the same container? Also, I was given what I believe is called an elephant plant that was going to be thrown out. The person who gave it to me didn't know its name. I researched pictures on the Internet; the leaves are huge on this plant. I was able to bring it back to life. It has layers of vines circling around the base of the plant. This is the best way for me to describe it. Does this plant have to be repotted, or is it best to leave it in the same pot? I have never owned a plant like this before, especially such a huge one, so I am new in how to care for it.
Christmas cactus and snake plants have similar water and light needs, so they will be fine planted together.
I believe the plant you have is a Elephant Ear Philodendron or Selloum Philodendron. You can repot it if you like, though they are pretty forgiving of a crowed pot. Do not trim those viney things at the base, they are aerial roots. I would recommend providing something for these roots to cling to, like a pole of some kind.