I have a crown of thorns plant and it's overgrown in the pot,can I transplant in the ground?
I am afraid that you are right outside of their habitable zone. A cooler than normal year may damage the plant pretty badly.
They can tolerate pruning, both root and top. Just be sure to do this when the weather is mild, and not at either extreme.
Here is an article that will help with the plant's care through the cooler months: https://www.gardeningknowhow.com/houseplants/crown-of-thorns/crown-of-thorns-houseplant.htm
Here is an article that will help you in the case that they do get a little frostbite: https://www.gardeningknowhow.com/houseplants/crown-of-thorns/frozen-crown-of-thorns-plant.htm
My Crown of Thorns has not blossomed ever, it has been about five years. It is also very thin and spindly. It is indoors and under a window next to the register. I soak it through every couple weeks. I have attached pictures.
They are usually very forgiving but do need a lot of light - 3 to 4 hours of direct sun a day. That is probably why it hasn't bloomed and looks lanky. A south window gives the most light. You may need to add a grow light if you don't have a window with direct light. Being next to a register isn't good for a plant so I would move it for that reason, too.
Make sure it is getting regular fertilizer, too.
https://www.gardeningknowhow.com/houseplants/crown-of-thorns/crown-of-thorns-houseplant.htm
You say to cut a leaf straight across to begin with--is this supposed to be cut a stem?
To take a cutting from crown of thorns, cut through a stem 3 or 4 inches from the outer tip of the stem. Choose a cutting that will have at least three pairs of leaves or buds on it. Remove the pair of leaves nearest the cut end. Leave the cutting in a warm area for two or three days till the end callouses over. Then it is ready to insert in potting mix.
https://www.gardeningknowhow.com/houseplants/crown-of-thorns/propagate-crown-thorns.htm
How do I remove Euphorbia milii plants from my yard?
We have some articles that will help you:
https://www.gardeningknowhow.com/garden-how-to/projects/removing-existing-plants.htm
https://www.gardeningknowhow.com/ornamental/trees/tgen/can-you-dig-up-an-established-plant.htm
It has wintered before in my bathtub (overhead skylight -some sun. Now I see a lot of yellow leaves falling. Is this normal, flowers are intact. Anything more to do? Also cabbage type plants in a pot outside (freeze tonight). Can this cabbage plant (5) winter in the bathtub beside the Crown of Thorns? Advice most appreciated, too late to plant outside.
Your plant may be getting a little too much water. Your tub sounds like a great place to spend the winter, and if you trim it back just a bit and be patient, it may grow happy again in the spring. However, make sure you only water it when it's dry down to about an inch in the soil, and be sure it's draining well.
Here's an article about your plant:
https://www.gardeningknowhow.com/houseplants/crown-of-thorns/crown-of-thorns-houseplant.htm
Your ornamental cabbage should be fine over the winter, as well. It is hardy outside to about 5 degrees F. Click this link for tips on caring for it:
https://www.gardeningknowhow.com/edible/vegetables/cabbage/ornamental-cabbage-care.htm
Hi, my Crown of Thorns Euphorbia Milli Venus is about 3 years old and always has nice flowers on top. However it has grown straight up with an almost 1 metre high trunk, and is very unwieldy in its pot. I am a gardening novice and don't understand what cutting at the "point of origin" means. Can you please explain whether I can simply cut the trunk and repot the flowering end?
You can pretty much cut it where you like. The point of origin just means if you want to cut a branch off, cut it where it meets the stem, rather than halfway leaving a stump.
If you cut off the top to propagate it, be sure to leave it lay till the cut end calluses over. Then it is ready to plant. I included instructions.
https://www.gardeningknowhow.com/houseplants/crown-of-thorns/cutting-back-crown-of-thorns.htm
https://www.gardeningknowhow.com/houseplants/crown-of-thorns/propagate-crown-thorns.htm
My Crown of Thorns house plant seems to be very healthy, except that it only puts out one blossom at a time instead of a nice full bloom. What could be the reason for this?
It may need to be pruned more regularly. Also make sure it is getting 3 to 4 hours of direct sun each day. And, it requires consistent fertilizing all year. In the winter you can cut the plant food to half strength, but in other months, it should be fed every two weeks or so. Here are two articles that should help: https://www.gardeningknowhow.com/houseplants/crown-of-thorns/crown-of-thorns-houseplant.htm
https://www.gardeningknowhow.com/houseplants/crown-of-thorns/cutting-back-crown-of-thorns.htm