How do I care for rhubarb after it is cut and can't be used for 2/3 days?
Rhubarb, if not used immediately, can be stored by refrigeration, canning, freezing or drying.
I have had a Rhubarb plant for three years. However, last fall I planted Garlic seeds close by. This spring the Rhubarb just hasn't appeared at all. Is this a coincidence?
I don't believe the garlic played any role in the loss of your Rhubarb.
Did the plant go to seed? This can rob the rhubarb of nutrients.
Here is a link about Rhubarb.
https://www.gardeningknowhow.com/edible/vegetables/rhubarb/grow-rhubarb.htm
We have some very old rhubarb plants that have produced great batches of rhubarb right up until last year, when the stalks have become very short (3-4 inches!) and the leaves seem to have holes in them after I mulched the plants with old straw. I've read that the plants should be 3-4 feet apart, but over the years they've grown closer together. Do they need to be divided, transplanted elsewhere and should the plants have 3-4 feet to grow?
Overcrowding will significantly reduce yields and even lead to other issues, such as fungal problems from lack of air circulation. Therefore, digging them up and dividing the plants will greatly help, keeping them spaced apart at least 3 feet between one another. This article will help you with dividing:
https://www.gardeningknowhow.com/garden-how-to/propagation/propgen/dividing-plants.htm
I have several rhubarb plants in my garden. Some are 3 yrs old, others 2 yrs old. The older ones are producing very large stalks and leaves, and the stalks are not turning red. The younger are smaller and have red stalks. Is there a variety that only produces green stalks, and are these safe to eat? Thanks.
It depends on the variety. Some varieties should be red when harvested, while others should be harvested when green because the stalks never turn red. If you have a red variety, wait until the stalks are red to harvest. Here is an article that you may find helpful: https://www.gardeningknowhow.com/edible/vegetables/rhubarb/harvesting-rhubarb.htm
Does copper compound come in liquid form or in granules? I have a problem with my rhubarb and that's what they need.
You should be able to find both liquid and or granular forms of copper compounds.
Your local garden centers or garden sections of a home improvement center will carry these products.
https://www.gardeningknowhow.com/edible/vegetables/rhubarb/brown-splotches-on-rhubarb.htm
http://dnr.wi.gov/lakes/plants/factsheets/CopperFactsheet.pdf
This is my second year for one of my rhubarb plants. When spring came, the plant grew nicely and then it flowered. The stalks never turned red so I clipped the plant and thought that maybe the second time the stalks would be the red color but they're not. Can you cut the green stalks and use them the same way I'm using the red ones? I make rhubarb pies and a butter crisp dessert. Thanks.
It depends on the variety. Some varieties should be red when harvested, while others should be harvested when green because the stalks never turn red. If you have a red variety, wait until the stalks are red to harvest. After harvesting, you can trim the plants back or leave them alone until after winter. Here is an article that you may find helpful: https://www.gardeningknowhow.com/edible/vegetables/rhubarb/harvesting-rhubarb.htm
My first year with a rhubarb plant. Looks good with huge leaves but says not to cut anything. The color isn't red, though. It's green. Will it turn red next year? Planted in May.
Not all rhubarb stalks turn red. There are many cultivars of rhubarb - the color depends on both the cultivar and how it was grown (rhubarb favors cool temperatures and abundant sunlight). Here are some links with more information:
https://www.organicgardener.com.au/blogs/why-my-rhubarb-green
http://www.washingtonpost.com/wp-dyn/content/article/2008/03/05/AR2008030501136.html