They are in pots and I live in Austin, Tx. What is the white residue and how can I get rid of it? Some of the plants have dead leaves near the bottom of the plant. I water daily as they wilt?
If the white residue you are seeing looks like cotton, it's most likely mealybugs. I know that the plants I've grown over the years have had them. Neem oil usually kills the pest. always follow package directions.
The article at this link has further information on the plant: https://www.gardeningknowhow.com/ornamental/shrubs/african-bush-daisy/growing-bush-daisies.htm
My husband bought me a bush daisy that attracts butterflies and hummingbirds. Do I need to transplant in a pot and bring in during winter?
Yes, since this is a warm climate plants, it may be best to grow it in a container that can be moved inside over winter. Here is more information on caring for this plant: https://www.gardeningknowhow.com/ornamental/shrubs/african-bush-daisy/growing-bush-daisies.htm
What is the difference between Bush Daisy and Cape Daisy?
This link gives a great tutorial on your very question!
Should my Montauk Daily plant be cut back prior to the bloom in the Fall? I live in the northeast and the plant stems do get quite long.
A good way to prune these plants is to cut them back by half on Dec 1 and June 1.
I am caring for family members yard while they are gone for the summer. Other than pruning off the dead flowers, I think these plants could use cutting back. Much of the lower plant lies flat along the ground...with a large woody stem...then leaves and lots of blooms on the end. But! Will this destroy the plant? I don't want to do that.
Deadheading and cutting back no more than 1/3 of the plant can help it to regenerate. Restorative pruning should be done in Spring, but doing so in Autumn won't hurt. This article will offer more information on the plant: https://www.gardeningknowhow.com/ornamental/shrubs/african-bush-daisy/growing-bush-daisies.htm
Yes, you can cut back the bush daisy. There is still plenty of warm weather ahead so you won't be chancing a freeze damaging the plant. Here is more info about the bush daisy:
https://www.gardeningknowhow.com/ornamental/shrubs/african-bush-daisy/growing-bush-daisies.htm
When do I split montauk daisy mums? When and how do you pinch back these mums?
They should be pinched back when they are young to promote branching. Once they have bloomed, then it is to late to pinch.
They can be cut back by half, and pruned back by pinching in EARLY Summer, or LATE Spring. This can help promote blooms.
They can be divided during dormancy, or during slow growth, and even in early spring, when they are starting to show new growth.
This article will help you to care for these plants: https://www.gardeningknowhow.com/ornamental/flowers/montauk-daisy/growing-montauk-daisies.htm
My plant looks green and healthy but they bloomed only once few years ago.
Is your daisy sited in full sun? It also needs moist, well-draining soil. Each spring feed it with an all purpose fertilizer.
Here is more:
https://www.gardeningknowhow.com/ornamental/shrubs/african-bush-daisy/growing-bush-daisies.htm