my parents have a few and they're planted 6' apart, and are trimmed to about 5' tall almost every year. when my dad skips a year or two they grew to about 8' tall and about 6' wide.

i moved to old town katy recently and on some of the old properties (50+ years) the rhods/azaleas are hugh, as in 10-12' tall and about as wide, almost covers one side of the house. another property had them lining the drive way and they're kept trimmed to about 8' tall.

i planted a few in our front yard about 6' apart but will keep them trimmed to about 6'x6'

Here is a link that might be useful: check out the bottom pic

The size 5x5 is the size when 10 years old normally. In shade they grow taller and in full sun they tend to stay that size more or less. Rhododendrons are healthier if they are allowed some air to breath. So for a very health plant, plant 6 or 7 feet apart. You can plant on a zigzag line so that from the front, they look closer together. Or you can plant in two staggered rows so that they look closer together.

In reality, most people plant 4' apart. I have done this. What happens is that they grow together. You only get flowers on the front and on the top after they grow together. I have a rhododendron bed where about 40 plants were planted in two rows about 4.5 feet apart 40 years ago. I anticipated future growth and planted in groups of 4 of the same variety. It now looks like each group of 4 is a very gigantic plant. It is an interesting effect. The plants have stayed healthy, but shade each other and are somewhat open in their growth.

Thank you for your ideas. Well, I planted them about 5.5' apart. I hope that works.

houstontexas123 - Thanks for the link. Those rhodies are amazingly stunning!