Can I use this sign to say a plant or a business is growing?
No, this specific sign is used for people or animals growing taller and maturing. For plants, you would use the sign for "spring up" or "sprout." For a business or economy, you would use a sign indicating expansion, increase, or improvement.
Does it matter exactly how high I raise my hand?
For the general concept of "growing up," raising your hand from your chest to your shoulder or head height is standard. However, you can adjust the starting and ending heights to visually show exactly how tall someone grew during a specific story.
Should I use my right or left hand?
You should use your dominant hand for this sign. If you are right-handed, use your right hand; if you are left-handed, use your left. Keep your non-dominant hand relaxed at your side, as this is a one-handed sign.