Hydranges are easily groen form cuttings, just plant them where they don't get the hot afternoon sun.

Viola is a weed in my garden, it turns up in just about every pot, another one is forget me not.

If you take cuttings plant them in soil in a pot and wait them to take, you have a better chance of them growing.

Herbs are good at filling places also.

Another way to fill the backyard is with large pots, just remember to put saucers under them