Question
We have a steep hill that goes down to a paved driveway and to the lake.  Right now on the steep hill  are railroad ties along with steps. Also have plants.  We are looking to take all of this out and doing something else like boulders with plants or rocks.  Would there be a problem with taking all of this out railroad ties and all and planting grass.  Maybe some shrubs and having a fence at top to keep from children and etc falling.  Also want to hear about whether problem with erosion and grass if we plant. thanks

Answer
Afer re-reading this question a few times, I am a bit unclear - You want to remove a railroad tie retaining walls & steps with plantings and replace with boulders and grass?

How would you mow it?  Generally, you do not want to mow on a slope greater than 8% (12:1), due to the increased risk of fall or injury.  Better to stay at or below 5% slope (20:1) with grasses, especially if you have a ride-on mower.

If you are thinking of a rail to keep people from falling over it, I would *NOT* plant grass on this slope.

There are other bank/erosion control type plants that are easier to maintain (types & species depend on your region), such as Juniper, certain Sedges & clumping grasses, trailing Ivy, Gazania/African Daisies, roses, even Day Lilies.  One to avoid would be Ice Plant or difficult plants to maintain like blackberries or willows.

The boulders are a nice idea.  How would you get the larger ones on the hillside?  I have placed them on hills with a crane or during inital construction, but it is not an easy task on an existing slope.

If you want to change the look, check out this website for slope-planting guidance:

http://www.laspilitas.com/garden/howto/slope.html
http://www.humeseeds.com/hilside.htm

~M