Answer: English ivy, Hedera helix, is usually planted at regular intervals over the area you want covered. About 18 inches apart measuring from the middle of each plant to the next is typical. The plants are small starts and are often sold in peat pots and are relatively inexpensive.
You would need to kill the grass out (possibly wiht an herbicide containing glyphosate applied very carefully in accordance with the label instructions), amend the soil for planting and then plant the ivy. You would then need to mulch around it and keep it watered until it takes hold and becomes established.
On a steep hill, you may want to stagger your planting over a period of years to avoid causing erosion. You would plant in bands running horizontally, starting with a strip across the uphill side, working your way down the hill in increments. This, plus using a larger and heavier form of mulch such as bark nuggets, will help avoid causing a major erosion problem while you are waiting for the ivy to fill in. Once the ivy covers the ground, it is relatively drought tolerant and will hold the soil quite well.
Prior to planting you might want to run some basic soil tests and then base your soil amendments on the results of the tests. Your county extension (228-6881) should be able to help you with the tests and interpreting the results.
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