How much rain before calling in the backups (sprinkler)?

Washington Post Gardening columnist Adrian Higgins answered questions recently in an online chat. Here is an edited excerpt.

Q: I bought a nifty water gauge so I could know how much it has rained, but how much is enough? I have a mixture of grassy areas, ornamental bushes and evergreen hedges. How much must it have rained in a week before I drag out the sprinkler?

A: In general, an inch a week is ideal. The difficulty with your question is that different plants have different needs, and younger plants need watering more often than older ones. Lawns need more water than shrubs and trees, which is why automatic irrigation systems pose so many problems.

Q: I have an asparagus plant that's overtaking the bed I put it in. Any suggestions as to when and how to move it?

A: They're coming out of dormancy now, so I'm not sure I would move them at this time. I'd probably wait until the fall and count on a big harvest this spring.

Q: I have seen a lot of lovely redbuds out now. Do they do best in shade, partial shade or sun?

A: They are happiest with some light shade. They will do OK in full sun but should be mulched (correctly) and watered when it turns dry.

Q: My house is on a small hillside. All the soil on one side has disappeared, and the steps are precarious. What can I plant (with late-morning light) to help ground replaced dirt?

A: The order of repair is to bring in more soil, grade it and then stabilize it with some fabric. Then you can plant through the fabric until the new plants develop a network of roots to bind the soil. You have lots of options for shade-loving ground covers. Stay away from ivy and pachysandra.

Q: I'm renting a house for about a year and would like to grow vegetables, but space is limited. I had a large garden at my old house. (I miss it!) I'm thinking about doing container gardens on my deck. What vegetables do you think would do well in a large container? I worry that even if the container is 12 to 18 inches tall, the roots won't have room.

A: You might try some determinate varieties of tomato, but mostly I would do greens. Swiss chard might take the heat of summer better than others.