Ask the gardening expert

I have 5-year-old lilacs that have never flowered. They get about six hours of sunlight a day — longer when the leaves are not on the trees. I added lime in the spring and again last fall. Last spring, I did light pruning for shape, then added cow manure and super-phosphate. Do I need to do anything more this spring? Any suggestions?

Lilacs do best in full sun all day long. Too much shade can definitely reduce flowering.

The two most common reason for not flowering are pruning at the wrong time, and the fact that new plants are slow to bloom. Lilacs bloom on wood grown the year before, so any pruning for size or shape should be done in late spring right after the normal blooming season. Pruning in late summer or fall or early spring will remove flowering wood and flower buds.

Finally, lilacs are tolerant of a wide range of pH and soil fertility. Before adding additional lime or fertilizer you should probably run some basic soil tests to check the pH. Lime is extremely long-acting and usually does not need to be added annually. Your local Master Gardeners would be happy to help you with the tests and interpreting the results.

I planted horseradish roots last spring. They over-wintered in the garden. Will I be able to harvest this spring and get a good crop?

Horseradish is usually harvested a little at a time, especially in the fall when it is said to improve in flavor. To harvest, simply remove a portion of a side root, leaving the rest in the ground to continue growing. Alternatively, if you have planted a number of roots, dig them individually over a longer period of time. You will be amazed at the size of the root of an established plant.

Celeste Lindsay is a WSU Master Gardener. Send questions to lindsay8@pacifier.com.