Q: I went to a garden presentation and a woman in the audience said that she grows great sweet peas by putting ashes on her garden. Does this really work?

A: In general, we advise caution when using ashes in the garden. Wood ashes do contain some nutrients plants need, but they also contain heavy metals. And wood ashes can change the pH of your garden soil. They are sometimes used as a liming agent, to make soils more alkaline. But you may or may not want your soil to be more alkaline. A lot of the flowers and vegetables people like to grow prefer a more neutral or acid soil. Some plants, such as blueberries, require acid soil.

Before changing your soil’s pH, it’s best to find out what its pH already is. In fact, before you add anything to your soil, we recommend having a soil test.

Some sources do say sweet peas prefer a more alkaline soil. Still, it’s impossible to say whether the ashes are what’s making a difference with this gardener’s sweet peas. To find out for sure, you’d need to do a controlled experiment: growing some sweet pea plants side by side, keeping all of the other conditions the same — same variety, same sun exposure, same fertilizing and watering — but giving some plants ashes. Might be fun to try it and see.

Q: When can I start fertilizing my lawn?

A: Not yet. It’s best to fertilize lawns in summer and fall. Fertilizing in spring can cause stress to the grass and can lead to more disease in lawns. It results in a flush of growth at the tips, at the expense of the development of strong roots.

Fertilizing in very early spring, before the lawn has greened up and started growing, can also harm the environment (and waste money!). The fertilizer won’t get taken up by the plants and will just run off, becoming a water pollutant.

If you apply a weed killer to your lawn in spring, try to find one that does not also contain fertilizer.

Q: How about raking?

A: Make sure the lawn is completely dry before you rake or you run the risk of damaging the grass roots. If it squishes when you walk on it, don’t rake.