Just Ask: Mulch guards roses from invading fungi

Q: I want to grow roses without a lot of pesticides and heard that some type of mulch would keep black spot off the roses. Is this true? What type of mulch?

-- G.R., e-mail

M.B.: Yes, a mulch or frosting of bark, wood chips or steer manure will help prevent but not cure black spot and other fungal diseases on roses. The explanation is that there are spores of these fungi in the soil that are splashed onto the rose plants when it rains. By spreading a 1- to 2-inch mulch on top of the soil in the spring, you can seal in some of these overwintering disease spores. Any type of mulch will help, but organic mulch like bark, steer manure or compost also will improve your soil, keep out weeds and seal in moisture.

Q: I have seen bougainvilleas for sale at the nurseries and know this colorful vine from my California days. Will it survive here?

-- W.P., West Seattle

M.B.: Well sure, bougainvilleas will happily bloom all summer as the glamorous stars hogging all the attention on the patio, but get ready for a major meltdown once the first frost hits. Bougainvilleas are patio tropics perfect for pots and should be enjoyed like annuals, then added to the compost pile in the fall like the fair-weather friends that they are. The one advantage of growing bougainvilleas here is that they won't take over your garden or your life with overly ambitious growth, as they do in California. Like some Hollywood stars, bougainvilleas also can be prickly and create a bit of a mess (falling petals) wherever they live.

Q: I want to grow some plants on my sunny balcony in containers that are 3 feet wide and 3 feet high. I do not want to water a lot. Any suggestions?

-- P.P., e-mail

M.B. For lots of foliage drama without the drinking problems, look for plants that store moisture in their leaves, such as sedums and succulents. Containers that are 3 feet deep also can support lots of flowering plants, especially if you use a potting soil that holds extra water (Miracle-Gro makes a water-saver mix), or add water-saving polymers to your soil. Heat-loving bloomers include ivy geraniums, annual vines like Thungbergia or black-eyed Susan vine, golden hop vine and annuals such as zinnias, African daisy, cleome or spider flower and gloriosa daisy or black-eyed Susan (Rubeckia hirta). With pots as big as yours, you also might consider flowering shrubs such as Tree Mallow (Lavatera 'Barnsley'), hardy hibiscus, hebes and yucca.