Gardening by Judith Adam More and better roses The most practical way to keep roses blooming is by providing fertilizer that encourages flower development. Commercial rose fertilizers contain the major elements of plant growth – nitrogen, phosphorous and potassium – in an analysis that is specific to flower bud development. The middle number in the analysis will always be higher; for example, 10-15-10. Roses can be fertilized in spring after buds break and twigs with leaves are present along the canes. A second application can be made in late June to early July when the first flush of rose blooms is finishing; and a third application in late summer (in the first two weeks of August). Following this schedule will keep rose shrubs producing flowers through the full growing season and into early autumn. The schedule is focused on maximum flower production within the available weeks before frost shuts down plant’s productivity. With so much focus on producing blooms, there is little energy directed toward enlarging the shrub with new cane growth. Consequently, roses that are aggressively fertilized over several years may eventually suffer structural exhaustion. Too much is being asked of the woody plant canes without any structural growth of new wood. The plant may eventually appear diminished and become less productive. An effective way to get more rose production over a longer period of years is to encourage growth of the full shrub. As a rose shrub produces flowers over the growing season, it should also be replacing older wood with new canes that will enlarge the plant. A simple way to provide essential elements to trigger new rose cane growth is by providing common Epsom salt, which contains magnesium and sulfur. Magnesium assists in chlorophyll production, part of the energy needed for cane growth, and also enhances petal size and colour. Sulfur is essential to protein production, an important element in growth. Provided together, magnesium and sulfur encourage new cane development from the lower portions of the shrub, providing architecture for increased flowering wood. Supplying Epsom salt every year usually results in growing new cane wood. Epsom salt doesn’t replace standard rose fertilizer, but is used as an amendment to healthy growth. Spring is the most important time to provide Epsom salt, when the plant is ready for strong growth. Apply ½ cup of Epsom salt to the soil surrounding an established shrub, keeping it away from direct contact with the plant base. Use a hand cultivator or trowel to work the Epsom salt into the top layer of soil and water it thoroughly. Use ¼ cup of Epsom salt mixed into the hole when installing new rose plants, and up to ½ cup worked into the topsoil for established roses. The Epsom salt can be provided every four to six weeks through the growing season to enhance the size and colour of flower petals. It’s finally summer and we should enjoy the moment, while considering how to get the best from roses blooming in the garden right now. But the early arrival of fall bulb catalogues suggests the intriguing possibility of perennial spring bulb bloom. There are new ideas to consider! Getting the most from favourite seasonal plants 46 | www.snowbirds.org
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