Chrysanthemums (Dendranthema grandiflorum) come in every color but blue, giving gardeners a wide range of options for enhancing and complimenting their landscape's palette. Also known as a mum, this flowering perennial originates from Asia. Today, it thrives throughout North America in U.S. Department of Agriculture plant hardiness zones 5 through 9. With the proper care, mums can provide years of vibrant blossoms and lush, green foliage.
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If you buy mature mums from a nursery or garden store and set them out in a shady spot, they'll continue to bloom that first year. They'll bloom poorly, however, or stop blooming completely in subsequent years. For the healthiest plants, the greenest foliage and the most flowers year after year, mums require full sunlight. That's at least six hours of direct sunlight every day. More is always better.
Consider placing mums on an east- or west-facing side of the landscape to increase their sun exposure.
Plant Spacing and Soil Conditioning
Most varieties of mums need at least 18 inches of space between each plant. Take this into consideration when initially planting mums, whether you're starting them from juvenile plants or more mature versions.
Mums are not picky about soil conditions and can grow well in any garden soil used for growing vegetables and other plants. They do prefer slightly acidic soil with a pH reading hovering around 6.5. Soil pH testing kits are generally available at garden stores.
Additionally, mums do best when grown in soil that's rich in organic matter. Before planting mums, mix 3 to 4 inches of well-aged compost into the top 8 to 10 inches of soil. This improves the soil's aeration, moisture retention and nutrient levels. After planting, add a couple inches of mulch around the mums every spring. Mulch protects the soil, reduces water evaporation and blocks out weeds. It also adds organic matter to the underlying soil as the mulch decomposes.
Mums do best in consistently moist, but not soggy, soil. Water the mums whenever the top inch of soil dries out. When watering, use enough irrigation to moisten the soil to a depth of 4 to 6 inches. For mature mums that quickly soak up water, you may find yourself watering the flowers once every couple of days.
Water mums in the morning. This gives the plant the initial moisture it needs to get through the hottest part of the day. It also provides the plant enough time to dry out before cooler evening temperatures set in. This reduces the risk of foliar diseases.
Always water mums at their base. Avoid getting the flower plant's leaves wet as that increases the risk of diseases.
When you first plant the mums, set a nutrient foundation by fertilizing the planting site with 2 pounds of 5-10-5 fertilizer for every 50 square feet of soil, mixing the fertilizer into the top 6 inches of soil.
For an established flower bed, fertilize the mums once in the middle of summer. Use 4 tablespoons of 5-10-5 fertilizer for each plant, sprinkling the fertilizer in a 12-inch radius around the base of the mum.
Water mums immediately after fertilizing. This carries the fertilizer down to the plant's roots and minimizes any risk of nitrogen burns.
Pruning is optional, but it encourages the mums to grow in tight, bushy shapes. As the mums start to produce new growth every spring, use your fingers to pinch off the top inch of growth from the ends of each growing stem. The stem will produce new side branches at the pinched spot.
When those new branches are 6 inches long, pinch off an inch from their growing tips. Continue this process throughout the year until the plant starts producing blossoms (typically toward the end of summer).