Dear Master Gardener: Which annuals need to be deadheaded and which ones don't?
Answer: Deadheading (removing faded flowers) promotes continued blooming by preventing plants from setting seeds. Deadheading will stimulate new flowers and keep the plant tidy all season. To deadhead your plants, pinch off below the old flowers with your fingers or snip them off with a pruning shears. Annuals that benefit from deadheading include: Cosmos, Dahlias, Geranium (Pelargonium), Heliotrope, Marigold, Petunias, Snapdragon and Zinnia.
Most annuals are self-cleaning and do not need to be deadheaded. This means the old blooms fall off naturally. Some plants that will continue to bloom without deadheading include: Ageratum, Angelonia, Begonia, Bidens, Browallia, Calibrachoa, Canna, Cleome, Diascia, Diamond Frost Euphorbia, Impatiens, Lantana, Lobelia, Osteospermum, Scaevola, Supertunia petunias, Torenia, and Verbena.
Dear Master Gardener: I have a garden on the north side of my house with the typical ferns and hostas, but would like to add some color. Are there flowering plants that will perform well in shade?
Answer: Usually perennials have a fairly short bloom time, so you may want to choose those that also have attractive foliage. Most flowering shade plants are woodland plants that bloom in spring and early June. Adding some flowering annuals that are shade-tolerant, such as impatiens, wax begonia, browallia or torenia will give you continuous color all summer. The following flowering perennials do well in our area and are considered "deer-resistant":
Old-fashioned bleeding heart (Dicentra spectabilis) produces arching clusters of pink or white flowers in spring. The white variety, Alba, is not as vigorous as the pink. The plants usually go dormant after blooming, so if you decide to plant the common bleeding heart, you may want to plant some annuals around the clump to fill in the empty space. Fringed bleeding heart (Dicentra eximia) is a native wildflower with a long bloom season. The plants sport ferny, blue-green foliage topped with clusters of pendant, heart-shaped pink flowers from spring to fall if the soil is kept moist. You will find cultivars in red, pink or white. 'Burning Hearts' is a hybrid that has striking blue-gray foliage and blooms profusely in late spring/early summer. Under ideal conditions and care it may rebloom.
Bergenia has leathery, glossy, dark green leaves which are heart-shaped at the base. It has small, dark pink panicles of flowers and blooms in spring. It will tolerate full shade, but you will get more blooms if it is in part shade.
Astilbe have plumes of flowers that come in white, pink or red. Some species have drooping plumes, while others are more erect and fluffy. Depending on the species of Astilbe they can bloom anywhere from early to late summer and range from 8 to 36 inches in height.
Cimicifuga, also known as Actaea, is great to use as a vertical accent plant. It is a long-lived plant with eye-catching, bottlebrush-like wands of white or cream-colored flowers. Although it will tolerate deep shade, it performs best in light to medium shade. Cimicifuga thrive in rich, slightly acidic soil with lots of organic matter and soil that is kept consistently moist throughout the growing season. It blooms in August and September, depending on the cultivar.
Heuchera (coral bell) not only have dainty sprays of flowers, many have beautiful foliage too. Depending on the variety, flower colors will come in various shades of red, pink or white. There is a wide range of foliage coloration and leaves often change color as the season progresses. They grow best in light shade and need to be watered frequently.
Pulmonaria (lungwort) bloom in spring and early summer. Many cultivars have interesting fuzzy foliage with speckles or splotches of silver that are attractive throughout the season. The flowers, which attract hummingbirds, are bell-shaped with colors ranging from pink, blue, and purple, with some plants having all three colors in their flowers. 'Sissinghurst White' is the only white flowering cultivar. In order to thrive, they need to be planted in rich, well-drained soil high in organic matter and kept evenly moist.
Tiarella (foamflower) is a woodland wildflower that has attractive maple leaf-shaped foliage and spikes of small, starry white or pale pink flowers in late May and early June. It likes rich organic, moist soil.
There are many violets from which to choose. They also bloom in late spring and early summer. One thing to keep in mind about violets is they self-seed prolifically.
July Gardening Tips
• To keep plants producing, keep picking peas and beans-then later on-tomatoes, peppers and cucumbers.
• Prune summer-bearing and ever-bearing raspberry plants right after harvest. Remove all the older canes that bore fruit this summer by cutting them to the ground.
• Fertilize flowers in containers every week or two all summer long with a water-soluble fertilizer at half-strength.
• Leaf lettuce, spinach and radish turn bitter and bolt in July's heat. Pull them out of the garden and replace them with broccoli, cabbage, or cauliflower for fall harvest.
• Keep garden beds weed free. Weeds compete with other plants for space, light, water and nutrients, and may host insects that spread disease.
• Stop harvesting rhubarb and asparagus this month to ensure productivity next year.
• As soon as tomatoes set fruit, begin to monitor the lower leaves for Septoria leaf spot. Remove infected foliage and spray plants with a registered protective fungicide if the disease is severe. Mulching around the plants may help prevent disease organisms from splashing up from the soil.
• Mid-month, work additional fertilizer in a circle around tomato plants.
• When picking flowers for floral arrangements, pick them early in the morning before they begin to lose much moisture. Strip the lower leaves, then cut the base of the stems before plunging them into a vase of tepid water. Change the water every day or two. Or, dissolve floral preservative in the water before adding flowers.
• Cut back the old stems of Delphiniums to the fresh growth at the base of the plant to encourage new growth and a second flush of flowers.
• You can dig up weeds now, but don't spray with an herbicide until the fall when it is cooler. Fertilizer and herbicide applications can burn lawns during hot weather.
• During the growing season, trees need one inch of water per week to keep their roots hydrated. It is especially important to water evergreens well during hot, dry weather. Woody plants weakened by drought stress are more susceptible to insect pests, diseases and winter injury.
• July is a good month to prune maples, birch and other trees that bleed when pruned in late winter.
• Keep applying repellents to discourage rabbits, woodchucks and deer from feasting on your plants.
University of Minnesota Extension Master Gardeners are trained and certified volunteers for the University of Minnesota Extension. All information given in this column is based on university research. To ask a question, call the Master Gardener Help Line at 218-454-GROW (4769) and leave a recorded message. A Master Gardener will return your call.