Ask the Master Gardener: There's a difference between lutescent and viridescent hostas
Hostas with chartreuse, yellow, or gold coloring can be lutescent or viridescent.
Dear Master Gardener: I bought a Hosta and on the tag it says it’s lutescent. What does that mean?
Answer: Hostas with chartreuse, yellow, or gold coloring can be lutescent or viridescent. Those that are lutescent become more yellow as the season progresses and those that are viridescent become greener as the season progresses. Lutescent Hostas need more sunlight than viridescent hostas to bring out their coloring to its fullest.
Dear Master Gardener: Do daylilies need to be deadheaded?
Answer: Yes, daylilies (Hemerocallis) need to be deadheaded. Seed production tends to weaken plants, resulting in poor growth and reduced flowering in subsequent years. Snap off spent flower heads with your fingers. Once there are no longer any blooms you can cut the flower stalks to the base with pruners.
Dear Master Gardener: When should I prune my raspberries?
Answer: Raspberries need annual pruning to keep the plants looking good, increase productivity and reduce the chance of disease. Prune summer-bearing red and yellow raspberries after the last harvest. Cut all canes that have produced fruit to ground level and remove them. Thin summer-bearing raspberries at this time to increase airflow and reduce potential disease problems. Thin primocanes to four to five sturdy canes per foot of row. To get both fall and summer crops on fall-bearing raspberries, thin the canes as described for summer-bearing raspberries. The primocanes that produce the fall crop should not be removed (unless they have disease or insect problems) because they will produce fruit the following summer. Prune them back in the spring to about 12 inches above the support, or to the last visible node that had fruit, cutting off the dead tips.
Dear Master Gardener: Is a black cherry a good tree to put in?
Answer: Black cherry (Prunus serotina) is the largest native cherry in Minnesota (and North America). Like the black walnut, it is a prized hardwood for cabinetry. It isn’t used in the landscape very often because it can be kind of aggressive and weedy, is highly susceptible to ice damage, and is somewhat susceptible to a fungal disease called black knot. While it isn’t a specimen tree, it is well-suited for a naturalistic area or the edge of your yard, especially if you are willing to put in the time to properly manage it with pruning. The tree produces lovely white flowers in the spring, followed by edible fruit, which is a little bitter, but sometimes used to make jelly and wine, and to flavor certain liquors. The fall color is among the best of any tree in the Midwest — from golden yellow to apricot orange and scarlet, often on the same tree. As the tree matures, the beautiful bark becomes flaky and looks like burnt potato chips, giving it the nickname “potato chip tree.” It is a fabulous pollinator plant — the leaves host a variety of beneficial insects, including caterpillars of many butterfly species, and birds devour the berries. If you decide to plant a black cherry tree, it performs best in well-drained soil in full to part sun.
Dear Master Gardener: My coneflowers have some weird-looking flowers. Some have petals on only part of the blossom, others have only green petals, and still others have strange, bushy growths and flowers. What’s wrong with them?
Answer: Aliens have not invaded your flower beds. The symptoms you describe sound like aster yellows, a common garden disease. It also frequently affects asters (as the name implies), chrysanthemums, cosmos and marigolds, as well as vegetables such as carrots and potatoes.
It is caused by microscopic organisms called phytoplasmas and is transmitted by leafhopper insects. Symptoms become especially severe in warm weather and include, besides those you mention, stunting or dwarfing, yellowing of foliage, spindly stems and other distortions. Carrots are also very susceptible and when affected display hairy roots and short, clumpy greens. Once plants are affected, they cannot be cured. Remove the entire diseased plants promptly and discard them. Some gardeners avoid planting an affected variety in the same spot for several years because the disease organisms can persist in the soil.
Dear Master Gardener: I have some beautiful bluebells growing at the edge of the woods, but now they are spreading rapidly, even into our lawn. How can I manage them or get rid of them?
Answer: I strongly suspect that you have creeping bellflower, which as its common name implies, likes to spread. It is a perennial that is very invasive, especially in moist, shady areas. Its basal leaves are large and heart-shaped but as the plant grows upward the leaves narrow and a flower stalk 1-2 feet tall emerges. In bloom the flower stalk produces numerous downward facing, blue-violet, bell-shaped flowers mostly on one side of the flower stalk. They bloom from July-October. Creeping bellflower is very difficult to eradicate, largely because of its deep and complex root system. The main root is a large, fleshy tuber, often 6 inches deep. But there are numerous shallow fibrous offshoot roots that can extend some distance and break off easily in hand removal. Creeping bellflower is resistant to 2-4-D but responds to glyphosate (Roundup). Because glyphosate kills everything it touches, it is best applied to bellflower by pouring some into a small dish and while wearing waterproof gloves, wiping the bellflower leaves individually with a sponge or cloth. This is best done in late spring or early fall and may require several years of treatment, depending upon the extent of the infestation.
You may get your garden questions answered by calling the new Master Gardener Help Line at 218-824-1068 and leaving a message. A Master Gardener will return your call. Or, emailing me at firstname.lastname@example.org and I will answer you in the column if space allows.
University of Minnesota Extension Master Gardeners are trained and certified volunteers for the University of Minnesota Extension. Information given in this column is based on university research.