Dear Master Gardener: Some of my blue hostas have turned green. They are in a place with the afternoon sun. Why have they lost their beautiful blue color?
Answer: Blue hostas should be in more shady areas to maintain their blue color. They do best in places where they receive filtered or dappled sunlight for most of the day. If they receive sunlight, it is best to have morning sunlight, as it is less intense. Blue hostas are not actually blue. The top layer of a blue hosta leaf is coated with a glaucous coating that gives it a blue appearance. The more a leaf has a glaucous coating, the bluer it will appear. Hostas are typically bluer when they emerge, then many take on a blue-green or green hue later in the growing season. Some retain their blue color until autumn. This phenomenon depends on genetic makeup, light levels and the degree of summer heat. When blue hostas are exposed to scorching sun, harsh watering, or certain pesticides, the wax coating melts and once it’s gone, the leaves won’t return to their blue color this season. The following blue hostas retain their blue color the best, if planted correctly: Abiqua Drinking Gourd, Big Daddy, Blue Hawaii, Blue Angel, Blue Umbrellas, Hadspen Blue, Halcyon, Krossa Regal, Love Pat, Powder Blue, Prairie Sky , Silver Bay , and Outremer.
Dear Master Gardener: I visited my brother near Mankato and he had yucca plants growing in his garden. I was so surprised to see them growing up in Minnesota! I thought it was a desert plant that you might see in Arizona or New Mexico. Is it an annual that he grows or a perennial that can grow in Minnesota?
Answer: Yucca filamentosa (Adam’s Needle Yucca) is a perennial that can grow successfully in parts of Minnesota. According to the United States Department of Agriculture, the natural range of this plant is in Wisconsin and Illinois, but not in Minnesota. This plant is hardy to zone 4b. Mankato’s hardiness zone is 4b, but most of Crow Wing County is in zone 3b. If you have a microclimate in your yard – perhaps a sheltered south side of your home – you can try yucca. It is a very showy plant with its sword-shaped leaves and large spike of creamy white bell-shaped flowers. Adam’s Needle Yucca is a long-lived perennial that should be planted in full sun. It reaches a height and spread of 4 feet at maturity, so give it some room. It also has a tenacious root system, therefore, plant it in its permanent home.
Dear Master Gardener: We moved into a new house last spring and there was a large and beautiful garden of perennials. Unfortunately, I spent a lot of time trying to eradicate quackgrass and wild onions from the garden. Is there a way to get rid of weeds without using toxic chemicals?
Answer: Quackgrass, a perennial weed, can invade flower gardens (or vegetable gardens) which makes its eradication extremely difficult. Quackgrass grows from seeds or underground rhizomes and reaches a height of about 1 to 4 feet. Stems are smooth with three to six joints. It has thin, flat, bright green leaf blades with a seed spike that appears in July and grows 3 to 8 inches long. This perennial weed reproduces by seeds and rhizomes. Each quackgrass plant produces about 25 seeds that remain viable in the soil for three to five years. The rhizomes are yellow to white, 1/8 inch in diameter, with distinct joints or nodes about every inch. Each node is capable of producing fibrous roots and sending a new blade of grass through the ground. One plant can produce 300 stems of rhizomes each year.
To eradicate them without using chemicals, pull up and/or dig up plants as shoots appear, following along the roots to remove as much as possible. The rhizomes will need to be dug by hand as much as possible without breaking them into the ground as any cutting of the rhizomes means rapid plant multiplication. Use mulch as much as possible to smother the plants, but unfortunately the rhizomes will crawl until there’s an area they can send up a sprout. If you compost, dry the uprooted roots in the sun before composting. You can also eliminate them by constantly cutting the strands of quackgrass with a hoe or trowel. Without photosynthesis, the plant will not be able to store food reserves in the rhizomes and will eventually die.
You not only have one annoying weed, but two! Wild onions are a big nuisance because they spread by both underground bulbs and seeds. They are quite hardy, tolerate both sunny and shady areas, and can also be difficult to eradicate. Getting rid of wild onions in a flower garden requires perseverance, as it can take several years. Although it’s not easy, pulling them up is an option. It is much easier to pull them out when the soil is moist. Grab each wild onion plant at its base and pull it up from the ground. Unfortunately, corms or corms can remain in the ground and you will see new leaves emerge later, so try to remove any corms and plant roots left in the ground using a fine trowel. Another option is to continually prune wild onions on the ground with pruners, so that the foliage of the pruned plants cannot photosynthesize. Do not put wild onions in your compost. Burn it or bury it in a separate place so nature can decompose it without contaminating your compost pile.
Dear Master Gardener: I love hydrangeas! Which are the best performers in our region?
Answer: What’s not to like about hydrangeas?! They have showy summer blooms and many landscape uses. There are several cultivars of Hydrangea arborescens that do well in our climate. Annabelle has white flowers and is 5 feet by 5 feet. Endless Summer Bella Anna is dark pink and Bounty is white – both mature at 3ft by 3ft.
There are at least 16 cultivars of Hydrangea paniculata that are hardy here. Some highly recommended include: Limelight (white to lime green, 8ft by 7ft), Pinky Winky (ivory, 9ft by 9ft), Quick Fire (white to pinkish, 7ft by 7ft), Tardiva (ivory, 9ft 9ft), Unique (ivory, 10ft by 10ft), Vanilla Strawberry (white to red, 6ft by 5ft), and White Diamonds (white to green, 4ft by 5ft). If you want a small hydrangea with lots of flower power, Bobo is covered in large white blooms that turn pink as the blooms mature. It reaches 30 to 36 inches in height and width at maturity.
You can get your garden questions answered by calling the new Master Gardener Helpline at 218-824-1068 and leaving a message. A master gardener will call you back. Or, email me at [email protected] and I’ll reply in the column if space permits.
The University of Minnesota Extension Master Gardeners are trained and certified volunteers for the University of Minnesota Extension. The information provided in this column is based on academic research.