Dear Master Gardener: How do you divide peonies and when should you cut them down for the winter? Also, can balloon flowers be divided?
Answer: When it comes to peonies (Paeonia) it is important to place them carefully because they do not like to be disturbed. With that said, they can be divided by digging up the entire clump, then splitting it into halves or quarters with a sharp knife or shovel. This can be a challenge because the roots are thick and brittle. Keep in mind that the smaller the division, the longer it will take for them to bloom again. Proper planting depth is critical because if they are planted too deep your plant may bloom very little or not at all. Try to divide any perennials 4-6 weeks before the ground freezes so the plant’s roots become established. It is important to remember not to cut down peony foliage until it is damaged by frost.
Balloon flowers (Platycodon grandiflorus) also do not like to be disturbed. They have a gnarled, brittle root system and dividing them is not recommended. If you decide to try and divide your balloon flower it will most likely not bloom for a year or two after division.
Dear Master Gardener: What should I do to prepare my garden for winter?
Answer: The leaves tumbling down into our yard is nature’s way of telling us it’s time to get the garden ready for winter. When dying leaves drift onto the ground, they give the earth food that’s vital for the buds of spring. Here are some suggestions for winter preparation:
- Pull up dying plants that have had insect or disease problems — you don’t want pests or diseases wintering in your garden. Burn or bag any diseased plants — don’t toss them onto your compost pile.
- If you cut back your perennials, leave them 4 to 6 inches tall. The energy in the upper plant flows to the root systems, where it’s stored for the winter. Wait until the plant is dead, and then cut it back. Otherwise, you can leave healthy perennials standing, as the leaves and stems provide shelter for beneficial insects and the seed heads are tasty treats for birds. In addition, if we don’t get adequate snow cover, the foliage left standing provides some insulation for the plant’s crown.
- Remove slimy leaves — pests love slime! Hostas and Solomon’s seal, for example, can both get pretty slimy.
- Dig out all of the weeds and give your gardens enough water to keep plants moist in the winter.
- Plant your spring-flowering bulbs, such as daffodils, muscari, snowdrops, tulips, and crocuses. Remember that each bulb should be planted at a depth that is three times the height of the bulb.
- Spread 1 to 6 inches of compost or composted manure over your garden, which will enrich your soil with nutrients.
- Polish your gardening gear. The organized gardener can wind up the season by cleaning and sharpening all of their garden tools and putting them away for the winter.
Dear Master Gardener: My hollyhocks had orange spots on the lower leaves, then dark red bumps developed on the undersides of the leaves beneath the orange spots. What is this and what should I do about it?
Answer: It sounds like hollyhock rust, which is a common fungal leaf disease of hollyhocks (Alcea rosea). This disease can spread quickly and is spread by wind, splashing rain, or overhead watering. Warm and humid temperatures also encourage the growth of the fungus. According to the University of Wisconsin Extension, once symptoms of hollyhock rust appear, control can be difficult. If you observe the disease very early in its development, remove symptomatic leaves and dispose of them in your municipal garbage (if allowed) or by burying them deeply. Next year you can apply a fungicide specifically labeled for use on hollyhocks, but do it before symptoms occur, and follow the directions carefully. Remove all hollyhock debris in your fall clean-up. Do not use seeds from infected plants.
Dear Master Gardener: I would like more fall color in my perennial garden and am considering asters. Is it a good choice? What care do they need?
Answer: Asters (Symphyotrichum) are a great choice for adding fall color. They come in red, blue, purple, lavender and white. Many varieties are hardy in our zone 3. Asters grow in full sun to partial shade, but those grown in full sun will be bushier, have more blossoms, and have stronger stems than those grown in partial shade. Plant them in well-drained soil and water them regularly. Good air circulation is important because they are prone to powdery mildew and rust can also be a problem on certain cultivars. In spring give them a little compost or other organic fertilizer, but do not over-fertilize or they will get leggy and bloom less. In June the plants should be pinched back to about six inches to keep the plant bushy and to prolong the bloom. Asters multiply easily and should be divided every three to four years. They make good cut flowers.
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 email@example.com 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.