Ask the Master Gardener: Keeping a garden colorful through autumn

There are a number of plants that bloom in the fall.

Actaea (Cimicifuga) plant. Photo by Jennifer Knutson

Dear Master Gardener: I would like to keep my garden looking colorful through the fall. What plants bloom in September?

Answer: There are some wonderful perennials that bloom in the fall that will provide your garden with color. Aconitum (monkshood) has attractive foliage and flowers that look like monks’ hoods. They come in blue, purple, pink, and white and prefer part to full shade. They bloom in September and October, depending on the cultivar. Keep in mind that all parts of Aconitum are poisonous, so wear gloves when handling them. Another vertical accent plant for the shade garden is Actaea, formerly known as Cimicifuga, (snakeroot). It ranges in height from 3-8 feet (depending on the cultivar) and has striking dark foliage with showy spikes of flowers.

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Asters and mums also bloom in September. The University of Minnesota has developed many lovely, hardy mums for cold climates. Chelone (turtlehead) has pink, snapdragon-like flowers and blooms late summer/early fall. Maiden grass and prairie dropseed are two ornamental grasses that bloom into fall.

Dear Master Gardener: I am growing lavender for the first time. What do I do with it?


Answer: Lavender is a member of the mint family and one of the most popular of all herbs due to the distinctive fragrance of its dried flowers and the oil distilled from them. Unfortunately, it is only hardy to zone 5 and not a perennial here. It is typically used in sachets, perfumes, potpourris, and cooking. Most varieties of lavender can be used in cooking, but if you have Lavandula angustifolia, it has the sweetest fragrance among all the species of lavender and is the one most often used in cooking. The flowers give dishes a subtly sweet, citrusy flavor and are sometimes used in cakes. You can make lavender infused sugar to use for baking or adding to beverages, such as tea or lemonade. Recipes can be found on the internet.

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To harvest your lavender, cut the stems just as the flowers start to open — this is the stage that the spikes will have the strongest scent. Tie the stalks in small bunches and hang them upside down in a cool, dark, well-ventilated place to dry. Once dry, store the bunches in plastic containers with tight fitting lids in a cool, dark, dry place. Sunlight and air exposure will shorten the storage life of lavender.

Dear Master Gardener: Is fall a good time to divide and plant peonies?

Answer: September is the best time to both divide and plant peonies. To divide your peony, dig up the clump saving as many of the roots as possible and divide it with a shovel, sharp knife or saw, making sure you have three to five healthy buds per root. When you plant your peony divisions, cover the roots so the buds (eyes) are pointing up, making sure that no more than two inches of soil covers the top of the buds. If you plant them deeper than two inches they may never bloom. Peonies should be planted in well-drained, rich garden soil, where they will receive at least six hours of sunlight. You should not expect the division of an old plant to flower the first year after planting and you may want to nip off any flower buds that appear the first year to strengthen the root system.

Dear Master Gardener: I heard about jumping worms on the news. How do I know if I have them and will they harm my gardens?

Answer: Jumping worms are an invasive type of earthworm native to Asia. There are no earthworms native to Minnesota. Jumping worms get their name from the unusual behavior they exhibit when disturbed — they move like a snake, are very active, and sometimes appear to be jumping. It is identifiable by a light-colored ring that extends around its body. Researchers at the University of Minnesota have confirmed jumping worms in Minnesota. They, and their eggs, may be distributed in commercial mulch or from community compost piles. They are able to survive in shredded pine, cedar, and spruce mulch and have often been observed in mulched garden beds. They are usually spread by moving potted landscape plants, soil, sod, compost, mulch, and fishing bait from one place to another. Earthworms purchased for fishing bait or vermicomposting may be contaminated with jumping worms — so be on the lookout. These worms are able to rapidly infest gardens and forest floors and transform the topsoil and mulch into dry, granular pellets that look like coffee grounds. They strip important nutrients from topsoil, which combined with the lack of an organic layer, kills fragile plants and increases erosion. This means invasive species like buckthorn can completely take over an affected area. And yes, they can harm, in fact kill, your garden plants.

Please do your part in the prevention and spread of jumping worms. Don’t buy worms advertised as jumping worms, snake worms, Alabama jumpers, or crazy worms for any reason. Inspect plants, mulch, soil, compost, and bait for jumping worms. Dispose of unwanted bait worms in the trash and never release any worm into the environment. Although common bait worms are a different species than jumping worms, they are still harmful to forests. If your soil looks like coffee grounds and you find unusually active worms in your mulch, you may have jumping worms. Report any suspected jumping worms to the DNR and destroy them if you see them by sealing them in a bag and throwing it away in the trash.


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 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.

A photo of Aconitum (monkshood) taken Oct. 25 last year, when the plant was still blooming. Photo by Jennifer Knutson

A photo of Aconitum (monkshood) taken Oct. 25 last year, when the plant was still blooming. Photo by Jennifer Knutson

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