Ask the Master Gardener: Tips for harvesting rhubarb

Begin picking rhubarb stalks as soon as they have reached their full length. Each variety is different and can vary from about 1 to 2 feet in length. Hold the stalk firmly, pull and twist. Immediately after harvesting, use a knife to cut off the leaves from the stalk.

A picture of rhubarb stocks tied together.
Bundles of rhubarb.
Contributed / Metro Newspaper Service

Dear Master Gardener: What’s the best way to harvest rhubarb? Also, my neighbor told me that if my rhubarb gets a flower, I am supposed to break it off and I’m not supposed to pick and eat rhubarb after mid-July. Why?

Answer: Begin picking rhubarb stalks as soon as they have reached their full length. Each variety is different and can vary from about 1 to 2 feet in length. Hold the stalk firmly, pull and twist. Immediately after harvesting, use a knife to cut off the leaves from the stalk. They are toxic and leaving them on can speed up wilting of the stalks. Harvesting season for rhubarb lasts until the end of June. After that time, allow the plant to keep all its leaves to build up energy for next year. It’s a common myth that the entire plant becomes toxic later in the summer but that is not true. If you want to pull a few stalks every once in a while later in the summer to prepare a dish, you will not harm the plant vigor or health. The stalks may be tougher though.

Your neighbor is correct about a flower stalk emerging from the plant. Cut it off as soon as you see it. If the plant flowers and sets seed, it will waste energy that should be stored for next year’s crop.

Dear Master Gardener: I’d like to grow hollyhocks. Can I start them from seed right now?

Answer: Hollyhocks are those old-fashioned flowers that our grandmothers grew and lately there has been a renewed interest in growing them. Like foxgloves, most of the old-fashioned hollyhocks are biennial, meaning they complete their life cycle in two years. The first-year growth results in a rosette of leaves near the ground. The second-year growth results in stem growth, flowering, and seed formation, followed by the death of the plant. Gardeners who grow hollyhocks often allow some of the plants to go to seed so they get new plants every year. There are some new varieties that are considered perennial but they may not live for more than a few years. If you deadhead the flowers right after they bloom so they don’t produce seed, it will give the plants a better chance of coming back.


If you start hollyhocks from seed this year you probably won’t see flowers until next year and then they will most likely die. If you want flowers this year, you may want to get potted plants at a local garden center. Then let some of the plants drop seeds to get more plants in the future. Plant them in a sunny location and space them 12-18 inches apart.

Dear Master Gardener: Is this morel mushroom season? Where do I look for them?

Answer: The morel mushroom is prized for culinary use and is probably the most recognizable and sought-after edible mushroom. Morels usually emerge in the spring when there has been adequate rainfall. In southern Minnesota they can be found in late April through May and in northern Minnesota they can be found into June. Morels are most commonly found in woodlands or woodland edges. There is a common myth that they only grow near dead elms, but you can also find morels growing under or around decaying ash, oak, maple, poplar and apple trees. It is crucial that you positively identify mushrooms you pick and eat as there are poisonous look-alikes and some can be fatal. Here is an old mushroom hunters’ adage that is good to follow: “When in doubt, throw it out.”

Dear Master Gardener: I would like to introduce my children ages 5 and 7 to gardening this year. Are there any books for children this age that can teach them basic gardening at their level?

Answer: Yes, and what a great idea! It is proven by research that reading aloud to children helps them build a larger vocabulary, provides a model of fluent reading and encourages reading for enjoyment. Reading gardening books aloud to children can be beneficial for starting conversations around gardening. It’s actually how I began my love of gardening — my grandfather gave me a children’s book on flowers at a young age, then walked me through his flower gardens teaching me the flower names and telling me facts about them.

“From Seed to Plant” by Gail Gibbons is a wonderful resource with beautiful drawings that introduces elementary-aged children to the relationship between seeds and plants. “How a Seed Grows” by Helene Jordan helps children understand the difference between various seeds and how they become trees, fruits, and vegetables. “A Seed is Sleepy” by Dianna Aston and Sylvia Long is a beautiful book that introduces children to fascinating seed and plant facts. “The Flower Alphabet Book” by Jerry Pallotta not only introduces readers to different flowers, but works on unfamiliar letter sounds and pronunciation that children may not be familiar with beforehand. There are also interesting tidbits such as what flower is used to make a doll, which flower flavors tea, and which flower farmers feed to chickens.

Dear Master Gardener: What’s the latest on jumping worms?

Answer: Unfortunately, there are jumping worms in Minnesota. And, unfortunately, jumping worms have spread all over the Minnesota Landscape Arboretum because they inadvertently used wood chips from an infected pile on all their garden beds, walking paths and trees.


Jumping worms are an invasive species that move like a snake and sometimes seem to be jumping. It is identifiable by a flat, light-colored ring that extends around its body. 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. No earthworms are native to Minnesota. Jumping worms are native to Asia and spread by moving potted plants, soil, compost, mulch and fishing bait. They are able to rapidly infest gardens and forest floors and will 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. 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. Remove and destroy them if you see them by sealing them in a bag and throwing it away in the trash.

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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.

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