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Bolt to rub out ‘bolting’ rhubarb

Fertilize each spring, divide your patch every five years and stop harvesting st

Dear master gardener: My rhubarb plant has sent up a large white flower. What should I do about it?

Flower production is a natural part of rhubarb’s reproduction cycle and is called “bolting.” It leads to the production of seed, which you don’t want because the seed-produced plant is inferior to the parent plant. Also, plant vigor and next year’s crop will be reduced if the flower is left to mature and set seed.

The flower takes energy from the plant, resulting in fewer and inferior stalks.  So remove the flower as soon as it appears, which may happen more than once, especially early in the season. Some varieties of rhubarb are more prone to bolting than others, as are older plants.

There are several things you can do to keep your rhubarb in top shape: fertilize each spring with a 10-10-10 fertilizer, divide your patch every five years and stop harvesting the stalks by July 4.

Dear master gardener: I was on a garden tour last summer and saw a plant with purple spikes and silvery leaves that was about 2-1/2 to 3 feet tall. What is this plant and is it easy to grow?

From your description you may have seen Nepeta (Catmint) or Perovskia (Russian Sage). Both are easy to grow. Catmints come in different sizes, but the largest, hardiest and longest-flowering is “Six Hills Giant.” It grows to about 3 feet and has deep violet-blue flowers with silver-gray, scented foliage.

Another popular cultivar is “Walker’s Low,” which grows to about 30 inches, has a nice round form, blue-violet flowers and a long season of bloom. A good plant for the edge of a garden is “Dropmore,” which grows to about 18 inches and has blue flowers with scented, gray-green foliage. Catmints require full to part sun, and once they are established, they are drought-tolerant.

After Catmint has bloomed you can cut it back to get more blooms later in the summer. They should be divided about every three years.

Perovskia (Russian Sage) is another perennial that fits your description. Technically, Russian Sage is hardy to Zone 4, but many people have good luck growing it here. It grows to about 3 feet, has lavender flower spikes and silvery foliage that is lightly scented. “Little Spire” is a dwarf variety that grows to about two feet.

Russian Sage needs a sunny spot with well-drained soil. It too is drought-tolerant and blooms for about six weeks in late summer. Do not cut the plant back more than 12 inches after the first frost, and it may be best to wait until early spring after the first year in the garden and then cut it back to about 12 inches. 

Dear master gardener: I am interested in doing some landscaping around my house and was wondering what shrubs stay lower than six feet.

There are many small shrubs from which to choose. There are evergreens that fit your description and are hardy to our zone. Globe arborvitaes reach a maximum size of 5 feet, are globe-shaped and tolerate full sun to full shade.

“Sea Green” juniper, also known as “Mint Julep,” gets 4 to 6 feet by 4 to 6 feet, has mint-green foliage and arching branches. There are also ground cover, or creeping junipers, such as “Blue Rug” and “Wilton Carpet.” Junipers prefer full sun.

Dwarf Globe Blue Spruce gets 3 to 5 feet by 5 to 6 feet, has silver-blue foliage and needs part to full sun. Dwarf mugo pine grows 3 by 5 feet and grows in full sun to partial shade.

A few of your many deciduous options are “Clavey’s Dwarf” honeysuckle (5 feet tall), “Emerald Mound” honeysuckle (3 feet tall), “Annabelle” hydrangea (5 feet by 5 feet), Rugosa rose (various sizes), dwarf Korean lilac (4 feet by 4 feet), Japanese barberry (4 feet by 4 feet) and dwarf European viburnum “Nanum” (2 feet by 3 feet).

“Northern Lights” azaleas, which come in a number of colors and sizes, would be yet another option. It is important to find out the mature size of shrubs and trees that will be planted around the foundation of your house and plant them with their mature size in mind. 

Dear master gardener: I have my first apartment and it has a balcony where I would like to have several containers of plants. Can you give me some basic hints on how to plant and grow them?

How about these 10 Commandments for growing container plants?

Thou shalt have drainage holes in thy pots. 

Thou shalt use good, fresh potting soil. 

Thou shalt choose sun plants for sunny sites, shade plants for shady sites. 

Thou shalt design for beauty and proportion. 

Thou shalt pack thy plants closely and tightly. 

Thou shalt water daily. 

Thou shalt fertilize weekly at half strength. 

Thou shalt deadhead regularly.

Thou shalt prune for shape and sturdiness.

Thou shalt love thy plants with all thy heart.

CROW WING COUNTY MASTER GARDENERS are trained and certified volunteers for the University of Minnesota Extension Service. All information given in this column is based on research and information provided by the University. To ask a question, call the Master Gardener Help Line at (218) 824-1000, extension 4040, and leave a message. A Master Gardener will return your call.