Some Flowers Turn Into Weeds

Flowering weed

Annuals that reseed themselves can make gardening easier, but some soon try to bully the rest of the plants.

In my opinion, some ornamental flowers are weeds once they are planted,” says Jerry Goodspeed, Utah State University Extension horticulturist. “Since most annuals are hybrids, during their first year they look great. However, in the following years they lose the genetic characteristics that made them special, and most revert back to their plain, old boring selves. There are four annuals on my hit list.”

One of the worst offenders is cosmos, he says. When they are planted from seed or transplanted the first year, they are pretty and almost nice to have around. But, every year after that the flowers become less attractive, and the plants become taller and uglier.

Another problem ornamental is calendula, Goodspeed says. They resemble marigolds in color and size. Again, that first year they perform admirably; but in subsequent years they become a real nuisance. The flowers fail to open as nicely, and the plants are more prone to die out early.

The last two annuals I can sort of tolerate are larkspur and alyssum,” he says. “Purple to pink-colored larkspur are a nice addition to most informal, cottage-style gardens. The colors of the flowers often remain pretty from generation to generation, but if they are not thinned on a regular basis they can shade and crowd out other flowers in the area. Pink, purple or white alyssum are used in many gardens as a low-growing groundcover. However, if allowed to reseed, most of the plants the following year are white. Occasionally a purple one ventures forth, but that’s the exception, not the rule. With time, alyssum produces fewer flowers and loses its appeal. Though those are the four worst, there are others that tend to take over the garden if left unchecked, Goodspeed says. Feverfew is a short-lived perennial that can take over a flower bed in a matter of minutes. It has a daisy type flower, with a dandelion attitude. Feverfew is also classified as an herb.

Blue flax produces nice blue flowers all season long,” he says. “Each morning this dainty perennial is covered with light blue flowers; but, by afternoon most of the flowers have fallen off. Even though this plant keeps re-seeding throughout the yard, I allow it to stay because I enjoy its color and foliage. It is easy to weed out, and adds a blue color to the landscape that is sometimes hard to find.”

Red valerian is a seedy plant that is not as easy to remove, Goodspeed says. If the many new plants that pop up are allowed a few minutes to set root, they can be really hard to pull out. This plant also has a tendency to try to grow in the middle of other perennials, shrubs and sidewalks. The advantages of this flower include its attractive red to pink blossoms, and the fact that it blooms for most of the summer.

The last perennial is a native to our mountains, he says. Hardy geraniums are one of the wildflowers in bloom in our high meadows. A few varieties available at local garden centers range from pink to a lavender-blue color. They are not terribly aggressive, but do have the ability to reseed and fill up a vacant area if allowed to spread. They are also relatively easy to weed, and are quite nice when in bloom.

Despite what I have just said, many of these flowers are found in nice, attractive yards,” Goodspeed says. When talking to people about their flowers and landscapes, I usually preface my remarks by letting them know that what I recommend is just my own opinion. Your own likes and dislikes are the most important when it comes to what to grow in your landscape. Treat my opinion like you do the fridge – take out and use what’s good, and let the rest sit until it is rotten enough to throw out.” 

For more information, contact your local USU County Extension office.


Dennis Hinkamp

Dennis Hinkamp

Dennis Hinkamp

Publication Specialist

Phone: (435) 797-1392

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