Ask a Master Gardener: No room for Scotch broom!

Ask a Master Gardener: No room for Scotch broom!

Question: This year the Scotch broom seems to be worse than ever! Why doesn't the county come out and spray it or pull it or in some way get rid of it?

Answer: You are certainly not the first person to complain about Scotch broom! This is the time of year when Scotch broom becomes a major concern as its highly visible flowers call attention to its invasive growth habit. Scotch broom was introduced as a garden ornamental by early settlers of the Pacific Coast. It has spread far beyond the bounds of cultivation and now covers many acres west of the Cascades from British Columbia to California.

Scotch broom spreads slowly, but persistently. Seed pods split suddenly at maturity and eject the seeds. Also, it is reported that ants aggressively collect the seed and assist in its dispersal. Birds also assist with spread, but how well the seeds survive digestion varies with the species of the bird.

According to Nancy Ness, director of the Grays Harbor County Noxious Weed Control Board, each county weed board has the option each year of designating target weeds to be controlled. Unfortunately, when weeds like Scotch broom get listed, they usually are placed in the "C" category, which means that the infestation is already so prolific, that enforced control is no longer feasible.

"The very best we can do is to educate the public on options for control. We are particularly concerned that people become aware of Scotch broom's potential as a fire hazard," said Ness.

Domestic goats are reported to browse Scotch broom without apparent ill effects. Given time, goats will probably control a patch of Scotch broom if the plants are not too tall.

Plants can also be controlled by grubbing out the crowns. After removing existing large plants, repeated cultivation will destroy seedlings of this weed. Cutting or mowing the plant down to ground level immediately after flowering has proven to be effective means of control.

Selected herbicides currently recommended by WSU weed scientists for Scotch broom control include triclopyr and glyphosate. Both of these materials can be found in most retail garden stores and nurseries, and provide effective control when used according to label directions.

Although many people complain about having hayfever symptoms of watery eyes and sneezing when Scotch broom is in bloom, more than likely the broom is not to blame. Scotch broom is insect pollinated. Being heavy and sticky, the pollen does not become airborne; thus the potential for an allergenic reaction is minimal except perhaps when an individual actually handles a plant in bloom. Most allergenic reactions which result in hayfever symptoms are the result of wind-borne pollen, such as grass pollen which is distributed in large amounts at about the same time that Scotch broom is in bloom.

Question: We really got caught off guard last week when the weather turned so warm. So many of our plants wilted and they still do not look very well despite our turning the sprinklers on. How can we make sure our plants get enough water?

Answer: Many homeowners fail to understand what the term "proper watering" means.

First of all, it means that if rainfall is sufficient in the region and at a particular site, the irrigation system does not have to be turned on, nor the landscape plants watered. When watering is necessary, doing it wisely will save time, money and of course water!

Here are some pointers to make sure your garden survives and flourishes through the warm summer months.

First, water deeply and infrequently. This pattern will help to develop deep, penetrating root systems, capable of mining water and nutrients from a larger volume of soil.

Make water applications uniform. This is accomplished via a properly designed and installed automatic irrigation system but can also be carried out with the thoughtful placement of a sprinkler.

Water efficiently. This means making water applications when environmental conditions will favor maximum utilization by the plant. Early mornings are best, while evening hours are the worst. Vegetable and fruit plantings are most efficiently watered via drip irrigation systems.

Part of efficient watering is delivery at a rate the soil will allow to infiltrate without run-off. Water going down the drain or on the sidewalk does not do the plant material any good.

Mulch where appropriate.

EDITOR'S NOTE: For answers to local gardening questions, contact Master Gardener Rachel Gana at 642-8723 or e-mail her at:

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