A weed is often defined as a plant that is growing where it is not wanted. However, the same plant growing in a field or where it does not interfere with our planned landscape is called a wildflower.
This article will review a few of the plants we commonly see blooming this time of year either in our yards or on the undeveloped land and roadways. Whether to eradicate these plants from your yard or include them in you landscape, familiarity is important.
You need to know this
Two wildflowers (or weeds) which people do need to be able to distinguish are the scorpionweed and the Arizona lupine. Scorpionweed (phacelia crenulata) is in the Boraginaciae family. It grows to about 16 inches tall and has violet-purple bell-shaped flowers in finely haired, terminal coils. The leaves are dark green, much divided, and hairy up to 5 inches long.
The name scorpionweed refers to the curling flowerheads which somewhat resemble the flexed tail of a scorpion in striking position. Any contact with scorpionweed can produce a skin rash very similar to poison oak. Therefore, be aware of walking through scorpionweed or of pets running through it since your clothing or pet's fur can transfer the plant fibers to you.
The Arizona lupine (lupinus arizonicus) is a member of the Fabaceae family (pea family). This annual has pale pink to purplish blooms but is usually a slightly paler color than the scorpionweed flower and blooms in an erect spear above bright green, palmately divided leaves.
Lupines are among the old dependables of spring flower displays. The name lupine comes from the Latin word meaning wolf and was applied to this plant because it was believed to rob the soil of its fertility.
Actually, in common with other members of the Pea family, it is capable of fixing nitrogen in the soil and actually improves the land on which it grows.
Yellow-cups are in bloom
Another yellow-colored wildflower you can see around town right now is a member of the Evening Primrose family and is commonly called yellow-cups. This lovely flower can grow up to almost 2 feet tall and has bright yellow flowers with four cup-shaped petals.
The leaves are green with a reddish tinge growing mostly in a basal rosette. This evening primrose blooms at sunrise instead of sunset like some of the other evening primroses.
Hold the mustard
Next is an invasive weed called Sahara mustard (brassica tournefortii). In just one year, it has multiplied in enormous amounts here in Lake Havasu City since this time last year. If this weed goes unchecked, it will become our No. 1 weed problem and will place scorpion weed on the No. 2 list. Sahara mustard is commonly known as African mustard, Asian mustard or wild turnip and is a member of the mustard family.
This is no ordinary weed and is very destructive. It is an early bloomer (December/January) and grows quickly. It will smother wildflowers such as lupine, poppies and verbena along with native plants such as creosote bush.
The plant also has high oxalic content so it may be toxic to our desert tortoises, and because of its aggressive growth pattern, affect wildlife by altering the availability of forage plants and habitat structure.
Identifying Sahara mustard is easy. Many of us may think it as a wildflower because of the yellow flowers that it produces, but don't let it fool you. Sahara mustard is an erect annual that can grow from 4 to 40 inches tall. The stems branch from the base of the plant and have rough, stinging hairs that can be hurtful if touched (but is not poisonous like scorpionweed and will not leave a rash).
When the leaves are crushed, they smell like cabbage or turnips. The basal rosette of the leaves can be 3 to 12 inches long and look like that of a dandelion plant. The leaves get smaller as they grow up the stem.
The flowers are small, less then a quarter of an inch, with four oblong yellow petals in the shape of an X. This flower will then turn into a fruit.
The fruits are narrow seed capsules that break open when mature and disperse seeds. The seeds are tiny and reddish brown. The mucilaginous coating on the seeds makes them both sticky when wet and waterproofs them. This is what allows the seeds to survive in dormant conditions up to two months or under water for two months.
One well-developed plant can produce between 750-9,000 seeds. Tests have shown that Sahara mustard may be self-fertile since fruit set is nearly 100 percent on most plants and can still germinate after sitting three years in dormancy.
Many ways for seeds to spread
Disbursement of the seeds comes in various ways: wind, water, animals and humans. They are disbursed by the wind through dried plants that pull up and travel like tumbleweeds, therefore dispersing the seeds; by water through rains that fill washes which flows into lakes and rivers; by animals, by both eating the seeds or by the seeds attaching to their skin/feathers.
And then there are humans who can distribute the seeds, either by walking through the mustard or the seeds attaching to the tires of vehicles and recreational vehicles (ATVs, dirt bikes, etc).
Either way, once established, it can move into wildland areas and sand dunes at an aggressive pace, so it is imperative that further establishment of this weed be prevented and that existing plants be eradicated.
Prevention the best medicine
Experiments to find effective ways to control Sahara mustard are ongoing. The best control is prevention and the best prevention is manual pulling of this plant prior to it "going to seed." The impact of Sahara mustard is high and is now on control strategies in several states and is on red flag alert here in Arizona. So, if you see this weed on your property, pull it now prior to it going to seed.
These are only a few of the weeds and wildflowers that you can see in your own yard or neighborhood at this time of year. Take a few minutes to enjoy their beautiful blooms and unique characteristics that allow them to live in our desert.
At the same token, eradicate the "bad guys" from your yard by putting down pre-emergent or pulling out the entire plant.
Interested in ponds or water features? A free workshop will be Saturday, May 9, in Kingman. Call The University of Arizona Mohave County Cooperative Extension for details at (928) 753-3788.