Foreign and invasive weeds in the Colorado landscape! These aliens are in the form of non-native weeds called “noxious” in Colorado. They’ve gotten that name because of their invasiveness, aggressiveness and the rate at which they spread. Noxious weeds are difficult to control, and most are very adaptable. They also can withstand a variety of harsh conditions, including climate extremes, drought and poor soils. There are approximately 1 million acres of noxious weeds in Colorado. The weeds cost Colorado residents more than $10 million annually in lost productivity. Noxious weeds often displace native plants. Many native species have been forced out of their natural habitat.
There are several noxious weeds in Colorado. Among the worst are leafy spurge, spotted knapweed, diffuse knapweed, Russian knapweed, Canada thistle, musk thistle, Dalmatian toadflax, yellow toadflax, field bindweed and purple loosestrife. Noxious weeds in Colorado have been divided into three categories:
List A weeds – elimination mandatory throughout Colorado.
List B weeds – plants whose continued spread should be stopped.
List C weeds – selected for recommended control methods.
Weed management includes cultural practices such as: avoiding overgrazing re-vegetating disturbed soils, and maintaining the vigor of desirable grasses or other plants that compete with weeds. The easiest time to control noxious weeds is when only a few plants are present. Mowing weeds before their seeds are mature will help prevent the seeds from spreading and will reduce weed vigor.
Biological control can involve using livestock such as sheep and goats to graze on weeds, which reduces their vigor. It also may involve introducing a specific disease or insect to affect weeds. Biological control has proven to be effective to varying degrees on some weeds. Planting desirable plants to outcompete the weeds can also be effective.
Herbicides may be used on noxious weeds as part of an integrated control strategy, often in combination with cultural and biological controls.
If you are planning on storing seeds for the future, be aware that different types of seeds should be stored under different conditions. Their ability to produce a plant depends on the time of seed harvest and the conditions of storage. Most seeds should be stored in a sealed, airtight container and kept in a cool, dark area. Mark the container with indelible ink including the plant and variety name, the date stored and other identification information.
There are three categories of seed storage based on the life of the seed. A viable seed is one that remains alive and is able to produce a live plant. Short-lived seeds are those that are viable for short periods, such as a few days or months under the right conditions. Medium-lived seeds are viable for two or three years if stored at low humidity and low temperatures. Long-lived seeds have hard seed coats. They are impermeable to water and can remain viable for up to 15 or 20 years.
To determine if stored seeds are still viable, take few of them, count them and place them in a pot or flat tray filled with potting mix. Water the seeds well and give them plenty of light. Keep the potting mix moist, and see how many seeds sprout. If more than half to three quarters of the seeds sprout, then the seeds have a good chance of germinating in the garden. Hybridized seeds, which are developed from a complex genetic process, are grown and sold for superior characteristics like large flowers and very tasty fruit. Seeds collected from these plants will seldom produce similar desirable plants from their seeds. Do not save or store these seeds; in most cases, the resulting plants will be a disappointment.
References from the Colorado Extension Program