Plant Competition and Weed Management



With above average precipitation this winter and spring, it has been a great year for growing weeds. When it comes to controlling weeds, we have the options of:

1) Mechanical Control (cultivation, burning, hand pulling)

2) Biological control (disease agents, grazing)

3) Cultural control (mowing, crop competition) and

4) Chemical control (herbicides). Many people go directly to the chemical control method, because it is usually the easiest with the fastest results.

However, if your goal is just to kill weeds, then you will literally spend a lifetime doing so, explains the importance of plant competition after you have killed your weeds.

Weed control should always be a means to an end, not an end unto itself. Ask yourself, if we could wave a magic wand and all of North America’s weed monocultures would disappear overnight, what would that leave us? 

Answer: a huge void that would be rapidly re-invaded with the same weeds or worse. In other words, we should always begin with the end in mind, a desirable plant community that is healthy, functional, and weed resistant.

Any landowner with a weed infestation should first ask the following question: Are there enough desirable competitive plants present on the property to promote recovery without planting if weed control and proper follow-up management is applied? 

Many landowners focus so intently on weed removal that they overlook the need for desirable competitive vegetation. Without this component, weed control is typically a waste of time, money, manpower, and herbicide!

Complete elimination of weeds in an area without ensuring sufficient desirable vegetation to colonize the site could result in a situation worse than the original weed infestation in just a few years. Without competition for soil moisture, sunlight, and nutrients, either the former weed infestation will move back in with a vengeance, or another weed species or combination of species will move in to fill the void. 

This can leave the landowner with a problem worse than he or she originally encountered.

So, what exactly is sufficient desirable vegetation to colonize the site? A general rule of thumb is that areas with more than 20% canopy cover of desired vegetation can usually recover naturally if performance of weeds is hindered.

If reseeding, remember the soil is an essential natural resource for plant establishment, and its conservation is the highest priority in those areas where seeding is necessary. 

Therefore, the retention and enhancement of soil should be a primary consideration in all management decisions, including seedbed preparation and choice of a seed mixture.

If the planted vegetation does not establish rapidly, valuable topsoil may be lost through wind and/or water erosion, leaving the site only suitable for undesirable vegetation (weeds). 

When soils are mismanaged, vegetation ceases to produce as it once did, weeds again start replacing desirable plant species, recreation and scenic values are decreased, and management options for the production of livestock forage and/or wildlife habitat become limited.

Therefore, the primary focus for weed-dominated sites is on revegetation that serves two primary functions: (1) holding the soil, and (2) competing with weeds.

Obviously, seed mixes should be chosen with the “end in mind,” as related to desired land use. Long-term land use could include any one or a combination of the following: livestock forage, wildlife habitat, hay production, esthetic value, etc. If the landowner has multiple land uses planned, the revegetation strategy should reflect this balance.

Assuring a healthy and desirable plant community following a weed control program can be as simple as selecting the appropriate weed management techniques and/or choosing the right combination of species to re-seed, along with appropriate seeding methods. 

There are several key factors to keep in consideration that will help meet land use objectives:

Weed control considerations; Seedbed preparation, Seed mixes, When to plant, How to plant, Seed depths, Fertilizing, Other soil amendments, Seeding success and maintenance.