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Controlling Invasive Weeds in Mendocino County: When and How to Mow


Whether to mow at all.

Not every wildland location needs to be mowed for wildfire hazard reduction.

Shady areas may not produce enough dry vegetation to be a hazard. Wet areas near streams and springs may stay sufficiently moist and green to act as a fuel break. Grasslands dominated by perennial grasses and late-blooming wildflowers may maintain green vegetation well into late summer.

Mowing Invasive weeds in Mendocino county may be advisable as part of an integrated weed management strategy, even if wildfire is not an issue. However, you can save time, money, use less gas, encourage desirable vegetation and reduce the risk of accidental ignition by only mowing when it is needed.

Timing your mowing.

When to start, how often, when to stop. Suppose you decided to mow a particular area. When is the right time to mow?
It depends on the reason you are mowing, the vegetation present, the weather and the soil’s moisture. Whether you are mowing for fuel reduction or to modify the plant composition of your fields, it is important to understand that mowing can favor some species over others, depending on when and how it is done.
Mowing early can be damaging to equipment and desirable vegetation if the soil is too damp.
Wait at least until the soil is dry enough to support the mower without forming ruts. The time can vary from one year to the next and from one location to the next.
It is important to know your property and pay attention to its condition throughout the year.
Mowing too early and often can favor certain late blooming weeds, such as yellow star thistle.
Mowing too late can disperse the seeds of non-native annual grasses, such as slender wild oat.
For Harding grass suppression, mow when plants are still green but seasonal moisture is almost exhausted.
To encourage desirable annuals (plants that die yearly and grow back only from seed) such as valley lupine or common madia, mow only before the plant has bolted (produced a flower stalk) or after the flowers have gone to seed and the seed is mature.

If it is necessary to mow when patches of desirable flowers are in bloom, mow around them if possible and return later to mow after seeds have matured. Remember, seeds usually ripen
several weeks after blooming.

If the desirable plants are mixed in with others that require mowing, try partial mowing in blocks, leaving other blocks to be mowed after going to seed. The following year, switch the areas to be mowed early and late, so that all areas have an opportunity to seed every other year.
Be creative with the pattern of partial mowing: curving swaths across a firebreak, concentric circles.

To discourage an annual weed, mow when it is in flower (grass has flowers too, even though they are not very showy). You can also mow before seed heads are fully matured — gather and sterilize (burn or thoroughly compost) clippings with seed heads still attached.

In particular, for yellow star thistle suppression, mow for the first time when the first star thistle flowers appear and then again about six weeks later to catch any flowers that grow back. This second mowing will usually occur in July, and must be conducted carefully to avoid starting a wildfire.

Perennials (plants that stay green all year or grow back from the roots after a dormant period)such as California oat grass (Danthonia californica) and the many beautiful native irises and lilies, can be encouraged by suppressing competing annuals that grow earlier and faster. There is an added advantage to perennial grasses: they reduce wildfire hazard because they stay green longer.

Height of mowing.
Setting the mower blade low is not usually recommended in wildland situations because of:
• increased risk of hitting rocks and creating sparks that could start a fire.
• increased damage to perennials when they are cut low.
• greater soil disturbance when the blade bites into the ground in uneven terrain, creating habitat for invading weeds.
• greater risk of damage to the mower blade from contact with soil, rocks and tree roots.
A blade height of at least 4 inches will reduce the likelihood of these problems in most situations.

It can be a challenge to simultaneously balance the requirements of wildfire fuel reduction and weed control. Developing a long-term management plan, on your own or with the assistance of professionals, can be of great assistance in meeting all of your land management goals.