17. Weed Control (part one)

Yikes, those weeds are out of control, what should I do?  I don’t want to use chemicals, but hand pulling is back breaking!  Are there some alternative, organic weed killers or other techniques out there that are environmentally friendly?  Yes, you have a lot of options and I’m sure there is something that will work for you…

First, to be clear: weeds are not some botanically specific category of plants, rather they are the unwanted ‘pest’ plants in your garden.  Typically they spread easily, and often invasively crowd out more desirable plants.  On one hand, a native plant could be a weed – for example Poison Oak is a California native plant, but I certainly don’t want it in my yard.  Conversely, the Dandelion is usually called a weed, but it can be used in salads, so it may have a place in the garden.

Why Fight the Weeds?

Why not let that pretty yellow flowering plant grow in your yard?  The very common weed form of Oxalis may look nice in the early spring, but it is a bad idea to let weeds like this thrive.  They are competing for and consuming the things that other plants need:  sunlight, soil nutrients, and water.  The longer you let weeds grow, the more widespread they become, not only the visible plant parts, but also the root system and underground bulbs.  Some weeds can re-sprout from any little part of the plant left in the soil.

Many weed species can flower and develop seeds in just a few weeks, and some can produce thousands of seeds from a single plant.  It is said that urban soils typically contain 6 or 7 year’s worth of weed seed, with more coming in on the breeze, and from birds and other critters, so this is a battle that will not be won overnight.  But fear not, it isn’t hopeless, you can stave off the invaders!  Your possible weed control techniques can be divided into a few categories:  Design Factors, Mechanical Methods and Herbicides.

Design Factors

There are several ways a good planting design helps to reduce weed growth.   First of all, don’t plan on leaving any bare areas in your garden.  By including some evergreen groundcovers in the planting design, such as Beach Strawberry (Fragaria chiloensis) or Yankee Point Ceanothus (Ceanothus griseus horizontalis ‘Yankee Point’), you can fill in the space between your larger shrubs and block sunlight from reaching the ground.  The way in which you water your garden also has an impact.  Use drip irrigation with emitters that only apply water to the root zones of the plants you want to grow, and you limit the water available for the weeds.  Lastly, the design should include the installation of a thick bark mulch layer in all planting beds.  This will reduce your weed problems by keeping sunlight from the soil surface where the weed seeds are trying to germinate.  Mulch also forces the weed to root in this loose material so that it is easier to pull.

Mechanical Weed Control

1.   Pulling  Weeds

Mechanical controls are techniques that involve tools and/or manual labor. Pulling weeds up by hand is the most common method.  It is most easily done when the soil is somewhat moist (but not saturated) and before the plant has gotten too big.   There are different weeds coming up at different times of year, so you have to keep an eye out for their growth patterns.  It is also very important to pull the weed before it has time to produce seeds.

Sometimes watering an area in advance is a good idea to allow for better weed removal.  You can take this further by “pre-sprouting” a planting bed, watering it thoroughly before planting and letting the weeds come up, then pulling them.   Other techniques commonly mentioned are hoeing and rototilling instead of hand pulling for large areas, but in most garden situations I think that stirring up the soil too much does more harm by bringing more weed seeds to the surface.

2.   Mowing

If you have a larger area and no time to hand pull, then at least cut the weeds down to the ground before they go to seed – many “lawns” are really just grassy weeds kept mown down.  This will keep things under control to some extent, but it is not going to eliminate all the weeds.   You will have to time things very well to prevent any of the weedy grasses from going to seed, but certainly there will be less seed added to the soil overall.  Mowing is also important in large areas near wild lands to reduce fire danger.

3.   Sheet Mulching

For big areas where you are starting from scratch, sheet mulching is one of the best options.  Basically you are laying down layers of compostable materials to smother all the plants in a given area and improve soil quality.  I’ve already talked about the details of sheet mulching, so refer to that for more information.

4.   Soil Solarization

An interesting option in areas with consistent sun is this technique where you put down a layer of clear plastic, seal the edges, and let the sun heat up the soil to kill weed seeds and other bad fungi and pests.  Read up on the details of this technique before doing it – you need a lot of sun, and you can’t leave it too long or it will start harming the beneficial living things deeper in the soil.  It also only kills off weed seed in the very top layer of soil, so be careful not to bring deeper soil to the surface, or you will have weeds anyway.

Herbicides

There is a lot of complexity to the options for herbicides – substances applied to the soil or the weed to eliminate it.  See Part Two for more on this subject.

Overall Strategies in the War on Weeds

If it all still seems overwhelming, consider the divide and conquer method, which I did when I started my garden.  Be realistic about your time and resources, and apply different methods to different parts of your yard accordingly.  I almost completely ignored the back edge of my property for the first few years, just doing a quick hand pulling of the weeds and mulching once a year, not obsessing about getting all the roots, just keeping things from going to seed.  In front of that I laid down a 6 foot wide strip of plastic sheeting topped by bark mulch to create a sort of “battle line”.  Then I simply mowed the center part of my yard for a few years to keep things from getting too out of control, eventually applying cardboard sheet mulch.  That left me with relatively smaller side beds and areas closer to the house for hand pulling of weeds.

After 5 years, I can definitely say that there are less weeds for me to worry about, so do what you can, and don’t despair!

References:

Golden Gate Gardening, by Pam Pierce

Bay Friendly Gardening Guide, https://rescapeca.org/wp-content/uploads/2016/01/Bay-Friendly-Gardening-Guide.pdf

Gaia’s Garden – A Guide to Home Scale Permaculture, by Toby Hemenway

The New Sunset Western Garden Book, published by Sunset, www.sunset.com