by Birgitt Evans, ABG Board member and Master Gardener
Using black paper mulch
It’s late May and most of the garden has been planted out. The next step is to keep everything alive and growing. There are two parts to this. First, it is important not to let other plants grow over everything and compete with the vegetables for water, light and nutrients. The second is to prevent animals from consuming or otherwise badly damaging plants.
Let’s start with competing plants, because they are simpler to tackle, if not less time consuming. We call something a “weed” when it grows somewhere we don’t want it. Beautiful, beneficial flowers such as calendula and borage produce lots of seeds and will easily replace themselves and then some. Are they weeds? Weeds also tend to be fast growing opportunists and so they will out compete vegetables for the above mentioned water, light and nutrients if the gardener doesn’t do something about them.
Over the past decades, chemical companies have created a variety of herbicides, many of which are highly toxic, to control weeds in fields. It turns out that weeds are highly adaptive and, even the herbicide we were told was “safe” – glyphosate – selects for toxin resistant weeds. In addition, most of these herbicides are toxic to humans to differing degrees. For instance, Atrazine is a potent endocrine disruptor found in 94% of U.S. drinking water tested by the USDA and Glyphosate is a carcinogen.
And so, let’s talk about physical methods for weed control. The easiest is to hand pick the weeds, ideally before they go to seed. At that stage they can go in the compost pile or be left on the ground to block light to other weed seeds and prevent them from germinating. If pulling weeds that have already gone to seed, put them in the green bin. If you have the space between plants, you can use a hoe to remove weeds. You can also prepare a bed, water it and wait for the weed seeds to germinate and then remove them without turning the soil and plant your crop. Chickens can also be let loose in a bed after harvest or before planting to eat weeds and insects. Keep them contained though or they will damage other plants.
Mulching the soil to keep light from weed seeds will prevent them from germinating to begin with. There are many forms of mulch. A good option for rows between beds is black plastic weed block that allows water to penetrate. It is made from petrochemicals, but I have some that shows no signs of deterioration after ten years of use. Alternatively, you could use wood chips or other organic matter on the paths. They will eventually break down into humus. However, weed seeds will germinate in wood chips. Around the vegetables, you can lay down a paper mulch before planting and then make holes in it to plant tomatoes, peppers, brassicas etc. It will break down into the soil by the end of the season. For plants like beans and root crops that don’t lend themselves to this, use a light straw – not hay – or leaf mulch.
Moving on to the animals, I dislike the terms “bad bugs” and “pests”. Both make a moral judgement about the value of organisms from a very limited human viewpoint. For instance, did you know that many bird species, including seed eaters, feed their chicks up to 70% caterpillars? No caterpillars, no birds. And yet, from the perspective of vegetable gardening, caterpillars can do a lot of damage to plants.
All organisms – with the exceptions of non-native invasive species – evolved in balance with all the other animals and plants in the ecosystem. All eat something and are, in turn, food for something else. It is only when things get out of balance that they do excessive damage to the vegetable garden. And so, it is the job of the gardener to provide food, water and shelter for the things that eat our plants so that they can, in turn, control pests for us. It is likewise important to step away from the ideal of “perfect produce” which is realistically only achieved by the use of excessive chemicals and culling of a significant portion of the harvest before it reaches the grocery store.
Alright, I understand that I lost a lot of people there who just want to stop the insects from eating their plants. So let’s talk about some ways to minimize damage until the birds and carnivorous insects show up in numbers sufficient to protect your plants. First, you need to know what is causing the damage. You may be able to see scale, aphid and spotted cucumber beetles on your plants, but more often, you will need to turn over the leaves or look in the soil around the plants for the culprit or go out at night with a flashlight to catch nocturnal feeders. And keep in mind that birds could be the culprits as well. To help, use the University of California diagnostic key. Only when you have identified the problem can you work out a solution.
There are certain invasive pests such as snails that will devour a garden before it gets going. For snails and slugs, a combination of hand picking and trapping will lower populations significantly. Hand pick after 10 PM at night in a garden that has been watered. You can also set out boards, pots or other objects in the garden for snails and slugs to gather underneath and then collect them that way. Some people throw salt on snails, but that seems cruel to me. I step on them or, better yet, take them to a friend with chickens or ducks thus converting snail biomass into egg biomass. In conjunction with hand picking you can sprinkle iron phosphate bait lightly on your cleared planting bed. Baits will help, but not wholly contain a bad infestation on their own.
Serious infestations will often need more than one tactic to reduce damage. We call this Integrated Pest Management or IPM. For example, aphids, scale and white flies produce a honeydew that feeds colonies of Argentine ants which protect them from predators. A stream of water will dislodge the aphids or scale, but you will also need to exclude the ants from the plant to keep them away. A sticky substance such as Tanglefoot applied over cardboard to the trunk of a woody plant will keep the ants from bringing more aphids. Alternatively, plant susceptible plants such as brassicas in the fall when aphids, scale and whiteflies (along with white cabbage butterflies) die off and you won’t have to deal with these pests.
You can also use floating row covers to exclude herbivorous pests, at least until the plants are large enough to sustain some damage. In general, use the least toxic method first. Sprays, even organic ones, will kill more than your intended target and may kill the ladybug larvae that were coming to eat your herbivorous pests. They should be used as a last resort.
For an array of solutions, refer to the UC Pest Notes. They have compiled 4 – 8 page notes on virtually everything that could be affecting your garden from aphids to voles and each one contains information on identification, life cycle, damage and management of the organism.
With a little elbow grease, investigation and ingenuity, you can overcome both plants and animals that might harm your crops and harvest a bountiful crop from your vegetable garden.