Summer Weed Management Strategies
Now is the time when those pesky weeds are really coming up full force in many gardens around the state, particularly if you have had rain in your area lately or have been sprinkler watering your garden. Generally, there is a “seed bank” or supply of weed seeds from previous growing seasons that are just waiting for the right growing conditions to germinate. If these seeds are near the surface from last year or brought back up to the surface from tillage, they will germinate and grow if they get moisture and exposure to sunlight. The easiest time to control them is while they are still young plants. It is much easier to go down a row in a garden to hoe through some seedling purslane before it has begun to creep along the ground and kill it than to wait until the weeds are larger and better adapted to regrow after being hoed out, for example. Seedling weeds have a very small, tender and shallow root system so they are easy to pull, hoe or cultivate out and chances are good that they will not regrow. Warm, sunny weather will give you the best chance for success since those weather conditions will more likely dry out and kill the dislodged and chopped seedlings. Avoid hoeing or cultivating right before a rain or sprinkler irrigation for best success as well.
Shallow Cultivation & Hoeing
Since more weed seeds may still be beneath the soil in your garden, it is a good idea to let them continue to be covered by the soil, which inhibits them from germinating to some extent. Therefore, using shallow cultivation or hoeing is often better than deeper tillage at this point in the season. Shallow cultivation near our vegetable plants is also less likely to damage the roots of those plants while still being an effective means of controlling young weeds. When vegetable and flower seedlings are still fairly small, hand weeding is probably the best approach but it is tedious work. I carefully work my way down the row, pulling out the individual weeds among the desirable plants. This is also a good time to thin out excess plants if needed, particularly in beets, carrots and other root crops. Weeding a clear strip about 4-6” on either side of the planted row is generally good enough. Then you can hoe the wider area between the rows without worrying that you are going to hoe out any of the vegetable plants. Hand cultivators or the old-fashioned high-wheel cultivators can also work very well. They will dig more deeply into the soil though, so they may bring up more weed seeds from deeper in the soil.
There are a number of different kinds of hoes. Most people are likely familiar with the rectangular shaped hoes. These often work best for digging holes for planting transplants or hoeing out larger weeds. The fact that the hoe blade is usually at about 90° to the handle makes them more difficult to use for shallow cultivation.
Small Bladed Hoes
I prefer to use a hoe with a smaller blade that is much wider than it is tall and also is mounted at less than 90° to the handle. This will facilitate making long pulling strokes to slice through the young seedling weed stems and roots while only digging about 1/2 to 1” into the soil.
Hoe with smaller curved blade.
Smaller curved bladed hoes work very well.
Stirrup, Oscillating & Scuffle Hoes
The stirrup, oscillating or scuffle style hoe works even more efficiently in that it can do the same thing both in the pulling and pushing stroke, so you can cover about twice the area in about the same time.
Scuffle hoe cuts weed stems and roots in both directions.
Oscillating scuffle hoe.
Sharpened, Diamond & Triangular Hoes
Sharpened, diamond or triangular shaped hoe blades can be used in the same fashion and work well for getting up close to plants. However, be careful, it is very easy to get a little too close and you have just taken out a nice bean or other vegetable plant.
Dutch Style Hoes
Dutch style hoes are also somewhat triangular in shape with the “cutting” edge on the lower inside of the triangular opening. It mostly cuts on the pull stroke. Making sure all of your hoes are good and sharp since this will also make them more effective and easier to use.
Dutch hoes work best in the pull stroke.
Rototillers are another popular means of weeding the garden. However, they probably should not be used until the vegetables are a bit larger, later in the season. It is very easy to bury small vegetable plants with soil thrown up by a powered tiller. That soil may smother young plants or it may contain diseased debris from last year that may then inoculate your young vegetable seedlings with the disease. So, consider hoeing the garden for the first round of weeding, then move to the rototiller for the next round of weeding if you wish.
Of course, mulches are a great option as well, as described in an earlier article. Mulches help to keep down weeds by shading the soil, reducing the chances that seeds can germinate and grow. Straw and grass clippings are probably the most common types of organic mulch but you have to be careful not to use any materials that might have been treated with a broadleaf herbicide. Otherwise damage to sensitive plants like tomatoes and potatoes is likely to occur.
Some people might be tempted to use herbicide in the vegetable garden to control weeds once their vegetables are growing. While this might seem like a quick and easy way to kill those little weeds, you could do much more damage than good, especially if you try to use something that is not labeled for use in a vegetable garden. Potatoes and especially tomatoes are especially sensitive to spray drift from broadleaf herbicides that have active ingredients like 2,4-D. They cause malformation of leaves, stretching of veins and curling of petioles and stems (see photo). Many herbicides are not very selective in what they kill and in some cases, are non-selective, meaning they will kill or damage pretty much anything that they come in contact with. The fact that we intend to eat our vegetables makes this issue much more important. If a vegetable crop is contaminated with a non-registered herbicide that produce should not be eaten, even if the plants look like they “grew out of” the damage caused by the herbicide application or drift. Testing has not been done to know what a safe level of herbicide residue in fruits and vegetables is for these products.
Crabgrass seedlings are also now showing up in lawns and around garden beds too. It is generally fairly easy to identify them by their wider and lighter-green colored leaves. It will often show up in bare areas in lawns or along garden beds. Many weed and feed lawn fertilizers contain crabgrass preventers. If one if these products was applied earlier this spring, before the seed started to germinate, that should have greatly reduced the amount of crabgrass that germinated in your lawn in the last few weeks. But, if you are still seeing crabgrass seedlings showing up in your lawn, you might still be able to control them if they are still at a young enough age.
Look for a lawn herbicide that says it will provide post-emergence control of crabgrass on the label. It will likely state that it contains the herbicide quinclorac but there are a few other active ingredients in different products available as well. Follow the label to see how to safely spray them over lawn grasses to kill the crabgrass without damaging the desirable lawn grasses. Once crabgrass grows to a point where its stems begin to sprawl along the ground, root down and produce seed heads, there really is no effective treatment that can be used. It is best to remember to apply a crabgrass preventer to those areas of the lawn to prevent those weed seeds from germinating next spring.