JOHN’S CORNER: NUT SEDGE CAN DRIVE GARDENER NUTS!
by John Ferguson
Questions from readers:
On 8/3/2016 3:56 PM: a reader wrote:
I read the lazy gardener newsletter and read all the books you recommend. I have gardened organically successfully for 35 years until 3 years ago. I have never used insecticides or herbicides and only used your compost and micro life fertilizer. The past 3 years I have been overrun with nut sedge. I have tried molasses drenches with no success. I have dug the nuts days, weeks and months on end. Every time I go to the nursery and ask for help they recommend roundup, image or sedge hammer. I have refused to use these products based on toxicity.
Do you have any suggestions for me? Thank you for any insight into this overwhelming problem.
ANSWER:
Nut sedge has been a major problem this year as the massive amount of rain created ideal conditions and spread the seeds everywhere. This includes my front lawn, which was under floodwater but had not had nut sedge in over 20 years. I have very healthy fertile soil, hence I have not needed to water my lawn in 3 years, and the nut sedge is now slowly disappearing. There are a few cultural controls:
General:
- Nut sedge grows geometrically from the roots. On week one you have one plant, by the second week there are five plants, the third week there are 25 plants, week 4 there are 125 plants, etc. Never let it go to seed or you will have hundreds of plants to deal with. Prevention is the key, never let it become established.
- Do not water as nut sedge loves moist soil. The best way to start to eliminate nut sedge organically is to eliminate the conditions that are causing it to thrive – poorly drained soil.
- Do not use water-soluble fertilizers as nut sedge loves nitrate.
- Aerate the soil if needed, as nut sedge tends to grow better in soils with low oxygen.
- Like all plants, especially the ones we classify as weeds, it has a role in nature and is trying to do something. If we change the conditions then it cannot compete as well.
- In the book “The Organic Lawn Care Manual”, Paul Tukey notes that nut sedge is a sign of low calcium levels; so have your soil tested and add lime, wood ash or greensand as recommended. Everyone agrees that this weed thrives in anaerobic (low oxygen) soils. Paul recommends using compost tea to introduce more life to the soil; Howard Garrett prefers liquid molasses. Feeding with bulk compost will help.
- Animals like ducks, geese and guinea hens will unearth and eat the tubers for you.
- Eat the nuts! The tubers of yellow nutsedge are so edible the plant is known as the “Earth Almond” and its grown professionally. One source says they taste like almonds; the USDA says “between fresh coconut and raisins”.
- Solarization – In case of extreme sedge weed infestation, solarization is a powerful option that will kill everything growing within the given area. By wetting the sedge area and covering the space with black polythene plastic sheets during days of hot sunshine, the combination of heat and suffocation will complete destroy plant matter beneath the sheet. Most bulbs and sedge seeds will remain unaffected by this process and further sedge weed control will be needed.
- The best control for nut sedge appears to be molasses, believe it or not. Drench problem spots with liquid horticultural molasses at ¼ to ½ cup per gallon of water. Start with about a gallon of drench per 9 – 10 sq. ft. This simple technique fires up the microbes in the soil and the nut sedge simply fades away. It takes a while to work and requires at least 2 – 3 applications. As opposed to toxic chemicals, it makes the soil healthier with every application (Howard Garrett website). Note: Research has shown that nut sedge does not like sugars, especially complex sugars found in molasses.
- Dry molasses consists of organic material, such as soy meal, that is sprayed with liquid molasses. It provides a carbon source, which triggers beneficial microorganisms to decompose organic matter in the soil (including nutgrass tubers) at an increased rate. For effective control the dry molasses used to control nutgrass should have a 42 percent sugar level. Dry molasses applied with a drop spreader at a rate of 20 pounds for a 1,000-square-foot area helps kill nutgrass. This treatment should be repeated 14 days later. Control individual plants by sprinkling a handful of the dry molasses on each one.
- If you continue to remove the new plants before they have a chance to replenish the reserves you can eventually starve and kill them. In order to do this, remove nut sedge plants before they have 5 or 6 leaves. This means eradication of any visible plants a minimum of once a week. Up to that stage new side tubers have not yet had time to form. The USDA says almost 60% of the energy is stored in the nut is used in the first sprouting. Another 20% in the second sprouting, IF the nut sedge is not allowed to grow and recharge the nut via sunlight.
Lawns:
- If the grass is cut high (at least 4 inches) then the grass St Augustine or Bermuda will tend to choke it out over time. On my mower I drilled holes in the frame about one inch higher that the highest factory setting and inserted a sheet metal screw for the “stop”. This allows me to grow taller grass. In nature, St. Augustine will grow 15-18 inches tall. When we cut it short, the grass becomes stressed and cannot compete as well.
- A couple times this year I waited till the St. Augustine was 8-10 inches tall before mowing so it would shade and choke the nut sedge.
- If there is only a small amount, one can take an eyedropper with agriculture vinegar and let a few drops run down the nut sedge stem where it can reach the roots and nut. This is tedious but does work.
Flowerbeds:
- Smothering can be effective. Sheet of cardboard from scrap cardboard boxes laid down between plants and covered with 4 inches of mulch. Without light the nut sedge will die. Note: If the cardboard becomes wet, the nut sedge will punch right through the cardboard and mulch.
- Shading – nut sedge needs lots of light. If they cannot get enough sunlight, they tend to die out, as they cannot compete. Let your landscape plants become very full and do not prune until the nut sedge has died off.
Chemical:
- Never use Round-Up as it creates soil conditions that favor nut sedge
If any reader has other organic methods that has worked for them please let us know.
