Some fall leaves provide color to a green carpet of of moss growing in the lawn.The Oregonian/Oregonlive.com
Reality can be skewed when there are a lot of places to get it. Books, magazines, newspapers, nurseries, and especially the internet and social media leave a lot of room for disagreement. So, how do you find the right answer for gardening questions?.
Nine experts from Oregon State University Extension Service stepped up to bust some common gardening myths. Read on to get some research-based answers to 10 common misconceptions.
REALITY: Trees are programmed to attain a certain height. Topping only temporarily delays the inevitable. The resulting sucker growth, which grows quickly to try to feed the damaged root system, is only loosely attached. This creates an even greater hazard. The trunk is also not a limb, so it can’t use the tree’s architecture and physiology to heal the wound caused by topping. This often leads to a slow death for the tree. – Al Shay, horticulturist and site manager for OSU’s Oak Creek Center for Urban Horticulture.
REALITY: Lime will not fix the problem. Moss prefers to grow in wet, shady conditions. Lawns with moss need more sunlight, i. e. trimming, pruning and thinning trees. If you like the trees the way they are, you will still have moss, but you might want to think about grass alternatives that can handle being in the shade. It also grows well in soils that aren’t good for plants, like those that are acidic (low pH) or, more importantly, don’t have enough nitrogen. Lawns, like a lot of cultivated plants prefer nitrogen-rich soils. Applying nitrogen-based fertilizer four times a year—two times in the fall and two times in the spring—and making sure the grass gets more sunlight will create a green, dense lawn that can beat moss. – Alec Kowalewski, OSU Extension turf specialist.
TRUE: For years, people have said that pine needles change the pH of the soil so that nothing can grow or that they hurt plants. The truth is pine needles do not make the soil more acidic. It is true that pine needles have a pH of 3. 2 to 3. 8 (neutral is 7. 0) when they drop from a tree. If you mix the newly fallen needles into the soil right away, the pH level may drop a little, but the plants would be fine with that.
If you leave the needles on the ground, they will break down on their own, and microbes (decomposers) in the soil will get rid of them. So, you can leave them there (if you’re not in a wildfire prone area). They make good mulch because they keep water in, keep weeds down, and eventually add nutrients back to the soil. You can also add them to a compost pile; they will slowly break down over time. If you run them through a shredder they will break down faster. There is a general rule that says you shouldn’t add more pine needles than 2010% of your compost pile.
If you can’t get other plants to grow under your pine trees, it’s probably because the evergreen roots are so many and shallow that they compete for water and food. The shady conditions under a tree can also make growing other plants a challenge. – Amy Jo Detweiler, OSU Extension horticulturist.
REALITY: Adding organic matter to soil in the form of compost makes the soil better and helps plants stay healthy over time. However, adding too much compost at once or over time can cause problems. As long as the percentage of organic matter in the soil is much higher than the ideal range of 5 to 8 percent, the soil may have too much phosphorus, which can slow plant growth and possibly leach into the water table. Also, some composts can be high in salts, which can also impact plant growth. – Weston Miller, OSU Extension horticulturist.
REALITY: Some types of bees nest in holes made by bee houses, but most types of bees nest in the ground. Canadian research shows that most of the holes in bee houses are filled with native wasps, which help get rid of pests, not native bees. So, bee houses still do good, but not necessarily the good that you might think. – Gail Langellotto, OSU Extension entomology specialist and state coordinator of the Master Gardener program.
MYTH: A tree’s roots only go as far as the height or diameter of the branch crown, also known as the drip line.
REALITY: Many trees extend many times beyond the branch crown diameter. For instance, magnolia extends 3. 7 times the diameter; red maple 3 times; poplar 3; locust 2. 9 and ash 1. 7. – Steve Renquist, OSU Extension horticulturist.
If a soil test shows that your soil doesn’t have enough magnesium and your plants aren’t growing well, try this. But in most soils and gardens, it can do more damage than good. – Steve Renquist, OSU Extension horticulturist.
MYTH: Before you fill in the hole to plant a new tree or shrub, you should dig it and add something to the soil.
REALITY: Adding organic matter to the soil is often a good idea, but it should be done all over the area, not just in a planting hole for one plant. Putting an organic matter into the soil only where you plant will probably slow the plant’s growth. This is because roots might stay in the amended soil and not grow into the native soil, which would keep the plant from growing roots in the amended soil. If the organic amendment isn’t broken down all the way, it may need nitrogen to break down even more. This will make plant roots compete for minerals, which will slow their growth. When the amendment breaks down, it will cause the plant to settle, and the root collar will sink below the soil. This will happen to large shrubs or trees. – Neil Bell, OSU Extension horticulturist.
People often think that the hobo and brown recluse spiders in this state cause necrotic bites, but the brown recluse doesn’t live here and the hobo spider doesn’t do that either. The hobo spider was taken off the list of poisonous spiders by the Centers for Disease Control and Prevention in 2015. The black widow is the most harmful spider to humans in the state. – Heather Stoven, OSU Extension entomology specialist.
MYTH: Watering on hot sunny days will burn the plants because the water droplets magnify the sun’s rays.
REALITY: It rains during the summer all around the world and plants are just fine. More of an issue is that the irrigation water will evaporate and not be as effective. Keep in mind, though, that very cold water on the leaves of sensitive houseplants like African violet can hurt them. – Brooke Edmunds, OSU Extension horticulturist.
Moss is a common problem in many lawns, especially those that are shady, compacted, acidic, or frequently wet The velvety green moss may look attractive at first, but over time it can take over and crowd out grass. This leads homeowners to ask does applying lime to raise the pH kill off the moss?
The short answer is no, lime does not directly kill moss already growing in your lawn However, adjusting soil pH with lime can help create an environment less favorable to moss growth Along with other cultural practices, liming is part of an integrated moss control plan.
How Does Lime Affect Moss?
Lime, also known as calcitic or dolomitic limestone, is an alkaline material used to raise the pH of acidic soils. Moss tends to thrive in acidic conditions, so applying lime can make the soil less hospitable for moss over time. However, it does not actually kill established moss.
There are a few reasons why liming alone will not eradicate moss
- Moss lacks true roots, so a change in soil chemistry does not impact it directly.
- Moss gets its nutrients from the air and rainfall, not soil.
- Lime takes time to alter pH deep in the soil profile. Surface moss remains unaffected.
- Moss may persist even in slightly alkaline soils if other conditions are favorable.
So while liming creates unfavorable soil conditions that discourage moss growth, it does not kill moss immediately. Lime should be combined with other moss removal methods for the best control.
When to Lime for Moss Control
Liming can be part of an integrated strategy to get rid of moss and keep it from returning. The ideal timing depends on what other steps you plan to take:
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If using mechanical removal, lime after dethatching or hand raking. Dethatching exposes the soil so lime can reach it.
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If applying chemical moss killers, lime first. The higher pH enhances the efficacy of iron-based products.
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If overseeding bare spots, apply lime 2-4 weeks before seeding. This allows it to begin working before new grass starts growing.
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For general moss prevention, lime in early spring or fall. This gets soil pH adjusted before moss spore germination.
Liming is most effective as a long-term preventive strategy, not a quick moss cure. Have your soil tested to determine exactly how much lime is required. It can take months to see the full benefits.
Using Lime With Other Moss Controls
While liming alone will not kill moss, it works well with other moss removal methods:
Mechanical Removal
Vigorously raking or dethatching physically removes moss. Dethatching in early spring pulls up dead moss and thatch, allowing lime to reach the soil. Rake vigorously to remove every trace of living moss.
Chemical Products
Iron-based liquid moss killers work by drying out and desiccating moss tissues. Applying lime first raises pH, which improves the efficiency of iron. Follow label directions carefully.
Improving Drainage
Fixing compacted soil, adjusting sprinklers, and improving drainage deprives moss of constant moisture. Good drainage allows lime to fully penetrate and raise pH throughout the root zone.
Overseeding
Bare patches left after moss removal invite new moss growth. Overseeding crowds out moss spores by thickening up the lawn. Lime before seeding gives grass an optimal pH for germination and growth.
Adjusting Shading
Reducing shade by pruning overhanging trees or improving air circulation makes conditions less welcoming for moss. Lime corrects pH in areas that get more sun exposure after shade removal.
How to Apply Lime for Moss Control
Follow these steps for successful moss control through liming:
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Have your soil tested to determine the exact pH and lime requirement. Do not guess when it comes to lime.
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Choose pelletized lime or a pulverized powder form that can penetrate the soil.
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Time applications appropriately based on your climate and the moss control methods used.
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Apply at the recommended rate. Under-applying will not sufficiently raise pH. Over-applying can harm grass.
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Water lightly after liming to move particles off grass blades and into the soil profile.
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Allow adequate time to see results. It takes months for lime to fully alter pH. Be patient.
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Retest soil pH every 2-3 years to determine if additional lime is needed.
The Drawbacks of Lime
While liming has benefits for moss control, there are some potential drawbacks:
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Does not provide instant moss killing unlike chemical herbicides.
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Requires precise application based on soil test recommendations to work properly.
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May temporarily damage grass if over-applied due to alkaline burn.
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Frequent re-application is often needed as lime gets used up in the soil over time.
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Benefits are not seen until lime has time to sink in and raise pH below moss level.
Combining Lime With Aeration and Fertilizer
For best results, use lime alongside core aeration and fertilization. Aerating reduces compaction and helps lime filter into the soil. Fertilizing encourages healthy, dense grass that resists moss.
Choose a balanced fertilizer with ample nitrogen for greening and growth. Check that phosphorus and potassium levels are also sufficient according to a soil test. Correct any deficiencies along with adjusting pH.
The Bottom Line
Does lime kill moss? No, it does not kill established moss. However, liming does change soil chemistry to favor grass over moss. Correcting pH is one piece of a comprehensive moss control plan. Be patient, as it may take many months to see the benefits of liming.
Lime works best when combined with mechanical removal, cultural improvements, chemical moss killers, overseeding, and proper mowing and fertilization practices. A vigorous, healthy lawn is your best defense against invasive moss growth long-term.
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Does Lime Kill Grass?
FAQ
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