“One simple hack that will make your apple tree double its crop.” “Hack” is the latest buzzword that saves you having to think of an appropriate noun. Gardening hints like this appear in swarms on the internet. Some come from reliable sources and the free garden advice they give is a valuable aid to gardeners faced with a problem. But not all such advice is trustworthy. While some tips are just ineffective, others are actually harmful. Applying them can be a gamble.
At times you’ll find hints as charts, infographics, or accompanied by pretty pictures. Graphics make them seem more reliable somehow. Novice gardeners have no previous experience to fall back on and don’t see anything wrong with the hint. But even experienced gardeners can be looking for answers to simple questions and jump at tips that could save them time or money.
It’s frustrating to pin your faith on a piece of advice and have it fail you.
5 Examples of Free Garden Advice That Falls Short of its Promise
Like so many other gardeners, I have been caught out by some of the tips that circulate the internet. Some seemed feasible so I didn’t bother to check them out. Others – well, they came from a normally reliable source, or I simply didn’t bother to think them through. Here’s a sample.
1. Use Broken Eggshells to Keep Slugs and Snails Away
The idea of spreading broken eggshells around my young beans to stop slugs and snails in their tracks certainly didn’t ring any warning bells. The sharp edges of the eggshells would surely discourage any adventuring slug and send it in the opposite direction… wouldn’t they? The answer is “No!” I had dutifully spread broken eggshells around susceptible plants and was disappointed to find that my treasured plants still got eaten and that that piece of free garden advice was a frustrating failure. Other gardeners have had similar experiences. See the experiments that All About Slugs conducted (plenty of pictures)
Takeaway Message: A barrier of broken eggshells doesn’t stop snails from reaching a plant
Why did the eggshells fail to stop the invaders? What didn’t this seemingly helpful free garden advice take into account? You will have noticed how slimy these creatures are. That slime not only protects them from drying out but it also allows them to crawl over rough and sharp objects. Eggshells present no barrier to them. Watch this slug crawl over a razor blade:
2. Bury an Egg Under a Tomato Plant
I should have realised that this piece of free garden advice wouldn’t work, but I simply didn’t consider the pros and cons. I had some eggs that were well past their “use by” date, but not rotten, and put them aside to bury under plants. The dog found them and had polished off several before I noticed but I still had half a dozen or so to use. I decided that they should go into containers, where plants use up nutrients quickly. I buried some eggs whole and punctured the shells of others.
Late in autumn I emptied the containers, removing the soil as well as dead plants. I was surprised to find some whole eggs (I took care not to break them at that stage). Where I had buried the eggs with punctured shells, I found broken shells and some unpleasantly smelly soil. Belatedly, I remembered that eggshells, even broken ones, take a long time to break down. (In the worm bin, finely ground eggshells disappeared relatively quickly but broken ones, even small pieces, were still visible many months later.) After a summer in the ground, a whole egg was slightly stained from the soil. The contents of the shell would eventually decompose but needed more time.
This hint doesn’t work in a growing season. My advice, based on this experience, is to eat your eggs and feed your plants with compost or an appropriate organic fertilizer.
3. Growing Seedlings in Eggshells
This tip has come to the fore in recent times. The idea is to plant a seedling in half an eggshell. When the seedling is big enough for the big, wide outdoors, you pop the whole thing into the ground without disturbing the roots. The shell breaks down and provides calcium for the plant.
When I first came across the tip, I thought it was cutsey but I didn’t see anything wrong with it – I’m too apt to take suggestions like that without thinking them through. I tried the idea with one seedling and soon realised that it had problems:
- There was no drainage (I don’t remember whether I added some drainage holes). The volume of soil in half an eggshell is very small, so it was difficult not to add too much water. With no drainage holes, the soil would be soggy until some of the water evaporated.
- Planting the seedling without first removing it from the eggshell is not good gardening practice. Eggshells take a long time to break down, so the young roots could not grow into the surrounding soil. This could stunt the growth of seedlings, especially plants of naturally small size.
- I had difficulty getting the eggshell pot to stand so that the plant was upright. What do other people do? Use egg cartons? Put the eggshell pots into egg cups?
This could be a fun idea for preschool classes but as an efficient way to grow seedlings I don’t rate it.
Takeaway message: Eggshells don’t make good seedling pots. Peat pots or pots and punnets that nurseries use are far more practical. Use them.
Incidentally, studies have shown that pieces of eggshell do not add calcium to the soil, although finely ground eggshell will do so if the soil is acidic. See Crushed Eggshells in the Soil
4. Cover Drainage Holes in Pots
This piece of free garden advice is an oldie: place a layer of gravel or pieces of terracotta, or both, in the bottom of a pot to improve drainage. This covering helps the water to drain out more freely, preventing soggy soil from collecting at the base of a pot. If I remember rightly, I first heard that from my mother. I’ve read it time and time again. I’ve done it… sometimes. It seemed reasonable, though, and I believed it worked but there are a lot of gaps in my knowledge of physics.
So, does gravel (or pieces of terracotta) in the bottom of the pot assist drainage? No. On the contrary, a layer of coarse material hinders the movement of water.
Linda Chalker-Scott, an associate professor at Puyallup Research and Extension Center, Washington State University explains in her book, The Informed Gardener, that water won’t drain from a fine soil to a coarser material such as gravel until the fine soil becomes saturated. That, of course, is the opposite effect to the one the gardener wants. Strangely, soil scientists discovered this phenomenon nearly a century ago but the myth is still alive and well.
Takeaway message from this is: fill your pots with your chosen potting medium and leave the drainage holes to do their job.
5. Apply Wound Dressings to Pruning Cuts
The purpose of wound dressings is to protect the wound from fungal infection or insect attacks. This was common practice when I started gardening. I remember people carrying around jars of grease for the purpose. Arborists seemed to prefer paint for the job. I learned that Vaseline (petroleum jelly) worked just as well as the commercial preparations. Then came the advice that tree wounds needed no dressings – they would heal themselves. I took the line of least resistance and sided with the “no dressing” faction.
To this day, some “authorities” advise you to dress tree wounds. Linda Chalker-Scott comments in The Informed Gardener (p.198) that those people usually have something to sell and she offers examples from the Internet. Wound dressings are not needed, she continues: they can in fact, be detrimental to the tree’s welfare. For instance, they can seal in wetness and decay, or provide food for pathogens. Who would want to do that to a poor tree from which a limb had just been severed?
The outcome of this dispute: practice good hygiene, using clean tool when you prune, do the work on a day when humidity is low, and let the tree recover in the natural way, without human interference.
5 Examples of Free Garden Advice that I Might Have Followed but Didn’t.
Here are five more pieces of advice given to gardeners but for various reasons I haven’t used them.
1. Use Coffee Grounds to Acidify Soil and Keep Slugs at Bay
How many times have you read that coffee grounds will keep slugs away from your plants? Some even say that coffee grounds will kill slugs. They don’t. Studies have shown that a concentrated caffeine spray will kill slugs and snails but coffee grounds contain very little caffeine: coffee grounds don’t even deter slugs, as Robert Pavlis demonstrated. It’s easy to see that coffee grounds are harmless to slugs and snails once you know that the grounds are low in caffeine and the animals’ slime protects them from rough and sharp objects.
So, with coffee grounds fallacy #1 under our belts, let’s see if the grounds will acidify soil, as we’re so frequently advised. It’s a known fact that coffee grounds are only mildly acidic and their pH changes as they decompose. So, as you probably guessed, coffee grounds won’t acidify the soil around you azaleas or turn your hydrangeas blue. They don’t make a good mulch either, because they can compact, making it difficult or impossible for water to penetrate. You’ll find a much fuller discussion of this in a PDF by Linda Chalker-Scott
Can you keep slugs and snails from your prize Hostas by surrounding them with coffee grounds? No.
2. Add Epsom salts to the bottom of the planting hole when planting tomatoes
I’ve seen this advised for peppers and some other plants as well as tomatoes. It’s been claimed that Epsom Salts (magnesium sulphate) will make the plants healthier, the fruit larger and most of all, prevent blossom end rot. If your soil has insufficient magnesium and sulphur, then Epsom salts could help. You won’t know this unless you have a soil test. If you add organic material such as compost to your garden, your soil is unlikely to magnesium or sulphur.
If you don’t add Epsom salts to the soil, how do you prevent blossom end rot? Well, you might do this simply by not adding Epsom salts. The story that magnesium sulphate will prevent the disease is just that – a fictitious story. Blossom end rot has been attributed to a calcium deficiency in the fruit but Epsom salts is a source of magnesium, not calcium. A Clemson Cooperative Extension report on the subject of blossom end rot advises growers not to use Epsom salts unless the results of a soil test recommend it.
Does Epsom salts make tomato plants grow better? No. And Robert Pavlis tells us also that the product does not fight plant disease or pests either.
3. Use Landscape Fabric or Weed Cloth for long term control of weeds
These products are made of plastic mesh, which manufacturers claim will control weeds. Weeds sprouting under the fabric can’t grow through it and neither can they survive on the upper surface, which you cover with a thin layer of dry mulch. So far, so good. But let’s see what really happens when you install this form of weed control.
- Perennial weeds in the ground under the mulch will before too long find a way through or around the mesh.
- Before long, the mulch will compact and ends of mesh will poke though. You can imagine how unattractive that is!
- Over the seasons, the much breaks down further, dust, leaves and other organic matter collect, decompose and fall through the mulch. That means there’s a thickening layer of compost and soil down there waiting for weed seeds to land – which they do. So, as well as perennial weeds pushing their way through, you have a top layer of weeds that have grown from stray seeds.
- Do you think I’m exaggerating? The backyard of the house where I am now living has weed mat in one area. The top mulch layer was gravel, a little smaller than pea size. In some places it is hidden by weed growth. I’ve tried hand weeding but some of the weeds have their roots entangled in the mesh and I can’t remove them. Lamium from a border is pushing its way through the mesh in places and elsewhere the mesh, especially frayed pieces, is sticking up through either gravel or weeds. Not a pretty sight!
- Once you get a build-up on top of the mesh, air and rain have difficulty reaching the soil underneath. If you have ornamental plants growing nearby with roots growing into the soil under the mesh, the plants will be short of water and nutrients.
The plastic mesh is not organic. It will sit there, not doing its job, until someone lifts it. With the accumulated matter on top of it, that becomes harder worker as each year passes. For more, see Busted: 4 gardening myths revealed
What’s the alternative? Organic mulches, such as wood chips.
4. When a tree gets too big it should be topped
Topping involves taking a chainsaw to a tree and cutting back the leader and scaffold branches (main upper branches) to stubs of the same height.
It sounds brutal and it is. Fortunately, many people don’t mean the above form of cutting when they ask for topping but others do know what it entails and shrug off the ugly result by commenting that “it’ll grow back.” It won’t. The tree is maimed for life.
Many years ago in my inexperienced days, I planted a Red Beech (Nothofagus fusca) in an unsuitable position, though I didn’t realise that at the time. Red Beech is a large forest tree. I like the foliage and the young tree looked amazing in the garden. The information on the label stated that the tree would grow to 4 metres. It grew slowly and took maybe ten years to reach that height. Then it kept on growing… and growing. It became entangled with the power lines and I had to do something.
I asked a tree surgeon to top it but he refused, saying that my only option was to remove the tree. The tree was magnificent but, sadly I agreed. The cost of removing it was more than I could afford. There’s a lesson to be learned from that experience: make sure you choose a suitable species for a specific place.
No reputable arborist will undertake the work of topping. Why?
- It weakens the tree. Topping removes the canopy and much of the food production area of the tree.
- The tree sends out multiple water spouts from below the cuts. These are vigorous, upright, unattractive branches. While the tree will return to its previous height, it won’t regain its former shape.
- Topping disfigures the tree. An unappealing broom-like growth replaces its natural form. Dead or ugly living stumps remain visible. Only years of expert pruning can restore its form and some of its former beauty
- A topped tree can form weak branches and become a hazard to people and property. If so, it is a legal liability to the owner.
- The wound caused by the topping are large and slow to heal. This leaves them open to attack by insects or disease, which could kill the tree.
Is there an alternative to topping?
- Choosing a tree that will grow to a suitable size is the obvious way to avoid topping but sometimes mature trees are part of the deal when you buy a property.
- There is a pruning alternative known as drop-crotching that will reduce a tree’s size. You can find out more about drop-crotch pruning and this whole topic from the Virginia Cooperative Extension
- If you have young trees, have them pruned correctly to avoid problems in the future.
- You can sometimes dig out relatively young trees and move them to another part of your yard or sell them.
Takeout message from this: topping a tree is a brutal act that maims it for life. Choose a kinder form of pruning instead. Better still, avoid planting the wrong tree in the wrong spot.
5. When you plant a tree or shrub, you need to amend the backfill
Amending the backfill means adding fertilizer or organic material to the bottom of the hole and the soil you have dug out to make the hole. Many garden books and website advise you to do this but there are scientific reasons why this is not good practice. Initially the more nutritious soil will benefit the new plant but soon it will encounter some or all of these problems:
- In dry weather, water will wick from the coarser filling material to the finer native soil around the hole. This means that the hole will dry out quickly and the plant will we short of water.
- The finer soil around the hole drains more slowly than the filler soil, so the latter will become soggy with water that won’t drain away. As a result, the roots might die.
- Once the roots of the new tree or shrub grow, they will reach the edge of the amended soil and find that the native soil around it has fewer nutrients and it harder to penetrate. Roots can start to grow around in circles instead of outwards: in effect, it becomes potbound.
- After a few years the organic matter in the filling hole will have decomposed and the level of the soil around the plant will sink. This allows water to collect and flood the roots.
Not a pleasant prospect for the plant, is it? Like me, you probably thought that feeding a new plant would help it to settle in better and grow well. Unfortunately our reasoning is incorrect. So what do we do?
The answer is simple and involves less work: backfill with soil you dug out and add the organic matter as a topdressing. It’s easy to do this annually if the soil needs it. Of course, if you want to dig in organic material over an extended area before you plant the tree, that’s a different matter. My information comes from Linda Chalker-Scott and you can read more or the topic in this PDF or in her book, The Informed Gardener.
Message from this: amending the backfill soil does not help a new tree or shrub. In fact it can be detrimental to its growth. Instead, you can add organic matter as a topdressing.
The widespread circulation of free garden advice on the internet has led to gardeners receiving well-meaning but incorrect or useless information and often passing it on to “help” others. Presumably they haven’t waited to test it. Even experienced gardeners can be using this spurious advice without realising that it isn’t doing the job. In most cases that’s harmless, though it’s stopping them from using something more effective instead.
Here is a list of the gardening tips that I have discussed. Most of them have scientific studies or reasoning to show that they aren’t effective. The rest have failed informal tests.
1. Use broken eggshells to keep slugs and snails away. Serious, though not scientific tests have shown that slugs and snails aren’t stopped by eggshells.
2. Bury an egg under a tomato plant to provide extra nutrition. Eggshells don’t decompose quickly enough for this to be effective
3. Grow seedlings in eggshells and plant shell and seedling together to provide extra nutrition and to avoid root disturbance. Lack of drainage is a problem here and eggshells don’t decompose quickly enough for the seedling’s roots to grow outwards. Its slow decomposition means that little or no extra calcium is provide
4. Cover drainage holes in pots. This does not, in fact, assist with proper water retention and drainage.
5. Apply wound dressings to pruning cuts. This policy can actually be detrimental to a tree’s health and recovery.
6. Use coffee grounds to acidify soil and to keep slugs and snails at bay. There is evidence that coffee grounds do neither of these.
7. Use landscape fabric or weed cloth for long term control of weeds. Don’t be deceived by manufacturers’ claims. The products don’t do what is claimed.
8. Add Epsom salts to the bottom of the planting holes when you are planting tomatoes. University scientists have discredited this practice.
9. Top a tree when it gets too big. This practice results in ugly or sometimes dead trees. You should never top a tree.
10. When you plant a tree or shrub, you need to amend the backfill. While this appears to be a helpful practice, it is in fact detrimental to a plant’s welfare.
I hope this helps you to avoid unproductive practices in the garden. I’m sure you have better use for your time and money. I’ve tried many of the hints that turn up on websites and social media and been taken in by some of them. But there are a lot of good ideas to try out. I hope you find what you want.
Please pass this on to gardening friends. And don’t forget to show your approval on social media sites. Thanks a million.
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