Crimes Against Horticulture – Landscaping Mistakes to Avoid

In the landscape business for over 25 years, I have seen it all. I have worked for large landscape businesses and now run my own landscape design/build service. Meeting with many clients over the years, working on large estates to small courtyard jobs, I feel that I have observed every mistake in the book before I enter the picture and meet with a client.

Sloppy Pruning

Correcting those mistakes, I have learned a lot of things not to do. Sloppy, inept pruning is the most prevalent mistake, even from so-called “professionals”.

Sloppy pruning: In pruning this tree, there are lots of surface cuts in the bark leading to disease entry
More sloppy pruning; Exposed and sloppy stubs and cuts in the bark! Awful!
Hacking off the top of a crape myrtle

From these experiences I have compiled the most common landscape mistakes that I see at clients properties – mistakes done by other landscaping companies or just regular homeowners.

Leaving tags on a planted shrub is a big no no. This tag was left on for years, girdled the trunk, and after removal of the shrub still remains on the stub.

Planting Incorrectly

By far, the most common mistake is planting incorrectly or more commonly too deeply. Normally, you would plant at the same level as the container that the plant is potted in, but sometimes, as in the case of a tree or large shrub, the plant is already planted too deep in the nursery pot. Nurserymen sometimes pile soil in the planting container too high around the trunk, burying the stem and roots and you don’t realize this when you plant the tree.

Trees need water, oxygen and warmth, so they naturally grow most of their roots close to the surface. If these surface roots are covered up, growth stops and roots wither and die. This occurs over time and the tree or shrub will slowly decline and you will keep watering the tree, because you think it needs more moisture. Over-watering is the second most common cause of tree death. Always stick you finger a couple of inches into the soil to check the moisture.


When you have large trees or shrubs-measure when you dig the hole
Measure, measure, measure!

For large trees it is very important to measure precisely before setting the root ball in the hole. Because once it is there, it is really hard to move a 100 pound or more root ball.

A containerized tree will flare at the base of the trunk at the soil line where it joins the root system – called the root collar or flare. If you can’t see the root flare, remove a bit of the top soil to see if you can uncover it. Sometimes, if you remove an inch or so of soil, you might uncover girdling roots, which are roots that have started to circle around the root ball, ultimately strangling the entire tree.

Check out this great video on planting a tree.

If the tree or shrub was recently planted and you have determined that it is too deep, it can be lifted and replanted, raising the root ball up to the proper height with the top of the root ball of a shrub or tree actually slightly above the existing soil grade. This practice is particularly helpful when planting in heavy clay soils that tend to drain poorly. Only dig the hole at the depth of the ultimate root ball height, but wider by about a foot of the diameter of the root ball. Make a shallow depression at the soil level to catch water and don’t mulch the tree heavily and absolutely don’t pile mulch around the trunk.

Create a saucer around a newly planted tree to catch and direct water to the root ball. Also, use the but end of a shovel to tamp soil firmly in to get rid of air pockets
You should see the trunk flare

Water several times as you plant the tree to settle the soil and eliminate air pockets and make sure the trunk comes out of the ground straight. Only stake the tree if it is located in a windy location. Go to How to Plant a Tree for more information.

Digging holes for Arborvitaes

Planting Containerized Plants: Don’t just Plop It Into the Ground

For perennials and shrubs, I always after removing the root ball from the pot, loosen the roots by scoring the root ball with a sharp knife or gently loosening the roots so that they aren’t packed tightly together. If you don’t do this on a root bound pot, the roots tend to circle round and round girdling the plant.

A root bound container should be scored all around with a soil knife to break up the root ball
The consequences of not breaking up the root ball of a containerized plant
Loosen up your root ball before planting

Most people are hesitant to do this, thinking it will damage the plant. In reality, you will give your plant a good head start in rooting in the surrounding soil.

Over Mulching

Mulch is a beautiful thing. It moderates soil temperature, discourages weeds and keeps moisture in. But like anything, too much of a good thing can be harmful. Excessive mulching is common and the time honored example which I see all the time, is mulch volcanoes. Seeing this pop up in the spring is a landscape ritual that I wish would go away. Mulch volcanoes are tree killers!! Piling up mulch around the base of a tree seems to be the common way of doing business for many landscape companies and they need to be educated on  proper mulching techniques.

Improperly planted and mulched tree
Over mulching is a death sentence for a tree or shrub

The proper method is 2-3 inches of mulch, keeping the mulch away from the trunk or stem of the plant. This depression ensures water will percolate right to the root ball where it is needed.

Planting Invasive (But Pretty!) Plants

How many have been suckered into buying a beautiful flowering plant only to find that it took over your entire property in less than one season? I have done that many times, thinking that I could keep it under control or just being seduced with a beautiful shot of a wonderful plant.

Gooseneck Loosestrife barely contained in a border

I fell in love with Gooseneck Loosestrife (Lysimachia chlethroides) many years ago and lived to regret it. It took several years to find and destroy it all before it took over my entire garden and ate up my house for dessert! Be wary of pass-along plants from friends and neighbors as they are usually the type of plant that makes itself at home and gobbles up the garden. Ask yourself why they are giving you a free plant! It is usually because they have a ton of it. In a catalog, if the description says that it is vigorous, steer clear of it. Do your research before planting anything. 

Another invasive example is Chameleon Plant (Houtuynnia cordata), which needs dynamite to get rid of. This is one of the toughest plants on the planet and you don’t want it near your beds.  Another hazard of pass-along plants is the hidden danger of introducing an invasive weed into your garden. I had a client who introduced Lesser Celandine (Fricaria verna) when she planted a friend’s gift plant. This noxious weed only shows surface growth in the early spring and disappears to a small tuber the rest of the year when you can’t see the plant. For this reason, I rarely accept pass-along plants.

Lesser celandine is an European introduction that will quickly take over your lawn

Perennial? Maybe and Maybe Not!

Boy, do I love Gaillardia. I try it most years, sometimes at least a dozen of them and maybe one overwinters for me. You might have a different experience than me in the mid-Atlantic with my crazy wet winter weather, but there are some perennials that I treat like annuals here. They just don’t survive my winters. Lavender, gaillardia, agastache, and some of the new coneflowers are a few of them. I am willing to try them but when they don’t come back, I give up expecting them to come back. I will plant them in the expectation of enjoying them for the one season and rejoice if a few come back. Many new plant introductions that seem too good to be true haven’t stood the test of time and been grown in all parts of the country. If you are planting many plants of one variety, be sure to test that plant with a few test plants for at least a year, before investing your money.

Gaillardia is an annual for me
One year I had 24 lavender plants that died!
I treat most agastache or anise hyssop as an annual

I wouldn’t be without agastache in my garden and went through a lot of varieties. I finally discovered ‘Rosie Posie’ Agastache, which is reliably hardy for me in the mid-Atlantic. It is a nice compact pink one and I will be planting this a lot! ‘Blue Fortune’ is my old stand by and you can always count on this one coming back.

‘Rosie Posie’ Agastache is reliably hardy
‘Blue Fortune’ Agastache

Lawn BooBoos

Lawns or turf grass are ubiquitous in the US and I realize it is a relatively low maintenance solution to maintaining extensive planting beds. But a common lawn mistake I see everywhere – people cut or scalp their grass too short! Using a too-low mowing height, allows the hot sun to penetrate into the blades and it can leave brown or bare-looking spots in the grass. Depleting the grass’s energy reserve, short mowing can weaken or kill your grass, leaving it vulnerable to weed invasion. Proper height mowing can lead to a drought tolerant healthier lawn. Go to Today’s Homeowner to get the proper height for your type of grass. But 2-4 inches  is usually the standard. Otherwise, if you want to attract more pollinators, embrace a weedy lawn and encourage dandelions, creeping charley, and white clover. Go to my post on Planting a Pollinator Friendly Lawn.

Scalping a lawn creates dead spots


We are creating an environment of fencing off everything from deer browsing. Necessary, but don’t create a monster. When you set up your fencing around a newly planted tree, don’t place the fence directly on the ground and have an issue with  weeds growing inside the cage because a weed eater can’t reach in and cut it. Raise your cage at least 6 inches off the ground and you can easily pass a weed eater underneath to groom the edges.  Otherwise, you have tall grass growing in and around your fencing. So simple, but effective.

Make sure your deer fencing is elevated at least 6 inches off the ground for maintenance

Also, maintain your fencing – especially deer fence. Deer will punch a hole right through a mesh fence and you need to walk your fence line regularly to make sure it is doing its job and repair any breaks.

Timely Weeding

We are living in a world of invasives taking over the earth. You can’t pull out all the bad things that surround you, but you can certainly control what arrives at your little patch of earth. And one of the most important invader to remove promptly and without delay is Japanese Stilt Grass, Microstegium vininneum. If you don’t attack it right away it will take over your entire property by leaps and bounds.

Woods near me have been invaded with the noxious Japanese Stilt Grass

Introduced about 100 years ago as packing material in shipments, Stilt Grass has colonized the entire east coast and is marching westwards.

An annual grass, it grows rapidly in shady sites and deer unfortunately leave it alone.  Appearing in June, it quickly forms lush mats of 2-3 foot high stems that form seeds which are dispersed far and wide to form next years growth. I have seen it take over entire swaths of ground in a year or two. If you see it start to invade, take immediate action and pull it out. Easy to pull out, when faced with large areas of it, people can get discouraged and give up. Having no wildlife value and pushing out native plants, this grass is bad news for your property.

Stilt grass before it goes to seed
Stilt grass going to seed; You don’t want your grass get to this stage as it will seed in for next season

Timing is everything. You must get it when it is still immature and hasn’t set seed as a single plant can produce between 100 to 1000 seeds. You can pull it or use an herbicide. I see dense mats of brown vegetation on the side of the highway when they spray with herbicides and know this is dead stilt grass.  And once winter kills it, the dead grass forms a smothering layer of dead material. Even goats won’t eat it!!

Removing a small area of stilt grass early will save you lots of hard work later. 

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