My biggest planting mistake was putting a Japanese anemone in a moist rich flower bed and I will forever pay for it. It's a bully! And spreads under the soil and right through other plants terribly. A tiny piece of root will sprout from virtually nothing. I've "almost" eradicated most of it...

It might have behaved in a different zone, soil, climate, love etc!

What's your biggest mistake? It could be a buying, planting, care, etc mistake also.... anything goes!

Not taking cuttings of my rhododendron fastigiatum while I still had one,

I have made so many garden mistakes. If you are not making mistakes, you are not gardening:)

Mine was planting running bamboo, mint and chives. They all went wild and took years to get rid of.

My forever garden mistake, and I never learn is to plant things too close together. I get instant gratification that way. But 2 months later I have a jungle of a mess to the point you can't even see some of the things I've planted! My begonias looked so great with the Trailing daisy. I looked forward to seeing pink and yellow flowers in bloom together! I've done this before...The trailing Daisy has taken over. Will ever learn???

Planting things in the wrong place then having to dig them up 2 years later to move them. Like putting a small tree next to my sewer line then realizing that tree will get really big and wreck my plumbing some day.

Planting Lily of the Valley in a place they loved. I am still pulling them out 10 years later.

Planting Purple Rain Salvia. They are invading the lawn and survive mowing.

Planting Lysimachia ciliata 'Firecracker' . Well, that wasn't exactly my fault. It was sent to me in error as a purple leaved yellow flowered Coreopsis verticillata 'Golden Gain' (that I ordered) and I didn't realize the difference at first. Purplish leaves, yellow flowers. It has taken years to reduce the damn things back to a small area where I think I am finally getting them all dug out.

Here's a weird problem. 3 decades ago, I brought some Snow-On-The-Mountain from my parents' NH place down here to MD. They still survive, but a patch seems to have reverted to a solid green weedy ancestor (same leaves and flowers etc). And it is taking over the landscape bed where I have hostas and Japanese Painted Ferns.

I ripped half of them out last week. If it EVER stops raining, I will rip out the rest. And cover the bed around the hostas with black plastic. The ferns will get individually moved under a edged Saucer Magnolia tree along with the surviving "normal" Snows. It is annoying as hell to have to keep moving the nice Snows away from the bad ones.

Compared with all THAT, the few dandelions blown over from my upwind neighbors' yard is minor, LOL!

One of my mistakes was planting a passion vine where it was very happy. I had sprouts 6 feet from the fence is was planted next to. I still tell people that I had to move to another city to be rid of it!

I was trying to think of a planting gone bad... like the "Little Shop of Horrors"

Then I realized that my major mistake was with the paperwork! Over the years, especially when I was employed, I bought hundreds of plants. I planted them, but no record of where.

Of course, I ended up with many plants without a proper name:)

Now that I am a sophisticated retired gentleman gardener, I cull anything I can not identify.

Not keeping the youpon holly in check...it's EVERYWHERE now

Thanks everyone for sharing. Hopefully more people will add to the thread as this is all very useful information.

Frank, I did the same mistake tossing away the plant tags my first 5 years of gardening. Now I keep them in a shoe box for my records and have a detailed plant excel sheet plus drawing references.

Planted 'Little Gem' magnolia too close to the house, Gorgeous tree now 25 years old, just wish I had a better place for it. Mom even said But Magnolia gets really big.. but being 30 ish at the time thought I knew better than Mom. It is my biggest mistake because taking it down would change the whole area from shade to sun, and be such a big job too, and such a loss.

Lily of the valley.

Asking hubby to put some sand on a path. He went overboard and moved wheelbarrows full of sand with stone ( were having construction at the house) on the path and the stones make the whole thing painful for bare feet and really hard to dig back out.

Removing Vinca major and NOT immediately mulching the area to prevent all the other crap sprouting.

Derril said:My biggest mistake was weed whacking weeds that were growing around the trees in the backyard. The line of trees is about 500 feet. It was a hot summer day and I wore shorts and a tank top. Whacked down all the weeds cleaned everything up. It sure looked good. Later now I had a nasty itching rash all over my legs, arms and neck. the weeds that I weed whacked was poison ivy. That was last summer and I still have a few scares on my legs

I can sure feel for you on that. One year, I pulled vine roots out of my asparagus bed in late Winter not knowing they were poison ivy roots (no leaves at the time). I had a miserable couple of weeks before it all went away!

And I had been pretty much immune to poison ivy before that. But so much triggerred a reaction.

Simple: Over-watering

Welcome to NGA SCPharmacist. I think most of us have been guilty of that one! Especially with succulents.

Oh. Also, planted Santa Rosa plum tree about six feet from the row of asparagus. Somehow I assumed SR plum was a small tree. Heck no, it's a really fast growing tree. And it suckers.

Not changing routine.
Changing routine.

my biggest is to like flowers and gardening , gone wild.

Starting Gardening! LOL

My biggest mistakes were planting things that got too big in the wrong places. They had to be removed and couldn't be saved due to their size. I've been doing better now.