Maybe not worst - but a dumb one. I sprinkled some kind of red pepper over my plants to keep the varmints off them but it burned the leaves badly.

Not adequately planning in advance before planting-planting too close or in too much shade.

Composting a whole pumpkin. The seeds don't decompose, they sprout.

moving to NJ! :)

Trusting my husband's judgement on topsoil. I let him add soil to a raised garden saying that he told me was good top soil. I have clay soil in my area and he dumped some of the worst clay soil mixed with 3/4 inch gravel. I'm constantly fighting the clay and picking out stones.

MINT

Obedient plant! I call it "disobedient plant". It can get into everything. Mixed with Iris is a particular problem! I've had to dig up whole garden beds to get every bit of plant out. Don't let it seed or you will really have a perennial problem! It grows in sun or shade and is very invasive.

Gooseneck loosestrife. x.x Knew nothing about it and bought & planted some in one of my new beds when I moved a few years ago. Now I wage an ongoing battle- I'm convinced I've pulled it all out each time, but it's always back at full strength in no time. We need a law requiring warning labels on plants likely to attempt world domination. :P

I've done these two:
Not adequately planning in advance before planting-planting too close or in too much shade.

Composting a whole pumpkin. The seeds don't decompose, they sprout.

But I also planted Echinops Ritro last year in my flower garden bed amongst the lilies. They were itty bitty seedlings given to me which are now almost 6 feet tall and now I can't barely find my lilies!

Stupidest garden mistake qualifies the time I grew this beautiful foliage plant from seed in a pot all summer, anticipating the gorgeous flower that just had be the pot of gold at the end of the rainbow. Fed it, nourished it, fawned over it only to be told by my dear sister that it was a weed!

Bought some bare-root plants through mail-order and planted them upside down. (That was my first year gardening--have improved a bit since!)

Two worst mistakes, buying plants from a new online nursery that were too cheap to be true and were, got disease infected plants. This is a tie so here's the other one, planting 'Houttuynia' (commonly called chameleon plant) in my yard, three pieces rapidly took over and I will forever have to pull this plant out of my beds.

"Bought some bare-root plants through mail-order and planted them upside down."

LOL, did you really do that?

Melissa - Moving to New Jersey??? Out by me, I love it! Truely rural, lots of farms, rolling hills, a slower attitude. Maybe you need to move out my way - (Hunterdon County).

Brought my indoor plants out for the summer and brought them in in the fall without spraying them for bugs. Real bad idea.

Not getting a large enough lot.
Not killing off the hosta before putting in the roses.
Letting the vinca get into my main rose bed.

Letting my wife plant decorative gourds in the middle of my vegetable garden. They ran up and over the tomatoes, out of the garden and into my raspberry patch.

do they have bush type gourd varieties?

Ha. That happened in my garden, only it was Pinetree's mistake not mine - I thought I was planting pumpkins until I saw these huge things with HANDLES hanging into the zinnias. I have cut away 90% of that gourd figuring I might as well get some birdhouses out of it but keep it in bounds. It is still setting fruit in late September and keeps trying to invade everything. Not a bug or speck on it. Got to give it credit for vigor.

Starting to garden! I confess I am a plant/flower addict (could be obsessive compulsive, cause all the catalogs that come to the house feed the addiction!) and I don't even have a lot of garden space. But every year I buy more and more, and then try to cram all the new "had to have" plants into the garden.

Being impulsive.

In an area about 5' wide by about 25' long right by my driveway, on the side of my house, I decided to do some trimming on the creeping juniper that had taken over the entire area, and was cascading over onto the driveway. In years past, I just cut evenly along the driveway, only to have it cascade back over in a very short time.

I decided this year, I was going to prune the whole area way back, and try to identify how many plants there are in there, and neaten things up. We bought the house already professionally landscaped, but allowed to become very overgrown. So I had no idea what was down under this green sea of growth.

Ended up hacking up the plants so bad (I am usually very good at trimming), I had to completely cut them out, and hack as much root out as humanly possible. Would you believe there were only three shrubs in this whole 25" x 5' area?

Now, under the shrubs are some very nice large landscaper rocks, but also about a ton of small rocks - not really river rocks, which over the years had become quite burried in dirt and needles. I started removing some to another area, but then gave up. My vision of a nice mulched area with a few plantings of shrubs and maybe a yucca in a curved rock area has been put on hold until the spring when I will see if I have some renewed strength.

Anyone know of an easy way to remove all those rocks?

Planting watermelons in a 3'x 3'raised bed. WOW!

Being new to gardening...I planted many climbing bushes out in the open. Now I have to construct elaborate trellises to keep them in control. Sheesh!

Unwittingly transplanting baby poison ivy to a more prominent spot because it was all shiny red and pretty.

Good thread! Good to know I'm not the only one making mistakes.
1st garden mistake- Planting fennel. The darned thing is coming up everywhere and it has a long tap root, can't be pulled out, has to be dug out. Yes, I know it is home to the Monarch butterfuly larvae, but I will find another plant which attracts the Monarch.

2nd- buying annuals at Crossroads Nursery. They were so root-bound, I doubted they could survive, but I planted them anyway. 7 of 8 died! I never had anything like that happen before. I thot about taking them back - on principle - they only cost $1.69 for 4, but decided it wouldn't really matter. This is a place which caters to large landscapers, not backyard gardeners. You can bet I'll never go there again.

ellenr

physalis-wouldn't grow worth one "lantern" last year; now took over all my beds; so much for sentimental childhood memories!