From my experience, here are the top bad ideas vs. good ideas:

1) Rose cone: Suffocate, fry, and deny your rose of water in the winter. It gets hot in there early spring, and the rose dies of drought and heat. Poking holes doesn't help, because water can't get to the base of the trunk (I killed one rose this way). A better method is to mound soil or mulch up to 12".

2) Horsemanure in the bottom of the planting hole: this idea came from Heirloom roses. Some of that got mixed up to the top while planting: rose gets yellowish & chlorotic, with brown fertilizer-burn spots on leaves. Horsemanure is meant for top-dressing only.

3) Sulphate to lower soil pH. a) it's very slow acting, needs mixing with moist soil and time to work b) acidity is enough to kill plants. I once had to replace the entire bed of soil when I used the entire bag of sulphate.

A safer way is using peat-moss to lower pH (zero damaging salt, and locks moisture in). It works wonder for my azaleas and rhododendrons. Roses Unlimited recommends 1/4 peat moss for the planting hole.

4) Alfalfa on top around the trunk. Many thanks to Melissa who blew the whistle, see "Rethinking Alfalfa in California." Alfalfa meal on top crusts and cakes like crazy glue around the trunk (nice way to burn some roots).

I still have this crust of alfalfa meal around my pine tree, after 2 months, and many all-night heavy rains.

A better way is alfalfa tea, and doing what Roses Unlimited recommends: mixing 2 cups of alfalfa meal in the planting hole, to ensure its breaking down in the wet soil.

Bloodmeal gives rapid boost of nitrogen (except for the small risk of Mad-Cow disease). Ammonium Sulphate is a FAST acidic source of nitrogen (downside is the salt that comes with chemical fertilizer).

5) Mulch with tree bark. This is a BAD idea ONLY for wet, rainy climate with clay soil deficient in nitrogen. Free municipal tree bark comes with poison ivy (two trips to the doc. for me). We also get a few varieties of ugly mushrooms on the mulch. Tree bark robs the soil of nitrogen as it breaks down.

I like mulching with horse manure from city stable better: zero weeds, and big growth spurt after a heavy rain.

6) Planting without checking the drainage. After digging a giant hole, dumping a bucket of water to see how well it drains is a must. I wasted time digging plants up, fixing drainage, and replanting them - since I forgot to check for drainage.

7) Shallow watering with a hose. Michaelg' post on the water meter is a great idea.

8) Banana Smoothie for rose (blend bananas & molass in a mixer). I didn't try that, but I chopped up whole mushy bananas and threw it around Eglantyne. She hates it and leaves turned brown.

A better way is recommended by Michaelg, Sammy, and Mike: Fresh banana peels around rosebush - they turn black within a few days, and look OK. The potassium from banana peels de-salt the fertilizers we use.

9) De-germed, white cornmeal from the grocery store. Eglantyne came in the mail badly blackspotted. I threw Walmart cornmeal around the bush. Edges of leaves turned black and got fried in the heat.

After 10 hours of rain and humid & hot weather, I dusted roses' leaves with WHOLEGRAIN cornmeal from the feed store. Nothing bad happened - leaves look fine. I'll know if this experiment against blackspot work by the end of our wet season in October.

10) Planting Austin roses in full sun. This is a bad idea, since my zone 5a intense sun is too hot compared to England's mild coastal weather.

From your own experience, what are the bad ideas and good ideas in growing roses? Many thanks.