For roses that set few hips, deadheading makes no difference. With once-bloomers that set hips, hips are desirable unless you want to encourage maximum growth in a young plant. Among repeating roses that set many hips, some will repeat fairly well without deadheading, others will not. Try them and see, make notes.

For deadheading large shrubs and climbers, use hedge shears or electric clippers and don't worry about where on the stem you cut. I have been doing this for 25 years, and I promise my roses don't mind it. I don't bother with ladders; just let the high parts go, unless you enjoy that chore.

OK, here is another conundrum. How many flowers can go to seed before a plant goes irreversibly into seeding mode? I ask this because I grow sweet peas and can never manage to find every seed pod. Is there a sort of minimum number before the plant thinks it is time to set seed? Does it take just one missed seedhead per plant? I have many annuals and although I try to keep up with deaheading, as the numbers increase (cornflowers, cosmos, nasturtiums, that sort of thing) my motivation (and will to live) vanishes. If it is fatal to miss even one seedhead, we may as well not bother at all. Please help an exhausted and bewildered gardener.
Oh Michael - take notes...I wish I was even slightly more efficient to manage to remember more than my name and phone number, never mind fill a notebook - not to say I haven't tried but entries usually start to thin around April and grind to a halt by mid June.

Suzy, are you reading my mind? Yesterday I was deadheading Mons Tiller with clippers that make it easier to snip-snip than to snap-snap, wondering if it was OK to leave them on the ground. Until this year I was an unhygienic gardener. I just dropped everything, but this year with the discovery of thrips and that other fungus that turns flowers into balls of gray fuzz (ah-ha, botrytis) I started deadheading with a bag in hand (or tied to my waist a la cottonpickers. However, yesterday I had no bag and my huge debris bag was full and too far away to throw to, so to the ground they fell. I hope this single act did not ruin the "perfection" of my garden - ha ha.

The subject of deadheading annuals/perennials is a dark cave for me and a big duh. I never know whether snapping is sufficient or how far down the stem to cut. Right now I have a 6-foot tall verbena bonariensis that needs to be brought into smaller bounds, hopefully to continue blooming. I know it self sows, but can it be trimmed and still continue blooming? And petunias...I gave them "haircuts" by lopping off the ends. Will they rebloom or has the heat done them in?

Your question re the "tipping point" of going to seed or not is good. I await the answer. I don't know if my pink Marguerite went to seed and didn't rebloom because I waited too long to deadhead or because it doesn't rebloom. The yellow one bloomed again after her haircut.

Sherry