I think it's good for all plants, unless you want to collect seed for yourself or the birds. Having a lot of flowers going to seed at one time on a plant can be a drain on the plant's energy and keep it from blooming or growing any more -a few don't generally hurt anything.
Sherry

Shari, I don't deadhead my tropical milkweed (A. curassavica) anymore. The first year I planted it I thought I should cut off the dead flowers and developing seed pods to keep the bloom going. I have found that they will continue to bloom and produce seedpods at the same time. The first year I didn't get ANY seeds from my tropicals because I deadheaded and removed the seedheads. So, by the time I let the plants set seed, the frost got them. I waited too long, and thus bit off my own nose to spite my face. Now, I just let them do their thing. These are considered annuals in my zone, though.

Most perennials have a specific bloom period, like spring, early summer, late summer, fall, etc. So, if you want to collect seed from them, you have to leave them alone to develop. I would prefer not to have a lot of seed from some things and those I deadhead religiously. I have heard this is true of a lot of the Buddleias, or butterfly bushes, and that they DO benefit from deadheading.

It's kind of a game of "timing". A lot of plants, like the pincushion flower for instance, benefit from deadheading, but if you want to be able to collect seeds, you have to let it set seed at the right time, close the end of its typical blooming perio. So, when you think that the bloom season for a particular plant is waning, you need to allow the remaining blooms to go to seed. Sometimes I guess right, but not always. There's always a risk of an early fall frost here in Oklahoma and consequently, it has interrupted the process of seed ripening.

I don't deadhead lantana, because it seems to keep on going and going and going for me not matter what, but a lot of them are sterile anyway, and I never save seed from them. Neither do I deadhead my ageratum. It blooms in the fall for a very long time, and then when it stops, it just stops. Very rigid bloom time for it. However, if you don't deadhead this one, it will come up everywhere. I don't mind, so I let it go.

Have you ever grown duranta from seed? I had one last year, and loved it. But I didn't collect any of the seed from it because I wasn't sure it would germinate.

I do deadhead marigolds, rudbeckia, salvia, pentas, cosmos, zinnias, etc., until fall. Then I let them set seed as well. If you have named cultivars, though, your seed may not come true. I wonder about the 'Black and Blue' salvia, which I have fallen in love with. It is a beauty! But, I don't know if the seed would come true.

Pentas I deadhead because they are difficult to grow from seed, so I don't care whether they set seed or not. I just buy them each year. They're pretty cheap. But, they may be perennial in your area, so you just keep deadheading them. They will benefit from it.

MissSherry is right - when a plant begins to set seed, it takes a lot of the plant's energy to do so. So, the trade off is that the foliage is likely to get pretty ragged looking. That said, on my perennial milkweeds, I want them to seed some seed this year so they will a) drop to the ground and germinate next spring or b) I can pick the pods once ripe to winter sow.

Whew - that was long, and probably totally confusing, huh?

Susan

Susan,

It may have been long but I read through the whole post!

I deadhead some of my A. curassavica but not all. Right now, I'm letting ALL go to seed so I can collect the seeds again. I send out so many seeds that I sort of do this in spurts.

Be sure to protect yourself when deadheading milkweed; the sap can be a real problem if it gets in your mouth or even worse, your eyes. Just ask some of the good people in this thread, lol!

There are some zinnias that don't need to be deadheaded. The 'Profusion' series keeps on performing until frost, as do the cute little Zinnia angustifolia, which are called the 'Crystal' series (I think).

Thanks for the info. It seems that it won't be detrimental to deadhead, so I'll just keep doing it to all my plants when I do my daily "walk around".
Shari

Slight change of topic....does anyone have a favorite tool for deadheading?

Yeah - my fingers - I'm very adept at deadheading. If the stems are tough, I use my clippers or garden scissors.

Susan

How can you tell when a flower has "gone to seed"? i have been collecting my rudbeckia deadheads thinking i would be able to collect the seeds after they dried out

In order to make sure the seeds on any plant have developed completely and will have the best chance of germinating, you need to leave the blossoms on the plant until a seed pod forms and then dries out and turns brown.