Scientest think there are chemical messengers that originate in the seed of annuals that trigger physiological responses that help tell the plant when it's time to check out. You can prolong the life of the plant to a certain extent by preventing the seed from maturing (deadheading), but there is also another mechanism at work that you cannot trump by deadheading. The plant's life cycle is also governed by a Circadian clock - an endogenous auto-regulatory mechanism that combines with or is triggered by photo-period duration (day length) to influence a wide range of plant cycles, including senescence (aging) and the timing of its death.

Plants also age in two ways, one is chronologically, the other ontogenetically. The former is the measure of how we also age, but the latter roughly has to do with the number of cell divisions in a plant. Some plants will enter irreversable decline after reaching a genetically predetermined ontogenetic age.

Al

Some plants are treated as annuals in a cold climate, when they may really be perennials in a mild climate.

Indeed - many, if not most of the plants we commonly refer to as herbs are perennials or biennials.

Al

a lot of annuals ....

are just cold intolerant plants ...

for example... a 4 o'clock.. is native of peru.... known.. i think.. as star of peru .. and a perennial ..

ergo .. bring them to z5.. and they are annuals ...

and they will not return ...

then you have to move to determining whether the seeds are hardy enough to winter over ... not all seeds can take the same cold temps .... in my z5 .. 4'clock seed will winter over.. if the vermin dont get them [the darn cardinals must have eaten a quarter million seeds this winter]"idiots.. i really cant believe they got every single one in a 10 x 20 foot bed>(but i digress....lol)... but in 30 years.. i have had one petunia .. and zero impatiens reseed ....

whether or not they will survive.. in a pot.. in a garage ... is an issue of what zone that garage is ... it will be a warmer zone than outside.. but may or may not be ok for the plant... plus all the problems of overwintering pots ...

if you want to keep your plants going. consider an indoor light structure... 4 fluorescents... learn how to propagate your plants... and keep them going indoors all winter .. it isnt easy .. but it will be your best shot ...

ken

"a lot of annuals ....

are just cold intolerant plants ..."

While true that many annuals are intolerant of cold, annuals are annuals and perennials are perennials. Intolerance of chill has nothing whatever to do with separating the two groups.

"ergo .. bring them to z5.. and they are annuals ...

and they will not return ..."

First - the statement is not true. Second - even if it was, it would be painting with much too broad a brush.

Where a plant is grown has no bearing on whether or not it is an annual. Just because we treat a perennial as an annual, doesn't change the fact that it is a perennial. A perennial is any plant that is capable of surviving for 3 or more growth cycles. Trees and shrubs are examples of perennials, and just because we kill a Ficus or scheff by forgetting to bring it indoors when the weather changes, doesn't alter its status as a perennial.

Al

I don't know why that is a difficult concept. My personal frustration is seed companies that don't recognize the difference. I know a plant is perennial and can't find it on their perennial list, so I then look and find it on the annual list. When I complain about that I am told "most people consider it an annual". Can we just change the facts by "consensus"? Al

Wow! I learn something new everytime you guys chime in!

Erdnuss, in answer to your question about herbs, I would say it depends on the herb. Rosemary is pretty cold tolerant. Many, though not all, varieties will overwinter outside in a pot in even the upper south, which is as far north as West Virginia, Kentucky, Missouri and Northwest Texas. I don't know where you live, but this might give you a clue. I also keep oregano, chives and thyme outside in pots all winter long without any problem. It could be that an unheated garage near an interior wall would be enough for you to overwinter oregano. Depending on where you live, you might or might not be able to leave chives and thyme outside, but again that unheated garage might do the trick for you.

Then there are the biennial herbs. I can ONLY grow parsley and cilantro outside in the winter. They die as soon as our hot weather moves in.

On the other hand, basil, an annual, needs really hot weather and is usually the first plant in my garden to die from frost each year. I have tried overwintering it inside under lights with less than acceptable results in the past. Like I said, it wants warmth.

Shhhh ... (in a secretive whisper) basil is a perennial, too. ;o)

Al

You know, at dinner, I wondered about that.... :) Perennial where? The equator?

If you think about how you're using the word, you'll realize you're not using it as a noun, but as an adjective - to mean it returns every year (or doesn't). It's not really proper to say that, "Basil is not perennial in my zone." Proper, would be "Basil is a perennial that is not hardy in my zone; therefore, I treat it as I would an annual."

Since basil is capable of living for 3 or more growth cycles, it can only be a perennial (even if a tender one), and where it grows - equator or north pole - can't change it to an annual.

At dinner, hmmm? ;o) You MUST be a plant person!

Al

I find it funny you guys mentioned basil....I had to go back and reread my post because that is one of my herbs I'm growing. I read somewhere that it was an annual which got me started on this whole topic so it's funny that with out me bringing up basil, you guys ended up talking about basil, hehe.

I wondered when you'd be back around ... (:^))

Al

I don't understand, Al. I have always understood that a perennial is a plant that returns each year (although it may poop out in fewer years than other perennials do). You say it's a plant that lives through multiple growth cycles. What's the difference? I guess what I want to know is how you know basil is a perennial and how you know it is capable of living for 3 or more growth cycles. I assume a growth cycle is a year of seasons: spring, summer, fall, winter. I am really interested. Fill me in!

Ok - let's take basil as an example. Basil is a perennial by virtue of the fact that it is capable of living for three growth cycles (years). We say three, because biennials (parsley, e.g.) live out their life cycle in two years. Any plant that can persist more than 2 years is a perennial.

I think where you're getting confused is in the difference between can and does, and you (like Ken) feel that if a perennial cannot survive the zone that it is growing it, that changes it to an annual. Actually, it would still be a perennial we only treat as an annual because it's not hardy enough to survive the zone.

Snapdragon is always a perennial, but if I grow a snapdragon in the ground, I must consider it's longevity as I would annuals because the cold will kill it. In your zone, they are likely to return year after year - if not your zone, then zone 8 for sure, but I think you get the point I was making. I have snapdragons growing as bonsai that are many years old. If they were annuals, I could not do that. Peppers (Capsicum) are another common garden plant that we in the north must treat as an annual, when actually they can live for years in containers (indoors) or more southerly locals.

Getting it yet? ;o)

Al

wow, Peppers are perennials? I have several pepper plants in pots and I just figured they were annuals and had to be tossed out at the end of the year.
I love you guys! Lol, I learn so much from all of you!

You should be thanked for putting up with the off-topic banter. ;o) You're a good sport.

Peppers are tender perennials, so they'll have to over-winter indoors if you're to try keeping them.

Al

Okay. So you're saying that any plant that can live for more than a year (growth cycle) in a greenhouse or other protected area is technically a perennial. That makes sense. Just curious, by this definition, are there any true annuals?

... that's more than two years.

Though there are exceptions, it would probably be easiest for you to think that plants that go from seed to seed in one year, and do not return the next, are annuals.

Completes life cycle & goes from seed to seed & dies after a year = annual
Takes 2 years to complete its life cycle = biennial
Capable of persisting for 3 growth cycles (years) or more = perennial

The geographical location a plant is grown in has nothing to do with whether a plant is a perennial or annual.

"... are there any true annuals?"

Yes, of course - many thousands of them.

Something I wrote a while back that is related & may give you more insight:

"First, let's make a differentiation between annual and perennial. Technically, and in most cases, an annual is a plant that germinates, flowers and dies within the period of one annual growth cycle. You can artificially prolong the life of annuals by preventing them from setting seed or by manipulating photoperiod (day length - more specifically, night length is actually the determining factor). Perennials are plants that are capable of living for three or more growth cycles. Trees are perennials.
We often mistakenly refer to plants such as Coleus, snapdragon, petunias, or Impatiens as annuals, simply because they will not overwinter in some zones, when in fact, they are all true perennials because they are capable of living for three growth cycles.

Annuals have adapted to their reproductive strategy for a number of reasons. 1) The plants die in order that they can translocate biological nutrients and minerals to the seed. 2) They die in order to leave growing space and return nutrients to the soil for the next generation. 3) The plants die so duff can insulate the seeds (with the dead leaves and stalks) against winter's cold. 4) It may be a timing issue to take advantage of a cultural opportunity to set seed early to gain a space advantage or to ride on autumn winds or the coats of migrating animals, etc

You might think the physiology of death in annuals would be through simple aging; that is, accumulated mechanical injury or tissue damage causing increased sensitivity to environmental stress, bringing on death. But actually, simple nutrient withdrawal/translocation to seeds from the leaves eventually brings on starvation or some other nutrient deficiency, causing death. That is, the seeds take what nutrients they need by diffusion from the adjacent cells and this causes those cells to become an energy sink, where the nutrients pass from the leaves to the seeds. Hormonal or chemical messengers are released by the developing flower or seed, or the photoperiod influenced leaves themselves, which causes the plant to begin degrading itself and transporting the resulting nutrients out of its cells into the developing seed.

In most cases, freezing temps are only the coup de grace, as the plant would have been already in the last stages of it's life cycle, ready to succumb, with or without the aid of Jack Frost."

I hope this was also helpful - I don't know what more I can offer.

Al

Donna, you need to think in terms of the reproductive cycle with these plants. Annuals are plants that, under normal conditions, develop from seed, grow vegetatively, flower, go to seed, then die....all within the first year.

If you take them from their environment, protect them from the frost and remove their seed heads....that still does not change their status as a true annual. Deadheading, by the way, is one way of extending an annual's flowering stage, but can't change the status of the plant, right?

A biennial will germinate and grow vegetatively that first year, but requires a winter dormant period in order to trigger the second part of the reproductive cycle. In the spring of the second year the flowering stage begins, followed by seed development. After that portion of the life cycle is complete, the plant will die.

Does that make it a bit easier? For some reason, this is a subject that seems to perplex a lot of people, and it's always worthy of a good discussion. By the way, those zinnias that you and I like so much? Annuals. ;-)

Believe it or not, I do understand every word that both of you have said, and it is, for the most part, no different than what I had understood previously. I guess the thing that threw me was basil itself. I have simply never ever seen it referred to as a perennial. You see, it does come up from seed and grow to the point of setting seed in one year, is killed by the cold and then doesn't return, and I have never heard of it doing anything different from that anywhere.

I think I fully understand the concept of planting perennials as annuals: tulips, snapdragons, some salvias, etc. Because they will bloom so well in their first life cycle, this trait can be exploited in areas where the weather is inadeqaute (either too cold or too warm) for them to perform well, or even at all, in succeeding years. I think I get that.

I understand biennials too: grow into a plant the first year, flower and set seed the second.

One thing I never thought about was that the reason annuals get "ratty" late in the season is because they are preparing (beginning?) to die now that their reproductive purpose has been fulfilled. This would include zinnias and marigolds, right? So, in effect, you are saying that these plants would die anyway, even if frost didn't get them first, right? (I get it that the inevitable can be delayed through deadheading, cutting back, etc.)
It's the basil that threw me. It does come up from seed, flower and set seed in one growth cycle. But once there is frost, it dies and does not return. I have never heard of it doing any differently anywhere else (or of being capable of it), short of being taken inside. I am going to take your word for it that the fact it can live inside makes it a perennial before I bore you all to death :).

Donna,

"One thing I never thought about was that the reason annuals get "ratty" late in the season is because they are preparing (beginning?) to die now that their reproductive purpose has been fulfilled. This would include zinnias and marigolds, right? So, in effect, you are saying that these plants would die anyway, even if frost didn't get them first, right? (I get it that the inevitable can be delayed through deadheading, cutting back, etc.)"

I know it is kind of spooky how fast the salmon die after laying eggs and spawning. One year in my Fort Worth garden we hadn't had a killing frost as of Christmas Day, but all of my zinnias just gradually succumbed to mildew and other foliage diseases. I sprayed with some Captan and Consan 20, to no avail.

As of right now, I don't know how long zinnias can live. Obviously, prompt deadheading can have a big effect, but I don't deadhead my "breeders" because I am saving seed from them. I used to think that making mature seed took all the "energy" from the plant so that it would die. I have some doubts about that now.

Last Fall, as a killing Frost approached, I took some cuttings from some of my favored plants and moved them indoors under lights. As they started to mature, I took some more cuttings from one of them (Thrips killed the others before I figured out what was happening) and this Spring I set them out into the garden. They are blooming now and have some mature seedheads (that I need to harvest). However, I am contemplating taking some cuttings from them and growing them indoors under lights again this Winter.

It has been nearly a year and a half since the original seed was planted and, although I have harvested seed twice from its plant and from its cutting plants and, shortly, a third time from their cutting plants, right now I don't see any obstruction to continuing this asexual propagation of the original plant. At some point some kind of hormonal change may kick in and stop this line, but I think there are varieties of coleus that have been propagated for many years from cuttings. I don't know whether coleus is an annual or a perennial normally treated as an annual.

I also don't know whether a cutting plant should be considered to be a "new" plant or as an extension of the original. It's an open question in my mind. There is a picture of a group of the second generation of those zinnia clones at the start of the It can be fun to breed your own zinnias - Part 6 message thread.

MM

I don't understand why Basil is being discussed here, but out of the seven Basils in my reference only one is classed a perennial and a tender one at that. Ocimum killimandscharicum an African native is not a culinary herb, but it is a perennial. Here in zone 9 I have never seen a Basil live more than one season. Al

Basil is being discussed because when I first started this thread, I was asking about herbs because I grow them and wanted to know if I could make them last even though they are said to be annuals.
We are talking about the difference between annuals and perennials here. Basil just happens to be one of the plants we ended up talking about which is good because it tends to be the one people go back and forth on whether or not it's an annuals or perennial.
:)

After I looked it up, I see there are more varieties of basil listed as annual than perennial, though there are many of both, so I'm sorry if I confused you, Erdnuss/Donna. ;o) What I said about annuals/perennials still holds true, but your plant could be either.

I have had O. basilicum 'Minimum' in a container for 5 years or longer.

Al