about dormancy

ATHENS, Greece

Hi to all friends !....i would like to ask something pls...

I am living in Athens Greece , which is ZONE 9b ( if i am not wrong)..i will use an example to make you understand what i want to mean.. i have many plants , and one of them is Hibiscus rosa sinensis which hardiness zone is 9-11....that means that can overwinter outside ? am i right?....
-i also read that it goes to dormancy in winter , so...my question is , should i bring the plant inside during winter or just because it's hardiness is below my zone here , can i left the plant outside to go dormant? ...now generally
for all plants that dormancy in winter and their hardiness zone is suitable for my zone area , can be left outside without doing anything?.. is there something i must take care for them?..hope you understand my meaning (sorry for my english mistakes)..

This message was edited Nov 28, 2013 8:54 AM

This message was edited Nov 28, 2013 8:58 AM

This message was edited Nov 28, 2013 9:02 AM

Durhamville, NY(Zone 5b)

Any plant that is listed as being hardy in your zone or lower can stay outside with no problems. That is was the zones mean.

Plants in pots are a different. The problem with pots is trying to figure out how much water they need if any. The other problem is that in zone 9b I'd expect the ground to never freeze, but a pot above the ground could freeze over night.

Contra Costa County, CA(Zone 9b)

Hibiscus rosa-sinensis does not lose its leaves in the winter. It may stop growing.
In some years it may freeze just a bit, the outer leaves may burn. In other years you could lose the whole plant.

For plants that are marginal like this there are a few things you can do.
1) Plant it in a protected spot, especially against a wall that will absorb heat through the day and radiate it out at night. Also, overhanging eaves will retain the heat, just make sure the plants are getting properly watered under there.

2) Keep it well watered. It is harder on a plant to face freezing conditions while they are also under stress from lack of water. A deep soaking about once a month through the winter, if the rains do not take care of it would be a good idea. In containers more often would probably be needed.

3) Keep it properly fertilized going into the fall and winter. In zone 9 many plants will grow somewhat less in the hottest part of the summer and put on some growth in the fall. If your soil is lacking phosphates, potassium, iron or trace minerals then feed with these. Do not feed a high nitrogen fertilizer. That would encourage too much tender leaf growth.

4) Monitor the weather. If there is a smooth transition from warm to cool to cold the plants can get ready for it and handle the cold better. If there is a sudden switch from warm to cold this can be too extreme for the plants. Protect the plants.

5) Protect frost tender or marginal plants.
a) Cloud Cover, a liquid that you spray on the leaves. Works really well.
b) Christmas lights. The tiny bit of added warmth might be just enough to help the plant through a cold winter night.
c) Plastic sheet tented over the plant. Use whatever stakes or support you need to keep the plastic above and away from the leaves. Add Xmas lights if you want.

ATHENS, Greece

still wondering something...

i am a little confused about dormancy....from the little i know , i think that plants need dormancy in order to stay alive during winter , but also need dormancy in order to rest for a while....is it true? ...if that's true , and considering the fact that plants like hibiscus , dormant in winter ....my question is why not prune their leaves and stems and take them indoors in a cool dark place to overwinter?
thanks for your replies already

Contra Costa County, CA(Zone 9b)

A plant may lose its leaves in winter. Many plants that lose their leaves do so based on the day length. They conserve energy and resources through the winter and as the days lengthen they start to grow again. Some of these plants need a certain amount of cold weather before they can break dormancy. It is no good trying to treat these plants like house plants or greenhouse plants. They might be tricked out of one or two dormant periods, but eventually they will go dormant. Many plants from temperate zones are like this. They evolved where the winter chill is too cold for them to grow.

A plant may keep its leaves, but not grow in the cold or dry periods. This is also dormancy, but is controlled by other factors such as rain or temperature. If conditions remain favorable all year (greenhouse or house plant) then the plant will not stop growing. Many plants from tropical and sub tropical climates are like this.

Hibiscus rosa-sinensis is one of those that can slow its growth if the conditions tell it to, such as when it is cold, but, if conditions are right they do just fine growing and flowering year round. They have no requirement for dormancy. They work well as a house plant or greenhouse plant. You should NOT strip the leaves, or cut it all back at once to try to make it do something that it does not need to do. They grow well in the ground in warmer zones. Winter cold is the controlling factor here (zone 9). If it gets cold, they will stop growing, but keep their leaves. If it gets too cold you can protect them as I suggested in my post above. You could also bring them into a protected location if they are in a container. If you prune them at this time it will simply stimulate new growth. They are not like many deciduous plants that will not grow until the spring. Hibiscus will grow when you prune them.

Durhamville, NY(Zone 5b)

In reference to cutting the plants down when they go dormant, it depends on the particular species. Some plants only flower on old wood for example. There isn't one blanket procedure for all plants of a certain hardiness.

Another example is things like pine,spruce and fir trees in the north. When they go dormant in the fall they just stop growing. They don't shed their needles and in fact don't really look much different in January than they do in August. If you cut them back though you'd stunt them or kill them.

Contra Costa County, CA(Zone 9b)

Certainly, there are variables like that, and you will want to research exactly how to handle each plant.

My answer was directed more toward the 'Don't all plants need to go dormant' part of the question. And the answer is in 3 parts.
'No, not all plants need to go dormant',
'there are different ways that plants can go dormant, and it does not always mean they lose all their leaves'.
'Do not enforce dormancy (by stripping all the leaves, or hard pruning) when the plant does not go dormant under normal conditions'

Durhamville, NY(Zone 5b)

Diana_K, It's funny we are both addressing the original poster, but I see where if one this reads down through it looks like you and I are kind of posting back and forth.

I was trying to encourage the original poster to ask about individual varieties as "plants" is too broad a category.

Contra Costa County, CA(Zone 9b)

That often happens- In some threads the OP may never show up again, but the thread goes on and on, perhaps changing its focus, but still of interest to others who may click on it.

Well, I think the focus of the OP was Hibiscus rosa-sinensis.
It is just barely hardy in my zone, 9b, and this is highly likely similar if not the same as Athens, Greece.

Around here, Hibiscus rosa-sinensis will stop growing for a while in the cold season, and may frost. If it frosts, prune off the damaged branches after the risk of frost is over. Winter is variable, and may present enough warm days that pruning any earlier will risk stimulating growth which is more tender to the frost. Also, even dead, the frosted leaves and branches will act to protect the growth lower on the plant, so that when the warmer weather comes it is healthy and can grow. The point being that it is ready to grow when anything stimulates it to grow. Not like certain dormant fruit trees that will not grow until they have accumulated X amount of hours below a certain temperature, or some other plants that are more closely attuned to day length.

Hibiscus in my greenhouse grows year round, in and out of flower through the warm (long day) season. I do not know if they are day length sensitive. They are sort of dormant (minimal growth) when it is cold, in the garden, so they are sensitive to that. But if they are in a warmer place (warmer zone, or greenhouse) they keep on growing.

While I was doing a little research to answer parts of this thread I read about an experiment with Japanese Maple (Acer palmatum).
They kept it in a long-day situation with lights, and it did not go dormant the first year, but after 2 years it did go dormant even though it was in a long day setting. So there is something to the OP's idea that some plants must have a dormant period and will self-enforce it, even if the environmental triggers say it should still be growing.

ATHENS, Greece

-So , if i understood well , for those plants that are marginal into my zone minimum temperatures , should take care for the coming winter months....especially those plants in pots ...those plants are mostly tropical / subtropical ones like the example (hibiscus)...
...on the contrary , plants that are native to temperate zones (like mine 9b) , do fall into dormancy by losing their leaves , or keep their leaves but not growing which is also dormancy ...am i right? pls correct me if i understood wrong!..
-So , for the native plants there isnt anything i can take care of ...even in case they are on pots??
...as for other not native plants (mostly tropical / subtropical ones) if they are marginal into my zone , must take care , perhaps bring them into a greenhouse?
..and as i undestood also those tropical plants (like hibiscus) will continue growing and flowering , just in case i keep them inside? ...and if yes , when those plants will finally take a break and rest?
...anyway "Thanks so much" for your help , and i estimate that very much
...by the way i have some hibiscus into my balcony , and they seem they have stop growing since some time ago..
...and just a new example ...another plant that is ZZ (Zamioculcas zamifolia) it's hardiness i read is zome 9 to 11 ...but they propose not to let it outside when the temperature begin to dip below 60 degrees F. (about 15 degrees of celcium)...and i wonder why , since its hardiness is zone 9 ? (which means min temp since -6,7 to -3,9)

This message was edited Dec 3, 2013 11:16 PM

This message was edited Dec 3, 2013 11:38 PM

Magnolia, TX(Zone 8b)

Too much water in the plant increases its tenderness to cold. Hibiscus if in a pot can be moved into greenhouses to overwinter, but shouldnt need any trimming. Greece has a good climate, but if your winter is dry/humid the plants are affected by this also. Wrapping some plants works for some areas during dormancies, extra mulching can work in some areas- but you are at the mercy of your winter severity as to whether the plants strength will allow it to survive that winter.

Contra Costa County, CA(Zone 9b)

I think you have it.

Some plants lose their leaves. Let them do their thing.
If they flower in the early spring you are risking losing the flowers if you prune when they are dormant. Best wait until after they flower, then prune.
If they flower on new wood they will grow some in the spring before flowering (often flowers are late spring to fall, not very early), so it is OK to prune when they are dormant, unless there are other issues.

Some plants do not lose their leaves, but go dormant simply by not growing for a while. Many conifers are like that. Many broad leaf plants do this, too. Often the trigger for going dormant is something like the temperature. If it is too cool, they simply take a break and stop growing. Sometimes plants that hold their leaves will still go dormant (stop growing) in response to light and dark hours. Many house plants do this, and often a complete description of the plant will include instructions to hold off watering, or at least reduce watering at certain times because of this.

For plants that are not tolerant of the cold in your zone then you must protect them in the winter. They may be listed for your zone with the note that they are OK outdoors only in the warm season. (Many house plants are like this) They are supposed to be brought in before the weather gets too cold.

There are all sorts of plants that fall in between these broad concepts, and this is where knowing your zone and having a good familiarity with the plant comes in. This comes with time. No one can tell you if a particular plant will work for you in your garden, and exactly how much protection it will need.
I know what works for me, and I protect certain plants in the garden, and move other plants as I know works in my location.

A zone is a broad category, a range of similar conditions that make it easy to decide if a plant is worth trying, if there is a good chance of it surviving and thriving. In your own garden you might notice that it tends to be colder or milder than what a map might show. You garden accordingly. This comes with experience.
It is easiest to fine tune your understanding of your own garden by watching the behavior of some of the plants that are suggested as marginal for your zone. This means that sometimes they are OK, and sometimes not. If you try a plant that is listed for your zone,and you lose it several times, then you might think your garden is a bit more extreme than average for your zone.
My own garden should be able to grow Bougainvillea but it keeps dying. So I know that my garden is really a bit colder than the map suggests.

Casper, WY(Zone 4a)

One fact not mentioned is that there are hardy perennials that need coldness to force them into dormancy in order to be able to bloom the following season. It applies mostly to cold hardy perennials.

Contra Costa County, CA(Zone 9b)

Good point.
The cold hardy perennials are often plants that go dormant, perhaps all the plant disappears with just the root mass (fibrous roots or some sort of mass like a bulb) under ground.

Many plants that come from cold temperate climates (snow most winters) will develop some chemical in the buds that enforces dormancy until that chemical is broken down. In fruit trees each variety is known to need X hours of temperatures under a certain temperatures. I think the cold hardy perennials are similar.
I know I had a nice Peony for several years until we had a mild-winter spell for several years. The peony died. Not enough chill in the winter for proper dormancy.

I will go back to my points in one of the posts above:

Get to know your garden.
How does it compare to other gardens in the same zone? Can you grow plants that 'they' say you should be able to?
Keep track of how the plants do in different areas, in the ground and in pots, under a tree or patio cover, against a wall and other places that can modify your climate.

In other words: Experience is really the best way to fine tune your garden knowledge so you know how things will work in your garden.

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