Hi Bernard,

We have huge drifts of these growing naturally in the garden and they are very lovely in Spring.

Like many other woodland spring flowers, A. nemorosa has evolved to exploit the short period between the end of the cold of winter and the start of summer by which time the deciduous canopy of leaves has fully opened to block out much of the light. As such they emerge, foliage first, around March time and die away again by June. Their emergence and lapse back into dormancy is triggered mainly by light levels, but water will play a part too.

When you say you planted yours out "last spring" I guess you mean spring of 2010 - i.e a few months ago? It sounds like the plants that you planted out have behaved more-or-less naturally whilst the ones you have under observation in pots have had their growing seasons extended by having greater access to light/water/food. From the plants' point of view they will keep going as long as they are able to effectively gather and store energy. As soon as it takes more energy to keep the growth going that they are able to obtain via photosynthesis etc., then they will become dormant.

A further factor for your plants will be that the ones in pots have been able to grow on undisturbed, whilst the ons you planted out will have had to adjust to new soil and conditions, and, as with any plant, it will take them a while to fully settle and get growing strongly once again.

Ilex, what a brilliant reply. At the moment, my gardening knowledge is very limited and I have the greatest difficulty in deciding whether a plant has become dormant or died. For this reason, when my primroses disappear, I never know whether I'll see them again.
I wonder if I might ask you a couple of supplementary questions? First, when would you suggest I should plant out the ones that are still in pots. Secondly, as we are now entering our fifth week without rain and the woodland areas where I'm trying to establish these and other appropriate plants is becoming very dry and I wonder if the anemones and other plants that become dormant will suffer unless I keep the topsoil damp.
I would very much appreciate your advice n these points.

Glad to be of help. :-)

Given the extremely dry summer that we are all having I would wait until early autumn before planting out your potted Anemones, at which time they should just be dormant rhizomes. That will give them a good long period to develop new roots and settle down in their new positions before coming back into growth next Spring.

One of the reasons that plants go into dormancy is to protect themselves from dessication, so your already planted Anemones will be better able to cope with the dry weather than other plants that are still in active growth. Remember they have evolved in sync with warm, dry summers and colder, wet winters, so this weather that we are having now (even though it seems unusual after so many wet summers and mild winters!) is actually roughly what they would be expecting.

As a general rule all dormant plants should be kept on the dry side (whether they are in the ground or not) since it's much easier for fungus and bacteria to strike in damp conditions and whilst the plants are unable to fully defend themselves.

Ilex, your help is invaluable. There is one other question - is there a name for the group of plants that behave like the Anemone by becoming dormant?

No problem.

All temperate growing plants have a dormancy period, most commonly in winter of course, but these Anemones and many other early Spring woodland-floor plants are summer dormant. Winter dormant plants are known as "brumate" whilst summer dormant are "aestivate", although they're more usually just referred to as summer dormant.

Ilex, you are so helpful that I am reluctant to take advantage of your good nature, but your answer raises yet another question in my mind. Not all plants that become dormant actually completely disappear leaving no sign above ground. Is there a separate category for those that disappear rather than just losing their leaves? Actually it strikes me that I might need a good book, although I have found that books which are probably written for the professional tend to add to my amateur's confusion! Thanks for your patience and I hope you aren't regretting answering my question in the first place.

Hi Bernard,

No, certainly not regretting answering your Question, am happy to be of help if I can.

You're right that plants that are in dormancy appear very different to us, as gardeners, but what they all have in common is that they are not in active growth. So an evergreen Rhododendron, for example, is just as much in dormancy in December as the Anemones will be in August, even though the Rhododendron appears, to the casual observer to be much the same all year round. Neither plant is completely inactive; the Anemone will be exchanging moisture and gases and the rhododendron will be having to maintain water to it's foliage, but it's the lack of active growth that defines dormancy in a plant.

The only thing that differs is the type of plant. So an Anemone is an herbaceous plant (technically known as a herb - though not in the culinary sense!) meaning that it retreats to it's underground storage system (in this case a rhizome) when it's dormant, where a Rhododendron is a woody shrub, which means it retains it's above-ground structure when dormant (and it's leaves too, since it is also an evergreen).

There are a variety of other categories too, and some plants are able to straddle different categories, particularly when grown well away from their native climates. For example Cestrum nocturnum (AKA Night Jasmine) normally behaves as an evergreen woody shrub in much of the tropics where it is grown, but becomes a deciduous herbaceous perennial when grown here. It's a survival strategy that allows the plant to shift it's energy and resources to the protection of an underground retreat when conditions become unfavourable, which in turn means it can successfully colonise less favourable territory.

Hope that makes sense!

Wow! How wonderful it must be to have such a deep understanding of the behaviour of plants and how generous of you to share your knowledge so unstintingly. I am very much obliged, Ilex.