Monday, 22 December 2014

Fagus sylvatica

Just a wee taste of summer today as we are in the shortest days of winter. This is the common beech, Fagus sylvatica, photographed at the end of April 2014. The leaves are expanding from their tiny concertina form through the heavily folded young leaves to the fully expanded mature form. Looking at this photograph, I can feel the sunshine and the anticipation.

At the other end of the year, the photograph below shows the same plant with the leaves in their winter form. Although they are now crisp and entirely dried out, they are equally attractive with bronze colouring and a neat pattern of veination.

Merry Christmas, wherever you all are!

Wednesday, 10 December 2014

How dark is it?

I've been trying to measure light intensity to get a clearer idea of how much variation there is in different plant growing environments. I'm going to take measurements in a number if different situations and list them here just for interest.

To understand how the photos were taken please see the page on measuring light intensity with a digital camera.

Some measurements:

March in Cambridge:
1/80th second exposure

December in Cambridge:
1.3 second exposure

Night time, with street lights,
in December in Cambridge:
30 second exposure

Indoors, after dark. 
8 second exposure

Saturday, 6 December 2014

Euphorbia and frost tolerance.

This is a Euphorbia plant showing plant frost tolerance at its best.When I took this photo the temperature was about -3 degrees C and everything around was very frozen, including my fingers. 

Some plants are able to tolerate a lot of freezing, and when the weather warms up, they carry on exactly as before, and looking as if nothing had happened. This Euphorbia is a good example. 

Some plants are not frost tolerant at all. I discovered this first-hand once when my plant growth room became confused by a heatwave outside and turned into a freezer inside. For a few hours the Kalanchoe plants inside looked like frozen versions of themselves, but when the room warmed up again they turned to mush. 

As I understand it, this is because the water in their cells had frozen into shards of ice and punctured the cell walls. In their normal state, plants are like massive structures made entirely from water-filled balloons. The little balloons are the tiny plant cells. If a plant has no frost tolerance mechanism, then in a good freeze, the ice shards will pop all of the little balloons that make up a plant's structure. When the water thaws again there is no structure to hold the plant up, and the whole thing just melts down to mush. 

Some plants, like the Euphorbia above, have mechanisms to prevent the cells from being popped. Scientists call these processes "cold acclimation". 

Summarised in a recent-ish paper (Hannah et al., 2005), it seems that plants are invoking a whole lot of different schemes to keep their cells safe during the coming frost. Plants are turning the expression of hundreds of different genes on or off, or up or down. Consequently, a whole range of activities in the plant are altered. Growth changes, and the cell walls are adjusted to make them more able to withstand the different challenge of cold weather. Salts and water are moved around to different locations in the plant. As I understand it, this is for safer storage of the water, as it might puncture cell walls if it was allowed to freeze in the wrong place, or in the wrong way. Lastly the production of antioxidants goes up, though I'm not clear on why that is or what it does. 

The real message for me is that cold acclimation is not just one single technique, or even five different techniques used by five different families of plants. It is a hugely complex system with many different layers of activity going on. 

The other interesting point is that these processes seem to occur when the plant starts to feel a bit chilly, in preparation for the actual freeze to come. This means that if we take a frost tolerant plant from a warm place, and plunge it into freezing temperatures without warning, then it might not be nearly so happy about the situation. There's a warning in that for those of us who buy plants from warm shops and take them straight home to the garden. 

So there we are. That's a little foray into the world of cold acclimation. As the winter weather ramps up this year, we will know that apparent inactivity of our garden plants is really just a graceful front. The plants have it all going on inside, as they get ready to glide effortlessly through another winter. 

Monday, 1 December 2014

Plants, light intensity and the camera

 Gardening and photography have rather a lot in common, in that they are both very dependent the availability of good light.

Plants grow best when they have plenty of light and cameras produce their best photographs under the same sort of conditions. If there is not enough light, plants become yellow and elongated, and cameras produce photos that are fuzzy or too dark.

In gardening there is always a lot of discussion of the business of "enough light" but rarely any clear definition of what constitutes "enough". There are phrases like "full sun" and "partial shade" but these refer to the number of hours in the day during which a given area of the garden will be bathed in the maximum available sunshine. This takes no account of the strength of sunshine available, which may vary significantly depending on the time of year and the location of the garden.

So here's a question: Can we measure the intensity of sunlight using a digital camera? I don't mean with a level of accuracy that runs to the nearest photon. What's needed here is just accuracy sufficient to support meaningful discussion of gardening conditions between people who may live in very different parts of the world. For example, could a gardener in Egypt describe his gardening conditions to a Canadian gardener by using his digital camera to take measurements of light intensity?

I've been experimenting with this a bit and here's one of my first attempts.

This photo was taken at the end of spring (29th March) with the following parameters:

1/80th second exposure

The photograph below was taken with the same camera, lens, and location, but on the first day of December, of the same year. 

1.3 second exposure

So can we calculate the difference in light intensity based on these parameters? To make it easier I have taken the second photograph using the manual setting on the camera, and I have set the ISO and aperture to the same levels as in the first photograph. 

I had to use a tripod to take the photograph, as the only paramater I wanted to vary was the exposure length. I ended up needing quite a long exposure, which would have introduced a lot of camera shake without a tripod. 


The answer is - Yes! It's actually pretty easy to make a direct comparison of light levels using a camera. However, it really helps if the same model of camera and lens is used to measure both samples, and it really very much helps if the camera has a manual mode to enable some parameters to be kept constant between both tests. 

The bottom line though, is that if you want to talk gardening with your distant friends, even friends who may currently be in a different season (perhaps Australia versus UK) or in a different latitude (e.g. Northern Scotland versus Botswana) then it's pretty easy to do it. 

I don't think we need to worry about expressing light intensity in Lux, or photons or anything tricky like that. As gardeners we could probably stick to expressing it in seconds of camera exposure time, on the understanding that all other parameters are kept the same between our location the location for comparison. 

The next question is to ask how this works with different models of camera, but that is a whole other thing. A question for another day I think. 

An add-on - 

MaryWilliams @PlantTeaching on Twitter has suggested that this work might also be done using a smart phone app. I've had a quick look online and it seems that there are already a number of light meter apps available. If you try this, please do write and let me know how it goes. I will compile the results from different locations. 

Good luck!

Sunday, 30 November 2014

Paeony goes full circle

As we reach the end of November our Paeony plant has finally come full circle. Here is the story of its year's growth.

Paeony plants are only visible above ground in the spring, summer and autumn. In winter their above-ground shoots die down. When the spring comes, new shoots appear at ground level and rapidly expand to form large shoots, about 2 feet tall. At the tip of each shoot, a large flower appears. When the flowers have set seed and the weather turns cold again, the nutrition from the shoots is drawn back into the storage structures under ground, and the shoots die back.

This is a paeony plant in the earliest few days of its spring growth, on the 13th March. The buds are clearly beginning to grow up and expand, but they have not got very far yet.

Partially expanded Paeony buds, 13th March.

The photo below shows a close up of one of these partially expanded buds.

A paeony shoot rapidly expanding at the beginning of spring.  This shoot is about 5 cm tall. 13th March.

After two days of further grown a similar bud on the same plant looks like this:

Partially expanded Paeony bud, 15th March. 

Two weeks later, the whole plant has exploded into growth, producing large green leaves, with large spherical flower buds at the tips of the shoots. 

Well expanded Paeony buds 29th March. 

Below is a close up of the shoot that was shown at the top of the page. It has clearly changed at great deal in only a couple of weeks, and is almost ready to flower. 

Well expanded Paeony buds 29th March. 

The plant flowers, but then remains much the same until about the end of August or a bit later. By the end of November the nutrition in the leaves has almost all been drawn back down into the underground storage tubers. The is clearly seen in the photo below, with all of the leaves turned brown and dry.

29th November of the same year. 
At this point it is quite reasonable to cut all of the old foliage off, which leaves the plant looking much as it did at the top of the page. The photo below shows the plant with its leaves all gone, and the new buds for next year all poking out, and ready to go.

29th November of the same year. 
 The photo below shows a close-up of these new shoots. They are ready to burst into growth as soon as the conditions signal to the plant that spring is firmly established. When that happens the buds will grow in exactly the same way as we saw in the first photographs above.

29th November of the same year. 

The paeony is a remarkable plant that is able to go through this explosive cycle of growth and renewal ever year. In particular it has the uncanny ability to shut down all of its used leaves at the same time as producing the new buds for next year. This must take some pretty serious organisation, as it is akin to waking up and going to sleep at the same time. Yet another fascinating area of botany just waiting to be explored.

Saturday, 29 November 2014

Geranium robertianum

Things are a bit quieter in the garden at this time of year. The weather is quite cold, reaching only 10 degrees C in the daytime and 5 degrees C at night. Most things have stopped growing. The main exceptions are nasturtiums (Tropaeolum), and herb robert (Geranium robertianum), the flower of which is shown below.

Taking the photo was hard because it is pretty dark even during the day at the moment. Whoever invented ISO-2500, they did me quite a favour. :-)

Specs for the photo:

aperture: f/7.1
1/160th second exposure

Happy November to you!

Sunday, 2 November 2014

How closely are these two plants related?

Sometimes we find two plants with unmistakable similarity, and we might wonder how closely they are related? Can we, as enthusiastic gardening bods, burrow into the scientific data online and figure this out for ourselves? Yes, we can!

Academic science is all made public via journals, and increasingly via big bioinformatics databases.

This means that if we want to find out how closely two plants are related then it only takes a couple of minutes work, and no expense to figure this out. 

First we go to the NCBI Taxonomy Browser:

We search for the first of the two plants that we are interested in: Iris reticulata Harmony

Iris reticulata Harmony
The complete lineage if the species is shown near to the top of the page under the word "Lineage":

cellular organisms;

The second plant that we are interested in is a marsh orchid, which I think is probably Dactylorhiza majalis.

A marsh orchid, probably Dactylorhiza majalis
Searching for this plant name gives the lineage below:

cellular organisms

If we take the two lineages of these plants and look for the categories in common we can see where the two species are believed to diverge, just below the  Asparagales:

                                         cellular organisms;














                             Iridaceae;                          Orchidaceae

                                  Iris                                     Orchidoideae




Clicking around in these pages it is possible to see that our two plants are also related to other plants in the Asparagales group, for example Agapanthoideae (African lily family), Allioideae (onion famly), and Asparagaceae (asparagus family).

So the answer is that they are pretty closely related, but there are a bunch of other things that are in that group too, which are also fairly different. 

It is very easy to find out which plants are also in this group, and we might like to consider growing some to see if they enjoy the same conditions as are two existing plants. Remember though, a marsh orchid that thrives in wet Scottish soil and a tropical orchid are unlikely to like the same ground, even though they may be in the same family group, so this is careful work. We definitely want to read up on these related plants before we go spending hard earned cash on plants. 

Good! So now we have done some bioinformatics with our gardening. That's a pretty good day by any measure. 

Sunday, 26 October 2014

Marsh orchid

The photographs below are of a group of Marsh orchids (a Dactylorhiza species, probably Dactylorhiza majalis.)

The plants grow wild in a large garden in the west of Scotland and one is a very nice large example. You can see the scale from the last photograph by comparing with the adjacent buttercups.

Aren't they stunning? :-)

Monday, 29 September 2014

Looking close up

Sometimes the garden can seem, at first glance, to be a bit less colourful and exciting than we might like. However, it turns out that there are all sorts of interesting things to see if we just go closer to the plants and have a good look. The plant below is a heather. It looks very beautiful and intricate close-up. 

The photo below shows how this same plant looks from only a foot away, so in this case it really is worth while getting up close for a proper look. 

What do you see in your garden, if you look really close-up?

Thursday, 25 September 2014

Why are strawberry seeds on the outside of the fruit: part 2.

Yesterday we formed a hypothesis about why strawberry seeds are on the outside of the fruit, when apple seeds are on the inside. 

Today we are going to have a look inside the strawberry flower and see if the anatomy backs up our theory. 

Below is a cross-section of a strawberry flower. The sexual organs are in the centre, with the female organs held on a tall column of tissue. The male organs are arranged in a ring around the female organs, and four of them are visible in this photo. The petals and sepals can also be seen flanking the male organs. 

The tall column in the centre is the part that will expand massively to make the strawberry fruit that we are so used to eating. The little green organs that sit all over the column are the many individual female organs. Each one of these tiny female organs has an ovary at the base and can produce one seed in the ovary.

The image below shows a close-up of this area of the flower. We can now clearly see each female organ, with a bean-shaped ovary at the base, a tall style reaching up, and the stigma at the top, where pollen will be deposited. It is very obvious from this photograph that that the ovary does indeed sit on the outside edge of the tissue that will later develop into the bright red strawberry fruit tissue. 

The photograph below shows a cross-section of the same small green strawberry that we looked at yesterday. As we can see, the fruit tissue has already increased hugely in size, and the seeds are already fairly mature, and sitting on the outside of the fruit. 

The photograph below show the fully mature ripe fruit in cross section. By this stage, the fruit tissue has grown even more, and the seeds are still visible on the outside edge. Small white lines of tissue are visible reaching out to each seed, and i assume that these are lines of vascular tissue taking food and water to the seed. This is just an assumption and I have not verified it.

So there we are. The inside of the strawberry flower seems to confirm our hypothesis that seeds grow on the outside of strawberries, because the ovaries sit on the outside of the nascent fruit tissue in even in the flower.

Wednesday, 24 September 2014

Why are strawberry seeds on the outside?

Why do strawberries have seeds on the outside, when apples have seeds on the inside? I wonder that every time I see a strawberry. Lets have a look and see what's going on. 

Below is a strawberry flower. In the centre is a large green blob covered in things that look like tiny green hairs. The hair-type things are the stamens and there are *lots* of them.

The carpels are the female part of the flower, on which pollen is deposited by insects. At the base of each carpel is an ovary containing an egg cell. The egg cell will be fertilized by the sperm that comes from the pollen. Together the fused pollen and sperm cells will develop into a seed. 

That means that for each of these tiny green hairs we will get one seed. So that explains why there are such a lot of tiny seeds. But why do they end up on the outside of the strawberry?

Well now we have to use our imaginations a bit. The critical question, as we recall, is why are apple seeds on the inside of the apple when strawberry seeds are on the outside? 

Lets think of the tasty part of the fruit as a big blob of tasty playdoh. Even in the newly opened flower, the very beginnings of this tasty playdoh are already present. In the strawberry's case, it seems to me that the ovaries just happen to be on the outside of the miniscule blob of playdoh, and so that's where the seeds develop. I assume, conversely that the apple ovaries are inside the blob of tiny blob of playdoh that is already present in the flower, and so when the apple develops, the seeds will be on the inside. Apples contain far fewer seeds, because their flowers have far fewer stamens.

These are my assumptions about the system. Tomorrow we will cut open a strawberry flower to test whether my assumptions are right.

So what happens when the flower starts to develop into a strawberry? First, the fused egg and sperm cells develop into a seed. At the same time the tasty fruit tissue develops and becomes larger. The photo below shows a tiny strawberry with its new green seeds and green strawberry tissue gradually developing. As the seeds mature, the fruit tissue enlarges and takes on its mature shape. 

A few days later, the fruit tissue is becoming larger and less green, while the seeds stay the same size and gradually get further apart. 

Finally the fruit tissue matures and takes on the rich red colour, telling us all that it is ready to eat. The seeds are sill visible on the surface, but are now much less prominent and much smaller in proportion to the mature fruit. 

So now we know. Strawberry seeds develop on the outside of the fruit, because the ovaries are on the outside of the rudimentary fruit tissue, even when the flower opens. In apples, conversely, the ovaries are right inside the fruit tissue, even at the time when the flower opens. 

Next time we look at a flower on a strawberry plant or apple tree, we can take careful note of the number of stamens. We know that we will be seeing just the same number of seeds on the fruit later in the year. We know exactly where they will be, and why. 

Just in case you were wondering, several strawberries were eaten during the making of this blog post. 

Wednesday, 17 September 2014

Bird Cherry Ermine

The Bird Cherry Ermine (Yponomeuta evonymella) do an amazing thing in the park near us every year. They colonise a whole row of Bird Cherry (Prunus padus) trees, eat all the leaves, and drape the trees all over in white webs, so that the trees resemble snowy Christmas trees. Below are some photos of the most recent colonisation.

Initially the trees look just like any other tree in summer - covered in leaves. Then the eggs are laid on the trees, and hatch into caterpillars. The caterpillars are there in their thousands and eat all the leaves completely away, so that not a single fragment of leaf is left.

In the distance the trees just look white. 

In close-up we can see the thick white webs on the twigs of the tree, and the caterpillars swarming all over them.

At the base of the tree, the webs fan out and the caterpillars can be seen marching away towards, what they hope is the next tree. They usually have to dodge round a bunch of curious children and lots of adults with cameras.

In the photo below you can see a grey area on the base of the trunk. This is a big pile of caterpillars. There are thousands of them on each tree.

The caterpillars do this for maybe a month or two each summer, and then they all vanish away to get on with their lives, and all of the trees' leaves grow back. A few weeks later, there is no sign at all that the caterpillars were ever there.

Tuesday, 16 September 2014


The plant below is Lunaria annua, better known as "Honesty". 

This is a beautiful flower, easy to grow, and very forgiving to the novice grower. It self-seeds freely and fills the garden willingly with flowers, with very little effort from the gardener. 

We all know the honesty plant when we see it. It is the one that produces these amazing seed pods, which are completely transparent. Initially the pods are green, but as they mature, it is possible to peel off the green outside layers, and reveal the beautiful translucent section, with the seeds visible in the middle. 

Honesty lives for two years, flowering in the second year, but once a population is established in the garden it self-seeds so freely that the garden is never without these flowers. 

What could be better?

Sunday, 7 September 2014

Composite flower developing

We previously looked at the parts of a composite flower, and in this page we're going to look at the development of the same flower. 

This photo shows the immature flower in close-up. As you can see the miniature flowers in the centre are maturing at different rates. The outer flowers are already mature, but the central flowers are still immature, with the male organs apparent, but the female organs still hidden. 

Immature flower of Osteospermum 'Tresco Purple'

This flower (below) is slightly more mature, and all of the tiny flowers in the centre have reached maturity, so that all of the female organs are all clearly visible.

Mature flower of Osteospermum 'Tresco Purple'

This developmental sequence is rather similar to that seen in the previous post "Guess what's going to be!"

Parts of a composite flower

We previously had a look at the parts of a simple flower, and in this post we have a composite flower. 

In the simple flower there was a cluster of sexual organs in the centre of the flower. The female organ was in the centre of the cluster and the male organs were in a ring round about. The composite flower still has a cluster of sexual organs in the centre. However, this cluster of organs is made up of several tiny individual flowers. 

Osteospermum 'Tresco Purple'

The close-up below shows the cluster of sexual organs in more detail. If you look closely you can see that each tiny flower has a central female organ with a sort of yellow cross on the top. Surrounding the female organ are a number of male organs which each have a green top. Then surrounding the male organs are some very small white petals.

If you count the female organs (with the crosses) then you can see that there are very many tiny flowers. This is why the whole big structure is called a composite flower. It is composed of many little flowers, with just one ring of big mature petals round the outside.

That's all you need to know to understand composite flowers. Next time you see a daisy, you can now give it a knowing look. :-)