Jorge, Plants

Green plants appear green due to a pigment called chlorophyll that primarily absorbs blue and red wavelengths of the visible light spectrum, but reflects a portion of green wavelengths. This green light enters our eyes and hits the light-sensitive retinas, in which there are cone cells, that once stimulated, sends a signal to our brain that interprets the information, giving the colour green. Therefore it can be stated that the colours of an object is dependent on what colours are reflected (or transmitted) back to our eyes. (Technically speaking,  visible wavelengths have no colour. Colour is created in the brain.)

Most humans are trichromats, and possess three types of cone cells sensitive to red, green and blue light, named L M and S respectively. Each cone allows us to distinguish around a hundred shades, so the total number of combinations is at least a million. Colour is determined by our brains that interpret the different ratios of these three colours.

The visible light spectrum ranges from approximately 400nm to about 700nm. Our brain attaches different colours to different wavelengths with blue at about 475nm, green at about 510nm and red at about 650nm. Picture Credit: Vanessaezekowitz (2007) licensed under CC BY-SA 3.0.

Not all humans, or all animals, perceive colour in the same way. Dichromats, such as dogs, possess two types of cone cells and can distinguish blue and yellow, but not red and green. Their vision is similar to some colour blind humans, who only have two working cone cells due to either an absence or a malfunction of a third type of cone cell. Not all colour blind humans are the same as they can have different combinations of working cone cells (or none at all), and thus are unable to see different colours, resulting in different colour spectrums.

Some animals are tetrachromatic and able to distinguish to four primary wavelengths of light. Birds, for example, are even able to view ultraviolet light, which is beyond the visible light spectrum. (Interestingly, humans with Aphakia can also view ultraviolet as their lens has been surgically removed. For the rest of us, our lens blocks this light.)

Some women are tetrachromatic as they possess four types of cone cells, which allows them to see a hundred million colours. The extra cone cell has its origin in their fathers’ colour blindness, who possess two working cone cells and one mutant one. This mutant one is passed on to the daughter, who then has four cone cells. It is probable that tetrachromats have to train themselves to see such an array of colours, as the natural world will not have such a diversity of colours for the brain to learn to use the fourth cone. As such, it is likely that most will go through life without recognising their potential.

The absorption spectrum of a bird’s (Estrildid finches) four cone cells.

So tetrachromats, both human and non-human, can distinguish many more hues of green than  the rest of us, and plantlife may appear very different. For animals like birds this may be very useful for distinguishing between plants to find sources of food or shelter.  For the rest of us, our trichromatic vision proves very useful in allowing us to quickly identify between opportunities for profit and sources of danger, such as when fruits are ripe.

Plants need to absorb light in order to carry out photosynthesis to produce glucose, which can be used for metabolism and growth, or stored as starch. Photosynthesis is a chemical reaction that inputs sunlight, water and carbon dioxide and outputs glucose and oxygen. It is a two step process, comprised of light-dependent and light independent reactions. In the former sunlight plays a key role by providing the chlorophyll with energy to kickstart the complicated chemical reaction.

In green plants, there are two types of chlorophyll: chlorophyll a and chlorophyll b that both absorb different spectrums of light. They both complement each other with a absorbing more red light and b absorbing more blue, and this allows the plants to fulfil its energy requirements. As you can see in the graph below, chlorophyll still absorbs green light but not to the same extent as they do red and blue.

Picture Credit: Daniele Pugliesi (2008) modified by M0tty licensed under CC BY-SA 3.0.

However, this is not the full story. The above graph represents the absorption spectra of extracted chlorophyll molecules. As part of a plant, chlorophyll never exist alone but are bound to molecules that influence what it absorbs, and as such plants absorb about 70% of green light.

There are other pigments (accessory pigments) inside green plants that play a role in photosynthesis such as carotenoids. They primarily absorb green and blue, but reflect yellow, orange and red. It is these pigments that give many plants’ leaves their autumnal colours, and signal the presence of ripe fruit, once the amount chlorophyll is reduced. These accessory pigments are useful as they allow the plant to capture more of the sun’s energy by broadening its absorption spectrum.

So, what about plants that aren’t green? While all plants that photosynthesise contain chlorophyll a, they can contain many different types of accessory pigments, giving them different colours. For example, many reddish-purple plants contain the pigment anthocyanin in such abundance that acts to mask the green chlorophyll pigments.

So, why do plants use red and blue light more so than green? And why do they not absorb all visible light (and henceforth appear black)?

It is believed that today’s plants evolved from a common ancestor (green algae) that used chlorophyll to photosynthesise. Why no alternative dominant pigment emerged is an unanswered question, although many hypotheses have been proposed. Evolution is a product of multiple processes such as random mutation, random selection and natural selection, and henceforth plants can’t design or choose the best pigment to use. It is therefore probable that once chlorophyll proved successful no new alternative dominant pigment emerged, thus enabling green plants to dominate the landscape. Although, there is a possibility that (primarily) utilising a narrow band of wavelengths (red and blue) for photosynthesis is mechanically superior, and this allowed early organisms to outcompete other lifeforms.

For more discussion on why plants use chlorophyll, and are henceforth green, can be found here, here and here.

Why do plants use the visible light spectrum for photosynthesis?

In general, plants only absorb trivial amounts of light outside of the the visible light spectrum. This is because the sun produces the most light in the visible light spectrum, and chlorophyll have evolved to utilise it. (If you look at the graph above, chlorophyll a’s absorption spectrum is almost exclusively confined within the visible light spectrum.) There are other mechanical reasons for this. Visible light is perfect as it provides just enough energy without causing damage to the plants’ cells. By contrast, ultraviolet is damaging and infrared contains insufficient energy. In addition, a lot of ultraviolet light is blocked by the ozone layer.

Jorge at PrimroseJorge works in the Primrose marketing team. He is an avid reader, although struggles to stick to one topic!

His ideal afternoon would involve a long walk, before settling down for scones.

Jorge is a journeyman gardener with experience in growing crops.

See all of Jorge’s posts.

Brian Rees, Decoration, Garden Design, How To

When you have a standard fence, it might seem too staunch or generic next to your artistically designed home and lawn. To help your fence match your design ideals without building a new one, there are several amendments that can be made without using a lot of tools. Although some of these project ideas are more advanced than others, all of them are suggestions that can become the curb appeal solution you have been looking for.

Fence in garden design

Beyond a simple coat of paint

Although adding a fresh coat of white paint to any fence makes it look clean, the white color might not fit in as well with your overall curb appeal as well as another one. Instead, consider using an exterior paint that will provide contrast against your current house paint color. For solid wooden fences you can also create a mural effect by using each individual fence post as one solid canvas.

Using the power of zip ties and decorations

Many fences cannot withstand a lot of extra weight from items hanging on them without shifting over time. However, decorations can be placed on the ground and leaned against two fences with ease. To create some extra security, use zip ties to hold the decorations in place. Good examples are large wooden stars that are repeated in a pattern along a fence in order to provide decorations that are appropriate for the lawn.

Having fun with DIY molded concrete features

Decorating a brick, stone or masonry fence may not be easy until you get a taste of custom concrete lawn decorations. In many instances, molds can be purchased online, and making a small batch of concrete is easily done with a bucket and a stick. Once the concrete is poured into the mold and sets, the end result is a decoration you can use for your current stone fence. In addition to plain concrete finishes, you can also paint concrete.

Creating a false hedge or window

When you need a strong fence but hate the way it looks, putting something in front of it is often the best solution. For example, by soaking long twigs, you can weave them onto poles to completely conceal your current fence to create a look that resembles ordered bramble. Other ways to conceal a fence include using strips of canvas fabric to hang on the fence as if they were curtains hiding a large door or window.

Decorative screening rolls

In the same vein, you can also get rolls of decorative garden screening to attach to your fence. Simply fix them in place and your existing fencing will be hidden, replaced by something much more attractive. It’s great for quickly creating a different feel, such as using bamboo screening to enhance an oriental theme or willow for an English country garden.

bamboo screening

Using ropes to create decorative effects

If you want your fence to create a visual backdrop but do not have a lot of money to spend on something that will get stolen or will blow away, consider buying some rope and doing some macrame. While it might take some tinkering with cheaper nylon rope to get the design you want, there are many simple knots that can be beautiful decorations for fences when the right type of rope or silk cord is used. Along with making knots, other items can be used to cinch two pieces of rope together to create a netted or quilted effect. For a more dramatic effect, use a larger diameter of rope.

Choosing the right creeping plants

When you have a fence that is difficult to decorate and local neighborhood housing codes deny your ability to decorate your fence in the way you want, the only remaining option is to pick something that will grow into and over your fence. Instead of picking a typical rosebush or boxwood hedge, consider using other types of unexpected plants that give you the height you are looking for. Good choices include newer types of grasses as well as classics like bamboo or Bermuda grass.

Hanging baskets on fences with no plants

Do you have a fence that looks boring and also hangs out in the dark all night? You can kill two birds with one stone by decorating a fence with hanging baskets, a but instead of putting plants inside of them, strings of LED lights can be used. In addition to metal hanging baskets overflowing with LED lights, there are also larger rectangular planters with open framing that can allow for more creativity when filled with outdoor LED light strings.

Using bamboo poles to create curb appeal

One of the hardest fences to decorate is the chain-link fence. While some chain-link fences have decorative plastic woven into the metal frame, these pieces soon crack, fade or become displaced. A better and sturdier solution is to weave pieces of green or freshly cut bamboo into the chain-link fence. If weaving the bamboo is not working, using string to tie bamboo to the chain-link fence is often just as beautiful to onlookers.

Brian ReesBrian Rees is a media relations representative for Exterior Expressions. In his spare time, he enjoys writing, music, and spending time outside.

Flowers, Gardening, George, How To, Infographics, Planting, Plants

No plants will survive very long without good watering, and it’s even more crucial for potted plants. They may not have the same access to rainwater, drainage or natural water reserves depending on where they are placed. So here is our handy infographic to remind you how to water pot plants for great growing!

If you’re looking to give your potted plants a fabulous new home, then you’re in luck. At Primrose we have an incredible selection of all kinds of planters available.

How to water pot plants

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Catch up on the previous post in the series: How to Repot a Plant.

Next up is Part 4: How to Choose the Right Planter for Your Garden.

George at PrimroseGeorge works in the Primrose marketing team. As a lover of all things filmic, he also gets involved with our TV ads and web videos.

George’s idea of the perfect time in the garden is a long afternoon sitting in the shade with a good book. A cool breeze, peace and quiet… But of course, he’s usually disturbed by his energetic wire fox terrier, Poppy!

He writes about his misadventures in repotting plants and new discoveries about cat repellers.

See all of George’s posts.

Gardening, George, Grow Your Own, Hedging, How To, Plants

Caring for topiary

Growing topiary is one of the most magical arts you can master as a gardener. We all love the huge hedge animals and blooming box clouds. But maintaining and caring for topiary plants can be a lot of effort, so we’ve broken down the steps into our top tips. Keep this checklist handy as you get to work on your creations!

  1. Plant your high hedges wide as they’ll need a lot of root space.
  2. Topiary needs aerated soil so make sure it doesn’t become waterlogged. Use good compost, bark mulch and grit.
  3. Feed your plants with slow release fertiliser granules, and Growmore once every spring.
  4. Water regularly over summer and give a light watering in winter.
  5. Sterilise your cutting equipment with antibacterial spray to avoid transfer of disease.

Clipping topiary hedges

  1. Clips your plants into shape once or twice a year. During summer is the best time to do this – start after frost season is definitely over and finish up by September.
  2. Only cut the topiary on an overcast day as bright sunlight will scorch the leaves.
  3. Experts recommend trimming first with power tools for speed, then cleaning up with sharp shears.
  4. If you’re training growing branches then use soft twine so it doesn’t cut into the wood.
  5. Watch out for signs of disease. Box hedges are particularly affected with box blight and box suckers. Yew can be hit with phytophthora root rot.
  6. If your topiary has been neglected then hard prune it in early spring to get it back into shape. Then give it plenty of feed and mulch.

Topiary maintenance

We hope these tips will get you started on the path to topiary perfection. If you have any other points on how to care for topiary then please share in the comments below!

George at PrimroseGeorge works in the Primrose marketing team. As a lover of all things filmic, he also gets involved with our TV ads and web videos.

George’s idea of the perfect time in the garden is a long afternoon sitting in the shade with a good book. A cool breeze, peace and quiet… But of course, he’s usually disturbed by his energetic wire fox terrier, Poppy!

He writes about his misadventures in repotting plants and new discoveries about cat repellers.

See all of George’s posts.