Do Plant Cuttings Need Light? (What About Darkness?)


Taking plant cuttings is a great way to get new plants for your garden without breaking the bank.  However, cuttings need certain light conditions to take root and grow into healthy plants.

So, do plant cuttings need light?  Plant cuttings taken from a stem or leaf will need light to root.  Root cuttings can be left in the dark until they grow shoots and leaves.  Plant cuttings need bright light for photosynthesis so they can make energy for new growth.  However, they should be kept out of direct sunlight, which can stress the new plant by overheating or dehydration.

Of course, light is not the only important factor for plant cuttings.  There is a balance between competing factors (such as light, water, and temperature) to ensure proper growth.

In this article, we’ll talk about what type of light plant cuttings need.  We’ll also answer some common questions about light for plant cuttings.

Let’s get going.

Do Plant Cuttings Need Light?

Some plant cuttings do need light in order to grow, and others do not.  For example, root cuttings do not need light until they start to form stems and leaves (after all, roots cannot use sunlight in photosynthesis – they need leaves for that!)

Stem cuttings and leaf cuttings are a different story.  These types of cuttings do need light for photosynthesis, which in turn allows them to produce roots.

plant cutting
Stem and leaf cuttings need light for photosynthesis, which allows them to produce energy for roots.

If a cutting has leaves, the energy for new roots will come from photosynthesis (which requires light).  If no leaves are present, the cutting will use energy reserves from its shoot (stem) to produce roots and leaves.

Light is important to plant cuttings for other reasons as well.  For example, according to the Michigan State University Extension:

“Light provides the energy for callus formation and the subsequent generation of adventitious roots.”

https://www.canr.msu.edu/uploads/resources/pdfs/lighting-of-cuttings.pdf

A callus is the spot where a plant heals over after an injury.  A callus helps to protect a plant cutting in two ways:

  • From diseases (bacterial, viral, or fungal) that threaten to infect an injured plant by invading through the cut area.
  • From dehydration (which is more likely when a plant is exposed to direct sunlight in a dry environment).

Adventitious roots on a plant grow from stem or leaf tissue.  They can form in response to stress and injury.

These adventitious roots are necessary for the plant to begin drawing water and nutrients from soil to continue growth.  Without the ability to form adventitious roots, a plant cutting could not survive to become a new plant.

Although light is important for plant cuttings, there is a balance to aim for:

  • Without enough light, stem or leaf cuttings will not be able to grow roots fast enough to survive.
  • With too much light, the plant will be stressed by heat, dehydration, or burned leaves.

The solution is to start with low light right after a cutting is taken.  Then, gradually increase light levels later on as roots form and the plant becomes more established.

The key is to provide more light gradually, rather than all at once (a sudden change to direct sunlight could stress plants).  You can learn more about hardening off plants in my article here.

daylight
Give plant cuttings bright light, but keep them out of direct sunlight until they are more established.

The Purdue University Extension suggests putting a plant cutting in a bright area, but out of direct sunlight.  That way, the leaves will get enough light for photosynthesis & energy production, but the cutting will not overheat.

If water loss in a dry climate is a concern, there are some steps you can take to reduce the risk of drying out the cutting:

  • First, water the plant well before taking a cutting (this will reduce water stress later).
  • Next, make sure to take the cutting early in the day (before temperatures rise).
  • After taking the cutting, remove some leaves to prevent water loss (which occurs via transpiration through the leaves).
  • Then, put the cutting in a plastic bag with a damp paper towel inside (this will retain moisture and keep the air around the cutting humid.)
  • Finally, keep the cutting out of direct sunlight (since this will cause faster water loss via evaporation).

You also have the option to build or buy a humidity dome to keep cuttings moist.  You can learn more about humidity domes in my article here.

Remember that for some plants, it can take months for roots to form.  To speed things up, remove any flowers or fruit from the cutting that would take energy away from root formation.

Do Cuttings Need Sunlight?

Cuttings do not need sunlight, and they can grow without sunlight (as long as they get artificial light instead).  In fact, according to the North Caroline State University Extension, it is a good idea to avoid direct sunlight for cuttings right after they are cut.

You have the option to provide cuttings with diffused sunlight or artificial light.

Diffused sunlight falls evenly with no bright or dark spots.  It is scattered and comes from every direction.

Diffused sunlight is not as harsh as direct sunlight.  Sunlight is diffused when:

  • It is blocked by clouds (such as on an overcast day).
  • It reflects off of other objects (such as the ground).

You can use any number of artificial light sources for plant cuttings, including:

  • Incandescent bulbs – These bulbs are not very energy efficient.  They give off lots of heat, so they might make it too hot for cuttings, especially in a small space.
  • Fluorescent bulbs – These bulbs are more energy efficient and give off less heat than incandescent bulbs.  You can find full-spectrum fluorescent bulbs, which mimic sunlight to provide more of the different types of light a plant needs to grow.
  • LED bulbs – These bulbs are the most energy efficient and give off very little heat.  You can find full-spectrum LED lights that provide more of the different types of light that plants need to grow.
LED lights
LEDs are energy efficient and do not give off much heat, so they could be used for cuttings.

How Much Light Do Plant Cuttings Need?

Root cuttings do not need light until shoots and leave start to form.  Plant cuttings from stems and leaves need less bright light right after they have been cut.

stem cutting
A stem cutting will need some sunlight so that the leaves can produce energy.
Image courtesy of user Kumar83 at Wikimedia Commons: https://commons.wikimedia.org/wiki/File:Stem_Cutting.jpg

As their root systems get established, they can tolerate more light without suffering from stress, overheating, drought, or burned leaves.

You can learn more about exact lighting requirements for plant cuttings in this article from the Michigan State University Extension.

Should Cuttings Be Kept In The Dark?

The University of Maine suggests that root cuttings can be kept in the dark until new shoots appear.  After all, the roots cannot do photosynthesis themselves (they need leaves for that!), so they don’t need sunlight right away.

However, stem and leaf cuttings should be placed in bright, indirect sunlight (diffused sunlight) or under artificial lights.

plant cutting
As plant cuttings grow, they can handle more light. Eventually they can transition to direct sunlight.

As plant cuttings become established and grow into new plants, they will have the same light and darkness requirements as the parent plant.

According to the Oregon State University Extension, photoperiodism affects whether plants flower.  Most plants can be categorized into a few categories:

  • Short Day – these plants form flowers only when day length is less than 12 hours (includes chrysanthemums and poinsettias.)
  • Long Day – these plants form flowers only when day length is more than 12 hours (includes lettuce, spinach, and potatoes.)
  • Day Neutral – these plants form flowers with no regard to day length (includes tomatoes and cucumbers.)

Depending on the plant, it may need a certain length of time in darkness to form flowers and fruit.

Do Cuttings In Water Need Sunlight?

Leaf and stem cuttings in water need some type of light for photosynthesis.  That way, they can produce the energy they need to form roots.

The light source for cuttings in water could be either sunlight or artificial light.

Do Cuttings Need Light To Root?

Stem and leaf cuttings do need light to root.  According to the University of Michigan, a lack of light will delay rooting.

Root cuttings do not need light, since they already have roots.  However, they will need light to continue growing once they form shoots and leaves.

How To Make Cuttings Root Faster

There is a way to make plant cuttings root faster and increase the chances of a successful propagation.  Rooting hormone promotes faster root formation from cuttings.

Auxins are one type of plant hormone that promotes root growth.  You can find rooting hormone online or at garden supply stores.

plant roots
Rooting hormone can help cuttings to develop roots faster.

When applied to the cut end of a plant cutting, rooting hormone speeds up the process of root formation.  This increases the chances of survival for a plant cutting (faster rooting means the plant can absorb water and nutrients from soil much sooner.)

Conclusion

Now you know how much light plant cuttings need and how to give it to them.  You also know how to help cuttings adjust to more light gradually.

I hope you found this article helpful.  If so, please share it with someone who can use the information.

If you want to read some of my most popular posts, check out the “Best of GreenUpSide” page here.  Enjoy!

~Jonathon

jonathon.david.madore

Hi, I'm Jon. Let's solve your gardening problems, spend more time growing, and get the best harvest every year!

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