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Direct Light, Indirect Light, etc

User
9 years ago

Tis the season for moving plants back outdoors and gradually acclimating them from indirect to more direct lighting. (Well not quite time for me yet actually, average last frost here is mid-May.) Anyway, I have found that the terminology for outdoor lighting is somewhat un-intuitive so I am working on making a table of lighting conditions to understand them better and would appreciate some help filling it in. What I have done is just listed a series of terms I have read through my research and if you can help provide a definition to fill in the blanks that would be great! (A generic example would also be helpful.) My hope/goal is that this will eventually become a useful guide for other beginners like me so I have taken the liberty to include some general advice I have read in other posts as well.

First a Quick Question

Can you begin acclimating plants earlier in the season when there is still a frost risk by bringing them back inside at night? Or is it generally a better practice that once the plant goes out it stays out?

Lighting Conditions

(Please feel free to add any others you can think of and I'll work on figuring out the forum's edit feature to add them to the list!)

  • Direct Light: I think I have this one pretty well covered--sunlight is directly hitting (lighting up) the leaves of the plant - or - to think about it differently, the plant is casting a shadow. (Example: A plant in the middle of a wide open field.)

Indirect Light: At the most basic level, this is light that does not directly hit the plant (kind of a circular definition if you ask me). What this really means is light that is reflected onto the plant, say from the ground or a wall. Imagine being in a dark room and shining a flashlight on the wall at an angle. There will be a very bright region (direct light) and not so bright regions on the periphery (indirect light). Some of the light may even reflect onto the ceiling. (Example: A plant against a North facing wall where the light is reflected off the ground or an opposite wall. Another example: Light from the Moon.)
Bright Indirect Light: Without fancy analytical devices, it is difficult to determine light intensity. A bit of a shortcut is that bright light will create sharp shadows, while dull light creates fuzzy shadows. (Still working on this one.)
Filtered/Dappled Light: This is kind of a transient lighting condition created using leaves, mesh screens, windows, shade cloths, etc. Generally plants in this condition are considered to have indirect light even though direct light may strike the plants (through gaps in the canopy or between the wire grid of a mesh screen). I think the basic idea is that as the day progresses or the wind blows, the time a specific part of the plant receives direct light is minimized such that the plant as a whole is indirectly lit.
Shade: Shade seems synonymous with...

Comments (9)

  • Crenda 10A SW FL
    9 years ago

    What is your thought on a screened area? My lanai is screened to protect from mosquitoes and other flying critters. (Hey, it's Florida and we have swampy areas all around us!) I have regular size screen, not the small hole stuff to keep noseeums out. I consider this to be direct sun because I sure can burn out there.

    I have noticed that some of the plants I moved from the lanai to an island out front with full sun have been getting sunburned. It's odd, since they have been on the lanai in full sun for months!

    Thanks for your thoughts. I like the lighting info you are compiling.

  • plasmid
    9 years ago

    Which succulents or cacti do you think would do well in an unfiltered north facing window? There's no eves on the house, so it's quite bright, but they will be getting no direct light. Thanks for the info!!

  • User
    Original Author
    9 years ago

    Well, I guess before I offer my thoughts I should give a bit of a disclaimer that I've only had plants for 2 years now (a Thanksgiving Cactus, Jade, and Aloe) and this is the first year I am acclimating them to outdoor light so I am by no means an expert on the subject of lighting or succulents in general really.

    Crenda, great question; I had completely forgotten about screens and the like! In my opinion I would tend to agree with you because it would seem to me that whenever the light goes between the grid those parts of the plant would get direct light. I've seen recommendations for using small screens, closely planted bamboo, etc to surround plants while acclimating them. Maybe the idea is that with the smaller holes/slits the plant only gets direct light in a particular section for a very short period of time. Hopefully somebody else will have a comment on this. On an off topic note, how do your succulents handle the FL humidity?

    Plasmid, again I have only a very limited experience with different types of succulents, but here goes. As I'm sure you've read, most people like to put plants in South facing windows which get the most direct light. This is usually for sun-loving arid plants. There are a few succulents that do like indirect light especially the jungle-dwelling Holiday Cacti (Thanksgiving - Schlumbergera truncata, Christmas - Schlumbergera x buckleyi, and Easter - Rhipsalidopsis gaertneri). TC is by far the most commonly sold probably followed by EC. They actually grow up in the trees (a class of plants called epiphytes) and are very shaded by the canopy. Most of what I have read suggests placing them in an East facing window. (Mine are currently in the South and do well, but we have an enormous Tulip tree shading that window.) These might do ok in a North window especially since it is unobstructed. Some other genera to check out might be Sansevieria, Senecio (especially rowleyanus - string of pearls), or Rhipsalis. I haven't grown any of these myself (yet!) so maybe some others can comment or provide other suggestions.

    Thanks for the discussions so far!

    Nathan

    This post was edited by Nathan.M on Tue, Apr 22, 14 at 10:14

  • Crenda 10A SW FL
    9 years ago

    Nathan - since I have gone to gritty mix for most plants, they have tolerated the humidity pretty well. I do have to water more during my dry season (winter) but generally don't even water those in pots during the summer. There are some exceptions, but when my day starts off with moisture dripping off the table, I figure the plants got it, too.

    I have very sandy soil that drains well, but I still amend it for better drainage. I have great luck with sedums, aloes, and agaves PIG. All my areas are also raised, so that helps. But I still hold my breath during the summers when I can get 15+ inches of rain a month.

    Some plants just won't do here. For example, Hubby really wanted me to plant lithops on the hill out front. I figure they'd be a pile of mush by late June . . . Most plants in pots go under the lanai when the rains start, but they get bright indirect light so they fare well.

  • xerophyte NYC
    9 years ago

    My experience with sun loving plants that have spent a winter indoors in poor lighting is that it is safe to put them right into sun as long as temps are cold, as in the early part of the growing season. As temps slowly go up, acclimation happens naturally.

    If you wait until temps are warm, what happens is that the plant wants to grow, but the chlorophyll is not ready and you get leaf damage. Put the plant into a cold situation, where it is not warm enough for sustained growth and let it naturally adjust to light. Many, many succulents have no issues dealing with cold especially for short periods and of course not soaking wet either.

    As for bright vs indirect etc, depending on where you live, even full sunshine outdoors may not compare to what some of these plants are designed to tolerate in their native lands. For me in NY, just about every succulent I grow has no problems in full sun as long as there is good air movement. When plants are dormant they are easier stowed away somewhere shady - for example, Conophytum in their summer slumber are content tucked away in a dark corner.

    x

  • User
    Original Author
    9 years ago

    Crenda, hooray for the gritty mix. As I said, I just started growing plants and fortunately have been able to use it from the get-go and that has helped me to really understand how plants work.

    Xerophyte, thanks your comments. I've read some of your past discussions and they have always been very interesting and informative. I've been curious about the interplay of light and temperature so thank you for mentioning that. That's great advice!

    I've done some more research and have updated the definitions in the opening post if anyone has any feedback on the descriptions.

    Nathan

  • jpaz
    9 years ago

    During cold days and at night during the winter months I maintain my small growing (miniature) cacti of Eastern Brazil (selected Arrojadoa, Micranthocereus, Arthrocereus & Discocactus in 2", 23þ" or 3ü" square plastic pots on a south facing windowsill. On sunny winter days when the temperature rises to around 70ðF (frequently in Arizona) they go outside on the patio under 30% shade cloth, coming inside as the temperature drops at nightfall. With the arrival of spring - when the daytime temperature climbs into the 80s and the nighttime temperatures are in the 50s - they stay outside until the arrival once again of winter temperatures.

    James
    Cultivating Cacti of Eastern Brazil

  • nomen_nudum
    9 years ago

    I too have some succulent plants require no shade cloth protection at all because they grow better in shaded areas in nature They've already made an outside transistion inside by use of windows, lighting and occasional trips outside when temps,& sun postions with time of day of the calender year permit.

    Not to change the subject or give away free passes for no shade cloth during indoor lighting to outside sun light transistions.

    Full sun on a baseball dimond or the mentioned empty field starts off as part sun and is equal to part shade earlier in the morning then gradually becomes full sun later in the day as the sun builds up in intensity.
    The part shade FULL sun at sunrise area also becomes less sun brighter then the mornings full sun as the sun sets given no obstcals are in the way to provide shade or shadows from any object.
    Slight babble or bad example but imagine it like this. A dence tree lines up to twenty feet can be concidered to be growing full sun to part shade every day untill there leaves fully open. When the leaves have fully opened the same tree line at five feet inside has become dabbled sun and full shade at twenty feet while your standing on the ground it's the tops of all the trees that are in full sun.

  • User
    Original Author
    9 years ago

    Sorry for my long absence; I've been working on my Ph.D. dissertation (chemistry). Just wanted to say a quick thank you to James (I really enjoyed the site you posted) and nomen_nudum for your additions.

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