0

I am planning some container plantings that will go on the north side of a deck railing very much like this one (in the Northern Hemisphere):enter image description here

Without the railing, this location would receive unobstructed sun from essentially sunrise to sunset. I am trying to understand how the presence of the railing changes the equation.

I have done some Python simulations to calculate the size/shape of the shadows cast by the railing and pickets (and how those shadows change over the course of the day/year). Those simulations indicate that there is a band of points right next to the railing that receive 4-6 hours of direct sunlight per day. That band is pretty narrow in the summer, but wider in the winter.

My question is whether this is the right way to "count" sun from the plants' perspective. In particular, any point next to the railing gets a cumulative 4-6 hours of sun, but a plant next to the railing is partially in shadow and partially in sun at all times because of the shadows cast by the pickets. Would this change how the plant "perceives" how much light it is receiving (relative being fully in sun for 4-6 hours and in shadow the rest of the day)?

4
  • 1
    Have you noticed that trees and other shrubs are casting shadows as well? This is just a railing, not a jungle roof.
    – Johannes_B
    Jan 3 at 4:24
  • 1
    do some math: youtube.com/watch?v=1ryTz3mA3qc Jan 3 at 4:47
  • @Johannes_B: There are no other obstructions. The railing is all that's there.
    – Matt
    Jan 3 at 15:10
  • @blackthumb: Thank you for your comment. I actually have done some math along these lines. I left it out of my original post because I was trying to simplify, but I've now edited the post to describe what I've done. In any case, the crux of my question is not really about the size of the shadows but rather about how to think about the fact that any plant next to the railing will be partially in sun and partially in shadow at all times and whether that introduces any special considerations.
    – Matt
    Jan 3 at 18:49
0

It depends on what you are growing; seasonal summer plantings will effectively get full sun (the railings are neither here nor there,they are relatively slim). But in winter, if it faces north, there will be no sun at all, and during spring and autumn, the amount of sunlight will be reduced, so that would not count as full sun.

If you wanted containers full of year round plants like shrubs, then choose those suited to partial shade.

0

The railings have a really negligible effect. It's much more important that it's oriented towards north. As you said it yourself: probably from early spring till mid autumn you'll receive full sun on the deck and should place there any summer plants accordingly. This means you shouldn't put there any plant that mustn't receive direct sunlight (as their leaves would be burned and they would die). If you'll bring out any plants from the house to keep them out there for the summer you should leave them in partial shade for a week or two for allowing them to adjust to direct sunlight. In the winter you'll probably barely have it illuminated, so only plants that don't need a lot of sunlight should be left there.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.