Protecting balcony plants from the sun.

I'm going to try and blog more...no really!
I did write a blog entry 5 years ago (!) about my garden, http://swisslemur.blogspot.ch/2010/07/garden.html and in many ways, it's all still true.  Here in Switzerland, balconies are for sitting on, not gardening.  Gardening takes place at the allotment, located an inconvenient distance away, and possibly only obtained through inheritance.
I still only have a balcony.....but there are going to be improvements this year.

The biggest problems I face with the balcony are:

1.  the pot plants dry out too quickly, and those along the outside rail bake in the sun; and
2. the aphids move in.....and they usually win.

My new victims 

The other problem I didn't mention, is that I'm overly-ambitious.  I've tried raising seedling inside in January (didn't work), growing eggplants (didn't work), Chinese vegetables....vegetables of any sort (really didn't work).  I've decided to focus on herbs.  I've become interested in ancient Greek and Roman recipes and they often use a number of herbs I'm unfamiliar with, but that provide a distinctive flavour profile - rue, lovage and fennel.   Mint and chervil and other herbs also make an appearance, but rue and lovage in particular, are quite new to me.
Now I just need to keep them alive.

Watering and insulation seem to be the key.

I would like to get self-watering planters but the main brand - Lechuza - is stonkingly expensive, especially here in Zürich, around 100 CHF per container.  And, that doesn't quite solve the problem of the heat soaking into the containers and damaging the roots.   I need to insulate the pots.  Most of the information on insulating plants is really for Winter.  It often snows here in Zürich so people wrap up their plants in hessian and fleece.  I've never tried it, I somehow think it will never snow and my balcony gardening is run along Darwinian lines - survival of the fittest (that goes for the house plants as well).

To insulate against the sun, I'm going to try a protective barrier on the outside of the planter: a drip-tray turned on it's side and lined with bubble wrap.  I don't have the bubble wrap yet but I'm trying out the drip-tray shield and measuring the temperatures.  The balcony faces roughly South (West-ish) so we get sun for nearly the whole day.  From lunchtime onwards it begins to shine directly on the house and I need to put the sun-shade out....it gets really hot.  Mornings are the coolest, when the sun shines obliquely across the planters on the railing.

I have an unprotected planter (with lovage) sitting on the table, roughly parallel with the middle planter on the railing (savoury) which is shielded by a drip-tray.  It's not a perfect set up because of the angle of the sun, but as the day progresses the planters will receive more direct sun.
I have a 'temperature gun' (infrared thermometer) and I took the first measurement at around 10.00am.  The top temperature in Zürich today is estimated to be 23 Celsius....it feels hotter.

I'm wondering how accurate the temperature gun is.  Anyway, I think midday will give a clearer indication.  I can see from the angle of the sun that they are receiving slightly different amounts of heat, but what I'm really interested in is the difference in temperature between the outside of the drip-tray shielding the planter and the side of the planter that is covers.  At the moment, nearly 4 degrees celsius is the difference.  Just out of interest I also checked the end of the planter that was facing the sun - it was 47 degrees Celsius!

Example using a drip-tray as sun shield

Morning - 10.00am
Unprotected planter:  Sunny side  20.2
                                   Shade side  13.3
Protected planter:       Drip-tray shield  18.1
                                   Sunny side 14.4
                                   Shade side  15.1

Midday readings:
Unprotected planter:  Sunny side  38
                                   Shade side  26
Protected planter:       Drip-tray shield  35
                                   Sunny side 28
                                   Shade side  22

Mid-afternoon - 3.00pm
Unprotected planter:  Sunny side  53
                                   Shade side  33.7
Protected planter:       Drip-tray shield   46.6
                                   Sunny side  38.5
                                   Shade side   31.9

Late-afternoon - 5.30pm
Unprotected planter:  Sunny side  37
                                   Shade side  31.5
Protected planter:       Drip-tray shield 32
                                   Sunny side 33
                                   Shade side   30

Experiment design is not something I have thought about since high school so there could be a number of reasons for this result, but I think some kind of shield will still help my pot plants on the railing.  The only downside is that by late afternoon the shields may have been trapping a little heat and the plant takes longer to cool down (5.30pm shield 32C planter 33C).
Just for comparison, the sides of the containers sitting on the balcony out of the direct sun average 22-27 C at 3.00pm.   I must be killing plants to expect them to survive on the railing.  Some parts of a shallow black container I have that were in direct sun registered 60 C.  It's scary how hot that balcony becomes....and it was only about 23C today.

I think I can improve the shields - use a lighter colour and line them with bubble wrap.


Next I need to improve my watering system.  I've tried a couple of bottles with holes drilled in the bottom.....not sure it's working.   The water seems to drain out too fast.  The search continues.