A Drip Mist System for Bonsai
by Brent Walston
Eventhough I spend nearly my entire life thinking about and growing
plants for bonsai, I find it too inconvenient to have to hand water my
own bonsai. I switched to an automatic system years ago. In some ways
it is more advantageous than hand watering. The disadvantage is that
you don't get to see your bonsai everyday to spot problems, unless you
have some other routine for visiting every plant every day.
The Advantages of Automatic WateringThe
advantages of automatic drip mist watering bonsai are convenience,
reliability, adequate and timely watering, and ease of inline
fertilization. With an automatic drip mist system you can apply water
very slowly for a long period of time and do it precisely when the
plant needs it the most, just before the heat of the day. I usually
water for an hour or more around noon with a fine mist that thoroughly
saturates the root ball.
How to Set Up Your SystemThe
type of drip system you use makes a big difference. Spray stakes and
drip emitters (one emitter per pot) in general do a poor job of
watering bonsai. In such loose mixes the water tends to go straight
down rather than out. I prefer a drip mist system sometimes called a
drip spray. This uses conventional drip system parts but the emitters
are sprayers. There are various types, but mine are Olson 'O' jets.
These fit into a rigid poly 1/4 inch riser that snaps into the standard
1/2 inch poly drip tube. I place these about every three feet along my
bonsai benches creating a complete coverage mist. As long as the
pressure is about 30 psi or higher the mist is almost fog like and it
works well, especially if there is a little breeze to stir the mist. At
lower pressures the O jets tend to 'pattern' and you can get dry spots.
For my larger bonsai that are lined up singularly on a narrow
bench, I just put these mist heads in strategic positions so that the
top of the soil gets a pretty much direct spray. I don't worry about
the foliage. It does get wet from the fog like mist, but the water is
mostly directed at the rootball.
You can operate such a system just by connecting to a hose bib
and turning it on and off manually. But the beauty of such a system is
that it can be easily automated with a hard wired irrigation timer and
electric 24V solenoid valve. Battery operated timers are just too
erratic for this purpose. With this system you can pretty much leave
for a week or two and your plants will be fine if you have someone check everyday to see if the system came on, and if
this person has the wherewithal to fix it if it breaks. In general, a
hard wired system is pretty fool proof if you have a nice fresh backup
Although these mist heads have larger diameter orifices than
traditional drip emitters, a filter is still a must. Fine mesh filters
tend to clog too often for me and really are not necessary since most
fine particles will pass right through the emitter anyway. I find that
about 60 mesh is right. This should be a fairly large filter so you
don't have to check it too often and to give you a larger reserve.
Netafim filters with 3/4 or 1 inch outlets are about the right size and
have a choice of filter meshes.
Adding a Fertilizer InjectorI
have been using fertilizer injectors for years, which you can plug
right into your system. However, they do tend to waste fertilizer with
an overhead spray system such as the above. I prefer to use the
injector with a hose and hand water to fertilize. You can easily set it
up to do either. If you have a regular drip system for your plants in
training pots, then an inline injector is very easy and efficient. Good
injectors are not cheap. There are two reliable companies making small
professional non electric injectors, Dosatron and Dosmatic. I have been
using Dosatrons for years. It is an all plastic/stainless injector that
uses the flow of the water through it to operate a piston which pumps
fertilizer concentrate into the water stream. They are fully adjustable
from about 60:1 to 500:1 with about an 11 gpm flow rate. The work very
well at both low and high flow rates. Price is currently about $300 US.
Reasonable Cost of the the SystemThis
system minus the timer, valve and injector is very inexpensive. 50 feet
of 1/2 inch tubing is around $5, fittings are about $.50 to $.75 and
emitters and risers are less than $.50. Filters are about $15. That
would get you started. Irrigation timers (found at almost any home
supply stores) can be found for about $50 to $100. Get an all digital
one, they tend to be more reliable than the old 'clockmotor' timers,
and more flexible too. Electric solenoid valves are about $10 to $15.
One hint on the valves, use an antisyphon valve with a good filter after
it. Bugs can, and do, enter through the vacuum break. Drip parts can be
found almost anywhere these days, but in case you can't find what you
want or you want to see everything that's possible using drip systems, go to:
Don't rely too heavily on an automated system. Bonsai rely on a water
supply every day in summer. Missing even a single day can often cause
irrepairable damage. Always check every day to make sure the system did its job.
copyright 2001 all rights reserved