Wednesday, July 13, 2011

Drip Watering Pots and Plant Containers by Gardener Dave

Some years ago I swore off clay pots in my landscaping layout. My reason for this is:  In our dry climate, small clay pots dry out “before you can put the hose away” – especially the unglazed ones.  Glazed pots fare a little better, but beware of the darker colors as they absorb radiant heat and can cook plant roots if they are in full sun all day.

I still like the look of unglazed clay pots, especially in groups with the largest in the center, or large-to-small arrangement. The “Italian style” pots with the thicker rounded rims are my favorites.  Hmmmm… now I’m talking about “my favorite unglazed pots”!  What convinced me to use them again after I had sworn off?

Drip watering on an automatic timer made the difference for me. I still avoid small ceramic pots due to their quick dryout – my smallest is about 11” in diameter and they go up from there.  I always use potting soil and always plant the pots with bright-colored annuals. I fill the bottom 2/3 of the pots with Perlite to avoid using large quantities of potting soil every year. This provides a “moisture sink” that roots can get down into. You can buy Perlite (or equivalent) in large sacks. It isn’t as cheap as empty pop cans or other such fillers, but I do keep it from year-to-year – currently my Perlite base has been in the pots for about 5 years. I fill the top 1/3 with good potting soil that includes some fertilizer. 

Water distribution to each of my drip circuits from the full-pressure timed lines is through a 15 or 20 psi pressure regulator and 1/2” plastic tubing. Small 1/4” tubing goes from the 1/2” distribution tube to the drip hose in each pot, using 1/4” barbed connectors. See pictures below for straight and tee types.

I prefer to use 1/4” “leaky hose” for watering inside the pots themselves. I have tried spot emitters in the past, but prefer the more distributed drip effect of the small hoses.  I use a proportional amount of the leaky hose, depending on the size of the pot.  For the smaller pots I run one turn of the drip hose just inside the rim of the pot, then one across the diameter of the pot between plants.  I use wire “staples” – made for holding down weed barrier cloth – to hold the tubing in place.  In larger pots, I may use two turns of the tubing inside the rim of the pot, with an “X” of tubing across the pot diameter. Also, be aware that some brands of the little leaky hoses are more “leaky” than others. You just have to try them to know the differences.

Mulch (if used) should be applied to the soil over the tubing.  Less water will be lost to evaporation if the hoses are under the mulch. I use my little leaky hoses for several years before replacing them.  I am on Lakewood (Denver) water, but it will depend on the mineral content of your water – more minerals will mean replacement at more frequent intervals, as minerals tend to eventually plug them up. One good thing about using the small leaky hose is that they can be easily cut shorter or spliced if you find that you are watering too much or too little.  Fine tuning is part of the process (it’s a hobby, right?)  Of course, the frequency and duration of watering as set by the timer(s) are basic to the whole drip watering approach. Experiment with these as necessary.  My pot circuits are set to run for 5 minutes every other day. This seems to be adequate even in hotter weather.  Use whatever works for you. Try to group plants with similar water needs on each circuit if you can.

If you successfully fine-tune your drip watered pots, you can go on vacation with confidence, knowing that your pots and containers will be correctly watered. I generally have my system up and totally fine-tuned by the time September is here.  JUST KIDDING!    ;o)

Gardener Dave