While bemoaning the extreme heat we’ve had and undoubtedly will continue to have, we can consider it the ideal time to solarize portions of the garden that have been infested with assorted pests – weeds and weed seeds, diseases, nematodes, and insects.  Solarization utilizes the beating heat of the sun to eradicate these pests.  The more direct hot sun, the more effective. 
     It’s a simple process, but must be left in place for a minimum of 6 weeks and preferably longer during the hottest time of year.  In cooler areas like the coast, a longer period may be necessary.
     In my Altadena garden years ago, I eradicated a 6’ X 5’ patch of Bermuda grass by leaving a padded black tarp on for 6 months, from May through November.   It was my Thanksgiving and Christmas presents to myself that “overdoing” the light- and water-exclusion technique resulted in nary a blade of Bermuda ever plaguing my garden again.
     The University of California has since developed its own technique that can be used in any scale garden or farm.  For a full discussion, go to http://ipm.ucanr.edu/PMG/PESTNOTES/pn74145.html
    
Here’re the basics

1.   Choose a time of year when days are long, air temperatures are high, skies are clear, and there is no wind.  Generally, in inland California, this will be June through August; along the coast, this will be August through September.
   
2. Using a clear plastic tarp, the top 6 inches of the soil will heat up to as high as 140°F, and the heat trapped down to 12-18 inches will kill a wide range of those problems.  The greatest effect is at the surface of the soil, and it decreases at deeper soil depths.  Control is best in the upper 6 inches.
   
3. Solarization can also improve soil structure availability of nitrogen and other essential nutrients for growing healthy plants.
4. Many beneficial soil organisms survive solarization or recolonize the soil quickly afterwards.

 
Here’s the method

1. Cultivate and remove plant matter, adding amendments since disturbing the soil after solarization may bring up new viable weed seeds and pathogens.
   
2. Level and smooth the soil bed so plastic will lie flat with few air pockets.
3. Irrigate the soil to at least 12 inches deep just before laying down the plastic.
4. Choose plastic:  clear or black?  Clear plastic will enable more heat to pass through into the soil.  Black plastic will absorb and deflect part of the heat; but when air temperatures are too low to kill weeds, the black’s light-exclusion may kill them.
   
5. Choose plastic thickness.  Use 1-mil thickness for greater heating, but it’ll more easily tear or break down more quickly in sunlight.  Use 2- or 4-mil in windy areas or for longer periods of time.  In cooler areas, use double layers with air spaces created by plastic bottles or PVC pipes between layers to raise soil temperatures.
   
6. Lay plastic close to the soil, and anchor so there will be no “sailing” during breeze gusts.
7. Leave in place for at least 6 weeks during the warmest time of year, so daily maximum temperatures in the top 6 inches of soil are at or above 110-125°F.  Leave in place longer to assure more success.
   
8. Remove plastic, and cultivate the soil as little as possible (less than 2 inches deep) to avoid bringing up viable weed seed and remaining pathogens.

 

     During the cool of these July evenings – although our mid-80s daytime temperatures are quite pleasant – I do my trimming in the summer garden.  Sometimes with a vengeance – like with overgrown snail vine basically smothering my species poinsettia – but most times with replanting or rooting in mind for more plants to passalong to friends.  Here are some of those techniques.
 
Trimming – Really, Ripping – Rose Suckers!
     Here’s your excuse to get out your anxieties and other negative feelings while ending up with positive results for you and your roses!   Rip off – actually tear rather than neatly trim -- rose suckers at their bases with an energetic and harsh downward and outward yank.  Don't be gentle and merely cut the suckers.  They’ll not resprout only if you damage the bud cells at the bases of the suckers. I’ve found greater and more permanent success with additionally smashing those basal ripped-off areas with a hammer!  We’re talking major destruction of the life force there!   Aaarrrggghhh!     

Trimming and Replanting Iris
     If your bearded iris clumps haven’t bloomed well for a year or two, and the clump is pretty large, chances are it’s too crowded and needs to be renovated. 
     Dig up the entire clump and break off and discard the older central rhizomes that have no foliage – even though they’re still firm and healthy-looking.  Never one to toss healthy plants, I’ve tried numerous times to replant these, but to no avail – it’s as if they’ve forgotten how to put out new buds – since they just sit there for a year’s life cycle without doing anything, and then finally just shrivel away.
       Let the young, healthy rhizomes dry out of the direct sun for several hours so a callous forms over the break before replanting them.  If there are rough breaks or mushy & discolored areas, cut these out and make a clean cut back into healthy flesh.
     Clip roots to two or three inches in length, removing the dead and dried-out old roots. 
     Remove individual dry outer leaf blades, and clip the green foliage to about an eight-inch fan.  
     Incorporate compost and bonemeal into the top six inches of soil.  
     Replant the rhizomes a foot apart, with roots straight down and the fan facing outward, since that’s the direction that it’ll continue growing.  Barely cover the rhizome with soil, and form a bit of a basin to hold water for the first few irrigations.  Fill those shallow basins three times to make sure the entire root zone area is moist and settled around the roots. 

Rooting The Trimmings of Semi-Hardwood Plants
     Root woody cuttings of semi-hardwood plants like azalea, chrysanthemum, fuchsia, geranium, hydrangea, and marguerite daisy. 
     Choose growth that is the conjunction of somewhat woody and still bright green and pliable.   Cut a five- or six- inch piece with about 6 nodes (where the leaves come out of the stem) – 3 of the woody section and 3 of the green section. 
     Strip off all of the leaves but the tiny young top growth and one or two well-developed leaves. You may need to remove some of the green and pliable growth.  If the well-developed leaves are large, cut them in half crosswise.  You want just enough green top growth to accomplish photosynthesis but not so much that keeping it alive will drain what energy there remains in the cutting before the bottom nodes manage to send out new roots.
     Trim the bottom of the cutting to about 1/8” under the bottom-most node.  You don’t want to leave much more than this, because chances are it may rot and potentially extend up into the rest of the cutting.
     Place the prepared cutting in light, sandy soil or planting mix up to the bottom leaf so about 3 nodes of the woody portion are under the soil mix, and the green portion is above the soil mix. 
     Sprinkle the foliage and thoroughly wet the soil mixture.  
     Place the container in filtered light in a sheltered location, and keep the soil mix moist until the rootings are well-established, in about a month.  Then the new plantlets can be transplanted, or you can wait longer until the new root systems are better developed.

Rooting Before Trimming Long Supple Branches
     Long, supple branches of azaleas, forsythias, salvia and viburnums can be rooted for new plants.  Bend branch tips to a shallow ditch a foot or so long.  Cover the branch with soil up to the top cluster of new foliage.  Hold it in place with a rock or other method.  Keep the soil moist.  Rootlets will form, and a new plant will be ready for transplanting in about a year.  Then you can cut it from the mother plant and transplant it to another location.