Weed control chemicals should be applied now

      If you have gardening questions, call the Master Gardeners' hot line at 257-5555 between 9 a.m. and noon Monday through Friday.
     
      This is the time of year weed control chemicals are applied to lawns, shrub areas and flower beds to control crabgrass and spurge. Crabgrass will begin to germinate, as the weather warms, in the next two to three weeks.
      It is important to apply these weedkillers now so the chemical has a chance to seal the surface and create a barrier to weed germination. These weedkillers can be purchased at nurseries and applied by do-it-yourselfers or contracted with commercial lawn care companies.
      If the weedkiller is applied dry, a short watering cycle is needed to wash the weedkiller off of the dry carrier and into the soil. Liquid weedkillers should also be followed by a short watering cycle. If the cycle is too long, the weedkiller will be washed away and it will not work properly.
      -- Pruning Shrubs for a Natural Look -- Most shrubs should be pruned to maintain their natural form. The reason for this is for appearance and also to reduce maintenance. Shrub pruning that most closely resembles the shrub's natural form means pruning less often, with fewer cuts and little clean-up.
      To maintain the natural shape of the shrub, prune the largest stems from the bottom of the shrub at, or very near, ground level. Annual removal of two to four of these stems will mean the shrub will be renewed every few years due to constant removal of the oldest stems.
      Removal of stems at the base "thins" out the stems, allowing more light to penetrate inside the shrub's canopy. Removal of these stems will invigorate new growth from the base. Light entering inside the canopy and reaching the base will cause new buds to break near the pruning cuts. This type of pruning will stimulate growth that maintains leaves from top to bottom.
      If a shrub is to be kept at six feet in height and grows one foot of new growth each year, then stems older than six years are removed at the base each spring.
      -- Pruning Shrubs to Encourage Density -- When stems are cut part way back to the base, the stem cut responds like it had a shot of fertilizer. On the tip of each branch rests a bud. This terminal bud keeps the side buds below it under control and from growing. Once the terminal bud has been removed or the branch damaged, side buds break in a mad rush to replace the damaged or removed bud.
      When a terminal bud is removed, two or three buds grow to replace it and try to fill the void left when the branch was cut. For every cut made, several branches will grow. This increases the density of the shrub where pruning cuts were made.
      Sometimes shrubs can be dense on one side and thin on the other. If this is the case, the side that is thin should have stems cut, removing the terminal buds. The other side should be thinned, removing stems that are crowding from the base.
      -- Pruning Shrubs to Keep Them Away From Walkways and Building -- The direction of new growth can be controlled by pruning stems near buds which are pointing in a desirable direction. If a shrub is growing too close to a sidewalk, making pruning cuts near buds that are pointing away from the sidewalk will direct that growth.
      After pruning, removing buds pointing toward the sidewalk or building, with a fingernail, will prevent growth into problem areas.
      -- Train Shrubs Early in Their Life in the Landscape -- Once a shrub has been pruned or trained for a few years to grow a certain way, it is very difficult to change its shape without a great deal of effort and a long period of unsightliness.
      An example would be a shrub that has been pruned with a hedge shears. Once this type of pruning has been done for several seasons, the shrub is "locked in" to this shape. To try to revert it to a natural form is nearly impossible. If a natural form is wanted, it is better to replace the shrub and start all over or cut it to the ground. Cutting it to the ground, called rejuvenation pruning, is an acceptable practice for shrubs that are relatively fast growers.
      -- Spring- vs. Summer-Flowering Shrubs -- Spring-flowering shrubs are pruned after blooming in the spring. Flower buds for next year are formed on wood grown after blooming. In other words, flowers are formed on the previous year's wood. Pruning spring-flowering shrubs in the early spring may mean that all of the flowers that were formed for the spring might be pruned off.
      Shrubs that bloom in the summer should be pruned just after blooming. This means the late summer or fall. Summer-flowering shrubs form their flowers on the current season's wood.
      Next week we will be returning to current phone questions.
     
     Bob Morris is a horticulture specialist with Nevada Cooperative Extension.