Almost all plants including drought and heat-tolerant species respond to the intense summer heat here in the Central Valley by significantly slowing their growth and their leaf and flower production. As nights grow longer and cooler in late August plants begin to recover their vigor, setting new buds and leaves. Central Valley gardens are at their best in September and October.

Deadhead flowering annuals and perennials and fertilize them in early September to encourage a rebloom later in fall. The fall rebloom can provide nectar and pollen for birds, bees and other beneficial insects until cold winter temperatures halt flowering. September and October are the best months to plant and transplant perrenials. If replacing tired-out, senescent plants or planting new varieties in fall, look for varieties or cultivars that will rebloom reliably in fall. 

Begin pre-pruning deciduous landscape plants in September and October. Just a little pre-pruning in fall makes the winter dormancy season pruning job much easier. Pre-pruning entails removing dead and broken branches and canes, removing any branches or canes that cross through the interior, and removing weak, spindly growth, suckers and water sprouts.It  is not a thorough pruning to reshape a plant or control growth or size, but rather a quick clean up or spruce up.

Summer pruning is a pruning technique which opens up the interior of the canopy of fruit and nut trees to allow sunlight into the interior and improve air circulation for better ripening.  Summer pruning is usually done from May to July. A late season minor version of summer pruning in September to remove any new branches growing through the interior can reduce shade in the interior and speed up late season ripening.

Several plant species send out very long unruly whips or canes in fall. All types of roses tend to produce long flexible ‘wild hair’ canes in September. Some are mostly leafless shoots. Cut those canes back to the base. Most climbing roses bloom best when the canes are trained to grow horizontally. In fall, cut off any canes that are growing downward or backwards or tie up long leafy canes to train them to grow horizontally. 

Japanese maples have four ‘pulses’ or growth spurts annually. In September you’ll often see long whip-like branches shooting straight out of the tree. Cut these off at the trunk or the origin branch making sure to make clean cuts at the rim of the ridged collar using a very sharp knife or even a box cutter. A careful cut will help reduce any bushy small twig growth at the site of the cut that will eventually deform the shape of the tree. Note any sunburned branches now so that when pruning leafless Japanese maples in late January you can preserve or encourage branch growth that will add leaf cover where needed.

Azaleas will maintain a naturally graceful shape without shearing if long wayward branches are trimmed back to a branch junction in fall.

Wisteria bloom on short spurs in spring. In late summer or fall trim off any long leafless shoots and reduce the number of stems in any congested clumps. 

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Written by UC Master Gardener Elinor Teague