Marin Master Gardeners
University of California
Marin Master Gardeners

Fall: a time for planning and planting

Autumn is a time of reflection and preparation for Marin gardeners. In our summer-dry, winter-wet climate, it is an ideal time for planting perennials and evergreens. Winter rains help establish sturdy roots to support lush spring growth. But don’t dash out to the nursery sales without a plan. What were your garden successes and failures? Which plants have become woody or overgrown? Have any disease-resistant varieties been introduced that could replace some of your problem plants? This is a good time to make or update a map of your landscape. It will aid your shopping expeditions and help you identify your plants in early spring. If you need help choosing plants, consult the Master Gardener Plant Selection Guide, an online resource created especially for Marin gardeners.

Add seasonal color
Although Marin may not have the spectacular fall colors of New England, a number of species glow under our brilliant autumn sunshine. A nursery visit now will give you an accurate view of foliage color. One well-placed shrub or tree that turns crimson or bright yellow in fall can make a profound design statement and herald the change of season. Among the good tree and shrub choices for Marin are:

•    Chinese pistache (Pistacia chinensis)
•    Crape myrtle (Lagerstroemia indica)
•    Heavenly bamboo (Nandina domestica)
•    Japanese maple (Acer palmatum)
•    Oregon grape (Mahonia aquifolium)
•    Persian parrotia (Parrotia persica)
•    Smoke tree (Cotinus coggygria)
•    Spicebush (Calycanthus occidentalis)
•    Western redbud (Cercis occidentalis)
•    Witch hazel (Hamamelis)

Plant California natives
Many California natives are best planted from seed right before the rains begin. Mix very small seed with a bit of sand for even distribution. Prepare the soil by loosening it with a rake, sow the seed and tamp down well to ensure good soil contact. A light covering of fine compost or straw will deter seed-eating birds. Some native species to try are:

•    Baby blue eyes (Nemophila menziesii)
•    California poppy (Eschscholzia californica)
•    Farewell-to-spring (Clarkia)
•    Meadowfoam (Limnanthes douglasii)
•    Tidy tips (Layia platyglossa)
•    Bunch grasses (Festuca californica, Nassella pulchra)

In addition to starting natives from seed, this is a great time to plant perennial and evergreen natives from the nursery, such as:

•    California buckwheat (Eriogonum)
•    California lilac (Ceanothus)
•    Coffeeberry (Rhamnus californica)
•    Coral bells (Heuchera)
•    Flowering currant (Ribes sanguineum)
•    Foothill penstemon (Penstemon heterophyllus)
•    Hollyleaf cherry (Prunus ilicifolia)
•    Manzanita (Arctostaphylos)

Renew your perennials
Herbaceous perennial plants benefit from getting cut back in fall. These are the plants that bloom in spring or summer and then require a trim to cut off old wood and spent blooms in order to promote new growth next season. Many gardeners cut back all their spent perennials in the fall to a height of 3 to 6 inches, but some prefer to leave the seed pods for the birds and then trim the plants back later. Do whatever works for your aesthetic. Cut the stems just above a node—the point where a leaf is attached—because new growth will sprout there. When pruning or shaping shrubby perennials like lavenders and santolinas, remove one third to one half of the growth, but take care not to cut back into bare wood.

Fall is a good time to divide crowded spring perennials, such as dianthus and iris, if needed. You also can divide geraniums, penstemons, daylilies, hostas, coneflowers and yarrow to control their size and renew their blooming. To divide perennials, simply use a sharp spade to dig out clumps of the expanding plant. These can be replanted elsewhere or, better yet, why not give them away as gifts?

It is a good idea to dig up dahlias and tuberous begonias to prevent their rotting in the wet ground or getting eaten by rodents. Store them in pots with some soil in a dry, cool, dark spot.

Feed your soil
The key to a healthy garden is healthy soil. By amending your soil each year, you will increase its capacity to hold air, water and nutrients. Spread a two to three-inch layer of compost or other organic soil amendment around your plants and cultivate it in. Around shallow-rooted plants like camellias, rhododendrons and Japanese maples, just leave the compost on the surface. If you have heavy clay soil, dig in an amendment with fir bark or rice hulls to increase air penetration.

One of the best things you can do for your garden is adding a layer of mulch, which is simply a two to three-inch layer of organic material that acts as a blanket on top of the soil. Mulch keeps weeds at bay and helps soil retain water. It cushions the soil from pounding rains, fosters root growth and allows worms and billions of helpful microorganisms to proliferate. Many materials make good mulch, including compost, fallen leaves, bark chips, rice hulls or alfalfa hay. Be careful to keep mulch four to six inches away from the trunks of plants to avoid crown rot.

For your bare vegetable beds, one of the cheapest sources of organic matter is a cover crop planted in the fall. A cover crop, also known as green manure, is typically a legume planted from seed in the “off season” to improve the condition and fertility of the soil. Legumes such as fava beans, crimson clover and vetch release nitrogen from their roots into the soil over the winter. When it’s time to plant your vegetables in spring, you can till the legumes into the soil or skim off the tops and add them to your compost bin.

Welcome the rains
In Marin, some of our warmest weather occurs in fall. Take advantage of these delightful autumn days to enjoy your garden, bearing in mind that this is prime time to prepare for the next growing season. Coddle your soil, trim your perennials, select a few new plants—and then put your garden to bed. Giving a little TLC to your garden today will pay handsome dividends. Soon the restorative rains of winter will arrive, and you and your garden can rest up till next season.


Contributors:
Faith Brown, Elizabeth Finley, Dot Zanotti Ingels, Diane Lynch, Marie Narlock

Webmaster Email: banielsen@ucanr.edu