Marin Master Gardeners
University of California
Marin Master Gardeners

Marin IJ Articles

Fall in your Garden

November 13, 2010
Dot Zanotti Ingels

AUTUMN IS MY favorite season. The air smells so fresh. It is a great time to savor memories of summer and shift gears into new kinds of plans and dreams.

Fall is also an important time in your garden. It is the time to put your garden to bed and to plan and plant for the future.

Much of the health of your garden depends on doing your fall chores. It is important to do a thorough general cleanup.

Clearing away diseased and damaged plant material at the end of the growing season is an essential fall chore. The fungi and bacteria, which cause so many garden problems, can proliferate over winter on contaminated leaves, stems and roots. Removing these havens for disease will reduce the chance of seeing blight, mildew, gray mold fungus, root rot, and wilt in next year's garden.

The amount of plant material you should remove depends on conditions in your particular garden. Obviously, any diseased material has to be cleared away. If a particular kind of disease has been a problem, it's also a good idea to remove the remains of any plant that is ordinarily susceptible to that problem, even if it looked healthy all season.

Roses, for example, are vulnerable to black spot, so it is a good idea to remove all the foliage even if it was healthy all summer. As a further precaution, some gardeners like to remove all plant material that has died after a frost. Pick up and discard any old fruit still hanging on the tree, or that has fallen to the ground.

Herbaceous perennial plants are left in the ground all winter, so good care in the fall will improve your chances for healthy growth in the spring. Most gardeners cut back all their spent perennial plants in the fall to a height of 3 to 6 inches, but some prefer to leave the seed pods for the birds. When you cut back perennials, it is a good idea to mark their location with a stake so you will know where they are in the spring. This also is a good time to make a sketch or map of your garden, indicating which perennials you have and where each one is located. That will make garden planning more fun during the winter as well as remind you of plant locations in early spring.

Fall is a good time to divide crowded spring perennials, such as dianthus and iris, if needed. Late-bloomers like geraniums, daylilies, hostas, coneflowers and yarrow also benefit from division. This controls their size and renews blooming.

If your dahlia bulbs have not come back annually in the past, it is a good idea to dig them up to avoid having them rot in the wet ground or get eaten by rodents. Store them in a dry, cool, dark space.

Removing all spent plant material -- roots, leaves and stems -- from the vegetable garden every fall is a good idea because vegetables are vulnerable to many diseases and pests.

When the insects have no late fall food source, they are more likely to be killed by cold weather. Removing dead foliage also removes a warm, comfortable home for small animals such as mice. Make note of where you planted your vegetables in the garden this year so you can rotate crops next year. This is one of the best and easiest ways to keep diseases and pests under control.

An annual garden can be treated like a vegetable garden. Remove all diseased material, and make mulch of the rest. Collecting seeds from your annual flowers before you pull them out can be a fun way to have your favorites in your garden next year for free.

Autumn also is a good time to clean your garden tools. Disease microorganisms also overwinter on the surface of stakes, tomato cages, trellises and other garden equipment. Remove all soil from the tools, and clean them with a 10 percent bleach solution or other disinfectant to protect your tools from spreading diseases. Apply a light layer of oil to prevent rusting if you will not be using them for a while. Wash your garden gloves, too.

Pulling weeds in the fall before they go to seed helps to reduce the number of seedlings you will need to pull in the spring. If there are seeds on the weeds, dispose of them in the green waste.

Now is the best time to plant trees, shrubs, native plants and perennials. The fall and winter rains help establish thriving root systems that will support lush top growth in spring. It's also the time to plant spring bulbs.

Check with the nursery when you buy your bulbs to learn how and where to plant them. It's an ideal time to plant peas, lettuces, onions, cabbages, kale, shallots and garlic, too.

Soils can get depleted of nutrients during the summer. You can easily keep the garden alive and active in winter by sowing cover crops or applying organic mulches in the fall.

One of the easiest and cheapest sources of organic matter is green manure in the form of a cover crop planted in the fall. Legumes such as fava beans and vetch planted in the fall add nitrogen to the soil. The bacteria that live in the roots of the legumes fix more nitrogen than the plant needs to support itself. Large amounts of nitrogen are released into the soil from the roots as the legume dies. Healthy autumn leaves add lots of organic matter and plant nutrients to garden soil. Shred them by running over them with a lawnmower and spread them on the garden.

Most importantly, remember to enjoy one of nature's most beautiful seasons while performing your fall gardening chores. You will be rewarded now and later.

The University of California Marin Master Gardeners are sponsored by UC Cooperative Extension. For questions about gardening, plant pests or diseases, call 499-4204 from 9 a.m. to noon, and 1 to 4 p.m. weekdays, or bring in samples or pictures

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