Signs of autumn are all around us. . .we've had some rain, trees are showing off their fall colors and losing their leaves, fewer plants are blooming, the days have gotten shorter with the nights getting chillier. While nature has its own way of coping with the colder winter months, there are plants in our gardens that can be sensitive to freezing temperatures. Citrus, succulents, perennials, young plants that recently went into the ground, and many tropical and subtropical plants can be vulnerable. But there are a few things you can do to help protect your garden during potential freezing spells.

Mulching Perennials

Perennials return year after year. Hardy ones will need little, if any, assistance to get through the cold months, but some may need protection. Mulching helps even the soil temperature, preventing the ground from freezing when the temperatures drop below 32°F/0°C. A layer of 2-3 inches is best. A deciduous plant's own dead leaves can help protect its crown and roots from the cold, so leave the leaves until next spring, adding more mulch as needed. Other sources of mulch include bark, straw, shredded branches, and compost.  

Trees and Shrubs

Trees and shrubs usually have an easier time getting through the winter if they are in good shape. However, if a freeze is forecasted, one of the most important things to do is to ensure they have been watered 2-3 days prior, especially if autumn has been dry. As with perennials, mulching with fallen leaves or other mulch will help protect the roots, but do not have mulch up against the tree trunk or plant stem, which could cause rot to occur.  

Wrapping trunks of young trees with blankets, towels or piping insulation will provide added protection.

Bulbs

Fall is the time to plant hardy spring-blooming bulbs, but some bulbs such as gladiolus, cannas and dahlias are sensitive to winter cold, and may not survive. You may wish to dig these up and store them over the winter.

Wait until after the first frost, then gently dig up the bulbs or tubers. Cut away any leaves and brush off as much soil as possible. Let them dry out in a cool spot for about a week. Label them so you'll remember what they are!  Pack them in a breathable box, such as a cardboard box, storing the bulbs so they don't touch each other, and cover them in sawdust or shredded newspapers. Keep them in a cool, dark location that is below 45°F, but doesn't freeze.

Citrus

Different types of citruses have different cold hardiness. The leaves, green wood and fruit are more frost sensitive than hard wood. Mandarins and kumquats are the most tolerant of cold, with oranges, lemons and limes being less tolerant. However, if a cold snap has colder than usual temperatures and/or lasts more than a short period, even mandarins and kumquats can suffer. Any ripe fruit should be removed prior to freezing temperatures.

Citrus plants can be protected by frost cloths which allow some light and air to penetrate and can stay on plants for a few days at a time. They can also lay directly on plant foliage. If you use other type of cloth such as burlap or cotton sheets, use stakes to hold the cloth away from the plant greenery. Remove it during daytime when temperatures are above freezing and sunny, and replace it each night prior to sunset. Whatever cloth you use, make sure the cloth goes all the way to the ground to capture radiant heat from the ground. If there is mulch around the plant, rake away during the day, if above freezing and sunny, to allow the soil to warm up. 

Roses

Some roses are more sensitive to cold than others. As a group, hybrid tea roses are the most vulnerable. Make sure they are watered prior to predicted freezing temperatures, protect the root zone with mulch on the soil mound. You may also wish to cover your sensitive roses with frost cloths.

Container Plants

As always, water the plant a few days prior to an expected freeze. Ideally, if you are able to pull plants in pots into the garage, shed, or other enclosed area, do so.  While not as effective as an enclosed area, moving container plants onto a patio, or up against the side of the house or garage, preferably beneath an overhang will provide some protection. If unable to move the container, you can cover them up with frost cloth as discussed in the citrus section.

What do do if frost damages your plants? Wait!

Frost damage occurs when the water inside the cells of a plant freeze, causing damage to the cellular walls, which harms the overall health of the plant. Frost damaged vegetation will wilt, turning brown or black, as if they have been scorched. The bark may crack, or split. In severe or prolonged periods of frost the plant can die.

If you see what appears to be frost damage, wait until late spring until all chance of frost has passed. Plants are resilient and can often recover on its own, producing new growth.  Pruning what seems to be damaged branches too soon can cause significantly more trauma, even death, to a vulnerable plant that might otherwise have recovered in the spring. 

Resources

• https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=22929
• https://sacmg.ucanr.edu/Frost_Protection/
• https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=45517
• http://ipm.ucanr.edu/PMG/GARDEN/ENVIRON/frostdamage.html

Denise Godbout-Avant has been a UC Cooperative Extension Master Gardener in Stanislaus County since 2020.

Does growing a vegetable garden sound like something you'd like to do, but you don't feel equipped? So, here's the deal. Find some dirt, and then plant. It's that simple. If you want to grow food, the first step is to find some dirt. Consider the usable ground you have. Take a look around. Maybe it's that patch of front lawn that you're tired of mowing, or haven't mowed at all. Could it be the bare spot in the back where the dog likes to poop? Step One is to find some dirt, and don't be judgy about the dirt you have. Your dirt is full of potential.

Dirt is made up of four things: minerals (from decomposed rock), air, water, and organic matter (Faber et al 38). The organic material originates from living organisms (or stuff that was once alive), and a single teaspoon of soil may contain as many as 4 billion bacteria, 1 million fungi, 20 million actinomycetes and 300,000 algae, (Faber et al 50) not to mention those friendly earthworms, which together with the beneficial microorganisms work to produce healthy soil. Even though dirt is packed with minerals, organic matter and microscopic critters, it still has space (pores) which hold water and air. Water isn't surprising, but why air? Plant roots and most microorganisms “breathe,” and the soil takes in oxygen and releases carbon dioxide.  Ideal soil for growing plants is 45% minerals, 5% organic materials, 25% water and 25% air (Faber et al 38).

So, what about that dirt you are eying as a potential vegetable garden? About half of soil is made of minerals, and soil minerals are categorized by size: sand particles are the biggest, silt is medium-sized, and clay particles are smallest. A quick test will help you learn more about your own dirt. First, take a small handful of moist soil. Rub the soil between your thumb and forefinger, and notice its characteristics. Is it sticky, smooth or gritty? Does it hold together, form a ribbon or thin strip, or fall apart? A sandy soil will feel gritty and crumble in your hand; a clay soil will feel sticky and form a strong ribbon, whereas silt feels smooth and slippery. Soil texture falls into three general categories based on particle size: coarse (sand), medium (silt), and fine (clay). The best soil for home gardens is a medium-textured “loam,” which means it has a relative balance of sand, silt and clay with 5 to 10% organic matter.

As you hold your own dirt in your hands, you may already be able to tell whether or not it has a favorable balance of minerals.  The appearance of your dirt when it's dry can offer clues, too. Does it shrink and crack into blocky structures? That would be clay. When you add water, does the water puddle easily (clay) or drain quickly (sand)? Even if you're not blessed with a perfect, loamy soil, that's ok. A sticky clay soil may be harder to work with, but clay plays a crucial role in soil fertility, so clay soil is often rich and holds moisture well. A sandy soil is less able to retain moisture and nutrients, but it's easier to work with. Fortunately, there are steps you can take to improve your dirt so that it moves away from the extremes and closer to a balanced loam.

Your objective is to give your dirt some tender loving care, and your soil will return the favor by giving you healthier plants and better produce. Your soil's mineral composition is what it is, but one element we can be altered is organic material. No matter what kind of dirt you have, adding organic matter will make it better. Organic materials include grass clippings, fallen leaves, straw, wood chips and bark, hulls, plant clippings (chopped small) and everyone's favorite...manure. Now, here's an important point: it takes time for the organic materials to break down and start to enrich the soil, to become usable to plants. So, what's the best and quickest way to get those things into your soil? Compost. Compost is already mostly decomposed organic matter, so it mixes into the soil and continues to decompose slowly, releasing nutrients to plants and improving soil texture.  Compost costs money, but you can also make your own in as little as 2 to 3 weeks at little or no cost. This article has a complete description of DIY compost: Compost in a Hurry (UC ANR Publication 8037).

Maybe you're thinking, why can't I just throw on my leaves or grass clippings and dig them in?  You can do that, but unfortunately, that reduces nitrogen (the nutrient plants need most) in your soil for a while because the soil microorganisms will be competing with your plants for nitrogen as the microbes eat up all those grass clippings and leaves. You would still end up needing to add nitrogen fertilizer. The next best thing to do with your organic material (if you're not using a compost bin) is to turn it into mulch.

Think of mulching as another method of composting that involves placing a thick layer of organic matter on top of the soil and letting it decompose very slowly. It's even better to put a layer of newspaper or cardboard on the ground first, wet it, and then spread out the organic material on top, about 4 inches thick. The organic matter and the paper or cardboard underneath will break down over the next 6 to 10 months. To add plants, push aside the mulch, expose the paper or cardboard, and cut an "X" large enough to accommodate your plant. Fold back the flaps, dig a hole, and add your plant. When done, lay the flaps back in place and re-cover with mulch. Remember that front lawn that you're thinking could be a vegetable garden? This method of sheet mulching is one way you get rid of the grass! Cover it, mulch it, forget about it. If you want to learn more about lawn removal, here's an article containing complete instructions: Lawn Removal: Do It Right.

Healthy soil produces healthy plants, and mulching and composting are two ways to turn your dirt into the rich loam that gardeners dream about. Even better, they require no chemicals, and you won't have to spend any money if you're resourceful.  In times like these, it's good to know you can get started gardening without emptying your wallet. It's simple. Find some dirt, and make it better!

UC Master Gardeners of Butte County are part of the University of California Cooperative Extension (UCCE) system. To learn more about us and our upcoming events, and for help with gardening in our area, visit our website. If you have a gardening question or problem, email the Hotline at mgbutte@ucanr.edu or leave a phone message on our Hotline at (530) 538-7201. To speak to a Master Gardener about a gardening issue, or to drop by the MG office during Hotline hours, see the most current information on our Ask Us Hotline webpage.

The Autumn Equinox signals a time of change in the seasons. The weather becomes cooler, the days shorter, skies turn a softer blue with occasional clouds, summer vegetable gardens are finishing up, and deciduous trees change colors and drop their leaves. By mid-November our neighborhoods and gardens will be littered with fallen leaves.

People often rake their leaves and put them out to be picked up as trash. I have always preferred to leave the leaves for my garden.

If you take a walk in a forest, you'll see leaf layers several inches deep around trees and bushes. Fallen leaves have a complex relationship with trees and nature, providing many benefits which can be reproduced to some extent in our gardens.

Natural Mulch

Leaf litter prevents rainwater and wind from carrying the soil's nutrients away. Water trickling through the leaf layer carries essential nutrients such as carbon, phosphorus, nitrogen, and other inorganic compounds, thus replenishing the soil.

Fallen leaves have the same weed suppression and moisture retention properties of shredded wood mulch—and they're free! Where mulch is desired as a decorative element, what could be more seasonally appropriate than a pile of brightly colored fall leaves? This natural mulch also provides insulating winter cover from cold temperatures for roots, seeds, and bulbs.

A Web of Life in Leaf Litter

Leaf litter isn't just free fertilizer and mulch. It provides food and shelter for a wide variety of living things including spiders, snails, worms, beetles, millipedes, mites, toads, frogs and more—these in turn support mammals, birds, reptiles, and amphibians that rely on these creatures for food.

Detritivores (organisms that eat dead or decaying plants or animals) break up and excrete leaf litter. Fungi and bacteria then take over and complete the recycling process converting these smaller pieces into nutrients which then sustain neighboring plants. They in turn help support biodiversity by becoming food themselves.

Some creatures use leaf litter and other dead vegetation to insulate themselves from winter's chill, while others, such as earthworms, feed on the litter, breaking it into smaller pieces.

Numerous bird species such as robins and towhees forage in the leaf layer searching for insects and other invertebrates to eat. 

Raking up leaves and putting them in the trash could have the unintended consequence of removing some of next year's garden butterflies and moths, many of which are pollinators. Most butterflies and moths overwinter in the landscape as an egg, caterpillar, chrysalis, or adult. In all but the warmest climates, they often use leaf litter for winter cover. Fritillaries and wooly bear caterpillars will tuck themselves into a pile of leaves for protection from cold weather and predators. Some Hairstreaks lay their eggs on fallen oak leaves, which become the first food of the caterpillars when they emerge. Swallowtail butterflies disguise their cocoons and chrysalises as dried leaves, blending in with the “real” leaves.

Bumble bees also rely on leaf litter for protection. At the end of summer, mated queen bumble bees burrow an inch or two into the earth to hibernate for winter. An extra thick layer of leaves is welcome protection from the elements.

All of which makes leaf litter an integral part of a complex web of life.

What You Can Do

Leaving the leaves where they are is ideal but isn't always practical for gardeners. If you have lawn, you can mulch the leaves with your mower, rake them up, and place them back in the garden around trees, shrubs, and plants. Spreading some of the chopped leaves around on your lawn will also nourish it. If possible, leave some leaves undisturbed in planters since shredded leaves will not provide the same cover as leaving them whole, and you may be destroying eggs, caterpillars, chrysalis, and other micro-creatures along with the chopped leaves.

Composting leaves is a terrific way to recycle and create a nutrient-rich garden soil amendment at the same time. Some gardeners opt for shredding their fall leaves for use in compost piles. Like people who mulch their lawn leaves with a mower, consider leaving some leaves undisturbed in garden beds and lawn edges. If space allows, you could create a leaf pile, allowing it to break down naturally, or add the leaves gradually to your compost pile over time. Such efforts will keep leaf litter critters safe and allow you to benefit from the rich garden gift that falls from the trees above.

While it is ideal to “leave the leaves” permanently—for the benefits mentioned above—if you do decide you need to clean your garden and remove the leaves in spring, try to wait until later in the season, so as to give the critters that have been protected by fallen leaves over the winter time to emerge and depart.

Some gardeners may be concerned that autumn leaves, matted down by rain or snow, could have a negative impact on their perennials. However, a thick layer of leaves provides additional insulation against chilly weather and protects newly planted perennials from frost which could damage tender roots and shoots. Anyone who has spotted fragile spring seedlings popping up in the woods knows that all but the most fragile of plants will erupt through the leaf litter in spring without trouble.

So, leave the leaves. While you can't perfectly emulate a forest, your garden will be healthier and more diversified, you'll help support a vast array of wildlife, and you'll reduce the strain on landfills. 

Denise Godbout-Avant has been a UCCE Stanislaus County Master Gardener since July 2020.

Join Susan Kornfeld on November 11, 2021 from 6:30pm-7:30pm at our Ask a Master Gardener Zoom Hour, as she leads the discussion on choosing mulch for your garden. Link to register for this online event.

Ask Master Gardeners about mulch and they will start ticking off benefits:  protects soil from compaction and extreme temperatures, improves soil structure and feeds soil microbiology, suppresses weeds, retains moisture, supplies nutrients, and supports the soil food web. But not all mulch is created equal. One mulch, arborist wood chips, can accomplish everything on the list, but isn't suited for use around veggies and delicate annuals; other mulches admirably fill those and other niches, and then there are a few that should generally be avoided.

First, what is mulch? Basically, anything that covers the ground. It can be organic, synthetic, or rock. It can even be a living ground cover. Vegetables are often mulched with straw or some mixture of shavings and manures – materials that not only protect the soil but rapidly break down. Trees, shrubs and woody perennials benefit from woody mulches that last years and feed both roots and soil biota. Flower beds can thrive with their own cuttings serving as mulch as can smaller, more delicate shrubs.

Stone mulches – rocks, gravels, pebbles, and decomposed granite (DG), are good for fire-scaping and so are useful near buildings and to break up planting beds into islands that discourage fire spread. They protect the soil from adverse weather but do not feed it. Most people line stone material with landscape cloth to facilitate its removal when desired and to keep the stone on the surface rather than sinking into the root area. Unfortunately, the landscape cloth will at some point need to be hauled to landfill.

Then there are the green and animal manures. Green manures include grass, shredded leaves, and small garden clippings. Animal manures are rich in nutrients but need to be composted before use. They are typically mixed with green manures or soil amendments. These mulches are useful in kitchen gardens and annual flower beds.

Bark mulch looks good and can feed soil eventually, but its purpose is to repel water and germs while gardeners want to invite microbes and retain moisture in the ground. Bark can also float away with rain or irrigation.

Arborist wood chips, on the other hand, are usually delivered freshly chipped after arborists prune or remove trees. This is the best mulch in terms of moisture retention, weed control, and sustainability. This chipped material is mostly wood but also includes bark and some green material. Because of this variety in size it resists compaction, feeds the soil, and invites colonization by a diverse soil biota. Best, it's usually free.

 What about other mulches?

- Inorganic mulches such as landscape cloth and plastic sheets can be useful in commercial farms, but they are less useful in home gardens and do not benefit the soil. Additionally, they deteriorate rapidly into landscape trash.

- Cocoa bean: this mulch was popular for a while because of its deep brown color and chocolate smell. But not only does it tend to become moldy if applied too thickly and to blow away easily when dry, but it is poisonous to dogs.

- Rubber mulch: Typically made out of tires it contains the same heavy metals tires have – cadmium, chromium, and zinc. As the mulch breaks down, these metals are released into the soil.

With all the good mulches to choose from, gardeners shouldn't forget living plants. Think about carpets of creeping thyme or meadows thick with clovers. They feed and protect the soil, suppress weeds – and do it all while looking great and attracting pollinators to your garden. What's not to like?