- Author: Brent McGhie
By Brent McGhie, Butte County Master Gardener, January 6, 2017.
Plummeting winter temperatures often lead to frost damage in plants. The damage occurs when ice crystals form within plant tissue, damaging their cells. Leaves and tender new growth are usually affected first. Initially, they will appear wilted. Then the wilted growth will turn brown or black and eventually become crispy. This means these affected parts of the plant have died.
It is tempting to remove frost-damaged plant growth immediately, but dead material should be left on the plant until the full extent of the damage is apparent in the spring. There are several reasons to wait. By allowing plenty of time for new growth to appear, the extent of any damage will be clearly apparent and it will be less likely that you will accidentally remove living tissue that survived a freeze. Additionally, dead material can actually provide an insulating effect and removing it too soon may expose additional tissues to future freezes. If you prune out dead material before another freeze hits, it is more likely that an even greater portion of the plant will be killed. In Chico and nearby areas of the valley floor, the danger of frost is usually over in late April, so it is prudent to wait at least until then, or later, before doing any pruning.
In citrus, if hardier growth (such as twigs or wood) has not been seriously damaged, it is normal for dead leaves to be rapidly shed. If the frost-killed leaves remain on the plant, this is an indication that twigs or branches have been seriously damaged. If larger branches or the trunk of a tree sustain cold damage, the bark will split and dead patches of curled, dry bark may appear. If a young citrus tree has been killed nearly to the ground, inspect it closely to determine if the damage extends below the graft union. The graft union is the junction where the fruit-producing part of the tree was grafted onto the rootstock. If new growth comes only from the rootstock, the tree will no longer be true to the type you originally planted and will usually be unproductive. In this case, the tree should be replaced or you can try your hand at budding a new top variety into the rootstock sprouts in late spring.
The only thing that should be done immediately after frost damage has occurred to citrus and other woody plants is whitewashing. Whitewash should be applied to the trunk and exposed limbs. This protects the bark from sunburn, which is more likely to occur if a plant becomes defoliated. Frost-damaged plants are more susceptible to disease and insects and sunburn increases this susceptibility. To make whitewash, mix equal parts of white interior latex paint with water. If the area to be painted is particularly rough and fissured, a thinner mixture can be applied for better penetration and coverage. You can dilute a thicker top-quality interior latex paint as much as 2:1 or 3:1, water to paint.
It is also important to note that frost-damaged plants are unbalanced: although their leaves have been reduced, they still have the same root system. This can result in extensive new growth over the entire plant once regrowth begins in the spring. To ensure that the plant reaches an acceptable balance between its leaves and its root system, the new shoots should grow at a moderate rate. It is recommended that little or no fertilizer be applied to these plants initially, and they should be irrigated less than usual until they have returned to a normal appearance. Too much nitrogen fertilizer, for example, can encourage sucker and water sprout growth, while too much water can damage roots.
Of course, it would be preferable to prevent frost damage from occurring in the first place. To read more about preventing frost damage and many other gardening topics, visit the Butte County Master Gardener website (http://ucanr.edu/sites/bcmg/). For specific information on frost protection, the following link will take you to our Real Dirt blog page on this topic: Frost Protection for Citrus
See also:
By Brent McGhie, Butte County Master Gardener, December 23, 2016.
There are several advantages to planting bare-root trees: they are usually less expensive, easier for gardeners to transport, and they will grow their roots entirely into native soil (rather than having to transition from potting mix into dissimilar native soil). Also, the ideal time to plant bare-root trees is in the winter, when you have a break from the demands of other garden chores.
Once the planting site has been prepared, it's time to select the tree. Trees with a trunk diameter between one-half and five-eighths of an inch usually become established faster than larger or smaller stock. If the root mass is visible, be sure it is well balanced, not “one-sided.” Remove any dead or damaged roots before planting. It is best to plant bare-root trees immediately after bringing them home, but if this is not possible, the roots should be covered with sawdust or compost and kept moist until planting.
To prevent the tree from settling too low in the ground, dig the planting hole no deeper than the tree's roots. To encourage root growth, the hole should be about twice as wide as the spread of the roots. If the soil contains a large amount of clay, the sides of the hole should be scored to aid outward root growth. Build a cone of soil in the center of the hole and spread the roots over the cone, with the bud union (where the tree was grafted onto the root stock) facing south west. This prevents sun-scald of the flat side of the trunk just above the bud union. Next, back-fill the hole with the same soil that was taken from it until the hole is half filled and gently firm the soil to eliminate large air pockets. Double check the planting depth, making sure the bud union is four to six inches above the soil surface. Finish filling the hole with the native soil and gently firm it once again. When properly planted, the tree's uppermost roots should be just slightly below the soil surface and the soil should slope gently away from the trunk, preventing water from accumulating there.
Thoroughly water the newly-planted tree to settle the soil around the roots. Unless the tree has been planted in wet, heavy clay soil, a basin should be built around the tree. (In clay soils, keeping the soil too wet can eliminate air spaces in the soil, “suffocating” the roots). The basin should be donut-shaped, with the tree sitting in an island of soil in the middle of the basin. Again, to discourage rot, make sure water drains away from the tree. The basin should be slightly wider than the planting hole, ensuring that the entire root area receives water. After growth has begun in spring, water the new tree once or twice per week, adjusting the schedule as needed for cool rainy periods or early hot spells.
Clear an area about 3 feet wide around the tree, eliminating weeds and grasses to keep them from competing with the tree for water and nutrients. To prevent future weed growth and conserve moisture, a layer of mulch 3 to 6 inches thick can be placed around the tree. However, to avoid crown rot, keep the mulch several inches away from the tree trunk. As a final step, remove the top of the tree by pruning back to a single trunk approximately 24 inches tall and paint the bark of the entire tree trunk with white interior latex paint diluted with water (two parts water to one part paint) as a whitewash to reflect excess heat. This prevents sunburn and the resulting invasion of wood-boring insects that can stunt or kill the new tree.
By Brent McGhie, Butte County Master Gardener, December 9, 2016.
While farmers have historically planted hedgerows around fields to delineate boundaries, provide windbreaks and keep livestock from wandering, University of California research shows that hedgerows also provide many unintended benefits. Hedgerows have significantly fewer crop pests and more beneficial insects, such as pollinators and predatory wasps, than conventional field edges and these benefits extend into adjacent croplands. Hedgerows also provide habitat for insect-eating birds and other wildlife. Native bees benefit from the undisturbed habitat, as well as the nectar and pollen that hedgerows can provide. Additionally, hedgerows are useful in controlling dust, reducing sound pollution, and preventing erosion.
Urban and suburban landowners can reap these benefits by planting smaller trees and large shrubs to establish mini-hedgerows instead of fences or hedges. A scaled-down hedgerow will still attract pollinators, beneficial insects and birds. Hedgerows can also create corridors between wild spaces, allowing wildlife to more safely move through neighborhoods. As landscape designer Rebecca Lindenmeyr says, “Hedgerows can provide a slice of wild on the outskirts of a landscape design.”
If you decide to create a hedgerow, try to choose plants with a variety of heights. Different types of wildlife are adapted to living at different levels above the ground. Also, generally speaking, wider is better when it comes to hedgerows. The wider the planting area, the more room there is for a greater diversity of plants. The greater the diversity of plants in a hedgerow, the more likely it is that wildlife will find a suitable habitat there. Look for plants that provide food for wildlife. Selecting a variety plants that produce flowers, fruit, nuts, seeds, or nectar at different times of the year increases your chances of providing food for the greatest diversity of wildlife species.
Native plants are a logical choice for use in hedgerows. They are familiar sources of food and shelter for local wildlife species, and are well adapted to the local climate and soils. Large native shrubs that are suitable for residential hedgerows in our area include California redbud, toyon, many species of Ceanothus and manzanita, coffeeberry, desert willow and coyote brush. California bush anemone, Cleveland and white sage and buckwheat are more moderately-sized natives that can also be useful in hedgerows. Smaller native perennials include deer grass, California fuchsia, milkweed and penstemon. An added bonus is that, once established, all of these natives are at least moderately “deer resistant.” It is important to recognize, however, that if they are hungry enough deer will eat virtually anything.
Three larger nonnative plants that deserve consideration for incorporation into hedgerows are rosemary, Chinese fringe flower and chaste tree. All are adapted to our climate, deer resistant, and relatively easy to manage. If you'd like to see what these plants look like in a garden setting, the chaste tree and most of the native plants mentioned above can be seen in the Demonstration Garden being developed by Butte County Master Gardeners at the Patrick Ranch Museum. Whatever plants you decide to use, enjoy the natural beauty and other benefits of your hedgerow!
For further information on residential hedgerows, consult the following sources for this article:
Butte Co. Master Gardeners. "Make Room for Hedgerows!" Butte County Gardening Guide and Three-Year Gardening Journal (2015): 104 (with thanks to Eve Werner).
By Carolyn Faulkner, Butte County Master Gardener, November 25, 2016.
For many gardeners, fall brings with it the excitement of selecting and planting spring-flowering bulbs.
The term “bulb” is commonly used to describe a wide range of plants that have underground structures in which they store their nutrient reserves. These reserves allow bulbs to survive and bloom from year to year, if conditions are right. Knowing the differences among the five bulb types can help you determine when and where to plant them.
The second type of bulb is the corm. Corms are actually stems modified for storage. These look like true bulbs but they do not grow outward in circular rings. Some have a furry covering and all are solid on the inside. Young buds, which will produce the stems and flowers, form on the topside of corms; roots and cormels (baby corms) emerge from the bottom. The Water Chestnut provides a good example of what the inside of a corm looks like. Flowering corms include gladiolus, crocus, freesia, and watsonia. The water lily is also a corm.
The third type of bulb is the rhizome. These have elongated underground stems which sometimes emerge above the soil surface. Some of these stems are thick, while others are the thickness of a blade of grass, but all produce leaf growth from the top, and roots that emerge from the underside. Examples of rhizomatous bulbs are bearded iris, cannas and calla lilies. The cattail is a rhizome. Unfortunately Bermuda grass and mint are also rhizomes, and their small underground stems allow them to spread easily and become invasive.
The fourth type of bulb is the tuber. Tubers are also underground stems, but not the base of the stem as in a corm. Tubers have multiple “eyes” (buds) and most of them prefer filtered sun. The potato and yam are tubers. Begonias, cyclamen and anemones are all examples of flowering tubers.
The fifth type of bulb is the tuberous root. These are roots that form around a central stem. The sweet potato is a tuberous root which is where it differs from the yam. Some examples of flowering plants that have tuberous roots are dahlias, agapanthus and day lilies.
The depth that each bulb is planted varies according to the type: some (like rhizomatous bearded iris) can be planted just below the surface, while others (like tulips) require deep planting of up to eight inches. Because bulb depth varies so widely, it is important to check sources before planting, but the general rule of thumb for plantingspring bulbsis toplant two to three times as deep as the bulbis tall.
Bulbs to plant in the fall for late winter and spring blooms include tulips, daffodils, crocuses, Dutch iris, and many types of lilies. Bulbs to plant in the late winter and early spring for summer flowers include dahlia, canna, begonia, and gladiolus. Light fertilizer can be applied just as the bulbs begin to grow.
Most bulbs like full sun, but there are some exceptions, such as hyacinthoides (bluebells) and many daffodils, which bloom in early spring before trees leaf out.
Most bulbs are perennials, and many do well in containers. Most bulbs prefer well-drained soil, but exceptions include the Summer Snowflake (Leucojum), Camassia quamash, and Lilium lancifolium (the orange tiger lily), cattail and (of course) the Water Lily, all of which like damp, even soggy, conditions.
Once bulbs have bloomed, do not cut back their leaves until they have turned yellow and are obviously dead. The bulbs require these leaves to manufacture carbohydrates and store energy for the next year, through photosynthesis. However, the flower stalks can be cut back to where the foliage begins. It is important to apply a complete fertilizer after bloom in the spring, spreading around the base of the leaves, and to continue minimal watering. Once leaves have been removed the bulb can be dug up and stored in a dark dry cool place or simply left in the ground. Be careful not to over-water. Unless your bulbs are among the water-tolerating exceptions, too much water will cause the bulbs to mildew or rot.
A helpful chart for bulb planting can be found at Sacramento Bulb Planting Schedule. Keep in mind, however, that our Butte County winters tend to be colder than those in Sacramento.
By Carolyn Melf, Butte County Master Gardener, November 11, 2016.
At this time of year bulbs are appearing at nurseries and big retail stores as well as in the garden catalogs that arrive in your mail box. Many bulbs (like tulips) need to be chilled for 8-10 weeks in your refrigerator before replanting for blooms the following spring. Consider growing bulbs that are better suited to our warm climate. They are easier to grow, most are perennial, and they look their best in warm temperatures.
Since most failure with bulbs can be traced back to problems during planting, give yourself time for proper planning and planting. Plant in November to early December in our mild climate urban areas (zones 8 and 9). Bulbs must be planted at the correct depth, usually in a hole 3 times as deep as the size of the bulb. Fertilizing with a bulb booster (such as 4-12-8) or with organic bulb food is a good idea: place a few grains of the fertilizer in the bottom of the hole, cover with a fine layer of soil so the bulb does not come into direct contact with the material, and then add the bulb and fill the hole with soil. “Which end of the bulb is up?” you might wonder --- usually the pointy end is up, and the roots face downwards. But some bulbs are long and narrow, making it difficult to tell which end is the top. You can plant such a bulb on its side – growth will respond to gravity with shoots growing up and roots growing down. After covering the bulbs with soil, water the planted area well. Moisture must be present 6 to 8 inches below the surface to encourage root growth. Finally, avoid walking on the bulbs and compacting the soil.
Alliums are ornamental cousins of onions that aren't usually bothered by animals. Globular clusters of white, yellow, pink, red, blue or purple flowers are carried on stalks that rise above the foliage. They come in a variety heights, as well as colors, and can blend into any garden.
Crinum, a tall member of the amaryllis family, is topped with a circle of trumpet-shaped flowers, usually white, pink or a combination of both. Plant so the neck of the bulb is just above the soil and give it plenty of water while it is growing.
Gloriosa Lily is a tuberous perennial with red and yellow lily-like flower heads. It can sprawl and scramble through other plants, climbing by means of tendrils at the ends of its leaves. Plant 1 to 2 inches deep, and 10 to 15 inches apart, in rich soil.
Watsonia has tallspikes of tubular blossoms which come in shades of red, orange, pink and white. They begin blooming in late winter and carry on into the spring.