Master Gardener News Blog
National Pollinator Week
By Linda Lewis Griffith UCCE Master Gardener
National Pollinator Week is June 20-26. It's a time to celebrate the hard-working hummingbirds, bats, bees, beetles, butterflies and flies that carry pollen from one plant to another and pollinate over 75 percent of the flowering plants and nearly 75 percent of our crops. Pollination occurs when pollen from the male part of the flower (stamen) is moved to the female part (stigma) of the same or another flower. Fertilization takes place and results in the production of flowers, fruits and seeds. Animals visit flowers in search of food and sometimes even mates, shelter and nest-building materials. Some animals, such as many types of bees, intentionally collect pollen; others, like butterflies and birds, move pollen incidentally because the pollen sticks on their body as they collect nectar from flowers. All of these animals are considered pollinators.
According to the U.S. Fish & Wildlife Service, pollination by honey bees in the United States alone contributed to over $19 billion worth of marketable crops in 2010.
Yet pollinators are in trouble. A recent study of the status of pollinators in North America by the National Academy of Sciences found that populations of honey bees (which are not native to North America) and some wild pollinators are declining. Drops in wild pollinators may be a result of habitat loss and degradation. A decrease in managed bee populations is linked to diseases caused by introduced parasites and pathogens.
There's plenty you can do to protect pollinators. The U.S. Fish & Wildlife Service offers these suggestions: Plant a pollinator garden. Choose plants that flower at different times of the year to provide nectar and pollen sources throughout the year.
- Provide a variety of flower colors and shapes to attract a wide range of different pollinators.
- Select native plants whenever possible. Native plants will attract more native pollinators and can serve as nesting sites for some species.
- Avoid or limit pesticide use. Pesticides kill more than the target pest. Some pesticide residues can harm pollinators for several days after the pesticide is applied. They also kill natural predators which can lead to even worse pest problems.
By Andrea Peck
It's that time of year again. The hills are fading into a fawn-like color. The verdant green has passed and our high hopes that this year will certainly be the year that fills our water cups is looking unlikely. Those of you who see the glass as half full have trained your eye away from the lush tropical jungle of your dreams and towards the most logical gardening solution: succulents. It's true that succulents have many redeeming features, but it is their handy knack for tolerating our less-than-stellar rain totals that brings us back to them time and again.
Succulents are a loosely defined group of plants that, simply stated, are able to respond to a dry environment by conserving water. Originating in areas, such as deserts, where lack of water and extreme heat and sun can wilt the best of plants, survival depends on the ability to store and “guard” water. Most succulents have thick leaves or stems that contain specialized cells that retain water when rain or irrigation is plentiful. Almost any plant that exhibits this propensity falls under the label 'succulent.' Interestingly, that includes the cactus family. In fact, cacti are succulents, though, succulents may not always be cacti.
You can spot a succulent by its generally ample, fleshy body. The leaves or the stem are built for water retention. Some plants have an accordion-shape which acts like elastic, stretching or contracting and allowing the plant to fill or shrink based on water availability. This folding shape also reduces sun exposure. Some plants grow tall which essentially allows them to create their own shade.
Many succulents have a waxy outer-coating that further prevents water loss. The waxy coating does not cover the stomates, however. Stomates are openings, like pores, that allow carbon dioxide in and oxygen out. Because stomates are openings, they also have the potential to allow water out. Luckily, the finely-tuned succulent has an answer for that. Succulents, unlike other plants, open their stomates during the night—when heat and dryness are minimal. Conversely, they close their stomates during the day—again another stab at water conservation. This is called CAM photosynthesis and, though it is a neat trick, it is a less efficient use of energy in comparison to the method used by other plants. This is one reason that succulents tend to be slow growing.
The leaves of succulents are also an adaptation. Most succulents have less leaves, some have no leaves, and others have spines. Having less leaves limits the surface area that is exposed to the sun. Cacti actually photosynthesize through the stem. Spines are modified leaves, but do not serve a “leaf” purpose. Instead, they protect the plant from thirsty herbivores and provide shade. Some spines are so thick and hair-like that they create a pocket of insulation which keeps the plant cool, moist and protected from the elements. Light-colored stems and spines are another important adaptation because they reflect heat away from the plant.
You may have already noticed in your own garden, that succulents have shallow roots. Sometimes a plant may have a tap root as well, which helps keep the plant in one place. Shallow roots are advantageous for picking up any bit of rain that happens to be in the vicinity.
Perhaps one of the most interesting facts that I learned while reading about succulents is that some, such as the organ pipe cactus, grow underneath a “nurse” tree. The plant seeds and germinates there, all the while taking advantage of the cooling shade. But, as it grows and its root system spreads, the cactus dominates the area, taking in so much water that the nurse plant eventually dies.
Despite that gruesome tidbit, succulents remain a great garden solution for dry times. Their unusual shapes, colors and statuesque height can bring real drama to your garden. Just make sure you watch for spines and don't fret if you forget to water them and they look dead. They probably are just all pinched up waiting for a good rain—kind of like the rest of us.
SUMMER PRUNING OF FRUIT TREES
By Leonard Cicerello UCCE Master Gardener
Do I really need to prune my fruit trees in the summer? Lloyd from Atascadero
It is common knowledge that fruit and nut trees are pruned in the winter when dormant. However, it is not common knowledge that they benefit from summer pruning as well. The purpose of winter pruning is to eliminate dead wood, crossing branches, and to restore the desired size of the tree while keeping fruiting wood for the following season. The reasons for summer pruning are much the same, but also work to eliminate excess growth and open up the tree to air and sunlight. Summer pruning is also an opportunity to thin the immature fruit.
Here is a basic guide to thinning fruit. First, it's important to note that citrus, cherries, olives, quince, figs, almonds, and pomegranates do not requiring thinning. Many stone fruits, however, do benefit greatly from this practice. Thin apricots to allow 3-4” between each fruit; plums 4-6” apart, plums 4-6” apart, peaches and nectarines 5-7” apart. For apples and pears, leave 1-2 fruit per spur. If left untouched, tree limbs can sag and even break under the heavy weight of excess fruit. Furthermore, the fruit size and quality will be subpar.
The topic for this month's UCCE Master Gardeners Advice to Grow By workshop is summer pruning. They will discuss choosing and preparing a planting site, developing a watering plan, choosing the right tree for the microclimate, and how to mulch. You will also learn which trees need pollinizers, and how to protect the tree from gophers and disease. They will also discuss chill and sunlight hours and different shaping techniques such as modified central leader, open center, espalier, and fruit bush. And, each attendee will receive a two-page handout with a summary of the workshop information.
The workshop will be June 18, 2016, at the Garden of Seven Sisters, 2156 Sierra Way in San Luis Obispo, from 10:00 am to 12:00 noon. Garden docents will be available after the workshop to answer questions until 1:00. You may want to bring sunscreen and a bottle of water. Come and join your fellow gardeners under the pergola in the garden.
Water Wise Gardening
By Lee Oliphant UCCE Master Gardener
Q. We have a water shortage in our area. How much water do my plants really need to survive? Pat M., Cambria
Water is essential for plants processes such as photosynthesis, nutrient uptake and transpiration, all of which directly affect a plant's growth and development. During drought conditions when soil moisture is lacking, a plant's growth and development are negatively affected.
Most garden plants need supplemental water when the rains have not sufficiently supplied adequate soil moisture. This is where you, the gardener, come in. Here are a few tips to keep your plants alive during a drought.
- An individual garden plant needs about 1” of water each week. Then, delve deeper into various watering guides to determine how much water your larger plants and trees need. Wouldn't it be wonderful if we could count on rainfall to provide it? But, alas, as custodians of our gardens we must provide for their minimal needs.
- Water only when the soil is dry. Use your hands or a trowel to check for moisture. When soil looks or feels dry 2-3 inches down, it's time to water shallow-rooted annuals. However, if you're caring for larger perennial plants or trees, dig deeper to evaluate the available soil moisture as these plants are deeper rooted than flowering annuals.
- Different plants have different water requirements. Shallow-rooted annuals, perennials, vegetables and newly planted landscapes will have different watering needs than larger, more established plantings. Trees and shrubs that are suited to our climate may need only occasional deep watering. The type of soil you have will dictate how often to water. For example, sandy soil dries out more quickly than clay.
- Water in the morning to give plants a chance to dry before dark. You'll lose less moisture to evaporation and discourage fungal diseases.
- Lastly, be sure to follow any local ordinances or recommendations for landscape water use.
For more information on water-wise gardening, visit the University of California Garden Website - http://cagardenweb.ucanr.edu/Drought_/ -
or the landscape watering guide for San Luis Obispo County - http://www.slowaterwiselandscaping.com/Watering-Guide/
Yellowing Citrus Leaves
Leslie E. Stevens UCCE Master Gardener
Bright green leaves sheltering colorful hanging fruit distinguish healthy citrus trees. Yellow leaves, on the other hand, spell trouble.
Causes are numerous, but often relate to improper irrigation and nutrient deficiencies. Other culprits include pests, bacteria, fungi and phytotoxicity caused by a variety of herbicides, fungicides and salt burn.
Water: As evergreens, citrus may require irrigation year-round to ensure good soil moisture to a depth of about 2 feet for mature trees. Conditions that are too wet or too dry can reduce the tree's ability to take up nutrients, especially nitrogen. Very dry root zones, an impact of the ongoing drought, have led to more nitrogen deficiencies seen in citrus. At the same time, it's important to ensure good drainage, since water-logged roots cannot adequately absorb soil nutrients. If you see a tree canopy of pale green-to-yellow leaves, check your soil moisture in the top two feet before applying fertilizers.
Allow the top 6 inches of soil to dry between watering, typically ranging from 7-to-14 days depending on weather and soil conditions. For this reason, citrus trees should not be planted in lawns or near heavily irrigated plants. Also ensure you have good soil moisture on the deep end of the rootzone so that roots can take up available nutrients.
Fertilizer: Citrus trees require regular doses of nitrogen, zinc, manganese, magnesium and iron to remain healthy and productive. Two or three applications of a slow-release citrus formula annually should do the trick. If you only manage a single dose per year, apply in early spring prior to flowering and fruit setting when nutrient demand is highest.
Mulches: A nutrient-rich mulch of yard waste consisting of wood chips, grass clippings and leaves can also be beneficial for citrus trees, according to the University of California. The high nitrogen in grass clippings offsets the high carbon of the wood chips, and the combination has been shown to be effective in suppressing Phytophthora root rot when present in the soil.
Also be sure to keep mulches at least 6 inches from tree trunks to discourage fungi and bacterial growth on trunk and roots.
Resources: Visit UC- IPM Website for colored pictures and detailed descriptions of common diseases and deficiencies negatively affecting citrus trees.