Master Gardener News Blog
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.
By Andrea Peck
Mail order is all the rage right now. It's so simple; you order what you want and it arrives on your doorstep contained in an oversized box and excess packaging. If you're really lucky you'll get bubble wrap. But, have you thought about ordering plants this way?
Apparently there is a whole plant market out there in cyberspace. You can virtually order any plant you like. We can all picture the scene: you are sitting alone in the dark of night, the glowing light of the computer screen is the only illumination in the room. You find the plant of your dreams. It's on Ebay. Maybe Amazon. The tiny picture gives away very little. Despite this you are convinced that your garden must possess this novel plant. Still, you pause. You notice that the vendor is located across the globe. Will your exotic grow in your microclimate? The price is enticingly low. (must be Ebay). But, here it is, after midnight—there are no rules. Impulse shopping seems like the very thing you need to do if only to feel like you have done something so that you can get back to bed and get some rest. You press the purchase button.
Sounds innocuous right?
Most of the time it is. In fact, let's face it, sending plants and seeds by mail is nothing new. There are large companies that make a fortune by tempting you with glossy, surely Photoshopped images that make you think you can smell the leaves upon the page. This is standard operating procedure.
There are times, however, that ordering a plant online can potentially cause havoc. This recent article describes the increasingly problematic occurrence of selling plants over the internet. Apparently, a number of vendors are selling invasive plants despite the fact that they are banned. Invasive plants not only pose a significant threat to the environment, but are often illegal to sell or purchase.
Banning the sale of invasive plants makes sense when you consider the threat that they impose. One notorious aquatic plant, giant salvinia, or kariba-weed, is capable of doubling in size every 8 to 10 days. The plant is so compact and thick that it basically smothers out sunlight and oxygen, killing the animals and plant life that live beneath it. Despite this, it has been sold recently through internet vendors. Generally, plants such as these are sold as aquarium or container species. Their ability to proliferate and grow easily is certainly a selling point. Whether online shopkeepers understand the ramifications of what they are selling—and the illegal aspect of it—remains to be seen.
When you consider the vastness of the internet, it's not difficult to see how containment of sales could present a problem. But, it is the inability to thoroughly regulate online sales that makes the job truly invasive. Considering the resources available to us, however, it does seem that these large online companies would find a simple way to monitor what is sold.
Until then, the impetus must depend on the consumer. Ultimately, it is the buyer who stands to lose his money—and much more. For more information I've included a link to the in Department of Agriculture's invasive species information site: https://www.invasivespeciesinfo.gov/index.shtml
By Jackie Woods UCCE Master Gardener
While most of us gardeners are happily focusing on outdoor projects, why not entertain the idea of purchasing a few indoor plants that are both easy to care for as well as beneficial to one's health? Indoor plants are esthetically pleasing to the eye and allow for all gardening enthusiasts to enjoy having an indoor garden as well. But did you know that certain indoor plants actually purify the air that we breathe by removing toxic agents?
Back in the late 1970's, high gasoline, heating and cooling costs took a toll on business and homeowners. In order to conserve energy and save money, buildings and homes were being designed to be more energy efficient. These design changes included maximizing insulation which in turn reduced fresh air exchange. When workers and homeowners occupied these super-efficient, air-tight buildings, various health issues such as itchy eyes, skin rashes, respiratory and sinus congestion, headaches and other allergy symptoms became more common. The symptoms collectively became known as ‘sick building syndrome.”
In 1989, the National Aeronautics Space Administration (NASA) came to the rescue by conducting a study in association with the Associated Landscape Contractors of America (ALCA) called the NASA Clean Air Study. This study researched ways to clean air in space stations using various houseplants. As all plants absorb carbon dioxide and release oxygen, these specific air-purifying plants (see partial list below) also eliminate toxic gases such as benzene, formaldehyde and trichloroethylene – gases which synthetic materials used in energy-efficient buildings were known to emit. By eliminating these toxins, air-purifying plants essentially neutralize the effects of ‘sick building syndrome.' The NASA research also states that efficient air cleaning is accomplished with at least one air-purifying plant per 100 square feet of office or living space.
Air-purifying plants are Barberton daisy (Gerbera jamesonii), English Ivy (Hedera helix), Florist's Chrysanthemum (Chrysanthemum morifolium), Peace Lily (Spathiphyllum “Mauna Loa”), Red-edged Dracaena (Dracaena marginata), Spider plant (Chlorophytum comosum,,Variegated snake plant, mother-in-law's tongue (Sansevieria trifasciata ‘Laurentii')
Other research-based plant studies also indicate that ornamental indoor plants can stimulate both the senses and the mind thus improving performance and mental cognition. So, why not hit the indoor nursery and pick up a few air-purifying plants today? Fill your workplace and home with mother-in-law tongue!
Fire Safe Landscaping
By Andrea Peck UCCE Master Gardener
This week's Advice to Grow by Workshop hails an important topic and an honored guest. Kim Corella from CalFire will be speaking on the topic of fire safety in the garden. Devastating and often deadly, fire is capable of igniting in an instant and clearing everything in its path. Despite the constant risk of fire in California, this is one threat that is seldom considered in our garden plan.
How do we embrace the natural habitat consistent with our area and maintain a safe, yet enjoyable landscape? The workshop will focus on the garden and its relation to native wildlife, habitat, and climate conditions. Learn which plants promote a fire-safe environment and which represent a hazard. Weeds, particularly certain annuals, have the potential to burn rapidly and serve as kindling or ‘fuel.' Learn to distinguish between ‘good choice' plants and those that are potential fire starters.
Where your home is located and how your garden is designed, are key factors in fire safety. Learn how the relationship between garden, landscape and home structures work together to fight or promote fire.
After the speaking portion of the workshop, you'll have the opportunity to tour the garden. The group will visit the fire-safe garden plot for a demonstration on how the zones have been utilized in planting. The workshop will continue with a critique session of the entire garden so that you can see areas that promote fire safety and those that could use a little work. Finally, for those hands-on learners or those who gave up their morning workout to attend, volunteers will be asked to lend a hand in the garden by doing thinning, trimming and overall fuel reduction maintenance. The workshop will be open for question and answers, so bring your questions.
Be prepared for the weather! Don't forget to bring a comfortable chair, water, sunscreen and a hat. The workshop takes place from 10:00 until 12:00 in the Garden of the Seven Sisters, located at 2156 Sierra Way, San Luis Obispo.
By Jutta Thoerner UCCE Master Gardener
What is greywater and how can I use it in my Garden? Alex in Creston
California has a Health and Safety Code (17922.12) for the definition of greywater. Summarized, it says that greywater is not contaminated by toilet discharge or unhealthy bodily wastes and presents no threat from contamination due to unhealthful processing. Graywater includes, but is not limited to, wastewater from bathtubs, showers, bathroom sink and clothes washing machine. It does not include wastewater from kitchen sinks or dishwashers.
It is most common is to install a 3-way valve to the hose of a washing machine. This valve separates graywater from water designated for the sewer, which is necessary in case bleach or powdered detergents are used or when a high groundwater level is present. On average, between 10 and 25 gallons are generated per load from a front loader and about 40 gallons from a top loader.
Because of the possible residues in graywater, only non-edible plants should be watered with graywater, making it well suited for your shrubs and trees. For example, in Creston 200 gallons of graywater generated weekly can keep four mature trees with medium to high water needs healthy. The soil type, climate zone and type of plants determines how far the graywater will stretch.
To stay compliant when greywater is released, you need a mulch basin. The basin can be combined with a branched drain system or you can pump the water into a surge tank. For a mulch basin, several inches of soil are replaced by coarse wood chip mulch. The graywater is discharged via pump into a mulch shield which sits inside the basin. For a gravity fed system, use a branched drain pipe system. A simple and inexpensive method is to direct the greywater into an airtight drum which can serve as a surge tank. Once the water is collected, it can be dispensed from a hose spigot attached to the drum, similar to rain water drums. It is recommended to get the help of a professional installer to keep you compliant and your plants healthy.