California had the worst fires in the last two years of its existence as a state. Hundreds of thousands of acres of brush and forest burned. More importantly thousands lost their homes as fires moved across urban/rural interfaces to destroy communities. The entire town of Paradise, California was burned to the ground. Here in Ventura County, the Thomas Fire was the state’s largest fire by the time it was done, and hundreds lost homes. No other time in history have we been so focused on what will burn, why it will burn, and what we can do to have a “firewise” landscape.… Continue reading this article “Flammability of Landscape Plants–Why the lists are BAD!”
Author: Jim Downer
Dr. Downer has 34 years of experience as a horticulture and plant pathology Advisor with the University of California Cooperative Extension in Ventura County. Dr. Downer’s academic training is from California Polytechnic Univ., Pomona, (BSc. horticulture & botany, 1981; MSc. Biology, 1983;. In 1998 he earned a Ph.D. in plant pathology, from University of California, Riverside. Dr. Downer’s research is focused on mulch, soil microbiology and disease suppression in mulched soils, diseases of shade trees and cultural practices to maintain landscape plants. Dr. Downer is a member of the American Society of Horticultural Science, the American Phytopathological Society, The International Soc. of Arboriculture, and the Western Chapter of the ISA, and the International Society for Horticultural Science. Dr. Downer is an Adjunct professor at California Polytechnic University in Pomona. Dr. Downer serves on the Board of the John Britton Fund for tree Research as the chair of the research advisory committee, and currently chairs the regional conference committee for WCISA. Dr. Downer has a love of shade trees, Shinrin roku (forest bathing/walking) tree work, wood working, horses, gardening, horticulture and the study of plants and their biology.
Fertilizer—Friend or Foe to disease causing organisms?
Gardeners that read this blog understand that minerals are absorbed mostly by plant roots as ions, and are essential for plant growth and development. Some minerals are required in parts per hundred, and are macro-nutrients while others are only required in parts per million or parts per billion, and are considered micronutrients. As long as enough of the 16 most essential minerals are available, plants grow and reproduce in a healthful way. When not enough of one of the essential elements are available, a deficiency occurs, and plants
may present deficiency symptoms.… Continue reading this article “Fertilizer—Friend or Foe to disease causing organisms?”
Trees and Turf a NO GO
It seems so simple to plant a tree. But to grow a tree is more difficult! In many parts of the United States there is enough water for trees and turfgrass, but it is often a bad idea to mix the two. You may have observed that sometimes young trees do not grow as well when planted in turfgrass. Certainly this is a generalized view and tree/turfgrass genetics are very different between their respective species. So it is natural to expect different outcomes when planting different species of trees in any landscape setting, turfgrass notwithstanding. … Continue reading this article “Trees and Turf a NO GO”
Fertilizers — a cautionary tale
Gardeners are assaulted with marketing campaigns nowhere better than in the fertilizer aisle of a garden center. There are so many choices and the labels suggest that fertilizing garden plants is a complicated process that requires specialized products.
Laws require that fertilizers list the proportion of the most important macronutrients on the front of the bag. Nitrogen, Phosphorus and Potassium abbreviated N, P, K, respectively, will always be shown with the ratio of their concentrations such as 5-10-15.… Continue reading this article “Fertilizers — a cautionary tale”
Soil compaction–the urban stress of death for shade trees
I was taught in horticulture school that the ideal soil is composed of 50% solids and 50% voids or spaces which are themselves composed of a variable amount of water from small amounts to as much as 25% water when the soil is at field capacity or the amount of water left in soil after gravity has pulled all the free water down in the profile. So the “ideal” soil always has 25% pore spaces or more depending on how much water is present.… Continue reading this article “Soil compaction–the urban stress of death for shade trees”
Is there a “Deathstar” in your garden?
If you follow national news, you may have noticed that Sudden Oak Death disease caused by Phytophthora ramorum has been found again in a new state and has escaped into retail commerce and thus into gardens. This is news because the disease is a killer of rhododendron, oak, camellia and many other ornamental plants. Yesterday I was measuring trees in a research plot here in California and I found that one of my subjects had turned brown and lost all its leaves.… Continue reading this article “Is there a “Deathstar” in your garden?”
The Dog Days are here
The dog days of summer are here and as we approach the longest day of the year (summer solstice is June 21st), we are also feeling the advance of high summer temperatures. Long days mean more evapotranspiration and water withdrawal from the soil. During these long days, plants photosynthesize more, grow more, and use the most water during the month of June. In fact evapotranspiration looks generally looks like a bell shaped curve when plotted by month (figure 1). … Continue reading this article “The Dog Days are here”
Amending Soils—Why??
I think the blog and garden professors web page is pretty full of research and benefit descriptions of mulching, particularly with arborist chips. A little less clear is the role of amendments in garden soils. I always like to ask the “why” questions for gardening practices. Like “why” prune trees? Why fertilize, etc? Ideally gardening practices should be founded on a basis of science and inquiry as to their necessity. Poor structure early structural training or a damaged canopy may prompt tree pruning, mineral nutrient deficiency symptoms may suggest
fertilization.… Continue reading this article “Amending Soils—Why??”
Problems with Planting Trees
Ok. I admit this blog is going to turn into a rant pretty quick because there seems to be a lot of ways to screw up a fairly simple horticultural practice—tree planting. Since Arbor days are happening/happened everywhere around now, its a good time to talk about how to plant trees. First let me state some simple and useful guidelines for a successful tree planting.
-When at all possible, plant trees bare-root. Even washing the container media away.… Continue reading this article “Problems with Planting Trees”
Understanding the mysteries of plant diseases: Prevention, Control and Cure (Part 3 of 3 in this blog series)
Understanding the mysteries of plant diseases: Prevention, Control and Cure (Part 3 of 3 in this blog series)
What next?
You’ve done your research and made a diagnosis—now what? Sometimes the plant has to be removed and never planted there again. Start over, do something else.
Controlling plant pathogens or abiotic disorders can be daunting, frustrating, even impossible. As I mentioned in the last blog early detection gives more options for control because the disease has not advanced to a degree where it can not be controlled.… Continue reading this article “Understanding the mysteries of plant diseases: Prevention, Control and Cure (Part 3 of 3 in this blog series)”