First, check that you are
not overwatering, or fertilizing your plants. Also, check that
aren't planting the
wrong plant in the wrong plant community; for example, desert plant in
redwood forest plant in desert, sun lover in shade, high-
(coastal bluff, ridge line) in a closed area (enclosed patio), or water
lover in dry spot. An upland, south- facing slope plant from Jamul
planted in a Santa Monica or San Francisco garden may be covered with
mildew, if it doesn't die of root rot. In the reverse situation, the
The naturally occurring non-plant members of a habitat, such as, but not limited to, insects, fungi and bacteria, play an important role in our California ecosystems. They evolved with California native plants, some apparently giving, as in the case of the nitrogen-fixing bacteria; some apparently taking, as in the case of the manzanita leaf-gall aphid. If the takers were a serious problem, all our plants in the wild would not exist. Spraying with insecticides and fungicides is a quick fix and in the long term makes the problem much worse. If you can live with some pests such as aphids, you will attract more insect-eating birds, have a healthier garden for doing so and in turn have less aphids on your plants. If your pests are out of control this is usually a sign of bad horticulture (eg. over/under watering, fertilizing, incorrect soil or incorrect location (a plant set out way beyond its normal range and under severe stress) Remember, in native ecosystems populations of all living things are usually in balance. For example, herbivores (rabbits) are controlled by predators (coyotes), insects (aphids) by birds ( Bushtits, Kinglets, etc,). Fungi and bacteria are a little more complicated, usually being controlled by the plant itself or by other bacteria or fungi.
No sprays needed. The few times in the past we did spray the garden plants (when we first started dealing with natives and didn't know any better), we ended up killing a lot of good stuff and the plants still looked sick. Native plants are for the most part unhybridized. They still have their natural protective abilities if you treat them right. Over watering them removes the plant's protections. Water for survival, not fast growth, and after a year or so the plant will give you faster growth.
Application of fertilizers, insecticides, fungicides and bactericides can also remove the native plant's natural immunity. It is funny that you can buy fertilizer with insecticide in it. Why do you need the insecticide?
Rock mulch for desert plants, tree mulch for forest plants, rock and tree mulch for chaparral plants.
irrigation causes all sorts of root problems and related pathogen
problems. If the plant is not growing correctly, try turning off the
drip or converting to spot sprays. Drip waterlogs the soils where it
waters and builds up salt in the soil. Most native plants need areated
soil and have trouble with high salts.
Plant the long term climax plants (usually the the trees that grow for a long time, but creosote also comes to mind)) leaving room for them to reach their full size without growing over each other or other plants. Die back occurs when sun lovers are in too much shade, so think ahead.
plants and drought tolerant plants in
general lose their disease resistance when they are watered more than
the minimum, particularly during the summer (after they grow their
roots the first summer).
The plants have to be under slight stress to keep their associated
fungi, bacteria and other companions happy. Water or fertilize too much
and the plant will exclude its companions and pathogens will take their
Clark et. Al. ; Clay 1989, 1990; Petrine et. al.; Petrini & Fisher; Preszler and Price; Rollenger and Langenheim
Prune a native plant into a poodle dog, and you usually have a dead poodle. Native plants like minimal (lazy man) pruning in late summer or fall. If you prune the lower branches off as in the picture to the right and left, then the trunk is not protected by the foliage, and is susceptible to sunburn (right), borers, and sapsuckers/woodpeckers (left).
Prune up the foliage and create those foo-foo shapes people seem to think are natural, and the stems burn off, get infected with borers, or get pecked to death. Instead, plant one of the manzanitas (Arctostaphylos spp.) like Ian's Bush, Dr. Hurd, Mama Bear, Louis Edmunds or Austin Griffiths, or Ceanothus cultivars like LT Blue that possess a naturally open form if you want that look. No plant mutilation necessary!
damage to plants is sometimes incorrectly
identified as disease damage.
A lot of customers get excited when they experience summer deciduous plants for the first time. Many native perennials shut down in summer, and come to life in late fall. This is normal and desirable. The flower show is better and less diseases occur when the monkey flowers, sages and other perennials are allowed to shutdown. Plant some evergreens (Manzanitas, Oaks, Toyon, Coffeeberry, and Ceanothus) with them so the whole flower bed doesn't shut down at once (ugly).
Narrow Leaf milkweed gets a golden aphid that the smaller birds eat. Almost every year it gets it. No biggy, it is part of the live cycle of the plant.
Oak trees will commonly get oak moth caterpillar. You do not need to spray the tree. The tree probably uses the caterpillar to covert the leaves into fertilizer and mulch on bad years.
Leaf gall on manzanitas.
This is a little insect that lives in the leafs. This usually is an occasional problem and the plant will drop these leaves in early winter. No biggy. Funny, some customers love the gall, and try to buy the plants that have it, other people are appalled the there is a BUG IN THE LEAF!
Also, called Oak Apples. There are hundreds of different kinds of oak galls. The galls are formed by the oak tree, usually in response to an insect.. Inside the gall, the young insects develop out of the rain and sun and protected from predators. Cool, huh! These oak galls are naturally found on oaks in the wild, and usually do not have a negative effect on the health of the tree. (Translation: no big deal)
On manzanitas it is either sunburn (they pruned the stems up too high), poor air flow or too much overhead watering (planted next to a lawn in a closed in yard).
Ceanothus stem die back occurs on some of the real coastal plants, particularly the low ones, when they are planted in the interior heat. The sun fries off the bark.
This disease is a fascinating natural phenomenon. The leaves of the sycamore tree emerge in the spring to then turn brown and wither and fall off. Supposedly the fungus that causes sycamore anthracnose is an obligate parasite, which means that the fungus needs a living host; if the fungus kills its host, it will also die. Since this fungus has evolved with the sycamore tree over millions of years, what happens is as follows: on drier years the tree is hardly affected and makes good growth and the fungus causes no or minimal damage and on wet years the fungus makes good growth and the tree can be defoliated, and make very little growth. (Translation: no big deal on some years, a big deal on other years, but trees will rarely die)
Die back of Aesculus californica: This is not dieback, it is a natural condition, called semi-dormancy. On the east coast, it is very noticeable that the leaves of the trees turn color and fall off the trees. The trees are not dead or dying, they are undergoing a “slowdown” period, a period in which they can avoid the harsh conditions of winter. In California, our harsh conditions occur in the summer. So, around late summer, the buckeye leaves turn brown and yellow, and many fall off, and the buckeye undergoes a period of semi-dormancy, and is semi-deciduous. (Translation: no big deal)
This problem is a root rot/wilt that occurs later in the season, around late summer, early fall. This disease occurs on plants 2 years or older. This disease occurs within one to several days or so following a heavy watering of the plant, by the gardener, done because the plant looked “stressed for water/wilty/thirsty/etc.” Every time, the disease occurs the same time of year, under the same conditions, and on plants two years of age or older. The organisms that cause this disease, grow lustily under warm (summer-fall), moist (your irrigation) conditions. (Translation: a big bad deal) To prevent this disease on upland plants: 1) give full-blown irrigation (water weekly, if soil is dry two inches down, with microspray emitters or by hand or by sprinkler), in the summer the first year only. 2) keep the mulch 2"-4" thick 3) Place a large (6" by 6" by 6" approximately) rock on the ground adjacent to and on the west side of each plant. Especially for Fremontodendron, plant on the east side of a building, a boulder pile, a thick rock wall, a mass of lower vegetation; in other words, something with enough mass to keep the soil cool! 4) Water indirectly, at the drip line or farther away.
Leaf Burn occurs for many reasons. The most common problems include drip irrigation(don't), planting plants from plant communities that are not like yours(Sierra plants in Bakersfield), salt spray from the ocean(can occur miles inland if the breeze is direct from ocean) and the high salt soils of some of the inland valleys. You can't really treat the soils to solve the problems, you'll need to rethink what to plant if you happen to live in one of these spots.
Mistletoe is a epiphyte that uses the tree as a substrate like a normal plant would use soil. It is hemiparasitic attaching itself to the xylem of its host but photosynthesizing (making it's own food). Because they are not able to absorb their nutrients and minerals from the soil the have to use whatever is absorbed by their host. This limits their size, as they can easily become nutrient deficient. They do not have true roots and are unable to be selective in what they absorb. It is common for people to think of mistletoe as a pest or as being harmful to the tree however most studies have found this to be unsubstantiated. In fact many studies have found the mistletoe to be very important to plants as well as animals. Mistletoe may act as a dumping ground for excess minerals that their host plant can not absorb. There are four species of the genus Phorodendron and three of the Arceuthobium genus. The Arceuthobium genus is found on conifers that is Pines, Firs, Spruce, Hemlock. Phorodendron is found on a wider variety of trees and shrubs including Juniper, Mesquite, Acacia, and Oaks.
Swellings/Nodules on roots of Ceanothus, Alder, (nitrogen-fixing bacteria Frankia) and Lupine (nitrogen-fixing bacteria Rhizobium)- Some people are getting very excited when they see these on our plants, so we thought we should let everyone know what they are and what they do, to clear up much speculation and misunderstanding!! These bacteria (Rhizobium and Frankia )were discovered many years ago. The root swellings are actually a combination of these symbiotic, nitrogen-fixing bacteria and the cells of the root that proliferate in response to the bacterial infection.
This is a good thing! The bacteria receive food from the plant in the form of carbohydrates (sugars) and so convert nitrogen from the air (N2 ), which plants cannot use, into ammonium ions (NH4+). These ions are then converted by other types of bacteria living in the soil to nitrite ions, then to nitrate ions (NO3-) which plants can use to make proteins, etc. The relationship between the plant and the bacteria is a close relationship where each party gains something, called mutualism. These nodules, or swellings, on the roots of some of our plants, are like little nitrogen factories, a natural form of fertilizer, made by the bacteria with the help of the plants, together, no charge! So much easier, cheaper, and more natural than going out and buying a bag of fertilizer and spreading it around the garden. You receive the reward and don’t have to do any of the work!! (Translation: a great deal!)