Early December Cold Snap May Cause Plant Damage
The early December cold snap with temperatures in the single digits or lower will test the hardiness of a lot of plants. Because of warm fall weather, many plants were not completely dormant when temperatures dropped into the single digits.
Look for plant damage when plants begin to grow next spring. The plants most likely to suffer damage are those planted in late summer or early fall. They may not have had time to establish a sufficient root system.
Another group is perennial plants including trees and shrubs planted in containers. They should be moved to a protected location such as a covered patio, garage or shed by mid November.
A few years ago we had temperatures down into the teens in December which damaged several broad leaf evergreen plants which are commonly planted in the Pacific Northwest. These were Escalonia, Viburnum Spring Bouquet, and Choisya (Mexican orange). In some cases plants were killed down to the ground. In others, some branches were killed and other branches damaged. I did not see a case where the entire plant was killed.
The first damage you will notice on these normally evergreen plants is loss of leaves on killed branches. If this occurs this year, simply prune off all the dead wood in the spring after growth starts. In some cases you may need to remove some undamaged tissue in order to shape plants. In most cases, plants will regrow near to their normal size in a single season.
I checked both USDA and Sunset hardiness zone ratings for all three of these plants. They are all rated as hardy in the main metro areas in western Washington and Oregon. However, Sunset cautions that damage can occur below 15 degrees on two of them.
Indoor Plant Watering and Fertilization
Many factors affect the frequency of watering needed for specific plants. What are the light and temperature where the plant is growing? How big is the plant in relation to the pot? What type of soil is it planted in?
The best single way to determine if a plant needs water is to feel the top of the soil with your finger. If the soil is dry on top, then it is probably time to water. After you have watered a plant several times you will find out about how long it takes to dry out. Wet soil is darker than dry soil, so after a while you can tell by color when a particular soil is starting to dry out. Not all potting soils are the same color, so you need to feel the soil a few times until you learn the relative color.
Since there are so many factors involved in how often a plant dries out, you should not try to water all plants at equal intervals. If you check plants every day or two for awhile you will find out which ones need frequent or infrequent watering.
Water quality is also important. Softened water has more sodium chloride than is good for plants. Sodium chloride or table salt damages plant roots and soil structure. Most cold water taps in the kitchen do not have softened water. However, cold water can slow plant growth, especially in the winter. I like to fill my watering can with cold water and let it sit until it reaches room temperature.
Older leaves turning yellow is a definite sign that plants are short of nitrogen fertilizer. Nitrogen is a key ingredient in chlorophyll, the compound which makes leaves green. Chlorophyll is necessary for the leaves to produce energy from photosynthesis. When nitrogen supply is limited, plants will remove nitrogen from older leaves and transfer it to new growth. This is a natural process which goes on all the time, but becomes accelerated when there is a shortage of nitrogen.
Other factors can also cause leaves to become lighter green. Overwatering can be a contributor.
I use a long lasting poly coated plant fertilizer such as Osmocote for my indoor plants. In most cases it lasts for 2 months or longer. The coated capsules release a little fertilizer every time plants are watered. However, capsules release a smaller amount of fertilizer toward the end of their life. I watch the leaf color to determine when I need to apply more fertilizer.
Since not all plants use fertilizer at the same rate, I apply additional liquid fertilizer to yellowing plants to give them a boost. When plants are overwatered, fertilizer is leached from the soil more quickly.
Another factor which can cause indoor plant yellowing is the development of an acid condition or low pH. The water in the Pacific Northwest has a naturally lower mineral content which gradually make the soil more acid. Small amounts of lime can counteract this condition.
Do you have overgrown shrubs which are beyond the size suitable for pruning? Has the outdoor uses of your landscape changed? One of the things I enjoy doing most is helping clients remodel their landscapes to fit changing needs. There is no charge for an initial consultation to make suggestions on possible improvements. I frequently do simple landscape sketches at minimal charge to create a new layout for the yard. These plans can be implemented by the client or I can give you an estimate for installation. Let me know how I can help you.
Dormant Pest Control
Many insects overwinter as eggs or pupae on the bark of dormant branches. Dormant Oil (a natural organic pesticide) will kill most overwintering insects including scale insects which are hard to control with other pesticides. If you have had insect problems with particular plants during the growing season, those insects may be overwintering on those same plants so they can attack again next spring or summer. Dormant Oil is also sold as Superior Spray Oil.
Winter Is the Best Time to Prune Many Plants
From now until the end of March is the best time to prune most plants. The major exception is spring flowering shrubs which set their flower buds last fall. Any pruning before their bloom will remove some of those flower buds. It is easier and faster to prune deciduous plants when their leaves are not present. It is particularly desirable to prune fruit trees every year before they start new growth starting the first year they are planted. Let me know if you would like to have me prune your fruit trees or teach you how to prune them yourself.