Stress is a normal condition for landscape plants. While plants can tolerate considerable stress, they may be weakened and made susceptible to attack by insects and diseases. A little TLC during the summer months will go a long way toward keeping trees, shrubs and perennials healthy and vigorous during the heat, drought and humidity of a typical summer.
The first and most important step in plant stress prevention is planting the right plant in the right place. Part of a good landscape plan is selection of plants suited to the various micro-environments of the home grounds. While a juniper will thrive in a hot, dry corner, a dogwood or Japanese maple planted nearby will probably show leaf scorch most years. But planting the juniper in a shady or poorly drained site is a waste of time. Even azaleas will grow poorly in very dense shade. Pruning up a few of the lower branches on over-story trees to provide a few hours of morning sun often dramatically improves the performance of light-starved plants.
When planting container grown trees and shrubs, tease the roots away from the root ball and spread them out in the planting hole. Teasing the roots is much different than taking out a knife and making vertical slices through the roots. Multiple vertical slices may sever up to 50% of the root system, setting the plant up for drought stress when hot weather comes. Root watering crystals (such as Agrosoke) can be a tremendous benefit when added at planting time. These crystals absorb moisture from the soil, but release it back into the soil between watering.
When planting trees with a soil ball (balled and burlapped), make sure that the burlap is not exposed to the air where it will wick water from the ball. Personally I like to remove the burlap entirely, once the plant is in the hole. Do not over-fertilize at planting time. This may stimulate excessive shoot growth at the expense of root growth, making the plant less drought tolerant. Mulching is essential for stress avoidance. It retains soil moisture, keeps the soil cool and eliminates competition from turf and weeds for moisture and nutrients. Compost makes excellent mulch since it provides a source of slow release nutrients, thereby promoting root growth. When mulching, do not pile the mulch around the base of the trunk (aka The Jersey Volcano). This will suffocate the plant, severely decreasing its lifespan. Instead, make a saucer with the mulch, building it up as you get to the edge of your planting area. This will allow water to drain directly to the root system where it is need most.
Don't hole up in the air-conditioned house during the hot summer and abandon your landscape. Check for signs of stress during the heat of the day. Even plants that wilt severely during mid-afternoon can recover by the following morning with a little TLC. But a few days of severe wilting can weaken a plant and interfere with fall root growth and cold hardiness development.
Other signs of summer stress include pale leaves and scorched leaf margins. These generally result from high leaf temperature and can occur even when soil moisture is seemingly sufficient. Careful watering, mulching and protection of Japanese maples and dogwoods from wind and afternoon sun will reduce the incidence of leaf scorch. Watch lilacs and dogwoods for powdery mildew in late summer. This can weaken plants as they head into winter, but can be prevented with a monthly application of Wilt-Pruf (an anti-dessicant that is normally used in the winter to prevent winter burn on evergreen leaves).
In general, the "supplement rainfall to make one-inch-per-week" rule for watering works well to prevent stress. Run a drip irrigation system with 1 gallon per hour emitters for an hour. Also stay away from overhead sprinklers – most of the water will evaporate before getting to the root zone, and is a waste of one of our precious resources. Although I would like to say we would have adequate moisture throughout the summer, our recent history proves differently.
Sunday, June 6, 2010
Sunday, May 9, 2010
Why Plants Fail to Bloom
Flowering plants that don't bloom as promised can be a big disappointment in your garden. Reasons for lack of blooming are as diverse as the palette of plants from which to choose, but a little detective work can usually pinpoint the trouble. The most common factors associated with blooming, or lack thereof, include light, plant age, nutrition, extreme temperatures and improper pruning.
Many woody plants must reach a certain age before they are mature enough to produce flowers. Fruit trees, such as apples and pears, can require as many as five or six years to become fruitful. Gingko trees can take up to 15 years to bloom (which could be a good thing!). The most common question I am asked is “Why doesn’t my wisteria bloom?” and the reason is wisteria can take anywhere from 7 to 10 years to bloom, so patience is a must. Add a stressful environment (drought, excessive moisture, etc) to a juvenile plant, and flowering may be delayed even further.
Plants that are old enough to flower, or have done so in the past, may quit doing so for a variety of reasons. Flowering may be sparse or completely absent when a plant is under stress, so be sure the plant is positioned in an appropriate location for that particular species. For example, some plants flower best in full sun; others may prefer the cooler conditions found in the shade. Some plants, such as peonies, will flower sparsely or not at all when grown in shade. Similarly, shade-loving plants, such as begonias, will not bloom well in full sun. In gardens where other trees and shrubs are nearby, light conditions can change drastically over time as landscape plants cast more shade, or removal of a large plant suddenly leaves formerly shaded plants exposed.
Some plants, such as chrysanthemums and poinsettias, flower in response to short day lengths, or more accurately, long nights. If the plants don't receive the appropriate break from light, their season of bloom will be delayed indefinitely.
Overfeeding plants with nitrogen can encourage them to produce lush foliage at the expense of blossoms. A lack of nutrients, particularly nitrogen, phosphorus and potassium, also may delay flowering. Stick with a balanced, low-analysis fertilizer, such as 5-10-5 or 10-6-4, to apply adequate nutrition without overdoing.
Some gardeners unknowingly remove flower potential from their plants by pruning at the wrong time of year. Landscape plants that bloom in early spring set their flower buds in autumn on last year's growth. If you prune these plants in late winter, you'll also be removing many or all of the flower buds. The rule of thumb is to prune spring-flowering shrubs and vines after blooms have faded.
Mother Nature can deal a blow to buds with extreme low winter temperatures or late frosts in spring after growth has begun. Though this past winter was relatively mild, we did have some spring cool-downs at night. And some plants may be winter hardy, but their flower buds are routinely killed, even by normal spring weather.
So if you have landscape plants that are not performing up to par, do your homework to find the appropriate requirements, and plan to replace the "duds" with plants that are better adapted to your growing conditions. Try moving the “duds” to other areas of your property with different soil, light and moisture conditions. You may be pleasantly surprised! Remember to plant the right plant in the right place. This rule of thumb, as simply as it may seem, is one of the most important.
Many woody plants must reach a certain age before they are mature enough to produce flowers. Fruit trees, such as apples and pears, can require as many as five or six years to become fruitful. Gingko trees can take up to 15 years to bloom (which could be a good thing!). The most common question I am asked is “Why doesn’t my wisteria bloom?” and the reason is wisteria can take anywhere from 7 to 10 years to bloom, so patience is a must. Add a stressful environment (drought, excessive moisture, etc) to a juvenile plant, and flowering may be delayed even further.
Plants that are old enough to flower, or have done so in the past, may quit doing so for a variety of reasons. Flowering may be sparse or completely absent when a plant is under stress, so be sure the plant is positioned in an appropriate location for that particular species. For example, some plants flower best in full sun; others may prefer the cooler conditions found in the shade. Some plants, such as peonies, will flower sparsely or not at all when grown in shade. Similarly, shade-loving plants, such as begonias, will not bloom well in full sun. In gardens where other trees and shrubs are nearby, light conditions can change drastically over time as landscape plants cast more shade, or removal of a large plant suddenly leaves formerly shaded plants exposed.
Some plants, such as chrysanthemums and poinsettias, flower in response to short day lengths, or more accurately, long nights. If the plants don't receive the appropriate break from light, their season of bloom will be delayed indefinitely.
Overfeeding plants with nitrogen can encourage them to produce lush foliage at the expense of blossoms. A lack of nutrients, particularly nitrogen, phosphorus and potassium, also may delay flowering. Stick with a balanced, low-analysis fertilizer, such as 5-10-5 or 10-6-4, to apply adequate nutrition without overdoing.
Some gardeners unknowingly remove flower potential from their plants by pruning at the wrong time of year. Landscape plants that bloom in early spring set their flower buds in autumn on last year's growth. If you prune these plants in late winter, you'll also be removing many or all of the flower buds. The rule of thumb is to prune spring-flowering shrubs and vines after blooms have faded.
Mother Nature can deal a blow to buds with extreme low winter temperatures or late frosts in spring after growth has begun. Though this past winter was relatively mild, we did have some spring cool-downs at night. And some plants may be winter hardy, but their flower buds are routinely killed, even by normal spring weather.
So if you have landscape plants that are not performing up to par, do your homework to find the appropriate requirements, and plan to replace the "duds" with plants that are better adapted to your growing conditions. Try moving the “duds” to other areas of your property with different soil, light and moisture conditions. You may be pleasantly surprised! Remember to plant the right plant in the right place. This rule of thumb, as simply as it may seem, is one of the most important.
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