| May 2008
Oklahoma Gardening Shows
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Oklahoma Gardening Information Sheet (#3445)
OETA air date: May 10 and 11, 2008
OETA airtime: Saturday 11:00 a.m., Sunday 3:30 p.m.
Harvesting Asparagus – In this segment Kim harvests asparagus (Asparagus officinalis). The shots of the plant, commonly called spears, are harvested and eaten. Only the young shoots of asparagus are eaten. Asparagus spears will start to emerge when the soil temperature reaches 50°F. Early in the season, we can harvest every 2 to 4 days. These early pickings or thinnings are called sprue asparagus, and often have very thin shoots.
As air temperatures increase, harvesting frequencies will increase to once per day. Harvest shoots when they are about 7 to 9 inches. Later in the season, spears may need to be harvested smaller, as warm air temperatures cause tips to open sooner.
We can use the tips to help us judge the quality of asparagus. When the tips of the spears start to loosen or fern out, fiber begins to develop at the base of the spears. The fiber makes the stems tough. Harvest before the tips begin to loosen, while it is still tight. Snap the spears off at the base. There is no need to cut asparagus below the soil with a knife. This may injure other buds on the crown that will send up new spears. The stub that is left in the soil after snapping will dry out and decompose. It is best to harvest in the morning when plants are coolest. After picking, immerse the spears in ice-cold water to remove the heat. Drain the water and place the spears in plastic bags to store in the refrigerator.
The length of harvest varies from year to year, depending on air temperature. In the first year after planting, only harvest asparagus for a short, three-week period. In the second year you can increase that harvest period to about 4 to 6 weeks, and by the third year you can begin harvesting for the full production period of about 6 to 8 weeks.
Many growers wonder when they should stop harvesting. A good rule of thumb is to stop harvesting when the diameter of 3/4 of the spears becomes small, less then 3/8 inch. Experience gained by growing the crop will make it easier for the gardener to know when to discontinue the harvest.
At the last harvest, snap all the spears off at ground level. This is the time to make your second application of nitrate fertilizer. New spears will emerge, fern out, and start gathering food to store for next year's crop.
Since asparagus often originates in maritime habitats, it thrives in soils that are too saline for normal weeds to grow in. An old garden practice was to use salt to suppress weeds in beds intended for asparagus. This is not a good idea. Salt will not harm the asparagus, but it can alter water penetration in the soil, and can be leached by rain into the rest of the garden, injuring other plants that are less salt tolerant than asparagus.
The main pest of asparagus is the asparagus beetle. This is a dark beetle with bright yellow and red markings. There is also a spotted asparagus beetle, which is reddish-orange and has black spots on it wings. The adults spend the winter under debris and when they emerge in the spring they feed on the tender tips of asparagus. The larvae of the common asparagus beetle can also feed on the developing shoots. They are gray to olive green in color and rather plump.
There are a number of practices to control these beetles. The common asparagus beetle lays its eggs on the shoots and often in the tips. Harvesting spears regularly generally provides adequate control of larvae by removing eggs before they hatch. You can hand remove beetles and larvae, or use a broom to knock larvae off the plant. They tend to have a difficult time crawling back to the spears. You might also find lady beetle larvae feeding on young asparagus beetle larvae.
The spotted asparagus beetle larvae feed inside the berries that develop on the ferns. Removing the berries is a good way to manage that beetle.
Asparagus is a useful companion plant for tomatoes: the tomato plant repels the asparagus beetle and the asparagus may repel some harmful root nematodes that affect tomato plants.
Fact Sheet HLA-6016 Asparagus Culture in the Home Garden tells you more about growing asparagus.
Hilling Potatoes – We need to hill the potatoes (Solanum tuberosum) that we planted earlier this season. Hilling is simply pulling the soil up around the potato plants. Hilling is critical to producing numerous large potatoes; it creates a space for the tubers to develop. The loose soil in a hill is ideal for tuber development. The hills also keep the tubers out of sunlight, which can cause tubers to turn green and produce harmful glycoalkaloids. Glycoalkaloids can be toxic, especially if eaten in large amounts, and some people are allergic to these compounds. It is best to keep your tubers out of sunlight, both during growth and after harvest.
Plants will need to be hilled when they reach about 8 inches high. Use a hoe to pull the soil up from both sides of the row and cover half of the exposed stem. Repeat this process in 2 to 3 weeks, adding another 3 to 4 inches of soil. Hill again 2 weeks later, adding only 1 to 2 inches of soil to the hill. Be sure there is enough soil on the hills to completely cover the developing tubers. Check periodically and add more soil if you find tubers poking through the surface.
Columbine – Columbine belongs to the genus Aquilegia, which has 60-70 species. Columbines are hardy herbaceous perennial plants found in meadows, woodlands, and in the mountains throughout the Northern Hemisphere. Columbines have a very distinctive flower. The flowers are more or less bell-shaped, with the five inner petals surrounded by colorful sepals. The petals and sepals are often different colors, creating beautiful color combinations. What is really spectacular is the way each petal is modified into an elongated nectar spur. Red columbine (Aquilegia canadense) is highly attractive to hummingbirds and is one of the first nectar sources available to the birds when they arrive in spring. You will also find a variety of moths feeding on columbines, such as the beautiful sphinx moth.
Several species are grown in gardens and numerous hybrids have been developed as well. Columbines are well suited to woodland gardens in Oklahoma. They do tolerate full sun, but due to extreme summer heat plants are best situated where they receive afternoon shade. They have deep tap roots and are fairly drought tolerant once established.
Most varieties grow between 1 and 3 feet tall, and about 1 foot wide. Columbines have an upright, bushy growth habit. In some species, the flowers face upwards, while in others they nod down. The plants self-sow and are very easy to propagate from seed. They are not very long-lived, so you may want to allow a few seedlings to grow up around the parent plant after it has been established for a few years.
Columbines make a wonderful addition to shady borders, woodland gardens, and rock gardens. The deeply lobed leaves continue to add color to garden after flowers fade. Foliage is very dark green or blue green, often turning maroon in fall.
SIP: Simple Irrigation Plan – In this segment Al Sutherland from Oklahoma Mesonet joins Kim to demonstrate the use of SIP – the Simple Irrigation Plan tool available on the internet. The Simple Irrigation Plan uses data from the Oklahoma Mesonet to scientifically estimate lawn grass water use. This takes the "guesswork" out of when and how long to water a lawn.
SIP uses weather data from the Oklahoma Mesonet to estimate the water use of Oklahoma lawns. With 120 Mesonet sites, you'll find one close by. With forecasts from the National Weather Service, SIP estimates water use for up to 3 1/2 days ahead.
The Simple Irrigation Plan can tell you when and how long to water bermudagrass, zoysiagrass or tall fescue. You can select from a wide variety of hose end sprinklers or automatic sprinkler systems. A watering Cost Calculator is included, so you can estimate what it costs to water your lawn.
Fresh, clean water has always been a precious resource. SIP is an online tool that can improve water use efficiency. Just as important as knowing when to water, SIP can also tell you when not to water.
Visit http://sip.mesonet.org/ and try SIP yourself!
Barb Cooks – Barbara Brown, Extension Food Specialist, makes a dish of potatoes, peppers and onions.
Announcements
Tulsa Garden Center and the Linnaeus Teaching Gardens will present two, two-hour seminars focused on growing, maintaining, and propagating annuals and perennials. The lectures will be held May 12 and 14 from 6:30 to 8:30 p.m. at the Tulsa Garden Center. For more information and to enroll call 746-1525 or visit www.tulsagardencenter.com/education.
Please contact your local Oklahoma Cooperative Extension Service Office for more educational information on garden-related topics. If you need further information about this week's show, call (405) 744-5404 or visit our website http://www.oklahomagardening.okstate.edu. Thank you for your continued support!
Sincerely,
Kim Rebek
Oklahoma Gardening Host********************************************************************************************************************
Oklahoma Gardening Information Sheet (#3444)
OETA air date: May 3 and 4, 2008
OETA airtime: Saturday 11:00 a.m., Sunday 3:30 p.m.
Mowing Height and Frequency – In this segment Kim discusses a sound mowing program for the lawn. The key to a good mowing plan is the 1/3 rule. This rule tells us to never remove more than 1/3 of the turfgrass leaves at a time. For example, if you will mow to a height of 2 inches, then you need to wait until the grass has reached 3 inches before mowing.
Following this rule, the height at which we maintain our lawn, to some extent determines how often we need to mow. Consider growing bermudagrass at a height of one inch. Following the rule of 1/3, the lawn would need to be mowed when it reaches 1.5 inches to maintain the low profile. Now consider growing that same bermudagrass at a height of 3 inches. It would not need mowing until it reached 4.5 inches in height, which is an extra inch of growth over the lower lawn. The interval between mowing would be longer to allow the turf to grow that extra inch.
Of course, several other factors influence the rate at which turf will grow, such as soil moisture, nutrients and temperature. However, following the rule of 1/3, we are basing our cuttings on plant growth, and the more growth allowed between cuttings, the less frequently we need to mow.
A good height to maintain bermudagrass is around 2-3 inches. Cool-season grasses should be maintained at 3 inches. You will want to increase the height during times of heat or water stress. The reason for this has to do with root growth. The root system grows somewhat proportional to the above ground growth. When turf is kept short, it develops a shallower root system, when it is maintained at a taller height, the root system grows deeper. During drought, that deeper root system can help reach limited water.
Another practice that will benefit the lawn is to leave grass clippings in place on the lawn rather than bagging and removing cuttings. When we remove clippings we remove valuable nutrients that can be returned to the lawn. You will also save time and energy by not bagging and prevent unnecessary waste from reaching the landfill.
Here are a few more mowing tips:
§ Alter mowing patterns from one week to the next to reduce wear and avoid compaction
§ Make turns on sidewalks and driveways, or make wide turns to avoid tearing turf
§ Avoid mowing wet grass
For more information on lawn maintenance read Fact Sheet HLA-6420.
Mower and Weed Eater Damage to Trees – In this segment we look at tree damage caused by mowing and trimming equipment. We see this type of damage so often scientists jokingly call it "Mower Blight" but it can be quite detrimental to tree health. Although large wounds are more serious, repeated small wounds can also cause trouble.
Wounds act as infection sites for disease agents, which will spread from the wound site into healthy tissue. A severe infection can completely girdle the tree, causing it to die. Decay organisms may also enter the wound and deteriorate the wood, which may cause splitting over time. The site of injury is usually located along the collar, where the roots flare out from the trunk. But you may also find damage a foot or more up the trunk.
The most severe injury occurs when the tree bark is loose or what we call slipping. Slipping is due to growth and occurs in early spring during leaf emergence, and in early fall during leaf drop. A large wound can form when the bark is slipping, even if the injury is minor.
If you catch a wound right away, you can try to reattach the bark. To do this, you must treat trees within a few hours after injury occurs. Reattach torn bark as close as possible to its exact pre-injury position and hold it in place with small tacks or staples.
Most tree injuries occur when people attempt to trim grass too closely around trunks with a push or riding mower or when using a weed eater. This injury can be prevented. If you must grow grass beneath trees, trim it with a hand trimmer. Better yet, avoid the problem altogether by mulching beneath trees. Mulch can be used to keep grass and weeds from growing at the base of the tree.
Spreading mulch or organic materials such as leaves, grass clippings or straw under and around trees will effectively control grass and weeds and help prevent "Mower Blight." Mulch will also conserve soil moisture by reducing evaporation and even stabilize soil temperatures, providing an insulating role. Mulching also gives trees the added benefit of reducing competition for water and nutrients with other plants.
Surround trees with a 4-6 foot ring of mulch laid at a depth of 2-3 inches. Do not use plastic beneath the mulch as a weed barrier, as this will cause roots to be drawn to the surface where they can be damaged by summer heat and winter cold. The mulch will act as a good weed barrier. Also, do not mound the mulch up against the trunk. We often see mulch piled high in a volcano shape around the trunk. This can cause a variety of problems such as surface roots, and can create an environment favorable to insect and disease attack. Leave a narrow, 2-4 inch circle around the trunk free of mulch. If weeds are problem in this area they can be removed by hand.
If trees are closely surrounded by grasses, the turf should be removed or killed. The safest grass killer that can be used near young trees is glyphosate which is sold as Roundup, Kleenup, Weed Away and Weed and Grass Killer. This herbicide will totally eliminate grasses, roots and all, yet is inactivated upon soil contact. Be sure to use a piece of wood, cardboard, etc., as a shield during spraying to prevent spray droplets from touching the trunks or foliage of your desirable plants.
Lawn mower and weed eater injury can be prevented. A mulched area around the tree trunk can provide protection from these types of damage. Make sure that everyone who works in your landscape is aware of the injury that can be caused by "Mower Blight."
Garden Design Series – Developing a Landscape Plan – Before you begin to plan the landscape or garden, you need to clearly define your goals. The big question you need to ask yourself is "How do you plan to use the yard or garden?" Make a list of the activities you intend to carry out in the landscape. This may include:
· Outdoor dining area
· Reading
· Sunbathing
· Sports / Play area for children
· Meditation/relaxation
· Hobbies
· Pet area
· Area(s) for specialty gardening such as cut flowers or wildlife habitat
· Vegetable, fruit or herb gardens
Be thorough and consider all members of the household. Get everyone involved to make sure everyone's needs are met. You might find each person has very different ideas or needs, work to meet as many as possible. As you are going through this, list the number of people that participate in each activity; this will help you to plan an appropriately sized area for each activity.
Identify any structures or hardscape that you may need to install to meet the desired landscape uses.
· Patio or deck to accommodate a dining area
· Play structure for kids
· Fenced area for pets
Make sure to consider long-term plans as well as immediate ones. Perhaps you someday plan to put in a swimming pool or hot tub. These should be included in your initial planning.
Determine what special features, if any, you might want to add to the landscape. Perhaps you want to include a fountain, sculpture or other unique feature in the garden. Are there specialty gardens you wish to install such as a rock garden, vegetable garden or wildlife habitat? Identify structures that might help you enjoy the landscape to its fullest. These may include pergolas for shade, benches and sitting areas, paths or steps. Each should be considered as part of the planning process.
Make sure to get the entire family involved in the planning stage so that everyone's needs are addressed. You might find family members have very different ideas or needs, work to meet as many as possible. Get the ideas down on paper; you can decide later which ones will realistically fit into your landscape plan. Once you have created a list of uses, you need to prioritize. If you have a small space available, determine which uses are most important to the family. Also think of creative ways to use the same room for multiple uses.
Horticulture Tips with David Hillock – David Hillock gives us tips for May and information on pine diseases.
Trees and Shrubs
· Prune and feed azaleas immediately after blooming.
· Insect Alert: (F-7306)
- Bagworms on juniper and arborvitae. (Late May)
- Elm leaf beetles and larvae on elms. (Late May)
- Mimosa webworms on mimosa and honey locust.
- Lace bugs on sycamore, pyrancantha and azalea.
· Soak new transplants and newly planted trees unless rainfall is abundant.
· Pine needle disease treatments are needed in mid-May. (F-7618)
Turfgrass
·Cool-season lawns can be fertilized again. If you did not fertilize cool-season grasses in March and April, do so now.
· Warm-season lawns may be fertilized again in May. (F-6420)
· Seeding of warm-season grasses such as bermudagrass, buffalograss, zoysiagrass and centipedegrass is best performed in mid-May through the end of June. The soil temperatures are warm enough for germination and adequate growing season is present to promote winter hardiness.
· Dollar spot disease of lawns can first become visible in mid-May. Make certain fertilizer applications have been adequate before ever applying a fungicide. (F-7658)
· Nutsedge plants become visible during this month. Post-emergent treatments are best applied for the first time this month (F-6421). Make certain warm-season grasses have completed green-up.
· The second application of pre-emergent annual grass herbicides can be applied in late-May or early June, depending upon timing of first application (F-6421). Check label for details.
· Vegetative establishment of warm-season grasses can continue. (F-6419)
Flowers
· Annual bedding plants can be set out for summer color.
· Plant summer bulbs such as cannas, dahlias, elephant ear, caladiums and gladiolus.
· Shake a leaf over white paper to look for spider mites. If the tiny specks begin to crawl, mites are present.
Water Gardens
· Clean out water garden and prepare for season. Divide and repot water garden plants.
· Begin feeding fish when water temperatures are over 50°F.
Fruits and Vegetables
· Plant watermelon, cantaloupe, cucumber, eggplant, okra, sweet potatoes, etc.
· Fruit spray programs should be faithfully continued during the next several weeks. (F-7319).
· Late May is the best time to control borers in the orchard. Check for label recommendations and controls.
Pine Diseases
There are a few pine diseases common in Oklahoma. The first is Dothistroma Needle Blight. This fungal disease attacks the needles of pines in the spring and summer and symptoms show up in fall. Early symptoms consist of yellow and tan spots, and water soaked bands on the needles. The tips of infected needles will die, leaving the base of the needle green. Infected needles will be shed prematurely. Copper fungicides will effectively control this disease. Spray twice, the first in mid-May and the second application in mid-June to July. In addition, collect and destroy fallen, infected needles.
The second disease is Diplodia Tip Blight. This fungal disease infects the plants through the young needles in spring. Blighted terminals are usually stunted, the needles turn brown, and the terminal buds exude an excessive amount of resin. The cones can also be attacked and minute black fruiting bodies can easily be seen on the scales of the cones (looking like someone dashed pepper all over them). Diplodia Tip Blight can be controlled by pruning and sanitation. As soon as blighted terminals and cones are noticed, the needles, twigs and cones should be pruned to healthy tissue and destroyed. Do not prune when the branches are wet. Copper based fungicides will control this disease too; it should be applied in early spring when the buds open and twice more at weekly intervals until the needles break through the sheaths.
Pinewood Nematode Disease is the third disease. It usually attacks non-native species such as Austrian, Scotch, and Japanese red and black pines. The nematode is actually carried to the tree by a long-horned beetle. When the beetle attacks a tree, the nematode is released into the wounds made by the insect, infect the tree and cause it to wilt rapidly. Within a few weeks the tree dies.
Control of this disease is best done through sanitation, resistant cultivars or species, and sometimes insecticide sprays to control the long-horned beetle. If a tree dies rapidly, we urge you to submit samples to the Plant Disease Diagnostic Laboratory for analysis. Rapid removal of these trees may slow the spread the disease and reduce its severity.
In almost each case above, especially with the nematode disease, these diseases are predisposed by stress of the trees. When stressed they are more susceptible to insect and disease attack. Another method for controlling disease then is to keep your plants healthy by proper watering and fertilization during the growing season.
For more information see fact sheet EPP-7618 Common Diseases of Conifers in Oklahoma.
Barb Cooks – Barbara Brown, Extension Food Specialist, makes stir-fried sugar snap peas.
Announcements
The Southern Region Master Gardener Conference will be held June 18-21, 2008 at the Clarion Meridian Hotel and Convention Center in Oklahoma City. The conference will include garden tours, a variety of seminars and workshops, and special events. For more information and to register, visit www.mastergardener2008.com.
Please contact your local Oklahoma Cooperative Extension Service Office for more educational information on garden-related topics. If you need further information about this week's show, call (405) 744-5404 or visit our website http://www.oklahomagardening.okstate.edu. Thank you for your continued support!
Sincerely,
Kim Rebek
Oklahoma Gardening Host
