Fall is the Best Time to Plant Trees

Planting Trees in Fall

Allen Robinson: Ask a Master Gardener

Sunday, September 30, 2018

Q: Is it true that fall is a good time to plant new trees? If so, what do I need to do to be successful? Alex R., Tulsa

A: Fall is clearly the best time to plant most container-grown deciduous trees and those with balled and burlapped (B&B) root balls. This is because, in the fall, the trees have huge energy stores that are used for growing new roots rather than producing leaves and fruit. This will allow the tree to enter the following growing season much better able to handle the summer stresses. Also, although the air temperatures are dropping, the ground temperatures are still warm enough to encourage good root development for some time. The exception to this rule is that evergreen trees and bare-rooted plants should be planted in early spring.

Of all of the newly planted trees that die in the first few years, the problem is almost always due to faulty planting techniques and inadequate aftercare. So let’s discuss this.

First, it is best to dig a wide but shallow, saucer-shaped hole two to three times the diameter of the tree’s root ball and no deeper than the root ball itself. If you simply dig a hole the size of the root ball, particularly in clay soil, it will be similar to planting it in a clay pot and the tree will be either too dry or too wet much of the time. If you are planting in shallow clay soils, the hole should be shallow enough to elevate the crown of the root ball 2-3 inches above grade to help with overall root system drainage.

When planting trees, it is recommended that you use only native soil for backfill. Studies have shown that trees do better if no amendments are added back to the native soil, as it may delay establishment and promote disease. If you decide to fertilize, apply a slow-release type only to the top of the soil after planting.

Eliminating grass from the tree’s base significantly improves growth rate and health. After planting, apply 2-4 inches of loose mulch in a 4- to 6-foot circle around the base of the tree and keep it well-mulched for the first three years. This circle will keep unwanted grass away from the dripline and commercial weed eaters away from the tree trunk.

All newly planted trees need supplemental watering for the first three years until a mature root system develops. They need at least 1 inch of water per week and more if extremely hot and windy conditions exist. Wilting of the trees’ leaves may indicate a need for more water, but be aware that too much water can also produce wilting. If in doubt, simply feel the sub-soil.

If the tree is on a slope or in a windy area, stake it only until the tree feels firm in the ground, which could take up to one year. After the first growing season, remove all stakes. If not removed, the stakes will adversely affect the tree’s structural integrity and delay tree growth.

For more detailed information on this subject, see OSU Fact Sheet L-440 (Tree Planting Guide).

Garden tips

• You can continue to replant or establish cool-season lawns like fescue until mid-month. The mowing height for fescue should be lowered to approximately 2½ inches for fall and winter cutting.

• Plant cool-season annuals like pansies, ornamental cabbage or kale, snapdragons and dusty miller when temperatures begin to cool. Begin planting spring-flowering bulbs like tulips, hyacinths, crocus and daffodils.

• There is still time to plant radishes and mustard in the fall garden. Use a cold frame device to plant spinach, lettuce and various other cool-season crops for production most of the winter.

• Take tropical water garden plants indoors when water temperatures near 50 degrees. Stop feeding fish at this temperature. Close the water garden for the winter by placing hardy plants in the deeper areas of the pool and cover it with bird netting to catch dropping leaves during the winter months.

Reseeding Fescue Lawns in Fall

Reseeding Tall Fescue in Fall

Brian Jervis: Ask a Master Gardener

Sunday, September 16, 2018

Q: It seems like my fescue thinned out this summer. How do I re-seed and when is the best time? DH

A: Fescue is a good choice for areas of your landscape that get some shade. It thrives in spring and winter but struggles with our Oklahoma summers. As a result, most of us need to re-seed our fescue each year to keep a thick, healthy turf.

Cool-season grasses, like fescue, germinate best when the soil temperature is in the 70-degree range. This happens in the spring and fall, but fall is the best time to re-seed as this gives your new fescue the fall, winter and spring to develop a healthy root system. The last half of September through the first half of October usually gives us the soil temperature we need.

Oklahoma is fortunate to have the Oklahoma Mesonet (mesonet.org), which provides us with a wealth of information, including the soil temperature for each county. At this writing, 2-inch soil temperature in Tulsa County is 72 degrees, so this is perfect.

For optimal results, we recommend purchasing seed with a blend of at least three different types of seed rather than a single cultivar. Doing so not only increases your likelihood of success, but also combining grasses tends to reduce the incidence of disease as each type tends to mask the weaknesses of the others.

It is also a good idea to prepare your soil rather than just sprinkle seed on the ground. The upper layer of soil tends to develop a crust so seeds dropped on this hard surface will either blow or wash away before having a chance to germinate. Breaking up the soil can be done with a rake or by perhaps renting a tiller or verticutter for difficult situations.

Seed should be sown evenly with either a rotary or drop spreader and applied at a rate of 3 to 6 pounds per 1,000 square feet when reseeding.

Seeds must have water to germinate, which typically means watering twice a day for a few minutes during the first two to three weeks. The key is to keep the seeds moist. Once the seedlings are 1 to 2 inches tall, you can begin watering less frequently and for longer periods.

Fertilization will also be necessary, and we recommend getting a soil test from the OSU Extension so that you will know exactly which nutrients your soil requires for best results.

One word of caution: If you plan to re-seed this fall, do not use a weed pre-emergent as this will not only work to prevent weeds from growing but will also prevent your new fescue from growing.

We have quite a bit of information at our Diagnostic Center and on our website to help you maintain your new and existing turf: click “Lawn & Garden Help” and then select “Turfgrass” for fact sheets and videos (tulsamastergardeners.org).

Garden tips

• Watch for fall specials at garden centers and nurseries because fall is a great time for planting many ornamentals. Choose spring-flowering bulbs as soon as available.
• Fertilize established fescue lawns with 1 pound of actual nitrogen fertilizer per 1,000 square feet now and again in November. Do not fertilize Bermuda or zoysia lawns until next spring. Late fertilization of these warm-season grasses may promote disease.
• September and early October is garlic-planting time with an aim for harvest in June of next year. There are many varieties from which to choose. OSU suggests German Red, Inchilium Red, Silverskin and Spanish Roja for varieties, which do well in our area.

Control of Bagworms on Trees and Shrubs

Control of Bagworms on Trees and Shrubs

Allen Robinson: Ask a Master Gardener

Sunday, September 2, 2018

Q: I am seeing lots of bagworms on my cedar trees and other trees right now. What can I do to get rid of them? Charlotte S., Tulsa

A: Bagworms are common pests on eastern red cedar, other junipers, arbor vitae and sometimes on bald cypress, elms, pines, willows, maples and others. They are unique in that once they form their protective bag later in the summer, insecticides are not helpful. Treatment should begin soon after the eggs hatch in late spring.

The cycle of worm production begins in the spring when eggs that have overwintered in bags hatch. Newly hatched larvae develop small, upright bags while feeding on the plant. Initially, the bags are less than ¼ inch but, when mature, they can reach up to 2 inches in length. Once mature, the larvae close off the bag and fix it to the tree. In mid-summer, the males emerge from bags, fly around and mate with females who never leave the bags. The females lay eggs in the bag and then die. The cycle begins anew in the following spring.

For smaller trees with small infestations, the easiest treatment is to simply pull the bags off and destroy them. This can be done at any time of the year. Be sure to burn them or place them in a well-sealed bag to destroy the bags and their viable eggs. Trees that have heavy infestations yearly should be treated with an insecticide because large numbers can completely defoliate and kill smaller trees.

Insecticide treatment must be done soon after the larvae hatch in late May or early June. No treatment is considered effective once the bag is closed. Be patient as most insecticides will require repeat applications every seven to 10 days for two to three treatments because not all eggs hatch at the same time or there may be migration (wind dispersal of small larvae during June) from other host trees.

There are two relatively safe organic insecticides. The safest is Bacillus thuringiensis kurstaki, or “Bt,” sold as Thuricide and other brands. The good news about this herbicide is that it is not harmful to people, pets or fish. It is a bacterium that infects the bagworm and causes it to starve. It must be sprayed directly on young larvae.

Another biological insecticide derived from a bacterium is Spinosad, a microbial agent that is sold in several brands including Fertilome Borer, Bagworm, Tent Caterpillar and Leaf Miner Spray. Spinosad has contact and systemic activity on target insects. It, too, has low toxicity and a good environmental profile. Be sure to always read all label directions.

Other nonorganic manufactured insecticides are labeled for bagworms and are effective in controlling young worms. However, these insecticides also kill the parasites and predators that normally keep bagworms under control.

So, while the most viable way to rid your trees of bagworms at this time of year is to pick them by hand and destroy them, consider keeping this information handy so that next year the problem can be dealt with in late spring.

Garden tips

• If your tomatoes are too tall and gangly, now is a good time to prune the top of the plants by as much as ⅓ to ½, depending on the plant. This will stimulate new limb growth and new fruit production after it cools.
• Reseeding fescue is best done from mid-September through mid-October. If you plan on reseeding, begin scouting for good seed now. Purchase a fescue blend of three or more varieties, with or without Kentucky bluegrass. Read the label on the seed bag. A good blend will have 0.01 percent or less of undesirable “other” crop seeds.
• In the fall, strawberry plants build up food reserves and form fruit buds for the next year’s crop. They should be fertilized between mid-August and mid-September with a nitrogen fertilizer, such as ammonium sulfate, at a rate of 1½ pounds per 100-foot row. Apply 1 inch of water if no rain is expected.
• You have all of September to plant cool-season vegetables like spinach, leaf lettuce, mustard and radishes, and until the middle of September to plant rutabagas, Swiss chard, garlic and turnips.
• The last nitrogen fertilizer application of the year on warm-season grasses should be applied no later than Sept. 15.