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Month-by-Month Gardening Guide: May

Fruits and Nuts:

Fruit trees, specifically apples, have a natural tendency to want to produce fruit only once every two years.  This can be especially noted in the year following a heavy crop.  Thinning a fruit crop is the answer to this natural condition.  Thinning fruit is also beneficial because it helps avoid limb breakage and improves the quality (appearance, taste) of the remaining fruit. Excessive fruit can also reduce development of young trees.  The best way to thin a crop is by hand.  Clusters of fruit should be broken up and fruit should be left well spaced on the limb.  Poles can be used for removing hard to reach fruit but it is a less accurate method than hand removal.  Proper spacing of apples should be 6-7 inches apart and peach should be 6-8 inches apart.  Chemical thinners are available to aide in fruit removal, but these are most commonly used by commercial orchardist.  Manual fruit removal should be delayed after bloom for four to six weeks since a natural drop will remove some of the fruit.  Apples should be about the size of a nickel when removed.

Stone fruit trees such as peach, cherry and plum should be sprayed this month to protect against peach tree borer.   The peach tree borer is a clearwing moth larva that bores into the trunk at the soil line.  Once inside, it can girdle the trunk, cutting off nutrient and water flow and making the tree more susceptible to diseases.  A common sign of borer presence is the gummy extract that exudes near entry holes most often near wounds or galls on the trunk. One preventative control against the borer includes a trunk spray of Thiodan 50WP this month.  Sprays should be directed to the trunk and basal part of scaffold limbs for best results.  New research in Michigan has also found that using pheromone ties can be an effective control.  Adult moths find each other in the orchard by releasing pheromones; by saturating the air with female pheromones in the ties, the male becomes disoriented and the two do not mate.  Thus fertile eggs are not laid and larvae are not produced to cause damage.  Ties need to be applied at the rate of 100 per acre in the prebloom to petal fall stage of peach to be effective.

Groundcovers and Lawns:

One common question is about mushrooms in lawns.  In most cases, the mushrooms are appearing where a tree used to stand a few years before and has since been removed.  In this situation, underground roots are continuing to decay and fungi are helping the process.  As part of their life cycle they produce mushrooms.  Short of digging up the roots, little can be done to remedy this problem.   However, if mushrooms are appearing in your lawn in a circular or crescent shape, you may have a turf disease called Fairy Rings.  This disease is caused by a fungi growing in lawns with a high organic matter level.  Old stumps buried in the lawn or a high thatch layer may cause Fairy Rings.  Typically, puffball mushrooms are seen in late summer or fall but a ring of very green grass or, in some cases, dead grass may be seen year round. The soil in this crescent may become very dry and difficult to wet.  The removal of thatch and proper management practices may help keep this problem from occurring.  Proper irrigation and aerification is also helpful.  If you already have a problem with Fairy Rings, extra watering of the rings or a fungicide drench may help the turf recover.

Of all the perennial grassy weeds that invade our lawns each year one of the more difficult to control after emergence is Dallisgrass.  Dallisgrass grows in clumps and also sends out rhizomes.  It is unsightly in lawns, because it shoots up a seed head several feet tall soon after the lawn has been mowed.  Because Dallisgrass is closely related to turfgrass, it is difficult to control without damaging the lawn.  Ideally, we want to control this and other perennial grasses (crabgrass, goosegrass) with a pre-emergence herbicide.  For control of Dallisgrass in tall fescue we are limited to a spot treatment with either MSMA or Roundup.  Because tall fescue can receive injury or may be killed by these two chemicals, direct your spray at the crown of the weed instead of all the runners to lessen the amount of turf damage.  In bermudagrass, MSMA can be broadcast over the lawn.  Some discoloration may occur for a couple of weeks but bermudagrass will recover.

Perennial Flowers and Vines:

May is the month when peonies bloom, unfortunately flowering only last for about a week.  A common question about peonies is why they didn’t bloom.  Many factors can be responsible for this including insect or disease problems, inadequate sunlight, excessive nitrogen or late freezes.  More often, bloom failure is found in young, immature plants that have been planted to deep.  Peonies should be set in a well-drained soil where the red buds of the plant are just two inches below the soil.  If your plants are mature and have bloomed before but don’t this year, they may be overcrowded and it is time to divide them this fall.  Peonies can grow two to four feet in height and taller varieties may require staking.  By the way, the ants seen on peonies are neither harmful nor helpful; they are just attracted to the nectar.

Thinning dead and damaged shoots of perennials during early growth stages will encourage stronger and healthier plants.  Pinching back new growth will also help produce bushier plants and increase flower development. Deadheading spent flowers may also promote additional flowering.

Delphinium, foxglove or lilies growing in windy sites may require staking to prevent lodging (falling over).  It is best to stake smaller plants when they first send up growth to avoid breakage.  Use a stake two-thirds the height of the plants mature size and secure the shoot to the stake with twine.  When done correctly the plants grow to cover the stakes.

Pansies will be reaching the end of temperature tolerance.  When they start to show stress, it’s time to replace them with summer annuals.

Trees and Shrubs:

Dogwood is one of Tennessee’s favorite picks for a colorful, low growing backyard tree.  However, it is also susceptible to many damaging diseases.  Of these, powdery mildew is one of the more common.  This disease appears like powder on the upper leaf surface and younger leaves can be twisted, elongated or leathery because of the infection.  Fungicidal sprays of Banner or Cleary’s 3336 applied at the first sign of problem can help.  Resistant cultivars are also available if you are thinking of planting a dogwood. ‘Cherokee Brave’ and most Cornus kousa cultivars are moderately resistant to the disease.  Three new varieties include ‘Jean’s Appalachian Snow’ a white bloomer with greenish-red berries, ‘Karen’s Appalachian Blush’ a white bloomer with pink edges and vivid red fall color and ‘Kay’s Appalachian Mist’ a white bloomer with red berries.  All three are very resistant to powdery mildew. Some general guidelines to follow when planting dogwoods are to select a location in the sun.  Although dogwoods naturally grow in the shade, disease pressure can be much higher in shade conditions.  Irrigation during periods of drought is a must for newly planted trees; however avoid getting water on the leaves since this creates a favorable situation for diseases.  Using mulch around the base of the tree will help hold moisture and prevent damage from occurring to the trunk.  Although trees can be planted in the spring the absolute best time for planting dogwoods is in the fall.

Junipers, cedars, arborvitae and white pine are often victims of insects; one insect you may have noticed ‘hanging out’ on small limbs in your landscape are the bagworms.  These pests actually become moths when mature, but the most commonly seen stage are the larvae in their ‘bag’ constructed of materials from the plant on which they feed. They are a foliage feeder and heavy infestations can caused considerable defoliation.  Because bagworms spend most of their life enclosed in a protective casing, there is a very small window to gain control of these pests.  Bags remain on the tree over winter, many containing hundreds of bagworm eggs.  In late April to mid May these eggs begin to hatch and the young larvae begin feeding on the plants.  Within a few months they can construct their own bag and will no longer be susceptible to pesticides.  Therefore, timing of sprays is crucial, applying when larvae are small and before a new casing is constructed.  Recommended sprays for bagworms include Sevin, Dipel, and Orthene.  One of the best non-chemical controls is to handpick the bags off the tree.  This can be very successful if you remove all the bags, but remember that one bag can hold over 100 eggs, so don’t miss any.

Vegetables and Herbs:

May is a great month to be in the vegetable garden because you have so many more vegetable options.  Beans (Bush Snap, Pole Snap, Bush Lima) can be planted this month and you can expect your first harvest in 60 to 65 days. Pole Limas will take an additional 30 days before harvest.   Cantaloupe can be planted and will be ready for harvest in 90 days.  Expect to harvest sweet corn in 90-95 days.  Other vegetable crops for summer planting include: Cucumbers, Eggplant, Okra, Peas, Peppers, Sweet Potato, Pumpkin, Squash, Tomatoes and Watermelon.  In general, expect to harvest vegetables between 60-80 days.  Primary exceptions include Sweet Potato, Pumpkin and Winter Squash, which take over 100 days to mature.

People often have questions about growing okra and many times those questions are focused on the lack or loss of blooms.  It is important to soil test before growing this vegetable since pH often plays a factor in fruit set.  The soil should have a pH between 5.8 and 6.5. Low pH, low calcium and low phosphorous can cause an okra plant to drop blooms; soil testing helps avoid this problem.  Sometimes, however, inadequate moisture or low bee pollination can also lead to bloom drop.  To avoid this problem water in periods of drought and avoid spraying chemicals when bees are present in the garden.

Another vegetable that causes fears because of bloom drop is the cucumber.  This should not be of concern however because cucumber vines have both female and male flowers.  The first flowers to appear are male which drop from the vine and do not bear fruit. Later flowers will be a mix of male and female flowers and pollination will occur.  For higher yields from your plants, side-dress with a high nitrogen fertilizer after flowers appear and again three weeks later. Do not over fertilize since that will encourage more vines and less fruit.

Beans are also a vegetable that should not be over-fertilized since too much nitrogen leads to more plant and less fruit. Fertilizer should be added at the time of planting by working it into the soil, later a side dressing can be applied after pods begin to develop or if the foliage is turning yellow.

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