Plant Answers  >  Gardening Calendar: May

Gardening Calendar


Plant: Fruit set of many vegetables are sensitive to high temperatures, so plant okra, Southern peas, peanuts, sweet corn, watermelons, cucumbers, squash, cantaloupes and eggplant during the first part of May for best results. High temperatures, both day and night, interfere with pollination and fruit set in many vegetables. Snap beans tend to drop their flowers readily under these conditions. Squash has a tendency to produce a large number of male flowers (the ones without the small fruit attached to the base of the bloom) and, consequently, few fruit. Okra, Southern peas and eggplants will continue to set fruit in the summer. Caladium corms are planted now. Wait until the soil warms and night temperatures are above 60 F. Caladiums prefer a loose, well-drained soil with plenty of organic matter. They thrive in shade with dappled light, and their colors of green-white, green-pink or green-red fit into almost any landscape. For more information about caladiums and for a listing of those which endure in the landscape, see:

Plant sun-loving, heat tolerant annual flowers such as portulaca, purslane, copper plants, lantanas, and ornamental peppers. Do not transplant vinca (periwinkle) until June after the rainy season is over. Seeds that may be sown directly in the warm soil include amaranthus, celosia, morning glory, sunflowers and zinnias. Plant hibiscus, bougainvillea or mandevilla vines in containers for tropical landscape color. If deer are a problem, choose from a special list:

Prune: Prune pillar or climbing roses as soon as they have finished their major bloom to allow time for the development of new canes for next spring's blooms. Prune storm-damaged tree branches immediately after damage occurs. Vigorous vines such as wisteria or landscape shrubs such as pyracanthas and elaeagnus will need frequent pruning during the active growing season.

Fertilize: If you have not applied fertilizer to the lawn, May is a good month to fertilize lawn grasses AFTER the lawn grass has been mowed twice. Slow release fertilizers are best because they feed throughout the growing season and do not leach (wash) into the ground water. Use a fertilizer spreader to get even distribution and use settings recommended on the fertilizer bag. Yellowing leaves with darker green veins signals symptoms of iron deficiency, which is common in alkaline soils. Apply iron sulfate (Copperas) onto mulches or decomposing organic material (compost) to make a slow-release, chelated product. Soils cannot be permanently made more acidic by the addition of sulfur or even pure sulfuric acid because of the buffered (hard-to-change) nature of the calcareous soils. Fertilize container plants and hanging baskets plants on a regular basis with a water-soluble fertilizer product and be sure that a slow-release fertilizer such as Osmocote has been mixed into the potting media at the label recommended amount.

Odd Jobs: After spring bulbs have finished flowering, wait until the foliage turns brown before cutting it off. Food is being manufactured and stored for next year's blooms. Mulch plants to reduce watering requirements, suppress weed growth and minimize soil temperature changes. Peach fruit should be thinned to six to eight inches apart along the fruiting branches which generally leaves about 600 fruit per mature tree; apples and pears should be thinned to one fruit per spur or cluster.

On the Lookout: To encourage more rapid re-blooming, pinch off old flowers on bedding plants after their first flower cycle is completed. Roses may encounter insect problems. Watch for aphids on tender new growth, thrips on flowers and cucumber beetles on foliage. Beetles are especially a problem if a vegetable garden is nearby. Fear not, this is the normal season of leaf shed for photinias, gardenias, ligustrums, pittosporums and magnolias.

For questions about various garden problems, consult the massive horticulture database of questions-and-answers at:

To learn how to effectively and efficiently search for information on Aggie Horticulture - PLANTanswers, see:

May Calendar by Dr. Tom Harris

· Get the begonias and impatiens in quickly if you expect them to fare well when the heat arrives. Wait to mid-month to plant periwinkles. Do not water overhead.
· Mandevilla, bougainvillea and Chinese hibiscus are great patio plants.
· Don't plant vinca until at least June 1.
· Deadhead (pinch/cut off) spent flowers to encourage more bloom.
· Hot weather plants include firebush, lantana, poinciana, esperanza, firespike, caladium, coleus, begonia, moss rose, hibiscus, bougainvillea, purslane, cannas and blue princess verbena.
· As the weather gets warmer, regular fertilizing of your pot plants with a water soluble product will bring rich color to your environment.
· Roses should be blooming with color. Continue to fertilize them for continued blooming.
· Let your wildflowers go to seed before mowing.

Fruits and Nuts
· Peaches are ready to harvest when the base color changes from green to yellow.
· This is the month for pecan casebearer. On or about May 10, apply lorsban or Malathion to reduce casebearer damage to your pecans.
· Pick peaches, apples and plums as soon as they ripen.
· Keep suckers pruned off your fruit trees-they come from the root stock and will take over if unattended.
· Keep fruit trees well watered as long as there is fruit on the tree.

· Control army worms and web worms with Bt or Malathion. Bt must be applied when the worms are feeding.
· If you collected bluebonnet seeds, hold them in paper bags until fall.
· Firebush for full sun and firespike for full shade are two of the best hummingbird plants. Hibiscus, cigar plant, dwarf Chinese trumpet creeper and firebush on the patio will bring hummingbirds in close for observation.

Shade Trees and Shrubs
· This is NOT a good month to prune oak trees. The oak wilt fungal spores and sap beetle carriers are active. If you must prune, be sure to paint with a latex-based paint immediately after cutting.
· If you have red-tipped photinias and the leaves are getting black spots with the whole plant turning yellow, bite the bullet and remove the affected plants and replace them with a holly species.
· If your red-tip photinias require constant pruning, consider replacing them with holly, nandina, xylosma, eleagnus, or pyracantha.
· Be careful with the weed-eater around young trees. One trip around the bark at the base will kill it.
· Summer weight oil does a good job of temporarily controlling scale on euonymous and other shrubs. Follow the instructions carefully.
· Leaf miners make translucent trails on the leaves of Texas red oak and other plants. They can be controlled early with Bt, but usually are not a major problem.

Turf Grass
· May is the best month for starting a new lawn. Our recommended grass varieties respond well to the warm weather and there is time for it to get established before the summer drought.
· Don't bag those lawn clippings. Let them fall to the soil to compost and return nutrients to the roots of the grass.
· May is the only month to fertilize buffalo grass.
· If you're starting a new Bermuda grass lawn, use 2-3 lbs. of seed per 1,000 sq. ft. on well-prepared soil and water twice a day. It will be up in 3-6 days and need mowing in about 3 weeks.
· Your St. Augustine grass will fill in drought-killed areas quickly if you can water regularly. Water when the grass doesn't spring back in your footprints as you walk across it.
· Place several tuna or cat food cans around the lawn and measure how long it takes the sprinklers to put 1 inch in the cans. That's how long you set the timer on the sprinkler system. Usually, a properly maintained system will put out an inch in 5-6 minutes. Running your system for this period of time is all that is necessary to maintain a nice, green lawn. Train your lawn to be drought resistant by only watering when the grass needs it and then water deeply. The equivalent of 1 inch of rain per week is all that is necessary to keep St. Augustine grass healthy.

· Tomatoes are ready to pick when they change from green to green-white color. For maximum production, pick them at this stage and let them ripen on the kitchen counter. If you leave tomatoes on the vine until they ripen, the vines will stop producing thinking they have "done their thing" for the year.
· Keep the tomatoes well watered and mulched to avoid blossom- end rot. Avoid watering the leaves.
· Side dress vegetables with 1 cup slow release lawn fertilizer per 20 feet of row every 6 weeks.
· Harvest, harvest, harvest. If you don't, production will slow or stop.


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