May Gardening By the Month

I say, if your knees aren’t green by the end of the day, you ought to seriously re-examine your life.” ~Bill Watterson, Calvin & Hobbes


(Salvia greggi, a favorite perennial in San Antonio gardens comes in a variety of colors ranging from the whitest of whites to the most vivid of reds and everything in between.)


Caladium Leaves1st WEEK:

Plant caladiums, coleus, begonias and firespike for color in shady locations. Check out our Shady Plant Handout for more suggestions categorized by dense shade and partial shade.

Do not let Amaryllis or Daylilies form fruits. Cut them off! Seed production takes food from future flowering.

If your lawn or plants are turning yellow, apply Fertilome micro nutrients watered into the soil. Results are slower with  “granular” soil application of iron, but also more permanent. Hi Yield Iron Plus followed by magnesium sulfate beats all. You can also use a foliar spray (for a quick response) to correct iron deficiency, which causes chlorosis (yellowing).

Fertilize your lawn with slow-release lawn fertilizer. Choose a fertilizer that is high in nitrogen and low in phosphorous and potassium. Many soil tests are showing high amounts of phosphorous and potassium. Some of the common formulas are 3-1-2, 4-1-2, and 19-5-9, with 19-5-9 being the favorite.

Fertilize established potted hibiscus and bougainvillea (every 4 to 6 wks. with granular hibiscus food and every 2 wks. with 30-10-10 Miracid on your patio.

Control ants in your compost pile by renewing the active composting. Turn the compost, wet it and add a cup of 19-5-9 fertilizer to increase the temperature of the pile.

Prune spirea, quince and Indian hawthorn shrubs after blooming is complete, if needed.

Onions are ready to be harvested when the tops fall over. Pull up and place the bulbs on the ground for a day or two to harden off and allow them to air dry for a couple of days before storing in a cool, dark, dry place with low humidity.

Harvest columbine seeds now. Place stalks in paper bag to collect seeds.

Zinnia, lantana, firebush, esperanza and VIP petunia planted in full sun will add color to your landscape. Plant caladiums, coleus, begonias and firespike in the shade.

Look for leaf spot on photinias and Indian hawthorns. Rake and remove leaves from beneath the shrubs and spray with a general fungicide. Acidifying with Hi Yield Iron Plus, then Epsom salts (magnesium sulfate), and then feeding with 19-5-9 will eradicate these problems.

Lookout for Spider mites turning needles of junipers, cypress, arborvitaes brown, generally from the insides of the plants outward, use acephate like Bonide Systemic Insecticide (Neem oil spray is also effective).

If grasshoppers are ravaging your gardens, use general-purpose insecticide, sweeping downward from top to bottom of plants. Resmethrin yard spray does very well here. Also look at using Nolo bait on large properties, using it completely by the “use by” date on the package.

Powdery mildew of crape myrtles, euonymus, zinnias, Cedar elms use general purpose fungicide such as Fertilome Systemic Fungicide or Daconil.

Watch out for nutsedge, use Image or Hi Yield Nutsedge Control which contains the active ingredient Halosulfuron-methyl.

Continue to spray pecan trees with zinc sulfate or chelated micro nutrients. Check new nutlets for PECAN NUT CASE BEARER. If treatment is necessary, use Malathion, Permethrin or liquid Sevin.

Fertilize container plants every week with liquid fertilizer. Use 1/2 rate (1 Tbsp per gallon).

Plant okra and southern peas.

Trim perennials of dead wood from last year. Prune suckers from crape myrtles.


squash2nd WEEK:

For highest quality, harvest crookneck, zucchini and other summer squash when they are immature and tender. Watch for powdery mildew which appears in wet, humid, cloudy weather.

Fertilize vegetables. Side dress tomatoes, carrots, beans, squash, okra, peppers and other vegetable with 1 cup of slow-release lawn fertilizer per 10 ft. of row.

Powdery mildew on roses and other plants is a problem. Control the disease with sulfur, Copper fungicide, Fertilome Systemic Fungicide and other labeled fungicides.

Re-apply Amaze, to keep grass burs from sprouting.

Mallow hibiscus, firebush, lantanas and other heat-loving plants have begun to grow. Give them an application of fertilizer at the rate recommended for each specific brand you are anticipating to use.

Now is a good time to seed Bermuda or buffalo grass in your full sun, prepped lawn areas.

Plant zinnias, marigolds and cockscomb (celosia) seeds.

Divide and transplant plumbago, impatiens and pentas.

Remove faded petunia flowers to prevent seed set or cut back half way to encourage a fresh crop of flowers.

Protect vegetables such as squash, eggplant, okra and tomatoes from harsh direct sunlight to keep them from burning or wilting.

Add compost around newly planted trees and shrubs. Mix in Espoma Biotone Soil Activator, or Happy Frog products with active soil microbes to give them a fantastic jump start.

Use an insecticide labeled specifically for PECAN NUT CASEBEARER to treat pecan trees against the boring insects. Spray only if you have had a problem in the past or see damage. Also, spray pecans with liquid zinc sulphate to prevent rosette.

Feed container-grown plants with an acidifying fertilizer, such as Miracid 30-10-10, or an organic fertilizer like Hasta Gro. Be sure to water before fertilizing.

Perennial selections in nurseries are excellent. Choose vigorous summer and fall blooming plants.

If you want to encourage butterflies in your garden, do not use insecticides, especially Bt products, which will kill the larvae.

Sharpen mower blades. Dull blades tear the grass, which makes plants more susceptible to disease.

Use scissors to thin out flowers you’re growing from seed. Thinning will improve the quality of the flowers and cutting scissors will not disturb roots.

New plants require frequent watering to establish their roots. Prolonged dry soil can cause permanent damage


sg110414_purple3rd WEEK:

Plant lantana (many new mounding varieties to check out), zinnias, vinca, gomphrena, salvia, moss rose, purslane, firebush and verbena for color in full sun.

Columbine seeds are mature. Plant them in containers in potting soil now and they will be ready to transplant in fall.

If you like glow-in-the-dark orange blooms during the hottest part of summer, plant Caesalpinia, or Pride of Barbados, now. It is a root-hardy shrub that will bloom the best in full sun.

Re-apply Iron Plus acidifying supplements to lawns and acid-loving shrubs and trees to avoid drought-stress chlorosis. Mulch those shrubs with pine bark mulch products.

The red powdery spots on the bottoms of snapdragon leaves are rust. It is time to relegate snaps to the compost pile.

The sucking insects are at work. Control SPIDER MITES with acephate like Bonide Systemic Insecticide. APHIDS, WHITEFLIES and LACE BUGS can also be controlled with Malathion and Bonide Systemic Insecticide. Bonide Systemic Insecticide works for all the sucking insects on non-food plants.

Control LEAF-ROLLERS and other CATERPILLARS on Cannas and other susceptible plants such as tomatoes and mountain laurels with “BT” spray or Captain Jack’s Spinosad biological sprays.

If trees are dropping leaves, it may be an adjustment to the dry weather and high temperatures. No treatment is required. Larger leafed trees tend to be more water hogs than smaller leafed trees.

Be careful with the string mower around tree trunks. Girdled trees will die. Partially girdled trees will grow slowly and be susceptible to other stresses. Raise mower blades to summer mowing height (2 1/2″-3″). Leave clippings on lawn; they nourish the grass.

Cut off all spent amaryllis and day lily blooms so that they will not form fruit.

Keep peach trees well-watered as long as there is fruit on the tree. Pick when the green background on the fruit changes to yellow.

Plant peppers, southern peas and okra.

Mulch shrubs well to help them to survive the hot, dry summer to come. Pine bark mulch rots over time and enriches soil as it goes into decomposition.


300salvia-evolution4th WEEK:

Water lawn only when blades first show signs (when your footprints do not spring up as you walk across the grass) of wilting in the morning. Add 3/4″ of water to encourage a deep root system. This usually means a 40-50 minute watering period. Avoid watering in the evenings.

Thrips are the culprits behind gnarled leaves and petals of your roses. Malathion, Sevin spray or Bonide systemic insecticide are the most effective.

Periwinkles (or Vinca) planted now will bloom through the summer in full sun. Be careful, however, to water the plants at their base or with drip irrigation. They are susceptible to a blight caused by water on their foliage or shallow infrequent watering. Heavy, deep watering will yield the best results.

Keep summer squash, peppers, tomatoes, green beans and other vegetables harvested to maximize production. To prevent BIRDS from pecking ripening tomatoes, hang a few red or orange Christmas bulbs or decorations on the plants now while the fruit is green. The birds will check out the bulbs and, not finding anything, will lose interest and pass up the real fruit when it ripens.

Plant esperanza and  mealy blue salvia varieties; both are water-wise summer bloomers.

Plant iris, spider lilies, gloriosa lilies and caladiums.

Trim fire-blight infected pear trees 18 inches below diseased limbs. Be sure to use clean equipment and disinfect often using a 90/10 mix of clorox and water between each cut.

If the weather has cooperated, we should have an abundance of ladybugs. Avoid use of pesticides and let the ladybugs do their work. Their larvae can eat as many as 400 aphids a day.

Check junipers, cedars and other evergreens for SPIDER MITES, which can cause stems to turn brown. Shake a branch over white paper and look for tiny specks, which are spider mites. Apply proper insecticide.


-Many thanks to my contributors:
PMA – Purple Martin Association, also visit their web site @ http://www.purplemartin,org
WBC – Wild Bird Center
CF – Calvin Finch, Bexar Co. extension agent for horticulture, Texas Agricultural Extension Service (courtesy S.A. Express-News)
MB – Malcom Beck, lecturer on Organic gardening and Founder of Gardenville Products
EO – Edna Ortiz, Bexar Co. extension agent for horticulture, Texas Agricultural Extension Service (courtesy S.A.Express-News)

NS – Neil Sperry, publisher of Neil Sperry’s Garden Magazine, also Garden Expert for S.A. Express-News, visit his web site @

SB – Steve Browne, meteorologist with KSAT (visit their web site @

C.S.C. – Chris S. Corby, Editor and Publisher of Texas Gardener magazine.

HW – Howard Walters, the Rambling Rosarian

HG – John Howard Garrett, aka the “Dirt Doctor”, (visit his web site @

AJW – A.J. “Pop” Warner, from his book “A Year In The Rose Garden”

TAE – Texas Agricultural Extension Service, Bexar County (courtesy S.A. Express-News)

LR – Lyn Rawe, Bexar Co. extension agent for horticulture, (visit their website @, Texas Cooperative Extension Service (courtesy S.A. Express-News)

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