Garden Checklist for
May and June 2000

By Dr. William C. Welch
Professor and Landscape Horticulturist
Texas A&M University, College Station, Texas

May

• Cut off old blossoms on spring-flowering annuals such as pansies, snapdragons, stock, and calendulas to prolong the flowering season.

• Continue to fertilize roses every four to six weeks with small amounts of a balanced fertilizer.

• Allow foliage of spring-flowering bulbs to mature and yellow before removing.

• Set out plants of portulaca and purslane in sunny areas. Root cuttings of your favorite colors by placing 3- to 4-inch stems in moist, sandy soils.

• It is not too late to sow directly into the soil seeds of sunflower, zinnia, morning glory, portulaca, marigold, cosmos, periwinkles, and gourds. Achimenes, cannas, dahlias, and other summer-flowering bulbs can also be planted in May.

• Pinch back the terminal growth on newly planted annual and perennial plants. This will result in shorter, more compact, well branched plants with more flowers.

• Time to plant caladium tubers, impatiens, coleus, begonias, and pentas in shady areas.

• Make cuttings of your favorite chrysanthemums and root them in a mixture of sand and peat moss. Cover cutting box with plastic and place in shaded area for 5 or 6 days to prevent wilting.

• Replace or replenish mulch materials in flower beds and shrub borders to conserve moisture and reduce weed growth.

• Prune climbing roses as they complete their spring bloom season. Remove dead or weak wood as needed.

June

• Take a critical look at your landscape while at the height of summer development. Make notes of how you think it can be better arranged, plants that need replacement, overgrown plants that need to be removed, and possible activity areas that can be enjoyed by family members.

• Check for insects and diseases. Destroy badly infested plants. Spider mites can be especially troublesome at this time. Select a chemical or organic control, or use insecticidal soap.

• Supplemental irrigation is essential for many ornamental plants such as coleus, caladium, geranium, dahlia, azalea, and camellia during the hot dry summer days ahead. Water lawn and garden thoroughly, but not too frequently. As a general rule, soak to a depth of 8 inches. Finish watering by early afternoon, to lessen the chance of disease.

• During the summer, soil moisture becomes extremely important and essential for good plant production. Because continual watering is oftentimes costly and time consuming, it pays to conserve the moisture around plants. This is best done by mulching. A good mulch will retain valuable moisture needed for plant growth, and improve overall gardening success. Mulches are usually applied 2 to 6 inches deep, depending on the material used. In general, the coarser the material, the deeper the mulch. For example, a 2-inch layer of cottonseed hulls will have about the same mulching effect as 6 inches of oat straw or 4 inches of coastal Bermuda hay.

• There is still time to plant some of the colorful, heat-tolerant summer annuals. Direct-seed zinnias and portulaca, and purchase plants of periwinkle, salvia, marigold, and purslane. Be sure to water transplants as needed until roots become established.

• Removing faded flowers from plants before they set seed will keep them growing and producing flowers. A light application of fertilizer every 4 to 6 weeks will also be helpful.

• House plants can be moved out of doors this month. Sink the pots in a cool, shaded garden bed to prevent them from drying out so quickly; water pots, container plants, and hanging baskets often. Monthly feedings with house plant fertilizer will encourage continued growth.

• Now is the time to plan for next spring. Consider digging and dividing any crowded spring bulbs. Once the bulbs have matured and the foliage has turned brown, it is time to spade them up and thin out the stand. Crowded bulbs produce fewer and smaller blooms. They usually need thinning every 3 to 4 years.

• June is the time to select daylily varieties as they reach their peak of bloom.

• Fertilize roses every 4 to 6 weeks. Apply a high-nitrogen fertilizer immediately after a flush of bloom.

• Continue to spray susceptible roses with a black-spot control such a Funginex every 7 to 10 days.

• Re-blooming salvias, such as Salvia greggii and S. Farinacea, should be pruned back periodically during the summer. To make the job easier, use hedging shears, and remove only the spent flowers and a few inches of stem below. Fall-blooming perennials, such as Mexican marigold mint (Tagetes lucida), chrysanthemums, physostegia, and Salvia leucantha, should be pruned in the same manner during the summer to keep them compact, reducing the need for staking. This type of pruning should be completed prior to September 1, since flower buds begin forming about that time.

This article appeared in the May-June 2000 issue of Lawn and Garden Update, edited by Dr. Douglas F. Welsh, and produced by Extension Horticulture, Texas Agricultural Extension Service, The Texas A&M University System, College Station, Texas.