May Gardening Tasks
Expand the categories below to learn more about what you need to do this month.
Vegetables
Keep a watchful eye out for cabbage worms, potato beetles, bean beetles, blister beetles, corn earworm, cucumber beetle, and squash vine borer in the garden. Good insecticides for the garden include carbaryl, Bt-dust (for caterpillars), spinosad, diatomaceous earth (for aphids), and pyrethrum dust.
Control weeds, too, because they compete for resources (light, water, nutrients) needed by your crops! Early discovery means early control! The best ways to control garden weeds include mulch (wheat straw, pine needles, leaves) or regular light cultivation with a hoe.
Think about using “trap crops” for control of leaffooted bugs on tomatoes. Some good trap crops include blooming sunflowers, some strains of sorghum and millet. Leaffooted bugs are more attracted to trap crops than tomatoes and may keep these pesky insects off your precious fruits.
Provide water at about 1” per week especially in dry periods. Uniform moisture prevents plant stress and encourages maximum productivity. Mulching helps encourage even moisture and discourages weeds. Preferably water via a soaker hose or drip system and if you use overhead watering, avoid wetting the leaves especially after 10 AM to minimize fungal issues.
Check your tomatoes and other susceptible crops for blossom end rot on the fruit as it begins to form. This is an indication of a calcium uptake issue. Don’t overfeed with ammoniacal N (from manures or cheap fertilizers containing ammonium sulfate or urea) or potash or magnesium. Lime to a pH of 6-6.5. Place a few tablespoons of gypsum (land plaster) in the soil beside the tomato at planting (or later) and water to help prevent this. Foliar sprays such as blossom end rot spray may also help alleviate the problem but only work marginally well. Nothing will "heal" the fruit with rot on it, so remove and discard them.
Treat fire ant nests in gardens areas with the organic called spinosad (baits and drenches).
Continue to plant herbs. Now you can focus on heat-loving herbs, including basil, oregano, and Mexican tarragon. Sage and rosemary can still be planted. Watch for downy mildew on your basil.
Some planting times for more common vegetables:
Cucumbers - Apr. 1 - May 15
Cantaloupes – March 20 – June 20
Lima beans – March 15 – June 1
Okra – April 1 – June 1
Tomatoes, Peppers – March 25 – May 1
Southern peas – April 1 – August 10
Sweet potato – April 15 - June 15
Squash, Zucchini - Apr. 1 - May 15
Try something different this summer such as New Zealand or Malabar spinach or yard-long beans.
Fruit Trees
Inspect fruit trees for fireblight. You can prune out fireblight damaged limbs, but the best defense is to plant a fireblight-resistant variety. Watch for aphids on apples, too. Do not use any insecticides on the trees until less than 10% of the blooms remain - you certainly do not want to hurt your bee pollinators. The fungicides you use will have no effect on them.
Planting early-, mid-, and late-blooming varieties of bluberries ensures several months of tasty berries.
Lawns
Spot treat for broadleaf and grassy weeds as required. Discourage insects, weeds, and disease by mowing correctly – at the right height, on a schedule, fertilizing and watering correctly and using an IPM (integrated pest management) approach for diseases and pests.
It’s time to begin watching for problems with brown patch and dollar spot in warm season grasses, especially if you had problems with one of them last year. Avoid excess nitrogen and excess watering (you only need about 1” of water per week in dry periods).
Control fire ants with approved fire ant baits and drenches. Call the Hall County Extension Service for details on lawn control of these pesky critters.
Remember - any time your warm season lawn is actively growing is a good time to aerate.
You should apply nitrogen to Bermuda and other warm season lawns this month when you see substantial greenup (50-75%). Be aware that when we have severe winters, you might experience winter kill to all or patches of especially St. Augustine, centipedegrass and possibly Bermuda. Zoysia should weather nicely but may be delayed in coming out after cold winters.
If you plan to plant a warm-season (centipede, zoysia, Bermuda, St. Augustine) lawn, the best time to plant is in the late spring and early to mid-summer. If you are planting Bermuda by seed, use the hulled seed at this time of year (you can seed with unhulled seed in the Fall – Fall warm season lawn planting is not recommended). Wait until the Fall for cool-season grasses (tall fescue or annual rye over bermuda).
There are two main types of nutsedges in our area - purple and yellow. You must identify which you have before you begin treatment. Herbicides must be applied when the nutsedge is actively growing, which means decent soil moisture and warm conditions. Understand that when you see sedges, this is usually an indicator that the soil is poorly drained or compacted there!
Flowers
Plant annual flowers for summer color. Plants that can take our summer heat include coleus, cosmos, coreopsis, tithonia, zinnia, flowering salvias, angelonia, wax begonia, verbena, New Guinea impatiens and ornamental pepper. Torenia (wishbone flower) is a good shade-loving substitute for disease-prone common impatiens. Hostas and coleus are good choices, too.
Mulch perennial and annual gardens for weed control and moisture retention. Begin pinching chrysanthemums in late May and into June for bushier plants.
Do not remove foliage from spring bulbs until it dies down naturally, as this foliage develops stronger blooms for next year.
Plant container gardens and hanging baskets using a good potting mix or potting mix and compost. Use a good balance of “thrillers, fillers and spillers” for interest.
Japanese beetles will defoliate and skeletonize plants in short order. Keep a sharp lookout for them. If you find an infestation use carbaryl. Observe all label precautions on mixing and use. Do not use dusts due to the problem with application - a spray made using the liquid form of the product will work fine.
You should be planting your Summer- and Fall-flowering bulbs in April and May, such as dahlias, gladiolus, cannas, and lilies. Be sure to plant after the soil temperature reaches 55-65 degrees F.
Planting early-, mid-, and late-blooming varieties of daylily ensures months of color from these low maintenance plants.
Trees
Prune spring flowering shrubs after bloom to shape plant and encourage flowers next year. Mulch around young trees and shrubs to conserve moisture and control weed growth. Use caution with string trimmers around trees and shrubs so as not to damage tender bark and potentially girdle woody plants.
While some yellowing of older leaves of gardenia is normal, yellowing of new growth usually indicates a micronutrient deficiency.
Bag worms can kill a tree if it is heavily infested. Inspect your trees periodically - bagworms seem to like juniper, arborvitae, and pines, but they are will attack many broadleaf shrubs and trees such as rose, sycamore, maple, elm, and black locust.. Hand-picking light infestations works well; applying a dust of the bacteria Bacillus thuringiensis (Btk) or spraying with spinosad will also take care of the problem.
Chewed or ragged leaves or stripped leaves on trees and shrubs often indicate caterpillars at work. Oak caterpillars and canker worms may appear in the Spring and completely defoliate oak trees. This will not kill the trees, but it will add some stress to them. The trees will develop more leaves. The chemical carbaryl, spinosad or Bacillus thuringiensis-kurastaki strain (Btk), will kill the worms, but treatment of a large tree is not practical nor safe and therefore is not recommended. However, if you have a small oak tree (less than 5-10 feet tall) infested with them that can be safely sprayed, an application of this insecticide will control them.
Rose leaves can become skeletonized by greenish caterpillar-like “rose slugs”. While these creatures resemble lepidopteran caterpillars (butterfly-moth caterpillars), they’re actually immature sawflies (a type of solitary wasp). They do not respond to treatments with Bt as true caterpillars would. Instead, use carbaryl or spinosad-based products for effective control.
Now is a good time to produce more woody plants by air layering, grafting, division, or cuttings.
Houseplants
Move plants outdoors for summer by gradually increasing the exposure to sunlight. If you have ferns and other plants indoors and suddenly bring them into full sun or bright light, they will experience sunburn! Most houseplants brought outdoors prefer subdued, dappled shade. Succulent plants, on the other hand, prefer strong light.
Fertilize potted plants to promote Summer development. Use a water soluble fertilizer such as 20-10-20 or 24-8-16 about twice a week foliage plants or once a month for succulents.
Physically rotate pots set on the ground to develop well-rounded plants and to keep from rooting in the soil if on the ground.
Four to six inch cuttings are a great way to start new plants, root in potting mix under low light. Repot plants into about one inch larger pots. Check and monitor for insects and diseases.
Call the Hall County Extension office at 770-535-8293 or email us at mastergardener@hallcounty.org for gardening, landscape, or lawn questions.
Miscellaneous
Harmful insects become more active as the weather warms. Watch for thrips, scale, and mites on ornamental plants. Be careful though, because not all insects are harmful. Be familiar with the good and bad insects that visit your landscape!
Manage weeds while they’re young through light cultivation, mulches or directed herbicides. Once weeds are mature, they’re often much harder to kill with herbicides.