Early September

Lawn Care

• Provide 1 inch of water per week. Adjust the amount of water based upon rainfall and temperatures.  Water more often in very hot weather and less frequently in cooler temperatures.
• Early to mid-September is one of the best times to plant grass seed.  The warm soil speeds up germination while the cooler air temperatures aid in growth and development.
• Incorporate fertilizer in the soil prior to seeding or sodding a new lawn.
• Now is a good time to correct poor quality lawns that have compacted soils and thatch problems.
• Keep mowing high.
• Fertilize to help your lawn recover from the stresses of summer.
• Fall is the best time to control perennial weeds, such as dandelion and plantain, as the chemicals are usually more effective, and the actively growing grass will quickly fill in the empty spaces.
• Complete all grub treatments by September 15^th; only treat lawns that have been diagnosed with a problem that needs control.
• Watch for leaf spot, mildew, and rust caused by cool, wet fall weather.

Plantings

• Take pictures and record successes, challenges and new ideas from your garden. This will make winter planning easier.
• Plant exciting fall blooming plants such as pansies, ornamental kale, mustard, mums, and more to extend your garden enjoyment after frost.
• Sub-Zero™ pansies bloom in fall, survive the winter, and bloom again in spring. Plant them around tulips, daffodils, and hyacinths for a colorful spring addition.
• Apply frost protection in late afternoon when the danger of frost is forecast.  Remove the protection in the morning once the temperature is warm.  Re-cover plants each night there is a danger of frost
• Move containers into the house, porch, or garage when there is a danger of frost.  Move them back outdoors during the day or when warmer weather returns.
• Move hibiscus, and other tropical plants to their indoor locations. These plants need bright light for the winter.  Place them in a south facing window or under artificial lighting for best results. Quarantine for a few weeks and monitor for insects.
• Check soil moisture before watering flower gardens.  Only water when the top few inches of soil begin to dry.  Continue to water thoroughly, but less frequently as cooler fall temperatures and rain showers will help with this job.
• Powdery mildew peaks in fall.  Make a note to replace the susceptible plants or use slightly shorter plants in front to mask the discolored foliage.
• Dig, divide, and transplant bearded iris.
• Leave Siberian iris leaves and seed pods intact for fall and winter interest.
• Divide spring and early summer flowering perennials.
• Take cuttings of browallia, coleus, fuchsia, geraniums, impatiens, wax begonias, and annual vinca you plan to overwinter indoors before frost hits.
• Move caladium, calla lilies, dahlias, and tuberous begonias indoors to be grown for the winter before the first killing frost. Care for them as you would your houseplants.
• Now is the time to dig, cure, and store tender bulbs such as tuberous begonias, caladiums, calla lilies, canna and dahlia indoors for the winter.
• When gladiolus foliage has browned, dig up corms and dry in the sun for a few days before storing in the basement.
• Thrips overwinter on the corms of gladiolus.  Discard the thrip-infested corms or treat with an insecticidal dust before storing.
• Fall clean-up improves the health and appearance of your summer blooming bulbs.  Remove and discard foliage.
• Plant autumn crocus.  These bulbs sprout leaves in the spring, the leaves fade, and pink or white leafless flowers appear in the fall.
• Move tropical vines indoors for winter as the temperatures cool, but before the first killing frost.
• Prune your tropical vines back just enough to make them manageable for their indoor home.  Isolate these plants for several weeks and monitor for insects.
• Plant sweet autumn clematis – this white flowering vine blooms in the fall and has a sweet fragrance.
• Keep adding perennials to your garden and landscape. The warm soil and cooler air temperatures are great for planting and establishing new perennials.

Roses

• Avoid late-season fertilization and pruning that stimulates growth. Limit pruning to dead, diseased, and damaged canes.
• Start acclimating miniature roses and tree roses to lower light levels if you plan on bringing them indoors for the winter.
• Continue planting balled-and-burlapped and container-grown shrubs.
• If your landscape suffered severe feeding damage from Japanese beetles, some borers, and other pests, check out soil applied insecticides; use one labeled for these pests in fall for control next season.

Fall Clean-up Begins

• Rake and destroy disease infested leaves to reduce the source of infection next season.
• Established plants benefit from supplemental watering during a dry fall.  Check the soil and water thoroughly when the top 4 to 6 inches are dry.

Trees

• Check tree trunks for gypsy moth egg masses.  The eggs are covered with a yellow hairy substance; remove and destroy any egg masses found.
• Fall applications of soil systemic insecticides can be made for spruce galls, birch leaf miners, Japanese beetles, gypsy moths, plant bugs, and several other pests.
• As the leaves fall, it is a good time to start pruning.  The bare trees make it easy to see the plant’s structure and determine which branches stay and which ones go.

Gardening

• Harvest pears when they are still light green in color.
• For indoor kitchen gardens, pot up chives and parsley.  Take cuttings of oregano, rosemary, sage, marjoram, mints, and winter savory for your indoor winter herb garden.
• Use a knife or pruning shears to harvest eggplants when the fruits are 6 to 8 inches long and glossy.
• Pick muskmelons when the fruit stem starts to separate from the fruit.  Wait for the crack to appear all around the stem for a fully ripe, great tasting melon.
• Harvest watermelons when the fruits are full sized, dull colored, and the portion touching the ground changes from white to cream.  Also, the tendrils nearest the fruit will curl and dry when the fruit is ripe.
• Continue harvesting tomatoes, peppers, and squash.
• Make one fall harvest of rhubarb before the first killing frost.  Cut the rest of the stalks back after a hard freeze.
• Continue watering the garden as needed.  Check container vegetable gardens every day and water whenever the top 2 to 3 inches of soil are dry.
• Leave ferny asparagus leaves and stems standing for the winter to help capture snow that will insulate the roots for winter.
• Prune out the stem tips on tomatoes, squash, and melons early this month to allow the plant to use its energy on ripening the existing fruits rather than producing more fruits that will not have time to mature.

Mid-September 

Lawn Care

• Provide 1 inch of water per week. Adjust the amount of water based upon rainfall and temperatures.  Water more often in very hot weather and less frequently in cooler temperatures.
• Early to mid-September is one of the best times to plant grass seed.  The warm soil speeds up germination while the cooler air temperatures aid in growth and development.
• It is still a good time to lay sod as the good growing conditions speed up the root development of newly laid sod.
• Control violets in the lawn with a broadleaf weed killer for difficult weeds; apply first in mid-September.  Repeat in late October if weeds are still present. (wait to treat creeping charlie) 

Plantings

• Transplant peonies now until after the tops are killed by frost although peonies rarely need transplanted.
• Prevent Iris borer by removing old iris leaves and debris.
• Water the garden and landscape as needed.  As the temperatures cool, you will need to water less frequently.
• Continue weeding all gardens.  Removing weeds now reduces the amount of weeds you will have to pull next year.
• Stop deadheading plants you want to develop seedpods for winter interest, such as fall-blooming rudbeckias, echinaceas (coneflowers), astilbes, and sedums.
• Cut back summer blooming perennials that have faded to improve their appearance and open up space for the fall flower display.
• Established plants benefit from supplemental watering during a dry fall.  Check the soil and water thoroughly when the top 4 to 6 inches are dry.
• Fall leaves: shred with your mower and leave on the lawn or rake, shred, and dig them into vegetable and annual flower beds. Or rake, shred with the mower and pile them in a compost pile.
• Check your trees for signs of nutrient deficiencies such as poor growth and off-color leaves; this may indicate the need to fertilize.

Gardening

• Protect tomatoes during first frosts for extended harvests.

Late September 

Lawn Care

• Provide 1 inch of water per week. Adjust the amount of water based upon rainfall and temperatures.  Water more often in very hot weather and less frequently in cooler temperatures.

Plantings

• Plant tulip bulbs outdoors in the northern part of Wisconsin (early October in the southern part of Wisconsin). Select healthy bulbs with a strong growing tip that are full-size, firm, and free from signs of insects and disease.
• It is still a good time to plant deciduous trees and shrubs right up to the first hard frosts. Water well and mulch after planting.
• Remove diseased and insect-infested plant material during fall clean-up to reduce the potential for problems next season.
• Watch for squirrels digging in the garden as they love to store their nuts in gardens where the soil is disturbed, and digging is easy.  Tolerate them or use repellants to deter them.
• Established plants benefit from supplemental watering during a dry fall.  Check the soil and water thoroughly when the top 4 to 6 inches are dry.

Gardening

• Protect tomatoes during first frosts for extended harvests.
• Cut out old fruiting canes from raspberries and remove any diseased canes.

Sources

Minnich, Jerry. The Wisconsin Garden Guide – The Complete Guide to Vegetables, Flowers, Herbs, Fruit, & Nuts, Lawn & Landscaping, Indoor Gardening. 3rd ed. Madison: Prairie Oak, 1995. Print. 

Myers, Melinda. Month by Month Gardening in Wisconsin: What to Do Each Month to Have a Beautiful Garden All Year. Franklin: Cool Springs, 2006. Print.