September Gardening Tips
Misty Kuceris ©2009

General maintenance
Bugs to watch and treat for during September
Diseases
Trees and shrubs to prune in September
Plants to divide in September
How to contact Misty

September: The month when nature starts preparing for winter and it does so with a vengeance. Plants, especially trees and shrubs, put more energy into growing roots. They want to make certain they’ll survive the winter. Fall annuals bring abundant color to your garden. And spring bulbs are ready for the planting.

General maintenance

• Plant trees and shrubs to enhance your landscape.
• Plant annuals such as pansies, ornamental cabbage and kale, and chrysanthemums (mums).
• If dry conditions continue, be sure to water your gardens with a deep, soak. You can use your garden hose and place it around the plants to create a slow drip, or you can use a soaker hose. To the best of your ability, avoid using a sprinkler system to water plants, shrubs, and trees. A great tool to help you determine if plants, shrubs, and trees have received enough water is the rapitest® mini moisture tester.
• If you’ve planted any new trees or shrubs within the last two years, give them a good watering during dry spells. You can water the trees or shrubs by using a slow drip from your garden hose around the base for about 20 to 30 minutes two or three times a week. If you want a simpler approach for your trees, consider using treegator®, a slow release watering bag for trees.
• Do not water crape myrtles that are over two years old at this time as that plant is already preparing for winter dormancy and overwatering can cause less flowering next spring.
• Weeding, weeding, and more weeding. This is important not only to maintain the beauty of your garden but also decrease the potential for bugs that can injure your plants. Bugs like to eat weeds just as much as other plants.
• Make certain that you have enough mulch to retain moisture in your garden and around trees and shrubs. Just remember to keep the mulch at least 2 inches away from the trunks and stems.
• Bring your houseplants back indoors. Check them for insects and diseases and spray if necessary.
• Check your plants, shrubs, and trees for insects and diseases. See the list below for the type of bugs you might find.

• Aphids – There are over 1,300 species of aphids which affect all sorts of plants. Aphids are sap suckers. Aphid damage varies, depending on the type, but some signs are: leaf curl, black excretion called honeydew (which attracts ants), sooty mold, leaf discoloration, or gall.
• Two-Spotted spider mite – Without a microscope it’s difficult to see these tiny spiders which are not insects. They cause serious injury to plants, especially conifers such as spruces. You might see a little webbing, but if not, you’ll see the discoloration to the leaf or needle and serious dieback. The best way to determine if the problem is spider mites is to have the sample looked at under a microscope. The good news is that these spider mites start disappearing as the weather cools down.
• Spruce spider mite – Without a microscope it’s difficult to see these tiny spiders which are not insects. Among some of the trees and shrubs which are attacked by the spruce spider mite are spruce, arborvitae, juniper, hemlock, pine, Douglas fir, Fraser fir, and larch. You’ll see the damage because the needles lose their color, become yellow, and eventually brown from dieback. These mites like to suck the chlorophyll out of the foliage. Fall and spring are the worst times for these mites.
• Twig girdler and twig pruner – These are two types of insects that eat the branches of trees: one from the inside out (the twig pruner) and one from the outside in (the twig girdler). The twig girdler, a beetle, prefers trees such as dogwood, redbud. Persimmon and oak trees. Branches fall to the ground and look as if they were cut through. The twig pruner, the larva of a beetle, eats the inside of a branch until it creates a smooth cut and the branch falls off. This larva prefers oak, maple, linden, elm, quince, and flowering fruit trees.
• Treehoppers (Thornbugs) – The nymphs of the treehoppers are very active and can be found on various twigs. They are often called thornbugs because they have spines running along the back. Most feed on trees and shrubs but only cause damage when eggs are laid in the twigs.
• Cooley spruce gall adelgid – The Cooley spruce gall adelgid is covered with a white thread substance that is waxy. It attacks both spruce and Douglas fir. It develops cucumber-shaped galls on the tips of new growth on spruces. No galls occur on Douglas firs. However, it sucks sap from the needles leaving them yellow and twisted.
• Eastern spruce gall adelgid – The eastern spruce gall attacks Norway spruce and creates a gall that is shaped like a pineapple.
• Fall webworm – These larvae (caterpillars) build silky tents at the terminal of a branches and feed on leaves. With over 100 tree hosts, you can find them on birch, cottonwood, crabapple, chokeberry, elm, linden, oak, poplar, roses, sycamore, willow and various fruit and nut trees. Larvae feed together in the confines of a silk tent located at the terminal of a branch. They skeletonize (eat) the leaf in their tents and incorporate leaves and branches into these tents. The first generation occurs May through July and the second generation occurs in August and September.
• Dogwood sawfly larva – Dogwood sawfly larva is not a caterpillar although often mistaken for one. There are different physical descriptions ranging from white with a dark brown/black head to small curling worms covered in a white powder found on the underside of a dogwood leaf. The larva is host specific, skeletonizing (eating) the Cornus species of dogwoods in particular the gray dogwood (Cornus racemosa) and the osier dogwood (Cornus sericea). Damage of defoliation can occur between June and early fall. Also, if you have cedar siding on your house, check it since it could provide pupation sites.
• Zimmerman Pine Moth – This is a moth which in mid-August and September lays eggs on the bark of most pine trees that turn into caterpillars which bore into the bark and overwinter. The larvae begin to chew on the bark around mid-April. Their damage can cause dieback of branches and eventually dieback of the pine. Signs of the Zimmerman pine moth in the summer are sawdust at the base of the tree and white to yellow pitch. The times to treat for this moth are in April and September. The white pine tree seems to be the less susceptible to this insect.
• Camellia scale – This sale is found on camellias, hollies (particularly Burford holly), privet, taxus, rhododendron, hydrangea, maple and English Ivy.
• Magnolia scale – Found on Magnolias, this is one of the largest scale insects. It can cause dieback when found on the branches and produces honeydew a sticky substance which attracts wasps and ants. You’ll also see a black in the area which is sooty mold plus a white, waxy powder.
• San Jose scale – This scale feeds on the sap of trigs and small branches are found on ornamental shrubs, shade trees, and fruit trees. There are a number of hosts, particularly those of the rose (Rosaceae) family. Some hosts include: apple, roses, cotoneaster, cherry, ash, lilac, and willow. It’s considered one of the most destructive scales and is dark in color and circular.
• Tuliptree scale – This scale, which attacks yellow-poplar (tulip tree) and magnolia, leaves honeydew which can attract wasps and ants. It causes both dieback of branches as well as thinning of leaves. This is the second largest scale found. It looks like Magnolia scale without the white, waxy powder.
• Japanese wax scale – Also called the Indian wax scale, this scale can be found on holly leaves as well as blueberry, camellia, citrus, fig, jasmine, pear, persimmon, plum and quince. They are a bright, white color. When dead the scales are a gray color. Often the leaves are also covered with sooty mold.
• White peach scale – This scale attacks over 100 host plants, such as, white peach, privet, mulberry, catalpa, and chinaberry. The scale is either dull white or yellow and infects bark, fruit, and leaves of the plants.
• Banded Ash borer – Adults, clearwing moths which are about one-inch long and look like a wasp, lay their eggs in the bark of Ash trees in August and September. Signs that the adults have laid eggs are brown frass around bark cracks and bark wounds. When this is seen, it’s important to look under the loose bark to see if any larvae are tunneling in the tree or if there are any empty pupae skins.
• Locust borer – This is a larva which you can’t see because it is inside of the black locust. The black beetle lays eggs into the tree and the larva tunnels through the plant causing structural damage.
• Mottled willow borer – This borer, also named the poplar and willow borer, likes cottonwood, poplar, and aspen as its hosts. Signs to watch for are wet bark or sawdust. There may even be a varnish stain on the bark. The larva is in the tree and cannot be seen.

If you’re unsure of what bugs are affecting your plants, stop by the nursery and talk to Misty Kuceris our plant specialist. Bring a sample and she’ll suggest the right remedy.

Diseases  back to top

Fungal diseases often occur on plants when the weather is hot, especially if a lot of rain occurs.
The fungal diseases to watch for are:

• Fungal leaf spot
• Powdery mildew
• Phomopsis blight
• Anthracnose

If you’re unsure as to what fungal disease is infecting your plant, stop by the nursery and talk to Misty Kuceris our plant specialist. Bring a sample and she’ll suggest the right remedy.

Trees and shrubs to prune in September  back to top

Pruning times vary for plants. September is the right month to prune the following trees and shrubs.

• Beech,
• Crape myrtles, although pruning in the fall can decrease winter hardiness. Therefore, the best time to prune is between January and March,
• Honeylocust,
• Linden,
• Sumac. Remove old stems to the ground.

Prune other trees and shrubs only if there is damage, a structural defeat, or the limb is hazardous.

Plants to divide in September back to top

Early fall is a great time to divide some of your plants that have just grown too large, such as:

• Astilbe
• Aster
• Bearded Iris
• Blacked-eyed Susan
• Daylily
• Echinacea (cone flower)
• Foxglove
• Liriope
• Peony
• Phlox
• Sedum
• Shasta daisies