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August Garden Tips

Yes, it does get hot and humid in Pittsburgh during August, and although it may be tempting to relax in our air conditioned homes, it is important for the health of your garden to get out and tend to the more critical tasks. Don't be intimidated by the long list. Odds are that only a few will apply to you.


  • Water deeply and well, rather than shallow and often -- this is especially important for tomatoes, which get various diseases from erratic watering. Educate yourself by digging down a bit to see how deeply the water has penetrated. Also, when running the sprinkler, set out a straight sided cup so you can gauge just how much you're applying in a set time period. Remember that a light daily sprinkle will only draw the roots closer to the surface.
  • Water the garden early in the day so plants can absorb the moisture before the hot sun dries the soil. Early watering also insures that the foliage dries before night. Foliage that remains wet over night is more susceptible to fungus diseases
  • Weeds in the garden are harmful because they rob your plants of water and nutrients, harbor insects and diseases. Every weed that produces seed means more trouble next year. Control weeds before they go to seed.
  • Change the water in your bird bath regularly, and keep it filled. Stagnate water is less healthy for the birds, and may become a breeding ground for mosquito larvae.
  • Continue to watch for insect, slug and snail, or disease damage throughout the garden, and take the necessary steps to control the problem.
  • Colorful plastic golf tees can be stuck in the ground to mark the location of dormant plants such as spring bulbs or perennials.
  • Do not add weeds with mature seed heads to the compost pile. Many weed seeds can remain viable and germinate for years as the compost is used.


  • Summer blooming shrubs should be pruned for shape after they have finished flowering. Remove any dead or diseased branches.
  • To reduce the number of pests on your fruit tree for the coming year, pick up and destroy all fallen fruit.
  • Now is not the time to prune any of the spring-blooming shrubs or trees. By this time flower buds have already started to form for next spring and any pruning you do will remove these buds. It is best to hold off pruning summer-flowering shrubs like Rose of Sharon and butterfly bush until early next spring. Spent blooms may be removed.
  • Wisterias can be pruned now and will be benefited by a hard pruning instead of a lighter trimming.
  • Late August through fall is a great time to plant evergreen trees and shrubs. The new plants will have several months to grow new roots and will beautify your yard this coming winter. Evergreen trees such as pine, spruce and fir can help save energy when planted (as a wind break) on the northwest side of your home. They will also provide welcome shelter for winter birds and will be gorgeous when covered with fresh snow.
  • It is important to water evergreens every week when we fail to receive an inch or more of rain. Do this from now until the ground is frozen.
  • Few flowering shrubs bloom in late summer, but many of the new hardy Knockout shrub roses will keep right on blooming into October. Look for spaces that lack interest and plant a rose.
  • Check out your grafted plants and remove any suckers growing up from beneath the grafted area.
  • Trees and shrubs (those purchased in pots) can be planted this month. Take time to properly prepare the soil by mixing in generous quantities Black Forest Organic Tree & Shrub Soil Mix.
  • Continue to fertilize roses, but go easy... Studies have shown that keeping your roses a little "hungry" helps them over-winter better. A lean diet prevents too much lush green growth that can be damaged during the winter. Use Espoma Rose Tone. As a non organic alternative you may use Bonide Guard and Grow. This material will fertilize while it protects the plant from insects.
  • Most climbing roses are best pruned as soon as they have finished blooming.
  • Plants and shrubs that provide color in the month of August include Rose of Sharon, Hydrangeas, and Butterfly Bush and shrub Roses. Visit us to see these beautiful plants in bloom.
  • Plant ornamental grasses such as Japanese Maiden Grass, Fountain Grass, or one of our native Switch Grasses for motion and contrast.
  • Do not fertilize flowering shrubs this late in the season. It will encourage new growth, which could be damaged by cold weather.


  • Take a few minutes to pick off the old dead flowers. A little time spent on grooming the plants will make a big difference in the overall appearance of the garden. By removing the spent flowers, the plants should continue to flower longer into the season. As the season progresses, start leaving a few flowering stems to provide seeds for birds and to catch snow for a more decorative winter garden.
  • Check water needs of hanging baskets daily, and sometimes twice daily, in the summer. Wind and sun dry them much more quickly than other containers. Fertilize container gardens regularly with Garden Elements Bud & Bloom Fertilizer or the organic Neptune Fish and Seaweed.
  • Apply fertilizer once every 2 weeks on annual flowers for increased flower production and overall optimum performance. Use Bloom boosting fertilizers such as Garden Elements Bud & Bloom or Master Start 5-20-10. These fertilizers have a high content of phosphorus, as indicated by the middle fertilizer number.
  • Apply pre-emergent weed controls, such as Preen, a pre-emergence herbicide, to flowers beds if you just can't keep up with weeding any other way. Don't apply it any where you intend to plant any seeds. Pull any existing weeds prior to application.      
  •  Don't let flower heads go to seed. "Deadhead" the plants -- lip or pinch off spent flowers. This keeps the plants from exerting energy to produce seed, and enables them to produce more flowers. You can let some flower heads go to seed, if you want them to reseed and come up again next year. Be mindful of the fact that seeds from hybrid annuals do not produce offspring that are true to the original plant.
  • Think about those hard to find spring flowering bulbs you want to plant this fall. Call in your special order to Erin at 412-364-8662.


  • Spring flowering perennials can be divided and transplanted this month and next. Be sure to do this during the coolest part of the day and water the plants thoroughly after transplanting.
  • A few perennials like catmint (Nepeta) will put on a second bloom if sheared to about 6 inches. For a good reference on perennial care, refer to The Well Tended Perennial Garden by Tracy DiSabato-Aust.
  • You can cut back the bearded irises now if the yellowing foliage bothers you. You can lift and separate the rhizomes at this time if it was not done last month. When dividing irises, make a careful inspection for the iris borer and destroy any infested roots. Lift the entire clump with a spading fork and discard the oldest, bloomed out sections in the middle. Cut back the foliage of the newest rhizomes to 6", and replant them with the top of the rhizome slightly above the soil surface. The soil should be prepared with Bumper Crop organic soil amendment and Espoma Garden Tone enriched fertilizer.
  • Oriental poppies have become dormant by late July and can now be divided with excellent success. Even if the roots are divided into 2 inch pieces and planted in a good soil, most of them will develop into new plants within a short period of time.
  • Peony seed pods should be removed. It will be beneficial to mix into the soil a high-phosphorous fertilizer such as Master Nursery Master Start 5-20-10, which will help in making good strong growing eyes for next year's stems.
  • Sprinkle forget-me-not seed around the garden this month. This perennial flower makes an attractive under planting for spring bulbs such as tulips.
  • The foliage of the native bleeding heart, Dicentra spectabilis, which has died and become unsightly, should be removed.
  • Lay the finished flower stalks of Foxglove on the ground where you want new plants to grow or sprinkle the seeds from the dried pods.
  • Chrysanthemums and hardy asters need fertilizer such as Master Nursery Master Start 5-20-10 and consistent watering during August.
  • Now is a good time to look around and note any existing 'blank' spots, places in the garden that are lacking either interest or color. Come to the garden center and select some plants that will bloom in late summer and early autumn. Planting at this time will require some extra care since temperatures may be high and rainfall may be low. New plants will need regular watering so that they become well established.
  • Some plants may need to be rejuvenated in late summer. If some of your perennials have turned brown or become tattered, cut them back and then give them some water and a bit of fertilizer to encourage new growth. Many perennials respond favorably to this kind of treatment. Those plants that don't re-grow now will do so next spring.
  • Perennials can surely be planted this month. Take time to properly prepare the soil by mixing in generous quantities Bumper Crop Organic Soil Amendment that contains top soil, peat moss and composted manure. If the soil is heavy and clay like, add Espoma Gypsum to make the soil more porous.
  • You may notice a dust or talcum-like powder on your roses, phlox, or lilacs this month. That's powdery mildew. It's a fungal disease, that while unsightly, it often causes little damage to ornamentals and garden plants. Applying a fungicide now will keep the disease from spreading. Use Bonide Copper Fungicide (for copper which is a natural sulfur based fungicide). Another alternative would be to include Bonide Fung-Onil, which contains a powerful chemical fungicide, as the third element into your spray rotation. One spraying will not, however get rid of the problem, so be prepared for subsequent applications as directed by the product's label.
    If you prefer not to use chemicals, thinning the plants to improve air circulation will help, as will pulling mulch away from plant stems.
    If you have perennial grasses invading your perennial garden you know that it is almost impossible to remove. The most effective solution is Bonide Grass Beater. This herbicide will kill the grass without harming broad leaf perennials.


  • Now is the time to start your fall and winter vegetables. Plant starters or seeds of green onions, carrots, beets, lettuce, spinach, radishes, and winter cauliflower directly into the garden early this month.
  • Clean up as you harvest. Toss overgrown or rotting produce on the compost heap, and remove infected plant matter to prevent attracting diseases and pests.
  • Continue to pinch the suckers off tomatoes. Suckers are miniature stems that grow out at a 45-degree angle right at the crotch of where the leaf stem attaches to the main stalk. If not removed, suckers will grow to the size of a whole new plant, creating a tangle of stems.
  • Many herbs self-sow if the flowers are not removed. They can produce seeds that can come up as volunteers the next spring.
  • Dry herbs in a cool, airy and shady place for best results.
  • If you've been trying to grow a very large pumpkin, for an end-of-the-summer fair or Halloween, early August is the time to do some pruning and fertilizing. Start by taking off all but one or two pumpkins from the vine. Pinch the ends off the vines to encourage development of the fruit already set on the vines.
  • Late Blight is a windborne fungal disease that affects tomatoes, peppers and potatoes. Unfortunately there is no cure for it. You can however protect your plants by spraying them with a preventative fungicide on a 7 to10 day schedule. Good organic fungicides to use for late blight control are Sulfur and Copper used in rotation. For example, you would spray a copper based fungicide, then 10 days later spray with a sulfur based fungicide, then for the next application switch back to the copper. We recommend using Bonide Liquid Copper Fungicide (for copper) and Serendade which contains a unique, patented strain of Bacillus subtilis which provides over 30 different lipopeptides that work synergistically to destroy disease pathogens and provide superior antimicrobial activity. Here is a U Tube clip of the product. http://youtu.be/2AmznGfQimA Another alternative would be to include Bonide Fung-Onil, a powerful chemical fungicide, as the third element that can be added to your spray rotation.
    If you notice any symptoms of late blight on your tomatoes or potatoes, pull the plants out immediately and put them in a plastic trash bag and discard them in the trash. Do not put them in your compost pile, as compost can stay warm enough for the disease to over-winter and affect your plants again the next season.
  • Apply Espoma Tomato Tone to your tomatoes if you note a lack of vigor or the loss of a healthy green foliage color.


  • The old canes should be cut from black raspberries and June bearing red raspberries now that the fruiting season is over. Removal of the old canes of ever bearing/fall red raspberries should be delayed until after mid October.
  • Fruit trees should be on a regular spray program. Give Mark a call and discuss your situation. 412-364-8662.


  • Mow often; it is one of the best defenses against weeds. If you haven't already, set your mower high for bluegrass and other cool-season grasses -- about 3 inches, do it now. Longer grass shades the soil, retains moisture and blocks weed seed germination.
  • Contrary to popular belief, a brown lawn isn't necessarily a dead lawn. Grasses go dormant in times of drought, but will quickly return to life with the fall rains. If a lush green lawn is important to you, and you don't mind mowing, water it regularly, and deeply. If you hate mowing grass, you may choose to just let your lawn go dormant
  • August is the best time to control grubs in the lawn. We recommend St. Gabriel Organics Milky Spore for natural control.


  • Continue to watch for insect or disease damage and take the necessary steps to control the problem. Bonide Systemic Houseplant Insect Control will provide protection for 8 weeks. Organic solutions include Hot Pepper Wax. Use Bonide Infuse systemic fungicide for disease problems.
  • Warmer and drier weather creates the necessity to water and mist your house plants more often.
  • Continue to feed houseplants with a good quality indoor plant food such as Shultz All Purpose Plant Food, or Neptune Fish and Seaweed which is a natural fertilizer.
  • If needed, re-pot root bound houseplants to a larger pot. Use Gardener's Gold Soil Mix when repotting houseplants.


  • Various pest problems can occur in August. Use Diatomaceous Earth, a natural product, to control crawling insects such as cockroaches, ants, slugs, silverfish, earwigs, fleas, spiders, millipedes, centipedes, and carpet beetles. Use indoors and outdoors.
  • If you do use chemicals, read the complete label and follow the directions EXACTLY.
  • Use Bonide Kleen Up to kill weeds and grasses in brick patios and walks.
  • Bagworms can defoliate evergreen trees, and the damage can be very evident at this time of year. An example is pictured to the right. Control at this time of the year can only be obtained by picking them off and destroying them. To prevent a reoccurrence next year, treat the infected plants this month with Bonide Annual Tree & Shrub which is an systemic insecticide.
  • If your roses experience insect problems use Bonide Guard & Grow which is a combination of a systemic insecticide and fertilizer. Guard & Grow will help prevent insect infestation later in the summer, as it feeds your roses. If leaf diseases such as Black Spot or Powdery Mildew are the problem, use Bonide Rose Rx.
  • Control slugs and snails on hosta and other plants with Sluggo.
  • Arborvitae and other conifers may begin to show spider mite damage (webbing on discolored/browning foliage, a branch tapped over a piece of white paper reveals very tiny red mites scurrying about). These mites thrive in dry, dusty conditions, so spraying plants regularly with water works as a good preventative. If already facing spider mite takeover, apply Bonide Annual Tree & Shrub. Be mindful that the reaction time for soil applied products is about 2 weeks.
  • Aphids and thrips are at their peak right now. Keep a very close eye on your plants and if you start seeing distorted foliage, damaged blooms or flowers not opening, thrips might be the problem. Aphids are pretty obvious. Consider using a systemic insecticide such Bonide Guard and Grow. For a quick organic fix try Capt. Jack Dead Bug Brew.
  • It is time to control aphids, lace bugs, birch borer, fall webworm, obscure scale, oystershell scale, or euonymus scale if they exist on your plants. Bonide Annual Tree & Shrub is the solution.
  • Lacebug can be controlled on azaleas, andromeda and other plants now with Bonide Annual Tree & Shrub drench.
  • If you have a problem with either dogs or cats disturbing your garden, spread Havahart Dog & Cat Get Away granules over the problem areas.

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