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Maine Home Garden News — July 2011


July is the month to . . .

By Liz Stanley, Extension Horticulture Program Coordinator, University of Maine Cooperative Extension, Knox, Lincoln & Waldo Counties, elizabeth.stanley@maine.edu, and Kayli Lee, Master Gardener Volunteer, Waldo & Lincoln Counties.

  • Give a pot of flowers, salad greens or vegetables to someone who doesn’t have a garden of their own.
  • If your plants have suffered during the cold, wet spring, consider replanting. The sun will shine again, so be ready to capture every ray!
  • Continue with succession planting to take full advantage of our short growing season: carrots, chard, broccoli, spinach, lettuce, bush beans, beets, etc.
  • Don’t forget to thin carrots, beets, and other root vegetables. When you thin lettuce for heading, you can replant the ones you pull up.
  • Scout your gardens for insect pests. Look around with a flashlight for nighttime marauders like cutworms and slugs.
  • Look for fertility problems in your plants. Learn what the signs are in leaves and fruit.
  • Keep your tomato plants pruned and trellised for good air circulation and water them at the base. Watch for signs of Early Blight of Tomato, Septoria Leaf Spot of Tomato, and Late Blight — Phytophthora infestans
  • Manage weeds. Keep them in check while they’re small, and don’t let them go to seed.
  • Collect organic material to keep your compost pile cooking. If the temperature starts to fall, turn the pile. Don’t add weed seeds or diseased plants.
  • When warm dry weather arrives, water newly planted trees, shrubs and flowers. It’s better to water weekly and deeply, than frequently and shallow.
  • Solarize an area with plastic while the sun is at peak strength. This will make a weed-free area for next year’s garden.
  • Visit local farms and farmers’ markets to help support Maine agriculture.  Sunday, July 24 is Open Farm Day across Maine. Click on the link for the schedule.
  • If you have excess produce, get to know a local food pantry, soup kitchen or neighbor and arrange to donate. More information can be found at the Maine Harvest for Hunger website.
  • If you’re away from home during the summer, be sure to have a neighbor harvest your garden so your plants continue to produce.
  • Keep harvesting and learn more about safely preserving what you’ve worked so hard to grow at UMaine Extension’s Food Preservation website.
  • Get a comfortable garden chair, put it in your garden, and sit in it often.

Debunking Old Gardening Myths: Caring for the Woody Plants in Your Home Landscape

By Marjorie Peronto, Extension Professor, University of Maine Cooperative Extension, Hancock County, marjorie.peronto@maine.edu

The trees and shrubs in our landscape are plants that we expect to live for many years, often to outlive us. Recent research has debunked many myths related to the proper management of these plants.

The Myth: Purchase the largest tree you can afford.

Current Thinking: In recent years, our perceived need for instantly mature-looking landscapes has resulted in a demand for planting large trees. However, research now shows that smaller trees establish their root systems more quickly after transplanting than larger trees. In one study over a ten year period, 1-inch-diameter trees, because they became established more quickly, actually outgrew trees that were 6 inches in diameter at planting time.

The Myth: When planting a tree or shrub, I should dig a deep hole and amend the soil with compost and peat moss.

Current Thinking: The hole that you dig should only be as deep as the rootball, and two to three times as wide. For most woody plants, 90 percent of their roots grow in the top 12 inches of soil, extending out laterally up to three times wider than the drip line. If a tree or shrub is planted too deeply, the roots may not be able to get the oxygen they need, and the plant will probably slowly die.

Should you amend the soil in the planting hole? Not usually. If the soil in the planting hole is amended so that it is too different from the surrounding native soil, the tree’s roots may never extend beyond the planting hole. This results in a small root system that circles in the planting hole. If you have chosen the plant best suited for your location, it should adapt well to the native soil. So, in most cases, don’t amend the backfill at all. The exception is if you are planting in soil that is either extremely gravelly or extremely heavy (perhaps construction site fill), then amend the soil up to 25 percent by volume. This improves the soil enough for roots to grow, but not so much as to prevent them from entering the native soil.

The Myth: When I plant a new tree, I need to stake it.

Current Thinking: Research has shown that trees that are not staked develop larger root systems, greater trunk diameter, and greater trunk taper than their staked counterparts. Small trees that are stable in the soil when swaying don’t need to be staked. Only stake newly planted trees in high wind areas, or when there is a limited root system as a result of digging and transplanting the tree. Even then, stake loosely, allowing the tree to sway somewhat in the wind, so it will develop normal trunk taper for resilience to future winds. In most instances, remove the stakes after one growing season.

The Myth: I should fertilize my trees and shrubs every year.

Current Thinking: As long as you are getting some slow healthy growth on your woody plants, leave them alone. Research shows that slower growing trees are typically stronger and more resilient than trees pushed into rapid growth with applied nitrogen, such as trees growing in frequently fertilized lawns. A slower growing tree or shrub that is under moderate nitrogen stress makes more efficient use of water and nutrients, has a more extensive root system, and has higher levels of stored carbohydrates and natural defense chemicals, making it more resistant to insect pests and diseases. That having been said, if your plant’s foliage shows clear signs of nutrient deficiency, then some feeding may be called for. The best approach in this case is to test your soil or have a leaf tissue analysis done, find out which nutrient is causing the deficiency problem, and fertilize accordingly.

The Myth: Watering my plants briefly every day is the best way to keep them moist.

Current Thinking: Frequent shallow watering causes your plants to develop very shallow root systems, leaving them much more vulnerable in times of drought. It is much better to give them a thorough, deep watering that saturates the root zone once a week, especially in the planting year. Consider setting up an inexpensive drip irrigation system that will deliver the water slowly over the entire root zone.

The Myth: When mulching my trees, I should pile the mulch in a mound against the trunk of the tree.

Current Thinking: Piling mulch next to the trunk keeps the trunk moist, causing the bark to rot, leaving it very susceptible to insect and disease infestation, as well as burrowing mice. Mulching is great for conserving soil moisture and keeping weed growth down, if it is done right. After planting, spread an organic mulch (shredded bark, pine needles, compost etc.) 2 to 3 inches deep over the entire planting area, starting two inches away from the trunk of the tree.

The benefits of mulch around our landscape trees and shrubs are directly related to many of the recommendations mentioned above. Over time, mulch improves soil structure in the root zone while conserving soil moisture and slowly adding nutrients to the soil as it decomposes.

The landscape management practices discussed in this article focus on recommendations designed to promote healthy trees and shrubs that are resistant to insect and disease attack and that will thrive in the sustainable landscape. Of course, selecting the plants that are best suited to your site is the single most critical factor for long term success.

For more information, see Bulletin #2366, Selecting, Planting, and Caring for Trees and Shrubs in the Maine Landscape, and our Native Trees and Shrubs for Maine Landscapes fact sheet series.


Cover Crops for Season’s End

By Caragh Fitzgerald, Extension Educator, University of Maine Cooperative Extension, Kennebec County, cfitzgerald@maine.edu

Gardeners should always be thinking about what’s coming next in the garden. At this time of year, one of the next things to consider is planting a cover crop as you finish up production from various areas of the garden.

A cover crop is something that is grown at a time when there is no edible or ornamental crop. Cover crops can provide a number of benefits: protection from soil erosion, increased soil organic matter, improved weed control, nutrient storage for the next season, and perhaps added nitrogen. “Green manure” is another name for a cover crop that is tilled into the soil.

While cover crops can be grown at any time of year, it is a good idea to have them in the ground during the fall and winter. By covering the soil, they can protect it from erosion caused by rain and melting snow. They can also take up any unused nutrients, particularly nitrogen. When the cover crop is incorporated in the spring, the nitrogen is released.

Here are four standard late summer or fall-planted cover crops to consider:

Oats: Oats are not cold tolerant; they will be killed by a Maine winter. In the spring there is no living plant material, just a mat of dead oat plants. Oats won’t provide much organic matter to the soil, but they will reduce soil erosion and store some nutrients from fall until spring. Oats are probably the easiest fall cover crop to manage, so it’s a great choice if you are new to this technique.

Seeding date: mid-August to early September (best at least 4 weeks before the first frost)

Seeding rate: 2.5 pounds/1000 square feet.

Winter rye (cereal rye): Rye germinates and grows quickly, and it can outgrow and shade many weeds. It can grow quite large and contribute a lot of organic material back to the soil. It can grow in a wide variety of soil conditions. These traits make winter rye a great cover crop, but it does require some attention in the spring. Winter rye can be hard to incorporate if it gets large and stemmy. Unless cut, these stems can wind around rototiller tines. Incorporating the rye early in the season or keeping it cut back before incorporation will minimize problems. Also, when rye decays after incorporation, it releases chemicals that inhibit seed germination (both weeds and crops). Waiting 1-2 weeks after incorporation will reduce this effect.

Seeding date: mid-August to mid September (best at least 4 weeks before the first frost)

Seeding rate: 2.0 – 3.7 pounds/1000 square feet, up to 7 pounds/1000 square feet if sown late

Annual ryegrass: Annual ryegrass is usually not winter-hardy in zones 5 and colder. However, like oats, a late summer planting can absorb excess nutrients and provide residue to protect the soil from erosion during the winter. It can be seeded in the late summer between rows of existing crops that will be harvested late in the fall. It will not compete too much with those crops, will tolerate some shade, and will provide some cover in the winter. Annual ryegrass requires earlier seeding and more fertile soils than oats.

Seeding date: July through August 15 (zone 5)

Seeding rate: 0.4 – 0.6 pounds/1000 square feet

Hairy vetch: Hairy vetch is a legume, which means that it can provide nitrogen to the crops that follow. This is a great benefit, especially for gardens that are managed organically. Remember, it’s actually a type of bacteria (Rhizobium species) that converts the nitrogen from the air into forms that plants can use.  This conversion process is called “nitrogen fixation.” Inoculating the seed or soil with the appropriate species of Rhizobia can be good insurance.

Proper soil conditions are critical for fixing nitrogen. The Rhizobia need pH of at least 5; adequate potassium, sulfur, molybdenum, zinc, and iron; and soil that is not waterlogged.  They also will not fix nitrogen if the soil already has high levels of nitrate present.  To get the most fixed nitrogen, you need to leave the vetch in the field for a while—typically until about the time it flowers in late May or early June.  You will want to mow the vetch in the spring before incorporating with a rototiller.  Otherwise, the vines will wrap around the tiller tines.  Compared to the other species listed above, hairy vetch will not germinate or grow as quickly, so it may not provide as much weed suppression or organic matter.

Seeding date: August 1 – September 10 (zone 5), July 15 – August 20 (zone 4).  (Usually best sown at least 6 weeks before the first frost)

Seeding rate: 0.9 pounds/1000 square feet broadcast

How to plant cover crops

As with vegetable seeds, good seed-to-soil contact is very important for getting good cover crop germination. Before planting, you should scratch up the soil with a rake or hand-cultivator. If the area has a lot of weeds or crop residue, you may want to incorporate it with a rototiller. You can then broadcast the seed and rake it in.  If you have access to a lawn roller, you can use it to gently pack the soil around the seed.

More resources

These four cover crops are good bets for late summer and fall planting. If you find that you have space available at other times of year, there are many other cover crops that can be useful in the garden, such as buckwheat or sorghum-sudangrass. For more information about other cover crop species or about cover crop management in general, three great resources are:

Sarrantonio, Marianne. 1994. Northeast cover crop handbook. Rodale Institute, Emmaus, PA. (Available locally from Fedco Seeds, Johnny’s Selected Seeds)

Sideman, Eric. Using green manures. MOFGA fact sheet #10. Available online at www.mofga.org (go to publications, then fact sheets).

(no author). Managing cover crops profitably, third edition. Sustainable Agriculture Network, Beltsville, MD. To order contact (301) 374-9696, sanpubs@sare.org, or order online at www.sare.org. Also available as a downloadable pdf at www.sare.org/Learning-Center/Books/Managing-Cover-Crops-Profitably-3rd-Edition.


University of Maine Cooperative Extension’s Maine Home Garden News is designed to equip home gardeners with practical, timely information.

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Maine Home Garden News was created in response to a continued increase in requests for information on gardening and includes timely and seasonal tips, as well as research-based articles on all aspects of gardening. Articles are written by UMaine Extension specialists, educators, and horticulture professionals, as well as Master Gardener Volunteers from around Maine, with Professor Richard Brzozowski serving as editor.

Information in this publication is provided purely for educational purposes. No responsibility is assumed for any problems associated with the use of products or services mentioned. No endorsement of products or companies is intended, nor is criticism of unnamed products or companies implied.

© 2011
Published and distributed in furtherance of Acts of Congress of May 8 and June 30, 1914, by the University of Maine Cooperative Extension, the Land Grant University of the state of Maine and the U.S. Department of Agriculture cooperating. Cooperative Extension and other agencies of the U.S.D.A. provide equal opportunities in programs and employment.

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Image Description: Late Blight on tomato plant

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Image Description: winter rye


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Cooperative Extension: Garden & Yard
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Phone: 207.581.3188, 800.287.0274 (in Maine) or 800.287.8957 (TDD)E-mail: extension@maine.edu
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