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Why are the leaves on my Japanese maple scorched?

April 14, 2020 • Leave a Comment

I have a dwarf Japanese maple that gets a lot of sun. Last summer I noticed many of the leaf edges were brown and curled. That was the first time I’ve noticed it. The maple is planted near the front of the house so I see it every time I come home. My neighbor had the same problem with his two trees as well.

Although Japanese maples (Acer palmatum) can handle full sun, they do need protection from strong afternoon sun, heat, and wind. Otherwise they respond with the leaf scorch you are observing. Since this was the first time you had seen it, review any changes to the ambient shade it might have originally received in afternoons. Consider your watering frequency. Water thoroughly but less frequently. Make sure the soil is enriched with organic compost and that it is well-drained. Clay soil retains water and drains slowly, encouraging roots to rot. Watering every day never gives the soil a chance to dry out. Provide 2 to 2-1/2 inches of mulch over the root zone to stabilize the surface moisture loss between waterings and keep the soil temperature cooler. If there is no ambient tree shade for the potent afternoon sun, be creative and mount a golf umbrella to a stake to give protection to your favorite welcome-home specimen.

Plant Focus: Pasque Flower

March 31, 2020 • 2 Comments

The spring days are growing longer, the birds are quickly emptying the feeders, and the flowers have begun to emerge. Bulbs like crocus and daffodils are in bloom, but in time, only the old, tattered foliage will remain. Some of the woodland wildflowers, like trillium and bluebells, are also in color, but they too will quickly disappear. Unlike so many early bloomers, pasque flower, will perform well in the spring and continue to be showy well into the summer.

Botanically referred to as Pulsatilla vulgaris, pasque flower sends up purple, reddish, pink or white 2-1/2 inch flowers in April and May. These flowers have 6 large petals (actually sepals) and a bright yellow center. After flowering begins, the spring leaves emerge and are equally showy. These leaves glisten with silky hairs that are exceptionally ornamental.

The performance has just begun, for when the spring flowers finish blooming, the seed pods form. These beautiful, silky, puff balls last well into the summer when all of the flowers have passed. The beautiful spring blossoms and clusters of seed pods make this an outstanding perennial for the front of the border or rock garden. Pasque flower grows 10 inches tall and 10 inches wide, and in our climate, it thrives in both full or partial sun. The plant will last for several years in most gardens, but performs best in a well-drained soil. Rarely does it suffer from insect or disease problems.

Pasque flower is somewhat difficult to find, but is well worth the effort. Young plants offered at garden centers quickly mature to showy clumps of vibrant flowers and striking foliage. ‘Rubra’ is the red form and the species is the purple form (just Pulsatilla vulgaris). These varieties are the easiest to locate, but I especially like the pink form, which, unfortunately, is rarely available. However, a more common German variety called ‘Papageno’ is a wonderful mixture which contains all colors, including the elusive pink.

Take advantage of the many features of this very underused perennial. Few spring-blooming perennials rival the extended display that pasque flower can provide. A tidy habit, wonderful flowers, and beautiful foliage are just some of the traits that make pasque flower a worthwhile addition to your garden.

Pasque flower

Botanical name: Pulsatilla vulgaris
Plant type: Perennial
Plant size: 10 inches wide and tall
Flower colors: Purple (most common), red, pink, or white
Flower size: 2-1/2 inches
Bloom period: April and May
Leaf colors: Silky green
Leaf size: Up to 6 inches long
Light: Full to partial sun
Soil: Prefers well-drained soil
Uses: Front of the perennial border or in the rock garden
Remarks: Leaves appear after the flowers. Silky hairs on the leaves make them glisten. Puffy seed heads form after the flower blooms are finished and are as attractive as the flowers.

George Papadelis is the owner of Telly’s Greenhouse in Troy and Shelby Township, MI.

Read more: Growing pasque flower from seed

Using the heat index to monitor insect and plant activity in the landscape

March 31, 2020 • Leave a Comment

by Steve Turner

Heat index is an important tool in determining insect and plant activity in the landscape. This is an effective way to determine when to begin looking for signs of problems or to take preventative measures.

The whole heat index system is based upon average degree days of 50 or above (called DD50), since most insect activity is triggered by temperatures of 50 degrees. 50 is used as a base, so for each degree above 50 the temperature rises, so does the DD50. For example, a 70 degree day would have a DD50 of 20. Entomologists have charted insects according to how many DD50s it takes for them to become active and develop into different life stages (egg, nymph, larva, and adult). For instance, it takes the birch leaf miner adult an average DD50 of 180 to emerge and start laying eggs in the tissue of birch leaves, while the larva needs 262 DD50s to become active.

You are now probably wondering how you are supposed to keep track of every degree above 50, add them all up, and use this information. The good news is you don’t have to—Mother Nature does it automatically. Just look at the plants around you and they will tell you when it’s time. Just like insects, plants are triggered by temperature to start and continue development as the season progresses. We use what are called phenological indicators to put the two together and read the signs that nature gives us. A good example would be lilacs: when the lilacs are blooming, we know that the birch leaf miner will be laying its eggs, so that’s when we need to start treating our birches to get the best control.

When we have erratic weather, you might as well throw your reference books out the window if they only specify dates. The plants in your landscape, however, are never wrong. They provide many excellent phenological indicators and also some that are just approximate. Many books and magazines will publish these indicators, so keep your eyes open for them. You can also discover and use your own. If you pay close attention to 1) when a problem is first noticed, and 2) what plant in your yard is coming into bloom or going through some other change at the same time as the problem, then often you can count on the two occurring at the same time next year. Make a note of it and when you see that same plant flowering next year, you will know to also check the other plant to see if the problem is indeed reoccurring.

Here are some common indicators that can help you keep your pest problems under control:

Eastern tent caterpillars egg hatch – red maple first bloom.
Gypsy moth egg hatch – PJM rhododendron bloom.
Elm, birch and box elder leaf miner – lilac bloom.
Cooley spruce gall aphid egg hatch – viburnum lantana bloom.

Steve Turner, Certified Arborist, is from Arboricultural Services in Fenton, MI.

You might also like: When is the best time to prune trees and shrubs?

Learn more about: Using Degree Days to Time Treatments for Insect Pests

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Pasque flower