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 Green Thumb Nursery - 319-393-5946 - Cedar Rapids, Iowa
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What is Downy Mildew and the Emerald Ash Borer?

April 3, 2014

Two hot button topics that keep appearing in the gardening world are the invasion of the Emerald Ash Borer and the spread of Impatiens Downy Mildew. Though these both pose issues for the every day gardener, they should not stop you from exploring and reinventing your garden. Whether you have Ash trees that need to be replaced, or have been using impatiens to bring color to your garden for years; we are here to help you find alternatives that bring color and beauty to your landscape.

What is Impatiens Downy Mildew

Impatiens Downy Mildew PhotoDowny Mildew is a disease that affects all seed-type impatiens (Impatiens walleriana) including Double Rosebud, Fusions/Exotics, and Butterfly.   Impatiens Downy Mildew wreaked havoc with garden impatiens last season and promises to be more destructive this year and into the future.  Symptoms include curling and yellowing of the leaves and a white fluffy/ downy substance on the underside of leaves. Once infected with the fungus all leaves and flowers drop, leaving “skeletonized” stems to collapse and die.  There is no cure currently.  All infected plant remains should be disposed of in the trash (NOT composted).  The disease may be introduced into the garden by infected plants...but spreads more quickly via airborne spores and can winter in the soil for as long as 8-10 years.  IDM thrives in cool (63-73F) moist conditions.  Not all impatiens are affected by IDM though. 

Impatiens that can safely be planted because they are immune to the disease include:

  • New Guinea Impatiens: Brilliant flower colors and some varieties even have colorful foliage as well. They are also more sun tolerant and thrive in containers as well as in your flower garden..
  • Fanfare Impatiens: Vigorous and free-flowering, these plants have spreading and mounded habit that allows them to fill large garden beds, containers and hanging baskets. The plants recover quickly from water stress without losing buds or blooms so they are perfect for the gardener who travels.
  • Sunpatiens: The truly wonderful thing about Sunpatiens is that they work well in full sun or shade! They add fabulous blocks of color to any area in your landscape.  Sunpatiens are a reliable and vigorous choice to fill your garden with color.

Photo of New Guinea Impatiens

Impatiens bring beautiful color to any shade garden, but they are not the only choice.  This is your chance to break out of your normal gardening routine and try something new!   There are many bright and colorful options!   In planning your spring planting , we suggest you consider the many varieties of perennial flowers that thrive in shade gardens as well as the annual varieties like impatiens that you may be accustomed to planting.  We have a great selection of both perennials and annuals that will be available this season.

A few examples of annuals for shady sites include:

  • Impatiens Downy Mildew PhotoColeus: Foliage plants that POP!  These plants bring an amazing array of color combinations and leaf textures with scalloped, toothed, or fringed leaf edges.   Great color that stands out in low light gardens and it is soooo easy to grow!
  • Torenia: Try this enchanting little wishbone flower, also dubbed clown flower for its vividly marked flowers that are said to resemble the face of a clown.  The flower shape resembles tiny snapdragons, mouths wide open and showing off delicate throats marked with a contrasting color.  This little clown flower blooms nonstop until frost.
  • Begonias: Begonias are excellent plants for shade gardens. The huge variety of begonia foliage and flowers makes these plants interesting as well as beautiful. Whether you grow begonias in a hanging basket, under trees or in a sunless area of your yard, they will provide texture and color during most of the growing season.



What is the Emerald Ash Borer?

Impatiens Downy Mildew PhotoEmerald Ash Borer is an emerald green insect that is the size of a penny. They bore into the trunks of ash trees killing the tree within a few years.  With no natural predator to keep them in check, they have spread across the United States leaving their trail of dead ash trees.

What can we do?

Ash trees are very prevalent in the Iowa landscape.  To insure that we have trees in place when the Ash trees are lost, we should start planting now!  Use this opportunity to diversify your landscape with a variety of trees.   There are many things to consider when thinking about what tree to plant: tree shape, fall color, growth rate and soil type should all be deciding factors.   Hackberries, Oaks, Maples and Locust are trees native to our area and there are many varieties within these tree "families" that will flourish here.  These trees are easy to grow, provide great shape and fall color and do well in most soil types.  But we also love Japanese Tree Lilacs and Royal Raindrops Crabs that are very ornamental but will still provide nice shade.  Please stop in to allow us to show you our great selection of trees...and ask to see the new Emerald City Tulip Tree!

Impatiens Downy Mildew Photo

We hope to see you soon so we can show you our other new plant treasures for 2014!