Mold, Mildew, Rust, Black Spot, Anthracnose - Welcome To The Northwest

We live in a maritime climate and what makes us unique from other parts of the country is the relative amount of moisture in the air and the mostly mild temperatures.  These conditions make for a fabulous growing environment for plants but they also are ideal for many foliar diseases that can drive gardeners nuts.  Here is what we can do to help mitigate these kinds of problems. 

Plant resistant varieties.  Some plants are just more prone to disease than others and even in the same group of plants there are good players and bad ones.  Roses are a classic example.  Always look for “disease resistance” on the label and try and find varieties that are recommended for the northwest.  This goes for all plants, not just roses. 

Plant in the right place.  Sun loving plants that are growing in the shade will have a much higher occurrence of mildew than if they are in full sun.  For that matter, any time a plant is under stress it will be more prone to disease.  This includes over or under fertilizing our plants and over or under watering.  A happy plant is a healthy plant. 

Modify the environment.  Improving light penetration and air flow are two key steps to take in reducing diseases.  Thin out trees to let more light into the garden.  Don’t plant too close to other plants.  Don’t over water the garden and leave moisture on the foliage all the time.  These are all simple steps that will reduce the incidence of disease. 

Act preemptively.  This may be the most important tactic in controlling diseases in the garden.  It is far easy to prevent a disease than it is to control it after the fact.  Anyone who has grown roses knows that by the time your rose looks like someone dumped a bag of powdered sugar on it it is too late to correct the problem.  Apply controls before you see the disease (in anticipation of potential problems) and you will be miles ahead of the game.  Systemic fungicides that are absorbed into the tissues work great as a preventative while contact forms need to be applied directly to the diseased areas to work.  Some newer products contain both types for better control.  Organic gardeners have had good luck applying regular treatments of compost tea which contain millions of microorganisms that somehow help control diseases. 

Use the appropriate remedy.  There are lots of fungicides on the market both natural and synthetic.  Some are labeled for edibles and some are labeled for strictly ornamentals.  Some are labeled for just lawns.  Make sure you use the correct product.   

If you want to learn more about keeping your garden healthy and free of diseases then join us this Saturday the 22nd at 10am for a one hour discussion on how, when and with what to control all the major diseases of the northwest.  You can register by either calling the nursery at 425-334-2002 or going to the email address below.

Steve Smith is owner of Sunnyside Nursery in Marysville and can be reached at the nursery at 425-334-2002 or email at