What’s that white stuff on my plants?

Powdery mildew is a common plant disease. It appears as splotches of white or gray on leaves and stems, as if the plant was dusted with talcum powder.  It comes as a surprise to some that powdery mildew can happen in the dry Colorado climate, but powdery mildews can be severe in warm, arid climates.  How bad powdery mildew becomes depends on several things, including the type, age and condition of the plant and the weather conditions. Powdery mildews are host plant specific, so cucumber and lilac side by side will be infected by different strains of powdery mildew. They won’t “give” each other the disease. That said, there are you can treat both plants with the same approach.  

Avoid overhead watering and do your watering in the early morning, so the plant has a chance to dry. Improve air circulation by pruning plants that are over-crowded or bushy.  Keep an eye on your plants and prune out any suspicious leaves when you first see them. Use a fungicide.

Fungicides rated for powdery mildew can be used on vegetables and ornamentals. You don’t have to have a specific fungicide for each plant type. Sulfur can be applied as a dust or spray. Note that Safer® Garden Fungicide is OMRI rated. Potassium bicarbonate is a highly effective fungicide. GreenCure® is rated for organic gardening.



Finally, clean up your garden in the fall. Fungus can overwinter in the debris left in the garden, so it’s best to remove all debris and dispose of it. Don’t add to your compost pile.  

It’s Time to Divide Bearded Iris

Over time, iris become crowded and they stop blooming, so it’s important to dig and divide iris about every 3-4 years in order to reinvigorate the plant. 

Iris grow in clumps and the root of an iris is called a rhizome. It is the rhizome that we are going to lift carefully, using a garden fork. You can use a shovel, but be careful to not damage the rhizomes.

Once out of the ground, cut or break apart the rhizomes into sections,  with a healthy set of leaves and firm, tan/white roots.

Get rid of rhizomes that are soft, mushy or have holes in them. Dust the rhizomes you keep with Sulfur. 

Next, cut the leaves back to about a third of their length.

You are now ready to re-plant. Iris rhizomes grow away from the toe, in the direction of the heel, so keep this in mind as you plant. Iris need well drained soil, so take time to amend your soil with Sheep, Peat and Compost. Add some Bone Meal and place the rhizome in the hole, roots spread out and cover with soil deep enough to just cover the top of the rhizome. Water well and add more soil if necessary. Your iris will establish themselves through the fall and early winter and be ready to bloom for you next spring.

This is the time of year when you notice that your geraniums have suddenly stopped blooming. If you look closely you might discover some holes in the buds. Your plants have fallen victim to tobacco budworms.

 Shown here, tobacco budworm caterpillars chew into the flower buds, the buds fail to open and your geranium stops blooming. Budworm will also damage petunias and penstemon, causing the plant to stop blooming. You can control budworm by applying products containing Bt (Bacillus thuringiensis).

 You can control budworm by applying products containing Bt (bacillus thuringiensis). Dipel is a dust which can be applied directly to the plant. Thuricide is a concentrate, which is mixed with water and sprayed on your plants. Dipel and Thuricide are biological controls that get rid of budworm.

 

Allowing spent flowers to remain on the plant can also slow down bloom production. You want to remove flowers as soon as they begin to fade, to encourage new flower buds. This is known as deadheading. Deadheading is the process of removing the flowers as they begin to fade. You want to remove the flower petals as well as the stem it’s connected to.

 

 

 

Follow the flower stem back to the main stem and clip it off, using a sharp pair of garden scissors. Check the plant and remove any fading flower clusters.

By keeping up on deadheading, watering regularly and fertilizing with a well-balanced fertilizer such as Fertilome 20-20-20, your geraniums will stay healthy and blooming for the rest of the season.

 

Summer Salvia Care

 

 



Salvia is a hardy, aromatic plant that attracts butterflies and bees. They tend to be heat and drought tolerant and they will perform well where other plants wouldn’t.

 

They do require some care and now is the time to give them some attention. 

 Fertilize with a balanced water-soluble fertilizer such as 20-20-20.

 

Remove spent flowers back to the nearest node, to encourage more blooming.

 

 

 

 

Around this time of the season, salvia can quickly go from magnificent upright stalks, to falling over and sprawling on the ground. Some stalks may even show browning. If this is the case, it’s time to give them a really good pruning. Trim your salvia very low now, by cutting the stalks back deeply to the ground, then fertilize with 20-20-20. The plant will reward you with renewed vigor and many more blossoms.

Pruning Roses

 

 

 Now is the time to ensure that your rose bushes continue to do well for the rest of the summer. Some maintenance on your rose will keep it healthy and blooming throughout the rest of the season. When the roses start to fade, it’s time to remove the spent blooms, before they begin to develop rose hips.  This is known as deadheading.

This is a young rose hip. Leaving it on the plant to mature and seed is generally a waste of energy that could be used to develop more leaves, a stronger root system and more abundant flowers.

 

Cut the bloom back to the first outward facing leaf. This is typically a 3-leaf or 5-leaf set. The idea is to remove the spent blossoms while leaving as much foliage in place as possible.  


 Soon after pruning, you should see a new branch emerging just above the cut you made.

 

 

 

 This is also a good time to feed your plants. Choose a well-balanced fertilizer such as Fertilome Rose Food or Mile High Rose Food. Both will supply the nutrients your roses need to stay healthy and blooming. 

 

 

Check the leaves on your rose bushes. This is the time of year when chlorosis can show up. If your rose bush leaves are pale green, yellow or yellow-white, it means they are anemic. They need iron.  Remedy the situation by applying liquid iron in the form of a spray, or granulated iron in pellet form.