P. Allen Smith: Perennials & Pests


The heat of summer is surely upon us, isn’t it, friends?

Photography by Suzanne Selby


While we may not feel motivated to get outdoors and garden this month, it’s a good time to enjoy the fruits of our spring labor. When August rolls around, I am always thankful I’ve taken the time to plant some fabulous perennials and shrubs that turn into real showstoppers in the summer heat. Let me tell you about three of my favorites at Moss Mountain Farm.

One perennial I couldn’t be without is a hibiscus called Summerific ‘Cranberry Crush’ (photo at top). Just look at those enormous dinner plate-sized blooms! If you want to make all of your neighbors jealous and draw the hummingbirds out for a show, try this late summer beauty. It thrives in our heat, but needs a lot of water, so be certain to plant it within reach of your hose or sprinklers.

Another colossus in the garden is one my favorite hydrangeas called ‘Limelight.’ I find these panicle hydrangeas are easier to grow here and can handle more sun than the typical big-leaf types. ‘Limelight’ usually doesn’t wilt in the sun and is less fussy about soil too, but when I planted mine, I made sure to amend the soil with compost and kept it watered well that first year until it was established. I love to use its enormous white flowers in my late summer and fall bouquets.

Sometimes the finer details make a plant special, and that is certainly the case with a new miniature butterfly bush I’ve fallen in love with this year. You might think of butterfly bush as a tall shrub, but Lo & Behold ‘Lilac Chip’ grows only 2 feet tall, at most. I’ve planted it along the pathway that leads down to my rose garden and in several containers. Butterflies and hummingbirds adore its fragrant, lavender-pink flowers that keep right on coming through the fall months. It’s seedless too, so it won’t become a nuisance in the garden. What’s not to like?

Now let’s get down and dirty with a couple of questions that have come in lately about pests and diseases in the garden.

Q: Help! Japanese beetles are eating everything in my garden! How can I get rid of this nasty garden pest?  

Ah yes, the king of the beetles! They sure can play dirty in the garden. They’ll eat just about anything, but they especially love rose-family plants, which includes perennial hibiscus, also known as rose mallow. These big, nasty beetles start off as grubs in your lawn and then emerge as adult beetles over the summer months before heading back down to lay their eggs under the turf in fall.

Your best bet to eliminate Japanese beetles is to attack them while they are still grubs. Bt, or Bacillus thuringiensis, is one of the most commonly used products. It’s a naturally occurring soil bacteria that attacks the soft grubs and does them in before they have the chance to turn into adult beetles. Milky Spore (Bacillus papillae) is also commonly sold for this same purpose, though it is more of a long-term solution to the problem, since it can take a few years to build up in your soil. Consult your local extension office to learn when to best apply these products to your lawn to prevent Japanese beetles in the future.

Q: My grandmother’s roses were healthy this spring, and they started to bloom beautifully, then the leaves started to turn yellow and fall off. Some of the leaves have spots on them, and they look pretty ragged. What can we do? We don’t want to lose her precious roses!  

Unfortunately, many roses are struggling this year due to our soggy start to the season coupled with our infamous humid nights. Your roses are suffering from a common fungal disease called black spot. It can attack all kinds of roses, but some of the older varieties can be more prone to disease. Newer hybrid roses tend to have better resistance to black spot and other fungal diseases.

Trying to treat roses that are heavily infected with black spot after the symptoms appear is like trying to heal a broken arm with a Band-Aid. For now, continue to water your roses at the root — be careful not to wet the foliage — and feed them through the season. Prune off the most infected foliage, but take care not to remove more than 20 percent of the plant.

Prevention is the key here, so plan to set up a spray regimen starting early next spring as soon as the new growth sprouts. Depending on what type of fungicide you use, you’ll need to spray your roses every 1 to 3 weeks and continue spraying throughout the season. Black spot can weaken roses over time and eventually win the war, so you’ll have to decide whether those roses are important enough to you to continue treatment, or to replace them with disease resistant cultivars instead.

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