Don’t miss your chance to fertilize, prune

July 10, 2013 

The middle of July brings questions on summer maintenance. This is your last chance to control the size of some fall and autumn blooming perennials by getting snippy with mums, phlox, sedum Autumn Joy and delphiniums. Continue to deadhead or remove faded flowers from annuals and perennials to encourage more summer blooms.

Lawn mowing should change a bit during the warm summer months. Even if you love a close-cropped lawn, this is the time of year to gradually allow the grass to grow taller between mowings. Just raise the mower each week until it is at the highest setting. The taller grass blades will help shade the soil and conserve moisture, plus they create shade that discourages clover and other sun-loving weeds.

Q: I am very upset. I have a new clematis vine called Nelly Moser. I was so excited to see many buds on the plant. One of the buds opened up to reveal lovely purple-striped petals on a huge flower. Then, shortly after I fertilized the plant, the buds fell off! I used a 20-20-20 plant food that I also use on my fuchsias. (My fuchsias are fine, so I know I did not mix up the plant food incorrectly.) What do you think? – P.L., Longview

A: I think your clematis just had a hissy fit because you dared to push a big meal right as she was getting ready for her grand performance. Clematis can be divas when it comes to the flower show.

They do not like being fertilized or moved or having their skinny stems knocked or damaged. Is the entire plant wilting? Clematis are also susceptible to a disease called clematis wilt that strikes suddenly. There is no cure. If your buds fell off but the vine looks otherwise OK, just water, don’t feed. I have a feeling you’ll be forgiven and old Nelly will sing “this bud’s for you” in another few weeks once she recovers from being fertilized while in bloom.

Q: I have a great new plant called Scabiosa mariposa. You told me it would attract butterflies. You were right. I love the round purple blooms. But after a few weeks, these flowers start to turn brown, though I see new buds emerging. Is it OK to cut off the brown flowers? Do I cut off the stem as well as the flower heads? Do I need to fertilize this plant? Will it come back next year? I am a beginning gardener. – R.B., Tacoma

A: Congratulations on your butterfly garden – Scabiosa, also known as pincushion flower because of the round shape of the blooms, is a nectar-rich perennial that attracts hummingbirds and butterflies. As a perennial, it will come back next year after going dormant during the winter.

The new variety you have is called mariposa because this is the Spanish word for butterfly and the flat flower heads make it easy for butterflies to sit on the blooms as they sip up nectar.

As for deadheading, yes, you should follow the stem of the faded flower all the way to the base of the plant and cut out the stem and faded bloom with one snip. This variety of Scabiosa will continue to bloom all summer, behaving like a free-flowering annual plant if you continue to remove faded flowers.

You do not need to fertilize scabiosa all summer long as you would a container garden or hanging basket of annuals. Many perennial plants will grow leggy and flop over if constantly fertilized. Use a slow-release plant food in the spring when you see signs of new growth. Another growing tip is to keep the foliage dry when you water. Scabiosa loves full sun and soil that drains quickly. Yellow leaves at the base of the plant means it might be getting too much water.

Q: I have some shrub roses that are growing out of control. Can I prune them back now? How far back can I go? Thanks. – P., email

A: There is still time to get snippy with your roses, but don’t delay because once the month of August arrives, roses do not like to be cut down to size. You can shorten any rose plant by one third of its height in July and always remove anything dead, diseased or damaged any time of the year. If you have shrub roses or landscape roses that are multi-branching such as the Flower Carpet or Drift rose, this is the time of year to prune back with confidence and remove all of the faded blooms. Give your newly pruned roses a shot of fertilizer to be rewarded with a late-summer flush of flowers and color that will continue until October.

Marianne Binetti has a degree in horticulture from Washington State University and is the author of several books. Reach her at binettigarden.com.

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