June’s the time to give your plants a picnic

June 6, 2012 

Think of June as the month to fertilize. You may notice your vegetable seedlings and annual plants experiencing a growth spurt right about now. With the weather warming, your plants are developing a huge appetite. This is your reminder to fertilize annuals and vegetables now.

Roses and perennials also would benefit from a feeding this month. If you still have not fertilized the lawn, make sure you do so early in the month before the hot weather arrives.

One plant you should not feed right now is the clematis vine in bud or bloom. Clematis is the queen of all vines here in the Northwest. They thrive in our cool summer weather, but if you give clematis a big dose of plant food just as it starts to bloom, it sometimes drops the flower buds before they open in a misguided effort to grow more foliage. Instead, pamper your clematis with an organic mulch placed on top of the roots but not quite touching the thin and delicate stems of this vine.

June is also the month to add hydrangeas to your garden. These summer blooming shrubs now come in a wider range of colors, sizes and flower types. Here are the most asked hydrangea-growing questions:

Q. How do I prune my giant hydrangea? I have figured out that when I prune my Bigleaf hydrangea back to keep it from blocking the front windows, it punishes me and does not flower again for a couple of years. Right now I can tell there are flower buds at the end of some branches, but this monster is over 5 feet and again blocking the window. – R., email

A. I vote you move this hydrangea to a new spot where it can spread out its branches and grow into the full-bodied shrub it was meant to be. Replace this giant old-fashioned hydrangea with a dwarf or ever-blooming hydrangea that can be more easily kept under control. Hydrangeas are happiest when they are left to grow natural and never pruned. The new varieties such as “Endless Summer” and “Blushing Bride” are an exception as you can cut back the branches in spring or summer and still get blooms. They will flower on new growth instead of 2-year-old wood like traditional Bigleaf hydrangeas.

Q. I was given a beautiful pink hydrangea for Mother’s Day. It has unusual blooms that are more flat than the round-ball hydrangea flowers. Do you know what type of hydrangea this is, and can I plant it outside? Will it survive the winter here and bloom again next year? – anonymous

A. It sounds like you’ve received one of the new gift hydrangeas called “Strawberries and Cream,” and the good news is it will thrive in our outdoor climate for years of enjoyment. The flowers you describe are called lace cap. The center blooms do not open, which gives the illusion of a lacy frill around a center cap of buds. Enjoy the blooms indoors, but by June remove the plant from its pot and replant it where there’s protection from the hot afternoon sun.

Hydrangeas love moist soil, and newly planted hydrangeas will need extra water the first summer into the fall until they establish a strong root system. There is no need to fertilize as you want this greenhouse-grown plant to harden off or acclimate to the outdoor life. A mulch over the roots during the first winter will help it to survive and grow into a tough shrub that flowers each summer.

Q. I had a blue hydrangea, but once I moved it closer to the house it turned more purple and almost lavender. Why do hydrangeas change from blue to pink? – P.P., Enumclaw

A. They come into the world looking blue in our naturally acidic soil of Western Washington. If you add lime around the roots of your Bigleaf hydrangeas, the acidity of the soil will change the color of the flowers to pink or lavender, depending on the amount of aluminum available in the soil. I suspect the color change in your case is caused by the cement foundation of your house. Enough lime may have leached from the concrete to make the soil less acid and so the flower color changes. To feminize your blue hydrangeas, you can add lime around the base of the shrubs. Start with just one-half cup of dolomite lime per plant – too much lime will turn the soil too alkaline and cause yellow leaves. Add aluminum sulfate to the soil to make it more acidic and to keep your hydrangeas a more manly blue.

Marianne Binetti is the author of “Easy Answers for Great Gardens” and eight other gardening books. She has a degree in horticulture from Washington State University and will answer questions at her website binettigarden.com.

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