Area soil great for rhodies but also great for moss

May 1, 2013 

Gardeners, your lawn needs your attention right now. This is the week you should get into your garden and fertilize grass with a slow release plant food.

Got moss? Buttercups? Then, add calcium in the form of Super Sweet lime. Our naturally acidic soil is great for growing rhododendrons, azaleas, blueberries and blue hydrangeas, but not so great for growing lawns. Adding calcium is an inexpensive way to raise the pH and make the soil less acidic. The lime in the calcium also helps to break up clay soils and improves drainage.

Our state flower is the rhododendron and to celebrate your civic pride, add a rhododendron to the garden this spring. We are lucky to have a world-class rhododendron collection in Federal Way as part of the Weyerhaeuser campus.

The Rhododendron Species Botanical Garden is spectacular this month and a walk through the 22-acre garden can afflict anyone with rhodie fever. Companion plants for rhododendrons also are on display, including the elusive Himalayan blue poppy in bloom right now at the garden, which is open for viewing from 10 a.m.-4 p.m. Tuesdays-Sundays. Admission is $5 for seniors and $8 for adults. For more info go to or call 253-838-4646.

So what is the species, rhododendron? This means a rhodie in its wild or natural form. Many of the rhododendrons you buy from nurseries have been bred or hybridized. In Federal Way, you can view more than 700 varieties of the species rhododendron including tropical species inside the conservatory.


Q. How big will my rhododendron grow? I prune it almost every year right after it blooms and still it keeps growing higher than my window. Help! N.P. Maple Valley

A. Check the size of the leaf on your rhododendron. The longer the leaf, the taller the plant wants to grow. Gigantic tree rhododendrons can have leaves over a foot long. Tiny rock garden rhodies have foliage the size of a mouse ear and the plants never grow more than a few inches tall. Don’t fight Mother Nature — move your ambitious rhodies to a place where they can spread out their elbows and replace them with a dwarf variety that has leaves about one inch long. A pink dwarf rhodie, in bloom now at local nurseries, is called Ginny Gee, and another compact variety with red flowers is called Scarlet Wonder. Both have neat and tidy growth habits.

Q. Can I grow happy rhododendrons without a sprinkler system? I am not much for summer watering and I think this is why I have lost rhododendrons in the past. Sign me “Guilty of plant murder.”

A. Happiness is just a bag of wood chips away. Rhododendrons can survive on rainfall alone in our climate as long as there is plenty of water-holding organic matter in the soil, such as wood chips or fine bark mulch. Be careful not to pile any mulch up around the neck of your rhododendrons. They hate wearing a turtle neck, and bark chips can repel light rainfall. Wood chips or arborist chips with a mix of foliage and wood will more easily absorb and hold moisture. The first summer in the garden, any newly planted shrub will need extra water until a root system is established. Rhododendrons also prefer shade from the hot afternoon sun.

Q. Why won’t my rhododendrons bloom? I have them planted in a shady area and they have beautiful green leaves and look healthy. They make buds that then turn into leaves. Should I use a rose and flower fertilizer? I have been using a rhododendron fertilizer but it has been three years and still no flowers! R., Olympia

A. You might have too much shade. If you have deep shade, choose rhodies with light green leaves and lighter flowers that bloom in shades of white and pale pink. One rhododendron variety that blooms early even in the shade is called Christmas Cheer and you can find this shade-lover at local nurseries. A lack of late summer water also can cause rhododendrons to form foliage over flowers. Rhododendrons are not heavy feeders so using a rose and flower food around your rhododendrons could do more harm than good.

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

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