Hydrangeas

Hydrangea selections:
Top Row (l-r): Hydrangea aspera 'Macrophylla', H. macrophylla 'Blaumeise', H. serrata 'Kiyosume'. Middle Row (l-r): H. macrophylla 'Mariesii Variegata', H. macrophylla 'Glowing Embers', H. quercifolia 'Little Honey'. Bottom Row (l-r): H. arborescens 'Annabelle', H. macrophylla 'Enziandon', H. paniculata 'Tardiva'.

In the Pacific Northwest, few shrubs can surpass hydrangeas for variety and summer color in the garden. Whether you're a budding gardener or an ardent collector, you can never seem to have enough of these beauties in your garden. Hydrangea flowers range in form from subtle, understated lacecaps to the largest mopheads so cherished in floral arrangements. Other varieties may climb or offer variegated or golden foliage as well. This truly amazing group of plants is only beginning to be appreciated and fully utilized in our gardens as new species and varieties are made available to the gardening public.

These plants love our maritime climate with relatively mild winters and cool summers. Our generous annual rainfall is most advantageous too although care must be taken to be sure that they are watered deeply during the summer.

It is generally best to plant hydrangeas in areas that do not receive afternoon sun, with the exception of H. paniculata cultivars. Hydrangeas prefer moist,well-drained soils that have been amended with plenty of organic matter and they benefit from regular watering during the summer months. Other than an occasional slug or two feeding on young leaves, all hydrangeas are generally pest-free.

Hydrangea macrophylla, H. serrata and H.quercifolia are best pruned lightly in early spring just as the buds swell on the stems. With selections of these species remove weak or spindly stems and lightly thin older stems that have started to branch (the weight of additional flowers on these branched stems will cause the plant to flop badly). As a general rule, it is helpful to try to make sure to leave at least four pairs of buds on the stems that you are keeping to ensure blooms. H. paniculata and H. arborescens bloom on the current season's growth and should be pruned back hard in February-March. H. aspera varieties should be pruned hard for their first three years at the cost of not blooming to promote a fuller, more attractive plant later. Climbers such as H. anomala petiolaris and Schizophragma hydrangeoides 'Moonlight' do not require pruning.

As a general rule, organic matter or additives like Aluminum Sulfate will make the soil more acidic (lower pH) and tend to turn most hydrangeas blue (except for white-flowering forms). Garden lime or the additive Potassium Nitrate will make soil more alkaline (raise pH) and tend to turn hydrangeas pink. Certain varieties may have a limited range of color due to breeding (ie. H. 'Glowing Embers' can be purple in acidic soil but never blue).

I hope that this clears up some of the confusion regarding these remarkable plants and that you might be inspired to try a few new varieties in your own garden. Happy gardening.

Cheers, Tim

June/July To-Do List

Rosa 'Pat Austin' - English Type (from David Austin)

Garden Tasks For June:

Check garden soil in beds for water and test sprinklers for coverage.


Finish buying summer annuals and planting summer containers this month.


Stake and train climbing plants.


Prune rhododendrons and other spring-bloomers such as lilacs before the end of the month to control size and still ensure that they bloom the following spring. Doing so later in summer or fall will not allow these plants adequate time to form flower buds for next spring.


Begin pruning broadleaf hedges (ie. laurel, privet, etc.) and continue through Sept..


Pinch tips of fuschias, asters and other late-blooming perennials for better bloom and sturdiness.

Begin staking dahlias and other flowers whose stems might be in danger of breaking under their own weight.




Garden Tasks For July:


Shop for summer 'fillers' where you have gaps in the garden.


Finish feeding with synthetic fertilizers (ie. Miracle-Gro, etc.) except for annuals.


Lift and divide iris rhizomes.


Prune back late-spring/early-summer bloomers like wisteria and philadelphus.

Continue pruning broadleaf hedges.

Coleus: The Queen of Foliage Plants

Coleus varieties:
Top row (l-r): 'Saturn', 'Lord Voldemort', 'Pistachio Nightmare', Middle row(l-r): 'Religious Radish', 'Sedona', 'Beckwith Gem', Bottom row: (unknown yellow variety), 'Alabama Sunset' and 'Fishnet Stockings.'


Coleus (Solenostemon scutellarioides) are summer annuals here in the Pacific Northwest although they are perennial in their native range in SE Asia and when planted in the mildest regions around the globe. It is safe to plant them in the PNW near the end of May each year when evening temperatures are in the mid-40's F. They more than compensate for their late start by providing glorious foliage all summer and a wealth of possibilities for combinations when paired with other plants. They are available in a wide range of colors and make perfect accents for mixing with other annuals in bedding schemes or in container plantings.

Previously grown in generations past as a Victorian conservatory (greenhouse) plant, earlier forms have been vastly improved upon in recent years by the efforts of superior breeders. Today's varieties are generally tolerant of both full sun or shade, making them extremely versatile without much worry about their light requirements (with the exception of some of the pale yellows, ie. 'The Line' which should be kept out of afternoon sun). They are generally very easy to grow if you purchase healthy plants at your local garden center. They require good drainage and regular feeding, as per other summer annuals. It is helpful to pinch off any flowers that may form on the terminal shoots to produce a fuller, more robust plant. Most varieties will grow to between 12 and 15" tall and wide although both larger and smaller varieties are available. Try Wells Medina Nursery in the Seattle area for an outstanding selection of these beauties.

Cheers, Tim

May To-Do List

Syringa vulgaris (Common Lilac)

To Do In May:

Finish mulching garden beds and applying organic fertilizers.

Continue treating for slugs with iron phosphate products like Sluggo.

Start staking and training climbing plants like clematis to prevent flowering stems from breaking.

Stake perennials such as peonies and delphiniums to prevent breakage of stems, especially if rainy or windy.

Continue to pull weeds before they go to seed. Pull or treat dandelions in lawns.

Shop for the remainder of your summer annuals and vegetables, although it is advised that you wait (if supplies hold out) on tomatoes, basil, coleus, New Guinea impatiens, zinnias and a few others until evening temperatures are above 50 degrees F. If you purchase tender annuals, you can keep them outside during the day and bring them into the garage at night until it is safe to plant them.

Deadhead rhododendrons as soon as they finish flowering.

Be careful to water if we suddenly have nice weather. As it gets warmer, the garden can dry out very quickly, especially new transplants.

Happy gardening. Cheers, Tim

April To-Do List

Yoshino Flowering Cherries in bloom on the University of Washington campus - 4/5/09


To Do In April:

Mulch garden beds with compost or manure .

Feed plants with organic, all-purpose fertilizers. Apply alfalfa meal to heavy-bloomers such as roses and dahlias.

Treat for slugs with iron phosphate products such as Sluggo.

Pull or treat weeds before they flower and go to seed. This will save you hours of work in the weeks and months ahead if you do a thorough job now.

Make sure that hoses, sprinklers, etc. are in good working order in case of an early dry spell in our weather.

Pay special attention to water containers and new plantings in the event of an early dry spell.

Begin to prune boxwood and other broadleaf evergreen hedging plants as needed. For spring bloomers such as Choisya ternata or Viburnum tinus, prune immediately after flowering.

Prune roses if you haven't done so already. New buds and shoots will be reddish in color.

Inspect perennials and roses for aphids and treat as necessary with insecticidal soap (not detergent soap) or other nontoxic solution. Be advised that pyrethrin-based insecticides are known to burn new growth on some plants and many stronger insecticides can kill off the aphids' natural predators (ie. ladybugs).

Shop at local nurseries for peak selection of trees and shrubs, especially hard-to-find items.

Only plant the hardiest of spring annuals and vegetebles until mid-May when evening temperatures are consistently above 45 degrees F.

Hardy spring annuals would include bacopa, lobelia, marigolds, pansies, petunias, snapdragons, dusty miller, etc.. Wait another month for zonal geraniums, coleus, impatiens, begonias, etc..

Hardy spring vegetables would include carrots, celery, lettuce, green onions, mustard greens, Swiss chard, broccoli transplants, parsley and most herbs. Wait to plant tomatoes and basil.

Tomatoes and basil should not be planted out in the garden until the evening lows are above 50 degrees F. Due to high demand you may need to buy them prematurely. If you do, you'll need to keep them outside during the day and then move them into the garage or a greenhouse at night to protect them. You may plant them when it is safe to do so in the days ahead.

Take time to get out and enjoy the beauty of spring. Take a stroll trough the Quad at the UW (see photo above), a trip to a public garden or just a walk around the neighborhood. We could all use some fresh air, Vitamin D and a few flowers to lift our spirits after all the nasty winter weather and gloomy economic news. Spring is here and summer is coming.

Cheers, Tim

Garden Peonies

Top row (l-r): 'Gay Paree', 'Festiva Maxima', 'Bowl of Beauty', Middle row (l-r): 'Red Charm', 'Comanche', 'Krinkled White', Bottom row (l-r): 'Kansas', 'Sarah Bernhardt', 'Illini Warrior'

Peonies are among the most beloved of all garden flowers available with its uses tracing back roughly two thousand years to China. Over four thousand varieties exist in cultivation today in a vast array of colors and forms. Many varieties are fragrant and virtually all possess attractive foliage that looks good all summer. They are exceptionally long-lived plants and their blooms make exceptional cut flowers.

The biggest challenge to growing peonies in the Pacific Northwest is keeping the plants free of Botrytis paeoniae, a devastating fungal disease that can occur when plants are not grow in optimal cultural conditions. This disease can be recognized as soft brown or brownish-red areas developing at the base of leaves and shoots which then wilt or collapse. Peonies require fertile, well-drained soil and would prefer four hours or more of direct afternoon sun. Aside from buying infected plants, you should be free of problems once you've made sure that you've sited your peonies properly.

When planting, it is also helpful to know that peonies resent being planted too deeply. Herbaceous peonies (those that die back completely each fall, stems and all) should be planted with their 'eyes' or growth buds right at the soil level. Tree peonies should be treated as shrubs, with the base of their stems kept at or above the soil level so that they don't develop root rot. Peonies also resent being overfertilized or disturbed after they've been planted. A little compost each spring is about all that they require.

When shopping, it is very important to avoid selecting varieties based solely on photographs from books or catalogs. This can be extremely disappointing. It is very helpful to observe varieties in bloom or to buy 'tried and true' varieties from reputable nurseries that are familiar with what grows well here in our region. It should be noted that peonies do vary in their bloom times by several weeks and many of the double-flowering varieties have a tendency to flop under all of our rain. Since many peonies require some staking, you may also wish to seek out some of the smaller dwarf and 'rock garden' types which are wonderfully maintenance-free. My final caveat is that young plants often do not bloom the first year and take about three years to become fully established. Your patience will be rewarded many times over.

Cheers, Tim

NPA 'March Mania' Plant Sale at BBG

Helleborus x hybridus - Rose Madder Strain


Important Reminder For Gardeners On A Budget:

NW Perennial Alliance's 'March Madness' Plant Sale
This Sunday March 8th at the Bellevue Botanical Garden (11 a.m. - 3 p.m.)

The NPA's annual spring sale (formerly known as the 'Hellebore Open House') has been an annual mecca for collectors of rare woodland plants and ephemerals. This year, however, they will also be selling off a massive number of plants that have been removed from the Bellevue Botanical Garden's NPA border during its current renovation for once-in-a-lifetime prices. Good garden plants, hellebores in particular, may not be available at these prices again anytime soon. Don't miss out on these good deals. Happy hunting. Cheers, Tim