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Bruce Bennett

May In The Seattle Garden By Bruce Bennett

Seattle Gardening In May

This month, I have taken to sitting on the back deck with my morning coffee in-hand and enjoying the fresh emerging beauty of springtime across the landscape.  The new ruby-tinted foliage of the Andromeda/Lily-of-the-Valley Shrub ‘Variegata’ (Pieris japonica) echoes the red flowers of the ten-foot-tall Rhododendron ‘Vulcan’ and the newly opened buds of Azalea ‘Hino Crimson’. 

These plants are color counterpointed by the whites of the shrub New Zealand Pittosporum/ Kohuhu ‘Variegata’ (Pittosporum tenuifolium – pictured right), COSTCO-size pots of cascading green and white Wintercreeper ‘Emerald Gaiety’ (Euonymus fortunei) and the upright exclamation points of Sweet Iris ‘Variegata’ (Iris palida). 

Later in the season, the flowers of Crabapple ‘Golden Raindrops’ (Malus transitoria) and Mountain Laurel ‘Olympic Fire’ (Kalmia latifolia – pictured left) will repeat this red  and white color combination.  The views and scents carried on the warming air make the work of gardening worth all the effort.  The background of deep burgundy leaves from the Purple Smoke Bush ‘Purple Robe” (Cotinus coggygria), added to the blooming bulbs and emerging hostas, make all the colors in the yard POP.  All this botanical wonder tells me we are in ‘the lovely month of May.’ 

We have passed the final major hurdle of winter – the Last Frost Date.  Depending on your local micro-zone, this date is somewhat flexible.  Even my own North Seattle dates will vary from one year to the next.  These days, I’d say that April 15 – 20 is appropriate for most USDA Zone 8/9 plants.  However, do remember that frost dates are based on historical climate data and are not set in stone.  Over-all climate change will have these dates moving earlier in the year. The probability of frost occurring after the spring frost date or before the first autumn frost date is 30%, which means there’s still a chance of inflicting itself upon our yards before or after the stated dates!  Always keep an eye on your local weather forecast and plan to protect tender new plants accordingly.  Regardless of when the big box stores and garden centers begin selling herbs and vegetable starts, for me, the planting of warm weather taste-treats, such as basil, cilantro and the all-important tomatoes, does not happen until after May 1.  As many of you already know, I’m a thrifty (AKA cheap) Connecticut Yankee and don’t intend to spend the money on these cold-tender plants more than once a year!

I usually say that I have a large ornamental and perennial garden. The fact is the entire area around the house is garden, with the only lawn to be seen in my surrounding neighbors’ yards (Hmmm, we may need to take a look at the topic lawn alternatives in the future – what do you think?).  In order to stay on top of gardening tasks, my wife and I keep a loose schedule of jobs to be completed. By the end of March, the planting beds have been spring-cleaned and last year’s perennials cut back, as well as the shrubs that that flower on new wood. There is a bit of bed edging to do and fertilizers or compost to spread.  In April, we transplanted and divided everything that needed it and, of course, started to add new plants to the ever-changing landscape.  Let’s face it, gardens are never done!  They continue to be works-in-progress and teach us that Life is all about change.

Now, it’s May and I can totally enjoy the beauty of last year’s work and this spring’s recent efforts.  The biggest job on the May ‘To-Do List’ is mulching. I think there will be some two yards of medium-ground bark mulch in my near future.  Remember, that one important reason to mulch is to keep the soil cool in the summer and retain moisture. If you are looking forward to planting annuals, let the soil warm up a bit more.  If you plant your annuals too early in cold soil, they will just sit there doing nothing until a bunny (Easter or otherwise) comes along to eat the tender growth. It’s best to wait until May 15 to plant annuals in the ground. While you are waiting, though, if you haven’t already done it, plant your pots. Soil in pots gains heat much quicker than ground soil, so, plant them. I usually do mine by the end of April. Should we get a frost warning, move them into the garage overnight or stick a garden stake in the center of them and throw a tarp, sheet or piece of plastic over their heads to make a temporary cloche.

As the bulbs finish flowering here and there in the yard, they should be deadheaded.  Cut just the spent flowers or entire flower stem off, but never the leaves. Cutting the leaves off prematurely will prevent the bulb from completing its photosynthesis process which allows the plant to convert the sun’s energy to necessary nutrients. In other words, the bulb will weaken and eventually disappear if you continue to cut off its green leaves. Wait until the leaves turn brown. You can fold the leaves with a rubber band to make browning leaves less noticeable.  Planting your bulbs among later emerging perennials (I like hardy geraniums for this job) and groundcovers will also help to camouflage the withering leaves.

During April and May, you have been enjoying the blooms of all early flowering shrubs. May is the time to prune those shrubs if you want to reduce their size or otherwise change their shape. Also check for damaged, diseased or crossing branches and cut them out.  If you pay attention to your azaleas, lilacs, rhododendrons, etc., you will notice that shortly after blooming they start setting next year’s buds. If you prune these shrubs in July, which many people do, you will get few-to-no flowers next year. Prune them shortly after they finish flowering before they set those new buds.

Now back to the mulch. Choosing the type of mulch to use is also a topic for another article. However, whatever you choose, wait until the soil is warm, then add two to four inches. Spread it carefully around your emerging perennials and shrubs and newly planted annuals. The mulch will not only make your garden look finished, it will also keep the soil cool in the heat of summer, help retain water, prevent weeds and add organic material to your soil. After spreading my mulch over a planting area, I like to use a pre-emergent, such as corn gluten, to prevent/reduce weed seed from germinating without damaging other plants that are already growing.  When your neighbor’s dandelion seeds blow into your garden, the pre-emergent will stop them from developing for up to three months. Just remember not to spread it anywhere you are counting on certain flowers to self-seed.

I think of March, April, and May as the building block months for gardens. When the above-mentioned tasks are completed and the mulch is spread, I see the hard work of the new gardening season is over (and I can rest my back). The remainder of the growing year consists of, basically, general light maintenance, watering, insect/disease vigilance and the all-round sensory enjoyment of what has been created (preferably from the back deck with a cup of coffee, in-hand of course).  Happy gardening all!

Contributing columnist, Bruce Bennett, is a WSU Master Gardener, lecturer and garden designer. If you have questions concerning this article, have a gardening question to ask concerning your own landscape or want to suggest a topic for a future column, contact Bruce at

The Garden Guy Chooses New Plants for 2024

Flowers Photo

As a home gardener, one of the satisfying rituals of spring is finding new garden treasures; those plants that are making their debut in the retail marketplaces. They are generally sports or hybrids of plants that have been on the market for years, with the new ones having a different sense of style and usage to them. Or, they can be new hybrids. Whether larger or smaller in size; darker, lighter or variegated leaves or larger flowers; etc., all have the ability to add something ‘extra’ to the humble part of your landscape that cries out to be noticed. A little dramatic? Perhaps. But, you get the gist of what I’m saying. No part of a landscape needs to be boring. It is worth too much in the way of underutilized garden space, monetary value and in satisfying your aesthetic senses to be just ‘Okay.’ A new vignette may be just the thing to enliven the space and create a smile on your face on your face when gazing at the site.

This year, growers and hybridizers seem to have outdone themselves and have brought a bumper crop of hundreds of new (and, of course, improved) plants to garden center shelves and tables. Although I have not actually viewed all of the new candidates, what I have seen at the Northwest Flower & Garden Show, area plant trials and wholesale growers’ beds, have provided me with several contenders for your attention. My prime considerations for Western Washington new plants-of-note include drought and heat tolerance (after root systems are established), disease resistance, low maintenance and, of course, presence in the garden. This year, my candidates for your horticultural scrutiny include perennials, grasses, shrubs and trees (sorry folks, I don’t do annuals). Seek them out, do your own research and evaluate their worthiness for that needy spot in your own yard…….

Artemisia x ‘Silver Lining” (White Sagebrush/Wormwood)

My top perennial choice doesn’t have much in the way of flowers, but, the foliage is a solid winner. A hybrid of two North American natives (the clumping Alaskan artemisia and the Western US artemisia) uses the best of its parentage to create a spectacular, durable foliage perennial. The broadly dissected silver leaves are showy from spring to fall. The mounded, low-wide habit maintains excellent form all season and resists opening up, like ‘Silver Mound’. Use this new perennial as a filler, color transition divider or backdrop in a landscape of flashy colors and or as spiller in mixed containers. Its yellow flowers are held on tall scapes and I would cut them off. In addition to its durability and excellent summer heat and drought tolerance, this artemisia will not rambunctiously spread through the garden as does its cousin, ‘Valerie Finnis.’ ‘Silver Lining’ forms a non-stoloniferous 15″ tall x 36” wide, winter deciduous ground cover with cutleaf silver foliage. Best results will be in average to dry soils, either sandy or clay. If those resilience attributes weren’t enough, this plant is also both deer and rabbit resistant.

Perennial runners-up include Agapanthus africanus ‘Bridal Veil’ (Lily-of-the-Nile), Brunnera macrophylla ‘Frostbite’ (Siberian Bugloss), Heliopsis helianthoides ‘Bit of Honey’ (Ox-eye Sunflower), Heuchera x ‘Forever Midnight’ (Coral Bells), and Teucrium fruticans ‘Harlequin’s Silver’ (Creeping Germander).

Panicum virgatum ‘Niagara Falls’ (Switch Grass)

This native from the Great Plains is an excellent grass in just about any landscape. With its late season seedheads and arching habit, ‘Niagara Falls’ is a good replacement for Miscanthus senesis. The powder blue leaf blades arch gracefully in the landscape, creating a soft cascading look. In early autumn, seed head plumes rise above the foliage creating a cream-colored cloud that gives the area texture and interest which will last through winter. Because of its foliage interest, this four-foot-tall grass is a multi-purpose plant that can be used in borders, containers, as specimen or in mass plantings. It is versatile and great looking, just what a plant should be!

It is an easy ornamental grass to grow in full sun to part shade and it will do well in just about any soil type in our part of the State. Remember to water it and cut it back in spring before the new growth appears and you have covered all of your maintenance bases. That’s right, save yourself some work and leave the buff-colored stalks to over-winter. In early fall, the seed head plumes that rise above the foliage will create a cream-colored cloud above the plant and will provide visual interest and bird habitat that will last through the winter doldrums.

Grass runners-up in this category include Amsonia hubrichtii ‘String Theory’ (Bluestar), Pennisetum alopecuroides ‘Lemon Squeeze’ (Fountain Grass) and Schizachyrium scoparium ‘Brush Strokes’ (Little Bluestem).

Hydrangea macrophylla ‘Eclipse’ (Big Leaf Hydrangea) is a shrub that has been receiving rave reviews from garden centers this spring. Probably because the shrub retains its dark foliage, rather than fading back to green, during the summer heat. The combination of the intense dark foliage and stand-out cranberry-red and white blooms makes for an excellent color counterpoint in just about any yard and, hopefully, a great dried-flower arrangement in a vase.

‘Eclipse’ is purported to have great disease resistance and low maintenance requirements. At three to five feet tall and wide, ‘Eclipse’ is size-appropriate for just about all smaller urban gardens. For its first three to five years, this hydrangea is a prime candidate for a porch or balcony container. After that, it will need annual pruning to keep it within bounds. As with most hydrangeas, this plant does best in morning sun and some afternoon shade. However, it can thrive in more sun in Western Washington if additional moisture is provided. ‘Eclipse’ is cold hardy down to Zone 5a and can take both our summer heat and winter cold snaps. If you are purchasing only one new plant this year, definitely consider the multi-faceted ‘Eclipse’ (and let me know how it does for you).

Shrub runners-up include Abelia x grandiflora ‘Angel’s Blush’ (Glossy Abelia), Calycanthus floridus, ‘Simply Sensational’ (Eastern Sweetshrub), Hydrangea paniculata ‘Little Hottie’ (Panicle Hydrangea), Ilex x meserveae ‘Little One’ (Blue Holly), Vaccinium corymbosum ‘Midnight Cascade’ (Hanging) Blueberry and Vitex agnus-castus ‘Queen Bee’ (Chastetree).

Cercis canadensis ‘Garden Gems Amethyst’ (Redbud) is a new dwarf tree which also features dark leaves and is compact enough to grow in a pot. It’s a slow grower that can reach eight to ten feet tall and wide, which is about half the size of a standard redbud. It flowers in early spring, sparkling with pink blooms before the foliage appears. In summer, the leaves will hold their amethyst color through our heat domes.

‘Amethyst’ is one of those plants I’d call a ‘nativar’ (a cultivar of a native plant, a Redbud in this case) that is pollinator-friendly, making it increasingly popular with the bee-lovers of our area. This new hybrid attracts pollinators and creates the perfect conversation piece in a small landscape or on a condo patio in full sun to part shade. If you don’t happen to care for the look of dark foliage, a sister (cousin?) Redbud will be coming out that has leaves which emerge red and then turn green. It’s called ‘Garden Gems Emerald.’

Tree runners-up include Heptacodium miconioides ‘Temple of Bloom’ (Seven-son Flower), Hesperocyparis arizonica ‘Crystal Frost’ (Arizona Cypress) and Thuja standishii × plicata ‘Leprechaun’(Leprechaun Arborvitae).

Readers should remember that this list is totally subjective. It is based on the plants I have seen and liked for their hardiness, versatility and’ WOW’ appeal that the neighbors don’t have. Use this list to kick-off your own horticultural sleuthing of those new additions at your favorite garden center. The downside of new-plant shopping is to remember the qualities of patience and perseverance. As new introductions, these little treasures may not appear in your area for a while. Do ask the garden center staff if the plant in question can be ordered or your name added to a Waitlist. That tact has worked for me many times over. Best of luck with this annual rite of Springtime and the newfound joy in your little patch of heaven. Happy gardening all!

Contributing columnist, Bruce Bennett, is a WSU Master Gardener, lecturer and garden designer. If you have questions concerning this article, have a gardening question to ask concerning your own landscape or want to suggest a topic for a future column, contact Bruce at

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