Category Archives: Shade Gardening

The Peterborough Garden Show

By Mary-Jane Pilgrim, Master Gardener

It’s coming in 25 days.  It can’t come soon enough.  In our city, “The Garden Show” is a true sign of spring.  It’s an occasion that brings together speakers, workshop leaders, vendors, horticultural society members, master gardeners, exhibitors and many others for one reason:  “For the Love of Gardening”.PGS-logo-small

This year marks the 19th fantastic show: 
April 26 – 28, 2019 (Friday 5-9pm, Saturday 10am-5pm & Sunday 10am-4pm).

And there’s great news ! The show has MOVED – to Fleming College’s brand new Trades and Technology Centre on Brealey Drive with lots of FREE parking and a $10, one-price ticket so you can enjoy the show all weekend.

The Peterborough and Area Master Gardeners will have a booth at the show, and will be happy to answer any gardening questions that you may have. Watch for our red aprons!

The theme “Coming Up Roses” is reflected in several of the amazing speakers along with educational and fun workshops and demos.

This award-winning show was honoured in 2017 with both a “Canada 150 Garden Experience”, and “Garden Event of the Year” by the Canadian Garden Council, so come and see what all the fuss is about.

You will find many of your old favourite vendors along with some new ones.

…and don’t forget the popular “Little Green Thumbs” Children’s Garden that is always teaming with liveliness and action! There are learning activities, face painting, crafts and even a take-home project. Their theme this year is “Miniature Gardens for Elves and Fairies”.

All the show profits go back into our community to fund scholarships for post-secondary students studying in horticulture-related fields,various local projects & Community Gardens.  Since 2002, the show has put over $200,000 back into our community.

Please save the date, visit and and learn why “Everything’s Coming Up Roses” in 2019.

Learn more about the incredible speakers, workshops, bus trips, places to stay and tickets here: peterboroughgardenshow.com.

 

Truth or Fiction? Are Black Walnuts Toxic in my Garden?

by Emma Murphy, Master Gardener

As a Master Gardener, one of the most common questions I get asked is about the toxicity of walnut trees (Juglans nigra).

“Well I heard that the juglone stuff in the roots kills everything and that I can’t plant anything under or anywhere near a walnut tree.”

Well yes Virginia, you can plant a garden under a walnut tree, and have it thrive. Let’s look at Exhibit 1 below – an established perennial bed under a walnut tree. It’s at our house, so I guarantee it’s real, and it’s been there since late 2007.

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Lots of lovely perennials here – hostas (Hosta spp.), daylilies (Hemerocallis), bearded iris (Iris germanica), summer phlox (Phlox paniculata), wild ginger (Asarum canadense), purple coneflower (Echinacea purpurea), ditch lilies (Hemerocallis fulva), although those last ones are doing just a little too well LOL. Don’t believe it’s a walnut tree? Here’s a photo from a bit further back on the street.

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Yes, she’s a big old lady – we think she was planted around the same time the house was built, making her about 140 years old. I think she’s getting a bit tired out – most years she doesn’t produce too many walnuts. Her slightly younger cousin is to the left of the barn in the background – LOTS of walnuts off her (and yes a garden under that one too).

So where does this fallacy come from that ‘nothing grows under a walnut’? Well certainly all parts of the walnut tree contain a chemical called juglone (heck it’s even in the Latin name!). Juglone is a chemical that affects other plants growing nearby (a phenomenon called allelopathy). Simply put, allelopathy involves “living or dead plant parts that release chemicals into the soil which have an effect on other plants—positive or negative.” For walnuts it seems like an attempt at self preservation, with juglone acting like a natural herbicide on other plants.

As Professor Linda Chalker-Scott explains in her recent (2019) peer-reviewed Washington State University Extension paper, damage to tomatoes and other crops near walnut trees in the 1920s caused people to believe that toxic chemicals were involved, and this perception persisted and became widespread despite there being no evidence (and this was before social media existed!). The US Department of Agriculture did field testing – no problems. When applied in a laboratory setting to seeds and seedlings it did cause stunting, wilting, and necrosis, but the specific way it did this was unclear. The most recent science suggests that juglone disrupts photosynthetic and respiratory pathways and interferes with water uptake in plants.

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So! It does affect plants – the laboratory says so. Well yes, and no. Field tests do not support the laboratory work, which doesn’t accurately mimic real life conditions in your average residential garden (again, for more detail read the excellent paper referenced above). Two very old University Extension papers (1973 and 1993) continue to be used to state which plants are ‘sensitive’ and which are ‘tolerant’. However these were simply observational papers—meaning that they correlate the presence of walnut trees with damage to other species but do not confirm a causative relationship. Neither should be considered good scientific evidence.

Gardening With Walnut Trees – My Story

I am sure the scientists, arboretums, farmers, and garden writers will continue to debate this topic for a while. Meanwhile, here’s our story. In 2007 I wanted a garden bed under our black walnut in my front yard. At the time I had heard the walnut horror stories, so I thought – well, how about I just don’t disturb the roots of the tree? (not a good thing to do when establishing any garden beds under a tree). I put good topsoil and compost down, making sure to minimize tearing up of the soil and roots, and planted, and watered, and waited. Things grew. Winter happened. Next spring plants came up. For the most part I just moved perennials that were already on site, although some hostas were new. Here’s the garden in 2008 in the fall.

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Fall asters (Astereae spp.), sedums (Sedum ‘Autumn Joy’ in this case), hostas (Hosta spp.), wild ginger (Asarum canadense), fall rudbeckias (Rudbeckia fulgida and triloba), purple coneflower (Echinacea purpurea), ninebark (Physocarpus opulifolius), iris (Iris spp.), astilbe (Astilbe spp.), sweet woodruff (Galium odoratum), Ozark sundrops (Oenothera macrocarpa), coral bells (Heuchera spp.), cranesbill (Geranium spp.). All doing just fine.

And 2009 below, in the spring. Irises (Iris spp.) lemon lilies (Hemerocallis lilioasphodelus), lungwort (Pulmonaria spp.), poppies (Papaver rhoeas), ditch lilies (Hemerocallis fulva), variegated solomon’s seal (Polygonatum odoratum ‘Variegatum’), bracken (Pteridium aquilinum), bleeding hearts (Dicentra spectabilis), daylilies (Hemerocallis spp.).

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Certainly, planting in general under walnuts is challenging – they cast dense shade and have extensive, water hungry root systems. Watering after establishment and for the first season is critical. We also had our walnut tree pruned professionally (it needed it) so it actually gets decent sunlight in the latter part of the afternoon. Like any fruit or nut tree they are messy, from their spring pollen to their leaves and nuts…oh those nuts.. 2017 was a crazy year – buckets of walnuts (I even had to engage my neighbours’ lovely children from across the street to help collect them) to 2018, with almost no walnuts. My trees are old too – although well pruned, their leaves drop at that first hard frost. 1

 

In Defence of Walnut Trees

Black walnuts are not all bad, and I will continue to treasure them in my yard. They are an amazing shade tree, are highly valued for their fine grained dark wood (for furniture), a great food source for wildlife and birds, and my white breasted nuthatches’ favourite spot to hide their seeds.

We have definitely had our challenges with our walnut trees, and I’ve learned a great deal over the past 20 years. But one thing I know – I can garden with them around. You can too.

Note: Black walnuts are not the only tree that produce juglone – other members of the Juglandaceae also produce it as well as hickory trees. Butternut, English walnut, bitternut hickory, pignut hickory, pecan, shagbark hickory, mockernut hickory are in the same family.

Shady Gardens

by Sharleen Pratt, Master Gardener in Training

Now that the colder weather has arrived and the days are shorter, it’s time to dream about next year and possibly plan a new garden. Do you despair at the challenges surrounding a shade garden? We can enjoy the cooling effects of the shade and experience a garden that regales all of the senses. When choosing plants, consider interesting foliage and texture rather than solely depending on flower colour.

If you are planting under mature trees, especially non-native maples you must always remember that those vigorous, feeder roots quickly out-compete new transplants for water and nutrients. Every fall add several layers of shredded leaves as well as compost for additional nutrients. Remember to water often the first year.

There are many wonderful bulbs that would give you that burst of colour in the early spring before the trees get their leaves. The sun coming through the branches in early spring is perfect for encouraging Daffodil (Narcissus hybrids), Grape Hyacinth (Muscari botryoides) and Siberian Squill (Scilla Siberica) to flower before the tree canopy is in full leaf.

Hosta (Plantain Lily) are a must have in a shade garden and provides variations in leaf size, shape and colour. This perennial has hundreds of species and thousands of cultivars and they are tough, reliable plants. Along with the Hosta, you might consider Bleeding Heart (Lamprocapnos spectabilis). Their flowers hang down like dangling hearts and are a real source of delight. The dryer soil under a canopy of trees would quicken their disappearance shortly after flowering and would work well under the emerging large leaves of the Hostas. Another old-fashioned perennial is the Heartleaf Bergenia (Bergenia cordifolia) that has large waxy, heart shaped leaves. It also has some fall interest when the leaves take on a reddish winter hue.IMG_4094

Lungwort (Pulmonaria) are also shade tolerant and their delicately patterned foliage draws the eye throughout the summer. There are several species, some of which are variegated which can add texture and colour to the shade garden. Another perennial to consider is the Brunnera ‘Jack Frost’. This plant was named as the Plant of the Year for 2012. It bears panicles of light blue flowers held above silver leaves with green veins and edges. Once established, they can be fairly drought tolerant. An overlooked plant is the Foamflower (Tiarella cordifolia). It is a native groundcover and is happy in both full to light shade. It bears tall racemes of delicate white or pale pink flowers for six weeks in early summer. They grow best in moist, humus-rich woodland soil.

To give the shady garden some texture and shape, look at some of the broadleaf evergreen shrubs. The Oregon Grape Holly (Mahonia aquifolium) prefers moist, well-drained, acid soil. It produces very fragrant yellow racemes in mid-spring, followed by globose, dark blue fruit. Another broadleaf evergreen for shade is the Rainbow Leucothoe (Leucothoe fontanesiana ‘Rainbow’) a member of the Heath family with white urn-shaped flowers.

Take a close look at your growing conditions and plant accordingly. Put a bench under a tree and once established, the shade garden will be a wonderful oasis to roam and sit with a cup of tea and take in all the many senses surrounding you.

A good article that lists many perennials and groundcovers for a shade garden can be found at Landscape Ontario.