More Green Giants | Ottawa Start

7 • POSTED ON August 23, 2005
More Green Giants
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Picking up where we left off last week, we take a look at a few more “green giants”, the tallest among the perennials. All plants listed are hardy in the Ottawa area and readily available at the local nurseries and garden centers.

Our gardening column is published every Tuesday on OttawaStart. Read previous columns here.

Let’s pick up where we left off last week and have a look at a few more “green giants”, the tallest among the perennials. All plants listed below are hardy in the Ottawa area and readily available at the local nurseries and garden centers.

Truly a “green giant”, Macleya cordata (or plume poppy), can reach a 10-foot height and should therefore be included in our list. It has deeply lobed, heart- shaped leaves, topped in summer with pinkish-cream plumes. So far, so good, but whether or not to recommend it - is another thing. Unfortunately, the plume poppy has a tendency to spread vigorously as well as to sow itself all over the place. Although new shoots are relatively easy to remove, careful forethought and planning are required before purchasing Macleya. Suffice it to say the plume poppy is one of those plants you end up donating to friends, relatives, acquaintances, perfect strangers and anyone else who is willing to accept it…

With its six-foot height, Aruncus doicus – Goat’s beard – is more modest than the plume poppy, but it is also better behaved. This member of the Rose family enjoys a semi-shaded spot in your garden in – preferably – moist soil where it will grow to four feet in width. The more moisture in the soil, the more sun it will tolerate but it is first and foremost a woodland plant. It loves dappled shade and does very well under the canopy of large deciduous trees. Its white flowers appear in June/July and are held two to three feet above the foliage. As is the case with Peonies, Aruncus does not like to be transplanted and it has a hard time re-establishing when divided. As long as you keep this in mind when you plant it – and allow it enough room for future growth – Aruncus is an easy-g(r)o(w)ing garden companion. Plant it and leave it alone; that’s probably the best advice I can give you.

Rheum palmatum – AKA ornamental rhubarb or Chinese rhubarb – may be a little harder to come by than the plants listed above, but it is certainly worth the effort. This exotic-looking plant is virtually maintenance-free and stands out beautifully in the garden, both in the border or as a stand-alone plant. It has large rhubarb-like leaves with pointy edges; it is bronze-red in spring, later fading to dark green and to top it all, tall spikes of reddish-pink flowers appearing in early summer.

I very much empathize with Crambe cordifolia (or Giant Seakale) and feel it is time to stand up for this beautiful plant. Why? Well, how would you feel if you were referred to as “a Baby’s Breath on steroids” or “a cross between a Baby’s Breath and a cabbage”? Crambe is Crambe; nothing more, nothing less. A low mound of deeply-lobed large green leaves, decorated with tall stalks full of star-shaped tiny white flowers in early summer. It’s another one of those “stick me in the soil and leave me alone” plants that do not like to be disturbed – unless you are dealing with seedlings that sometimes appear around the base of the plant. It does like good soil – as in fertile – but that applies to most of these tall plants; it is tough to grow this tall when there is not a whole lot to eat (…gardening is simple; just use common sense and you will be fine!).

Helianthus – the perennial sunflower Helianthus – the perennial sunflower – is another one of the 6-plus foot plants that should be included in this week’s list. Very tall and upright, forming a bushy clump of green leaves, topped with branching sprays of soft-yellow daisy-like flowers in late summer and early fall. The plant is currently residing in my own back garden, strategically positioned to block the view of the compost bin. It came to me via (in chronological order) my mother-in-law, her next-door neighbours, their neighbours from across the street and – most likely - a bird dropping (though we are not sure about the bird dropping; this is going back a long time and records in those days were not kept as meticulously as nowadays). The point is that this is – yet again – a long-lived plant that does seed itself, but never becomes a nuisance. Helianthus is very easy to care for and it is quite forgiving when it comes to soil types, but it does like full sun. In fact, the only negative thing I can come up with is that it can look a little droopy after a few hot, dry days. However, as soon as the sun sets or you water it, the leaves perk up.

I have explained the theory of leaves and water before, but just in case you missed that column, here is a quick recap. Plants take up moisture through their roots and lose it through their leaves. As long as the balance is intact, the plant will look fine. However, on sunny days, tall plants (with lots of leaves) evaporate more water than they can take up, which is why they droop. The same goes with plants that have been recently transplanted; the damaged root-system cannot take up as much water as it should and as a result, it will start to droop. If you transplant in summer, make sure to cut back at least half the leaves!

That’s all for this week but “stay tuned” for next week’s column; after several intensive sessions with my therapists, I have finally gathered enough courage to share some of my worst gardening mistakes with you. Personally, I like to refer to them as “unfortunate choices” or “overly enthusiastic planning” but certain people in circles close to me (well, they USED to be, anyway!) have been known to label them “blunders”, “what the heck where you thinking?” or – after hearing my explanation – “right…interesting” (personally, I found that last one always to be the most offensive; it’s like hearing the girl of your dreams say “I love you so much; you are like a brother to me!”).

Until next week, happy gardening.

René Trim

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About René
René Trim was educated and trained in The Netherlands, before moving to Canada in 2000. After studying the differences in climate and season faced by Ontario gardeners he established Trim Garden Design and Rescue in May 2002. A gardener since the 1980’s, he has a wealth of knowledge and experience, a vast library of reference materials from which to draw answers to various garden situations as well as an enthusiastic and professional staff.