The Things a Garden Centre Won’t Tell You

March 11, 2010

in Articles, From the USA, General Interest

by Suzanne Albinson

We are being informed, through literature and the media, about non-native plants that have escaped cultivation and now thrive in the wild.  They are a very serious threat to native species of plants, birds, insects, mammals and agriculture in all parts of the world. It is estimated that 5,000 non-native species threaten the natural areas of the USA alone. Ever since man started moving out to explore the world around him, he has popped seeds in his pockets, taken cuttings and dug up plants he coveted. Our gardens today would be very different if we only grew indigenous plants. No roses from Central Asia, no peonies from China, no herbs from the Mediterranean and not a lot of veggies.

Unfortunately, some of these introduced plants have done extremely well on our shores and have become a serious problem by migrating out of our gardens and into our roadsides and waterways. While I am sensitive to these dangers and won’t plant anything I know will cause problems, this is not the focus here. What I am concerned with in my own little piece of Eden are the annoying idiosyncrasies of plants that don’t pose a threat, just a nuisance.

It’s a peeve of mine that no one tells you the shortcomings of a particular plant. You very seldom see a list of plants with a column for their bad habits. Is it because the people who make up the lists haven’t actually grown any of the plants? Naturally, garden centres and nurserymen want you to buy their plants or seeds so they are not likely to tell you. Responsible nurserymen will answer your questions honestly but you have to know what questions to ask. When I find a plant for my garden I want to know what the plant is really like? Is it going to behave in the garden? Are there certain characteristics that I should know about that limits its usefulness? I need the good and the bad so that I can make an informed decision. All too often there are either glowing reports or sketchy descriptions. There are exceptions and good garden writers will characterize good and bad habits.

Researching on the Internet is fraught with danger. If you Google a plant and click on ‘Images’ for instance, the photographs can be completely wrong – wrong colour, wrong species, wrong cultivar. It’s only when you have a little knowledge that you know this occurs time and again. So pity the poor beginner.

I have discovered the little foibles of plants from years of gardening. Other gardeners may not have quite the same problems but many will be all too familiar with them.

We are told that Monarda didyma, Bee Balm, Lysimachia clethroides, Gooseneck Loosestrife, Physostegia virginiana, Obedience Plant and Ajuga reptans, Bugleweed are inclined to spread but not to what extent they spread and how difficult it is to get rid of them.

The things a garden centre won't tell you - Image 1

Monarda didyma 'Mahogany' and a Phlox paniculata

Monarda didyma spreads vigorously in good soil; fortunately it is easy to pull up but you must get every last bit of root otherwise it will become a new plant and start the process again. The same is true of Lysimachia clethroides, which is a pity as the flowers are sparkling white and last a long time in flower arrangements. Physostegia virginina, a threatened species in parts of its native habitat, is nevertheless an aggressive colonizer in good soil. These three plants could be added to more naturalistic prairie plantings where their spread would not be a problem and indeed might be encouraged.

Ajuga reptans is a great ground cover and will cover large areas rapidly but if you allow it to spread into lawns, you will never get it out. The mower just rides over it. If you have planted the burgundy leaved variety, then you will have burgundy blotches in your lawn, unless you dig them out by hand and get every bit of root. In borders the Ajuga insinuates itself among your other plants and if not wanted every bit has to be dug out. Years later you will still find plants coming up where you least expect them. They are particularly fond of rooting right down the middle of a thorny rose bush or cluster of peony stems.

The things a garden centre won't tell you - Image 2

Ajuga reptans insinuating itself through the Shade Border

Ah, Lily of the Valley, Convallaria majalis, the flower of our grandmothers, legends, symbolism and herbal medicine. But not the flower to put in our precious early spring gardens with their ephemeral beauties. This plant is a super thug! Keep it well away from anything you treasure. It spreads aggressively by underground rhizomes which produce stolons which produce new plants and so it goes on.

Certain cultivars of the splendid flowering crabapples, Malus hybrids, only flower well every other year. They will flower weakly in the off year but nothing like as profusely as their on year. So if, for instance, you are planting an allée of Malus ‘Golden Raindrops’ or planting one as a focal point in your garden and are looking forward to a wonderful annual display you will be disappointed.  You need to ask the nurseryman if the tree is an annual or biennial cultivar.

The things a garden centre won't tell you - Image 3

Malus 'Golden Raindrops' in a good flowering year

Syringa vulgaris, the common lilac, and many of the old shrub roses, produce loads of suckers and unless they are in lawns where you can mow them off, will sucker in your borders and become a thicket. Syringa vulgaris is prone to mildew and nothing is worse than a thicket of mildewed leaves.  Full sun in an open site is best for flowering and good air circulation to prevent mildew. The later Preston hybrid lilacs, Syringa prestoniae, bred in Canada, are a different kettle of fish. They are very hardy, more refined in habit, have larger leaves and stiffer blossoms, are not prone to mildew but don’t have the heady lilac perfume, which is not often stated. Syringa reticulata, the Japanese Lilac, is stunning in full flower and a very popular tree. But in some years the blossoms turn brown and cling on so you end up with a big tree with brown blobs until they eventually fall off. Not a good look.

Some of the older varieties of Phlox paniculata suffer terribly from mildew which disfigures the plants and certainly doesn’t add to the charm of your borders. It’s not a question of just the odd leaf becoming mildewed, the whole plant is affected. So the stems have to be cut down to ground level leaving a big hole in the border.  Fortunately some of the newer varieties such as P. paniculata ‘David’ are mildew resistant although even the resistant varieties can be affected in certain weather conditions especially if the stems are crowded. Phlox paniculata can spread into very large clumps so to keep the plant compact and avoid the possibility of mildew, some of the stems need to be cut out early on in the season.

Robinia pseudoacacia, the Black Locust, is a popular tree. It is a fast growing tree with a light, airy canopy, suitable to garden under. However, it is very brittle and branches break off easily in stormy weather. Its roots spread far and wide and annoying little treelets pop up in all sorts of places sometimes several yards from the parent tree. In the lawn, they can be mown off but in the borders they hide in among taller perennials and are not easy to spot and before you know it you have a small forest.

We all love poppies, especially Papaver somniferum, the Opium Poppy. It obliges us by seeding around prolifically and promiscuously and for the first year or two we don’t mind a bit. We look forward to the new seedlings to see what colours have resulted from their hanky panky. We love the green seed pods almost as much as the flowers. We forget about them as they turn brown and the myriad little seeds inside ripen and distribute themselves all over the place to start the cycle over again. The following years we have even more poppies and they are threatening to take over. Now we are having to pull them out in handfuls.

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Poppies seeding...

What about Papaver rupifragum ‘Flore Pleno’? Such a pretty, delicate orange flower and such a nice pale green rosette of leaves – for a thug! This little poppy is determined. It will seed itself over a large area and spread out of its allotted space in your hot border to your pastel border or into your pink and blue border.  Even if you pull off every flower before it turns to a seed pod, dig up every plant, there will be a seed hiding somewhere to pop up next year. Try to seed this poppy in a bit of gravelly soil on the edge of a driveway or parking area for instance where you wouldn’t mind it spreading around, and it might just refuse to germinate. No, it likes a bit of good soil, thank you.

Who doesn’t love Papaver orientale, the Oriental Poppy? Gorgeous, papery blossoms on sturdy stems from fresh green leaves in late spring. Over all too soon – flowers and leaves die right down and leave a gap in the border throughout the summer until fresh green leaves appear in autumn. A later blooming perennial or an annual is required to take its place to preserve the continuity.

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Papaver orientale 'Goliath'

A tidy gardener will not tolerate the dying blossoms of the popular Hemerocallis, daylily. They stay on the flower spike along with the new blossoms and detract from the charm of this plant. In some cultivars, such as Hemerocallis ‘Mary Todd’ with her sumptuous yellow blooms, the dying flowers droop, become slimy and cling on. The same also can be said for Platycodon grandiflorus, the Balloon Flower. Such beautiful buds and flowers, pity about the brown older flowers lingering on. A daily deadheading is needed to smarten up both these plants.

Aster novae-angliae ‘Purple Dome’ is a compact, profuse blooming fall plant; ideal, you would think, for the front of borders. It starts off green and fresh, spreads nicely and fills up with purple buds of promise. Unfortunately by the time the flowers open the lower leaves on this plant can be disfigured, turn black and the whole effect is ruined. Either rub off all the offending leaves or plant something lower growing in front.

Cleome hasslerana, Spider Flower, an attractive cottage garden flower, which seeds prolifically enough to become a nuisance, has nasty thorns and an unpleasant odor. Why bother?

Aquilegia vulgaris, Columbine, beautiful flowers that everyone coos over but can be so easily disfigured by leaf miners that the plant is just a collection of ugly leaves and flower stems. I’m afraid I disagree with the garden writer who said that it didn’t matter about the leaves as long as there were blossoms.

Achillea millefolium cultivars, Yarrow. There are some good colours now and I had high hopes for these plants. They all start out hearty, healthy, well budded, good clumps, then flop – the whole clump keels over into its neighbours just when you least expect it. You try and stand it up again but it’s all weak at the knees and won’t cooperate. You tell yourself that next year you will have to stake the clumps but you forget or convince yourself that this year they will stay upright but no, flop. Time to get rid of the whole lot. The common white yarrow so prevalent in the meadow as a diminuitive plant with perhaps one flower spike, put into a border with good soil grows to a vigorous bloomer of around three feet and in my garden stays upright – good in prairie plantings – but not everyone’s cup of tea.

Allium aflatunenense ‘Purple Sensation’, is a wonderful spring blooming member of the onion family with stately, medium purple globes that stand erect in the spring border. The seed heads are very attractive, turning from green to light brown which discharge black seeds all around the mother plant and have to be edited out religiously the following spring otherwise they get too crowded and the blossoms get smaller. It is still absolutely worth having. Dead head them before the seeds ripen or pop a paper bag over the head to contain the ripened seeds, cut off the stem at the base, then sprinkle the seeds elsewhere. The same goes for other members of the Allium family – they do seed around – but what a great family they are.

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Allium 'Purple Sensation'

Grasses, those recent designer plants which have been promoted from meadows into our borders, also have their problems. Many of the grasses, including Miscanthus sinensis ‘Purpurascens’, are terrific.  The Miscanthus makes a big statement in the garden, becoming a large, tight clump with tall plumes wafting about in the breeze. These plumes will stay erect even in very windy weather and throughout the winter, seemingly not bothered by sleet or snow. Which is more than you can say for other ornamental grasses. My experience is that the plumes of some of the Panicums, such as ‘Heavy Metal’ and ‘The Blues’ break in half with the first bit of wind or rain, spoiling the impression. All the large grasses are the devil to move once established as they have very tough root systems; and don’t cut them down in spring in windy weather or you will have dried blades of grass all over the garden. Wrap string tightly around the whole clump and cut it down with a long poled battery operated hedge trimmer. It works a treat.

I know other gardeners can relate many more experiences with plants. Perhaps it would behove us to compile a central data base of garden plants, a Wikiplantia perhaps, with all their pertinent information, good and bad, for us to delve into before we introduce any plant into our gardens or landscapes?

Suzanne Albinson

Comment from Michelle Chapman

Someone is trying to make that site – Gardenology

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