Tag Archives: ground cover plants

Cover the ground

Happy and easy care perennial impatiens

Happy and easy care perennial impatiens

I mentioned last week about my mother’s gardening mantra being ground cover which focussed my mind on the case for ground cover plants. Surprisingly, this preoccupation is a relatively recent phenomenon.

Back in the 1950s and 1960s ground cover plants hardly featured. It was all about trees and shrubs with little under planting. Now it is often regarded as a hallmark of good gardening to have no dirt showing at all – except in the vegetable garden. Mostly it is about packing the garden with layers of plants, each lower layer masking the stems and trunks of the taller ones while down the bottom is some low but strong growing ground hugger.

There is good sense to not having exposed dirt in a garden. Keeping it covered stops dirt splash in the rain, wind blown top soil in the wind and erosion in torrential downpours. A good thick layer of something, be it plant or mulch, can cut down on the germination of weed seeds lurking in the soil because it reduces the amount of sunshine and light that most need. It is also a great deal more attractive than the liverwort that colonises uncultivated ground in shaded areas.

There are ground covers and there are G-R-O-U-N-D C-O-V-E-R-S. Some modest little ones never get ideas above their station and just gently colonise an area, spreading in a quiet and acceptable manner. In this class, I would put the unassuming but pretty little scuttelaria which we have in both white and blue or the obliging corylopis and a number of the ajugas.

Then there are the rampant ones which, given even a hint of an invitation, will spread at an alarming rate. I once bought a punnet of such a plant which looked promising. I have long since lost its name but it had pretty white cup flowers and good green, fine foliage. That punnet held six plugs, each measuring about 2.5cm across. Within one season, each of those plugs measured a metre across. I have never seen anything spread so alarmingly. It took me two years to get rid of it entirely, all the time muttering that the people who propagated that plant for sale should be lined up and shot. For the same reason, I have eradicated the Orangeberry plant (Rubus pentalobus) and rampant violets. I don’t want lemon balm either. It stages a takeover bid, choking everything in its way. And the ornamental tradescantia is pushing its luck.

Zephyr beside the Acanthus mollis

Zephyr beside the Acanthus mollis

We are extremely cautious about the triffids too. These are the large growing perennials which spread and choke out much in their path, seeding their way through the garden. Acanthus mollis or bears’ breeches springs to mind as a good example. One can be striking but don’t turn your back on it and allow for the fact that every one needs at least a metre and a half of space. Too many and your garden looks as if it is full of cheapie plants as bulk fillers. We call it the ABG syndrome after we heard somebody’s garden described as being a case of Another Bloody Gunnera. Those particular triffids are now on the banned list in this country, as far as I know – the enormous rhubarb plants.

Endless plant lists without photos make dull reading, but I will offer up a very short list of recommended, well behaved ground cover plants which have proven their worth here and should be readily available. In shade areas, it is hard to go past hostas, farfugiums and ligularias but also the francoas (sonchifolia and ramosa- the Chilean bridal wreath flowers) and phlomis. We have a wonderful swathe of old fashioned perennial impatiens (busy lizzies) which have kept on keeping on for decades in frost free woodland conditions. They flower for 10 months of the year and require next to no attention.

The mottled foliage of pulmonaria (with the unromantic common name of lungwort)

The mottled foliage of pulmonaria (with the unromantic common name of lungwort)

In sunnier conditions, the sedums work well, as do coreopsis, smaller growing campanulas, phlox, asters – there is an endless list of possibilities. I am less keen on the widely used catmint (nepeta) which I regard as too strong a grower and essentially boring. I much prefer the mottled foliage and pretty flowers of the pulmonaria which fill a similar niche.

For those who find using perennials offputting, the permanence of ground cover shrubs sometimes appeals, especially flowering shrubs. We used to sell pretty little weeping camellias (Sweet Emily Kate and Quintessence) which, if not trained upright, would become ground cover. And somebody has apparently released a “ground cover” michelia. I know this because I have been asked for it but have not seen it yet.

But, ground cover shrubs in a mixed planting? I don’t recommend them. We tried Sweet Emily Kate and very soon discovered the drawbacks. There is nowhere for the spent flowers to drop to so all that happens is that slushy blooms and other garden debris sits on top of the plant, needing frequent picking over by hand.

If you want ground cover, keep to perennials or seasonal bulbs and annuals is my advice. If you want to reduce maintenance, mulch with something anonymous like compost or bark chip instead and bypass the ground cover altogether.

First published in the Waikato Times and reprinted here with their permission.

Plant Collector: Dicentra eximia alba

Dicentra eximia alba - a modest little plant for semi shade areas

Dicentra eximia alba – a modest little plant for semi shade areas

This particular dicentra hails from USA where it is widespread because it is not at all picky about temperatures. We use it as a ground cover in semi shaded conditions. It is fully deciduous so it disappears in autumn, to reappear with renewed vigour each spring. The foliage is technically described as finely cut and divided which means it looks ferny or maybe feathery. The flowers are little heart shaped pouches and feed the bees, particularly the humble bumbles. We have another form where the foliage is glaucous – in other words, blue-grey with the same white flowers, as well as pale pink forms. It is moderately poisonous to stock which is how it comes by its common name in USA of staggerweed, but that is not a problem in a garden situation. It forms rhizomes at or just below the soil level. Combine it with spring bulbs which flower first and as their foliage gets tatty after flowering, the fresh dicentra will mask it.

The pretty Dicentra spectabilis or Bleeding Heart with its dear little pink to red heart flowers hanging all down the stems is from Northern China, Japan and far eastern Russia – all places where it will get a good winter chill. I remember it as a common garden plant from my Dunedin childhood. Over the years, we have bought fine looking plants in full leaf and flower on several occasions but they fail entirely to reappear the second year. It is available in seed so the plan is to order a packet next season and raise a whole lot to experiment with different locations in the hope we can get it established.

First published in the Waikato Times and reprinted here with their permission.

The vexing issue of underplanting

A row of alternating annuals makes a statement, though it may not be the statement the gardener is aiming for

I had a day out and about looking at gardens recently and I was struck by the nature of under planting, though this preoccupation may have had more to do with my thoughts at the time. What I noticed about the under planting was how badly it was done in a couple of gardens. Bear with me, dear readers. You are going to have to imagine it because I know the garden owners so I was not going to whip out m’camera and take photos of the worst examples to embarrass them in the newspaper and on line.

Words like mishmash and hodgepodge came to mind as I looked at the bottom layer of plants in otherwise perfectly competent gardens. In other words, they had good upper layers of larger plants but when it came to the bottom layer of ground covers and under plantings, the selection criterion seemed solely that the plant should not reach more than 30cm in height. And there was one of this, one of that and one of the other, bunged in higgledy piggledy in most spaces.

Even worse, and I had to visit my local garden centre to set up a photo to demonstrate, is the horror of alternating annuals in a row along the edge. These certainly make a statement in the garden, though it may not be the statement that the gardener thinks when he or she plants them. I saw something similar (maybe with pansies and alyssum?) looking incongruous in a garden with otherwise high quality woody trees and shrubs and there were not any resident children to justify such a lapse in taste.

Nor am I a fan of edging plants, or indeed anything planted in rows other than proper hedges or vegetables, but that is a matter of style and personal taste. Fringes of mondo grass, liriope or anything else leave me cold but edging rows of matched annuals make me raise my eyebrows. Not even moderately tasteful white petunias cut the mustard when planted as an edging.

The contemporary look is to plant in blocks. The landscaper look is to plant in sharply defined geometric blocks each comprised of only one evergreen plant. Clivias are good, renga renga lilies are a bit untidy. Hellebores are probably acceptable, as is liriope or trachelospermum. Natives like prostrate muehlenbeckia are better.

Bergenia ciliata and Siberian irises – this gardener’s version of block planting

The middle ground is to gently block-plant but in more interesting combinations and in less rigidly defined grids. I am far more comfortable with that approach and it makes gardening interesting to play with different combinations. It also has advantages in making maintenance easier to group plants which require more frequent care – such as dead heading, staking, dividing, or grooming. Rectifying mistakes or bad decisions including eliminating invasive thugs is more localised if you are planting in blocks. I tend to blur the edges of my block plantings so that the overall look is softer and less delineated because that suits our style of gardening better. There is no doubt that if the upper layers of the garden are varied and mixed, some sort of unity in the bottom layer creates a more harmonious picture. I would argue that the flip side of the coin is also true: if your upper layers are rigidly conformist and consist of restrained plantings of only one or two different plants, ringing the changes with more complex and varied under plantings will make it a great deal more interesting.

Acceptable clivias

If you don’t want to go the block planting route, the old fashioned cottage garden genre may be an alternative. Essentially this is a jostle of perennials, annuals and bulbs in combination with small shrubs, often roses, where self seeding is encouraged. If you want a more modern look, you colour tone it rather than the traditional riot of random colour that nature achieves. If you like a tidy garden which is weed free, it is not an easy style to manage well. More often it is best viewed in passing, rather than looking at the detail.

Then, of course, you could ask yourself whether under planting is even necessary in some areas. The requirement that all garden beds and borders be layered with nary a glimpse of garden soil is relatively recent. In times past, it was fine to plant shrubs and trees without any bottom layer at all. It was called a shrubbery. Just don’t plant the shrubs too close together or you end up with a hedge. Each shrub needs to stand in its own space. As nature abhors a vacuum, mulch all the bare earth with something anonymous or you will grow a carpet of weeds. It is certainly easier to maintain than more complex plantings. It will probably look more attractive than the hodge podge assemblage of random plants I saw. It should look classier than the row of alternating annuals. Maybe it is time to start a movement called The Shrubbery Revival. Neo-shrubberies, maybe?

First published in the Waikato Times and reprinted here with their permission.

Death to the Orangeberry Plant

My rubus pentalobus is under a death sentence. What, you may wonder, is rubus pentalobus. It has taken me some time to get a grip on its proper name and I may soon forget it again but most of us know it as the orangeberry plant. It is a ground cover plant, marketed widely in recent years with a key selling point of producing edible fruit.

I am guessing that in its native Taiwan it may produce more fruit but it has the reputation of being very reluctant in this country. I was optimistic with the second season and a solid mat of it in a hot, sunny position. It put up a good number of small white flowers in spring but these translated into precious few orange berries in summer. And berries might be slightly overstating the case. Certainly they were orange but at little larger than a glass pin head and held singly, berries seemed an unjustifiably generous descriptor. Indeed, Mark just looked incredulous when we spotted the first fruit. It is difficult to describe the taste. I think the entire crop was two each so the best I can say is fruity, in moderation.

But it is not the ever so slightly disappointing harvest that had me donning the black hat to pronounce the death sentence. No. What the rubus lacks in fruiting capacity, it more than makes up in vigour. Knowing that it could be a little rampant, I used it in a defined border where I wanted the unity of a single ground cover to set off a little collection of topiaried camellias. It was confined by concrete edging on three sides and a box hedge on the fourth. Not that the rubus was going to let that stop its inexorable advance. The moment I turned my back, it would leap the concrete edging and get its roots into both the lawn and the gravel paths. I could cope with that, but its inclination to weasel its way through the buxus and even climb started to ring alarm bells. Ground covers that can moonlight as climbers are a worry. Added to that, after only two years, the ground is such a mat of congested roots that it is near impenetrable and the rubus is even threatening to overpower my valued camellia specimens. Spending several hours every couple of months trying to thin and contain the plant does not seem worth the effort to me.

I will not be digging the rubus to pot up and sell. That seems altogether irresponsible. Though if anyone has a large clay cliff they wish to retain, a precipice perhaps, a landslip or maybe a large stretch of coastal erosion which they were thinking of retaining with concrete slabs, this plant may be just the ticket. I would guess that it has the potential to turn up on Regional Council’s banned list sooner rather than later. We will be resorting to gyphosate to carry out the death sentence. The tangled mass of rampant root makes digging it out difficult. You have been warned. Keep this plant controlled and under close supervision.

A bonsai camellia under threat from the thuggish rubus pentalobus.

A bonsai camellia under threat from the thuggish rubus pentalobus.

Like his father before him, Mark has a deep distrust of plants with weed potential. Maintaining a large garden is a delicate balancing act at the best of times without allowing rampant colonisers to escape. There are no annual forget-me-nots here. Charming they may be, but they did not earn their common name lightly. Let them into your garden and it takes years to stop them seeding everywhere. Rampant seeders, subversive clumpers, overpowering thugs – no matter how pretty, such plants are not welcome. We have tended to add violets into the category of invaders with their inclination to spread and their resilience. Indeed, despite my best efforts in several places in the garden, clumps of violets keep staging a come back. And down in the paddock is a clump which Mark refers to as Grandma’s violets. In fact I think they are a relic of his great grandmother’s garden from the late 1800s. Now we think the violets will make a more acceptable ground cover than the rubus. Their invasive tendencies are not too serious. In 120 years, the rubus would have colonised the better part of Tikorangi whereas Grandma’s violets have just gently survived all competition and kept going. Their flowers are prettier than the rubus, too. I think they have earned a recall.