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 underplanting 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 and so I was not going to whip out my camera and take photos of the worst examples to embarrass them in the newspaper and online.
Words like mishmash and hodgepodge came to mind as I looked at the bottom layer of plants in otherwise perfectly competent gardens. They had good upper layers of larger plants, but when it came to the bottom layer of ground covers and underplantings, the selection criterion seemed solely that the plant should not be more than 30 centimetres high. 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 - was 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 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.
Neither 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.
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 that 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 underplantings will make it a great deal more interesting.
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 use the traditional riot of random colour that nature achieves. If you like a tidy garden that is weed free, it is not an easy style to manage well. More often it is best viewed in passing, rather than looked at in detail.
Then, of course, you could ask yourself whether underplanting 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?