The growing of plants in tubs must owe something to the difficulty that people have experienced in the past in having a garden in the open. In Southern Europe in particular, people lived for generations in fortified cities. Travelling across a more peaceful Europe today, it is still, in the 21st century, a marked feature that the landscape consists of vast areas of cultivation, but people do not live in isolated cottages in the fields. They live in towns, in which everyone is involved in the growing of fruit, or wine, or cereal crops, and all go out daily to the fields. The very farmhouses are often inside the towns.
Many of these country towns are filled with gardens in planters. Not being able to have the large gardens that people could enjoy in north America and Britain, countries where fortified cities against invaders were not necessary, the Europeans planted their trees and flowers in tubs on their balconies and terraces, above their walls, in the street beside their doors, and in every imaginable spot where plants can be grown in a house in a street of a town.
The use of landscape planters is sometimes seen where there is no need. A large garden in a temperate zone with perfectly hardy trees growing in pots is incongruous. There is a pretension to it that has nothing to do with either gardening or landscaping and the owner makes himself look ridiculous.
There are two reasons for using planters. The first is, as with the European fortified towns, that this is the only way to have a garden. A town house with little or no outside space can still have a magnificent garden in planters, on a roof terrace, on a patio behind the house, in a sunroom added to the front or back of the house, on a balcony, on a windowsill, inside the very rooms of the house. Planters open up whole new possibilities to people who have no garden space but feel the need to have beautiful growing things, with all the pleasure they give, around them.
The second reason for using planters is that they enable us to grow a variety of plants that will do well outside in the garden during the summer months but that need to be brought in during the winter months.
In the Botanic Garden at Leiden, there is an orangery. All through the winter, great mature orange and other trees in pots are gown inside. The pots are on permanent trolleys and in the summer months the trees are wheeled out and grow quite happily outside in northern Holland â not a country noted for its benign climate -in sheltered corners of this magnificent garden. The Dutch winter would most certainly kill them, so in mid-autumn they are wheeled back inside, to rest quietly and safely through the winter months.
In Basle, in Switzerland, every household goods shop sells little trolleys on which the citizens of Basle place their Myrtles or Oleanders, which will sit in the garden throughout the summer and be wheeled inside for the winter.
There are many charming plants which are too tender for the open that are perfectly happy in tubs and can be sheltered in an outhouse, protected with a blanket of horticultural fleece or straw, throughout the winter. In this way northern gardeners can have the pleasure of growing Olive, Pomegranate and Bay, none of which would survive a hard northern winter and all of which enjoy a period in the open. So also do Tree Ferns, Cycads, and half-hardy Palms, which can be grown in planters and moved outside in the summer.
Watering plants grown in planters is vital, as they cannot draw water up from the soil below. Regular feeding with a weak liquid manure is beneficial to all plants in tubs.
The planters themselves should be made of wood or of clay, both of which are porous and breathable, retain water and keep the roots at an even temperature inside. Pots are not happy in the long term in plastic planters as the plastic acts as a barrier and no oxygen is able to get to the roots. The loveliest containers of all are those made in the shape of the great Italian oil jars. It is no longer possible to buy the originals but many enterprising garden shops have recognised a demand for good clay pots in a wide variety of shapes and reproduction oil jars make excellent landscape planters.