The great lure of freshness and flavour, as well as the quest to introduce more leafy greens into the daily diet, is what I see. Gardens are shrinking rapidly and for young families, time is also the essence. As a result, growing herbs close at hand to the kitchen has great appeal.
First up you need a wall; modern gardens tend to have plenty of this vertical space. Obviously, homeowners with small garden and apartments are looking in this direction; so are those with larger gardens where the desire to get quick access to freshness is a driver. It is also a good idea to have such a planting near the barbecue so that you can ?pluck and plunk?.
Have a look at the possible locations throughout the day to see how much sun strikes the wall up which you are thinking of planting. North and west facing walls usually get the greatest number of hours of direct sun during summer where south and east facing walls are normally shaded for the second half of the day. Plants that produce flowers or fruit tend to need more light, where green leafy herbs are ok to grow in more shaded locations. Perth during the height of summer can be, in the words of the song - ?Just too darned hot? and vertical gardens exposed to afternoon sun will most likely need some shade protection.
A brief look around your garden centre will reveal as many as a dozen ready-to-go systems. Some need to be mounted on a wall with the help of an electric drill, others can be hooked over a fence and there are also freestanding models. One major factor to consider is the size of the pots. Small pots with a diameter of around 8cm will dry out much faster than larger models of around 15 to 20cm.
Many vertical systems are designed so that pots at the top of the system drain into the second run of pots immediately below. If the system has many layers, drainage delivers multiple helpings of water to the lowest levels. This effect needs to be considered when choosing and positioning your plants. For example, Mediterranean herbs such as thyme and rosemary need well-drained situations and are best positioned at the top of the system. Mint and its close relative basil as well as lemongrass, revel in wet soils and are best positioned at the lowest levels of a vertical garden.
Some vertical garden units have a watering system incorporated into the design. These can deliver water from a garden tap to drippers, positioned in the growing pots. If your system doesn?t have such a built-in irrigation set up, then you can create your own with spaghetti tube and variable flow emitters.
Tap mounted battery powered controllers open the door to automation as you can program these to deliver water to a plan. The best way to draw up such a program is to ?water and watch?. Visit the garden during the day to see how long it takes for the pots at different levels within the wall, to dry out. This knowledge then helps you to construct a program that allows you to supply moisture at the right time to keep your herbs well hydrated.
The short answer is, whichever varieties you like and use most. Every herb that I can think of (except a banana, technically a herb because it has a soft trunk) can be grown in a vertical garden. Here is a list to get your ideas going ? coriander, parsley, basil, mint, marjoram, thyme, rosemary, nasturtium, salvia, lemongrass, chives, chilli, tarragon, oregano, Vietnamese mint, fennel, chervil, dill, lovage, watercress, wild rocket, stevia (sugar bush) and ginger.
My approach is to regularly remove overgrown plants. These tend to stress quickly if water levels are not sufficient because the pots tend to be full of roots. Coriander tends to bolt into flower quickly in summer so I recommend new plantings every month. One great idea is to purchase additional pots for your system so that you can have some juniors ready to drop into the wall as required. This enables you to have a full wall of herbal action all year round.
The two main problems that most gardeners face with vertical gardens is over-watering and under-watering. Choosing a potting mix that allows free drainage and at the same time holds good supplies of moisture is the first essential. Baileys Premium Potting Mix is a great choice as it not only covers off on the moisture requirements but also has sufficient controlled-release fertilisers to supply up to 6 months of feeding to your plants.
For subsequent feeding, I would recommend using the new Soil Matters Garden food, applied directly to the surface of the potting mix and watered in immediately.