How to build a raised herb planter

2020 has not been a year any of us could have predicted (unless you are in fact Scott Z. Burns, writer of Contagion). One of the less miserable side effects of the great virus of 2020 seems to be that more of us are taking time out to be in the garden. Waiting lists for allotments in my area are now as much as three years rather than about 6-12 months! To get the most out of my garden, so I decided to add a raised herb planter and fill it with all my favourite herbs.

I have been spending time sprucing up the garden. I want to make use of every corner of my little piece of outdoors to grow lovely things; flowers and food.

Being limited on space, I have always prioritised what to grow, but this year I wanted to add herbs so that I could use them in cooking and making tea. I also want to avoid buying single portions of expensive herbs in plastic packaging.

I had a look online to find a herb planter, but I couldn’t find anything quite right for the space. I wanted a raised herb planter, so that I could quickly nip out and pick some herbs without doing my back in. It needed to be deep enough for the roots to bed in. It also needed to be the right length and height to sit in front of and underneath the conservatory window.

How to build a raised herb planter

The instructions below are intended to help you design your own raised herb planter, to fit your space.

Materials

• Timber – we used untreated pine but a good option would be sawn treated timber that’s ready for use outdoors. Try Wickes for timber.
• Screws (No.8 x 2”)
• Electric screwdriver
• Handsaw / jigsaw and workbench
• Filler
• Outdoor paint – we used Muted Clay from the Cuprinol Garden Shades* range. The paint protects the wood from rotting.
• Multipurpose compost and compost bags to line the planter
• Horticultural grit
• A selection of herbs suitable for the position of the planter (see below)

Here’s the design of the planter:

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First, cut your width (green) and depth (blue) panels to size, as well as the legs (yellow).

Sometimes it can be cut to size in store, but if not then you’ll need a workbench and handsaw to cut the required lengths. The bottom panels (red) will be cut to size later on.

A word on measurements

My measurements are included in the drawing above, but the point of this guide is to design and build a planter that suits your space. So rather than includ specific measurements for you to work from, instead, keep these pointers in mind:

• Draw out the planter first so you can work out your dimensions;
• Don’t make the planter too shallow. Mine is approximately 30cm deep to allow good depth for roots and thus stronger and bigger plants (each of the three panels is 9.4cm long, so the depth in just under 30cm in total);
• Cut the width panels first to the width you want the planter to be – for me, this was 150cm. You will need 6 width panels;
• Cut the depth (blue) panels next. Keep in mind that these will be a little shorter than the overall depth of the planter, as they slot inside the width panels. The wood I used is 1.8cm thick, so to get my preferred depth of 44cm (as I wanted it to sit on one row of paving slabs) the calculation is 44 – (2 x 1.8cm) = 40.4cm (or thereabouts). You will need 6 of these panels;
• The leg battens (yellow) will be cut to the exact height that you would like the planter to be. For me, this was 80cm, so that I could push it just underneath the overhanging windowsill above;
• The bottom (red) panels can be cut to size once the rest of the frame is put together, so that you can double check the size of the gap between the width panels.

Build the raised herb planter frame

Lay the leg battens (yellow) on the ground (we worked in the back garden) and rest a length of wood that forms the depth of the planter (blue) on top. You will see in the diagram above that the screw points are marked with dots. Line up the depth panel with the outer edge and top edge of the leg baton and screw into position. Three panels form the depth of the planter, so add two more panels beneath the first. They should be pushed together – no gaps. Do this for both ends of the planter.

Next, add the width (green) panels. It may help to have a friend or long suffering husband to help at this point. The width panel should line up with the newly attached depth panel (so a bit further out that the leg baton) – have a look at the diagram to see the position. This is why we do the depth panels first. That said, it wouldn’t matter if you did it the other way round. Screw the length panels to the leg batten as you did with the depth panels, on both sides. You should now have a box with no base.

Add the bottom panels

Next, you can cut the bottom panels to size. Measure the gap between the width panels and cut your panels; you’ll need to leave a little space (about 2cm) between each panel for drainage. You’ll see from the diagram that the two end panels have the corners cut out so that they fit against the leg baton. Mark out the corner that needs to be cut out either by drawing around the leg batten or just measuring out the dimensions of the batten. Cut the corner out with a handsaw or a jigsaw.

Turn the planter upside down, with legs pointing toward the sky. Start from one side, using a panel with corners cut out and position ready to screw in; a helping pair of hands may be useful. The bottom panels line up with the bottom of the width panels, so they sit inside the frame. Screw each bottom panel in position with screw entering from the front of the width panels and into the bottom panels.

Prep for painting

Finally, use filler to cover over the screws prior to painting.

Note, that we have added a strip of metal to the middle of the raised herb planter to hold the width strips in place. This is not essential (we had the metal left over from building our bin shed). You could strengthen the middle instead with a batten of wood or even by adding extra legs to the middle of the planter. You’ll need to judge the necessity based on the overall size of your planter – if it is quite wide, then extra support would be a good idea.

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Painting the raised herb planter

I painted my raised herb planter after putting it together though you will probably find it easier to paint it first, especially if not using treated wood, since it is important to get the paint in all the nooks and crannies to help stop it rotting. I’d recommend using treated wood ideally and painting before you put the planter together. I used three coats of Cuprinol.

Lining the raised herb planter and mixing compost

Next, it’s important to line the planter to add a protective waterproof layer. I used the compost bags my compost for the planter came in. The easiest way to do this is like so:

Put the full compost bags in the planter and cut them open (one by one) from the top. Using a staple gun, staple the bag to the planter, pushing it right into the edges at the bottom.

Fold the top edges onwards and staple those down too, so that the planter is lined all the way round.

You’ll need to shift the compost around to staple the bottoms so that the bags overlap a bit to avoid any gaps.

Do this all the way along and add in 10 to 20 litres of horticultural grit to help with drainage. Give the compost a good mix to distribute the grit evenly.

Once the planter is full, slice some holes in the compost bags from underneath, between the bottom panels, using a Stanley knife, to ensure water can drain. I made several slits of about 5cm in each gap.

What to plant?

I wanted quite a mix of herbs, but it’s important to consider the different conditions required by each herb. Always ready the care label on your herb plant or research its requirements.

My planter is in a part of the garden that gets sun all morning, but starts to get shadier on the left hand side first. I kept this in mind when planting and put plants that would cope with less sun in the left hand side and those that prefer as much sun as possible in the right hand side.

My planter is filled with compost, which is full of nutrients but mixed with grit for improved drainage. This will suit a good number of herbs but those that are happier in poor soil such as French tarragon and thyme won’t love it; they’d just grow leggy and limp.

Choosing your herbs

Choosing what to plant is the fun bit. The rules to follow are:

• Plant herbs you love! There’s no point growing herbs that you don’t enjoy eating (or at least looking at!)
• Keep in mind the growing conditions – how much sun and the type of soil especially – required for your herbs: always research first and read the care labels
• Consider whether the plant is annual (just lasts one season) or perennial (comes back every year).
• Evergreens will be green all year round.
• Hardy plants will survive outside but some not so hardy plants may need bringing indoors. Again, a bit of advance research, or at least a good read of the care card, is required. If a plant isn’t hardy for your climate, then you could plant it in its pot and bring it into a conservatory, greenhouse or even a cold frame over winter to help protect it from frost.

In my raised herb planter….

I plan to do a full blog on growing herbs in time, but here’s some ideas to get you started.

Mint

I have a few different varieties of mint, which I grow for teas and cocktails! Strawberry mint has leaves which do, when rubbed between your fingers, smell rather like strawberries and would be quite lovely in a mojito! I also have chocolate mint, which has a slightly chocolatey smell and another variety called After Eight which has such a strong pepperminty aroma that it really is reminiscent of everyone’s favourite after dinner mint.

Many mints tend to spread invasively and if planted in the ground, would quickly take over a border. I have kept mine confined by keeping the roots restricted in a pot, buried in the planter, with compost filled around the edge. Check whether your variety is invasive before direct planting.

I also grow lemon balm (scientific name: Melissa Officinalis, so it had to be done) which is a member of the mint family, so best to have it restricted to a pot as well.

Mint will do well in partial shade, so mine is planted at the end of my planter that goes shady first. It likes rich but well drained soil (check!). Mint plants are cheap to buy – try Hetty’s Herbs. You can also buy a plant from most supermarkets and divide it (as they tend to consist of lots of small plants in one pot rather than a single large healthy plant).

Mint is a herbaceous perennial, so it does back in winter but grows again each spring. The plant can be divided in autumn to stop the pot getting too congested.

Basil

I absolutely love basil and I’m growing several varieties this year.

Greek Basil – this is in the top left of the photo above. It is a small variety with mild flavoured leaves that are great in salads, sprinkled on pasta or served with tomatoes.

Sweet Basil – this is the type you usually find in the supermarket (middle left in the picture) and is wonderful in pesto or caprese salad.

Purple Basil – I have two varieties: ‘dark opal basil’ which I chose largely for variation in colour; it has a less sweet flavour than ‘supermarket’ basil and ‘purple ruffles’ which has a strong aniseed flavour and is good for cooking.

Lemon Basil (middle right in picture with lighter green leaves) – as you guessed, has a strong lemon scent and is great with fish or chicken dishes.

Thai Basil – has a stronger taste than supermarket basil and great in (unsurprisingly) Thai dishes!

There are many other varieties to try too: lime basil, spicy basil, cinnamon basil… the list goes on!

Basil likes rich, well drained soil in full sun. Mine is planted at the sunniest end of my planter and thrives despite being in shade from about 2pm onwards.

Basil is an annual plant that will die with frost. It will need to be replaced each year but luckily it’s very easy to grow from seeds or young plants are cheap. Supermarket plants can also be purchased and divided into lots of small plants – I divided my single Waitrose Greek Basil into 24 plants.

Fennel

Fennel doesn’t like being moved, though mine survived fine when I divided a pot of 6 plants and transplanted into my herb planter. Do keep this in mind though as direct sowing is recommended.

Fennel likes rich, well drained soil and will do ok in partial shade, so mine is planted toward the shadier end of my planter.

Dill

Just behind the fennel I have dill. It grows quickly from seed and smells wonderful. I like it with fish and in omelettes.

I find that dill can have a tendency to bolt, so it’s in the part of the planter that gets plenty of sun but is at the cooler end to help avoid it drying out which can encourage the plant to bolt.

Lemongrass

I love Asian food, so I am trying my hand at growing lemongrass. It is not very hardy, so I will need to dig it up each autumn and store it in a pot in my conservatory before planting out again.

The lemongrass is in the sunnier end of my planter.

Lemon Verbena

I am growing lemon verbena for herbal teas. It smells like sherbet lemons! It is not hardy and like the lemongrass, I will dig it up and store it in the conservatory for winter. Unlike lemon balm, lemon verbena is not invasive.

I hope this has given you some ideas for a raised herb planter! If you have any questions just pop a comment below 🙂

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