You’ve certainly seen a strawberry jar (also called a strawberry planter or strawberry pot) before. It’s that upright urn with planting pockets on the sides that was originally used, as the name suggests, for growing strawberries. The wicking effect of the terra cotta pot helped keep strawberry plants cool even on a sunny terrace while allowing the grower to cultivate many more plants than would have been possible in a pot with only a top opening.
Today’s strawberry jars are not always terra cotta, though. Plastic, resin, fibreglass, ceramic and even cement strawberry jars are now available. And strawberries are far from the only plants we grow in them. Succulents, herbs, annuals, alpines and many other plants are often displayed in strawberry jars.
Which pot material you choose depends on your tastes and your budget. Do make sure however that whatever strawberry jar you choose has a drainage hole at the bottom. If you do use the traditional terra cotta, make sure to soak the pot in water for 30 minutes before using it, otherwise it will absorb water from the potting mix and cause drought stress to your plants.
The Watering Dilemma
Growing plants in a strawberry pot would seem pretty obvious. After all, it’s a planted container: how different can that be from a flowerbox or flowerpot? In truth, though, there is a problem with strawberry pots: it’s not easy to get all the plants equally watered. Gardeners quickly find the lower plants dying of thirst even though the upper plants are doing fine. Water simply hasn’t been filtering down to the lower part of the pot. But if you water more heavily so the lower plants get their share, the upper plants are overwatered and start to rot. What a dilemma!
Fortunately, there is an easy solution… but you have to apply it before you pot up your strawberry jar!
The solution is to insert a watering pipe into the jar. Buy a length of PVC or ABS pipe (1” to 1 ½” pipe is ideal) and an end cap for the same. Cut the pipe about the same height as the jar. You’ll find pipe easy to cut with a metal saw. Now, using a quarter inch drill bit, drill holes right through the pipe. Start about 5 cm from the bottom of the pipe and drill other holes about every 5 cm. Close off the lower end of the pipe with the end cap: this gives you your water pipe. In the future, water by filling the pipe with water: it will flow out at all levels, ensuring both upper plants and lower plants get a fairly equal share.
Insert the water pipe into the centre of the jar, plugging the upper end with a rag so you won’t accidently pour potting mix. You’re now ready to plant.
It’s easiest to pot up a strawberry level by level, starting at the bottom.
Place a square of newspaper over the drainage hole to keep the soil from draining out (water will flow right through it, but the soil will remain behind).
No drainage layer is required, so just pre-moisten some potting mix and pour it into the bottom of the pot, up to just below the first planting pockets. (Most pre-blended container mixes work well, although you may want to mix in some compost and a slow-release fertilizer.) Unpot a plant and place it sideways in the pocket. In order to do so, you may need to compact the root ball or knock off some soil. Set the plant’s roots inside the main pot, on top of the growing mix. Repeat for the other openings on this level. Now cover the roots with mix and fill in the pot to just below the next series of pockets and insert more plants. Continue this process until you have planted all the pockets. Finish by adding three or four plants to the top opening. Don’t fill the pot quite to the brim with mix: leave a 3 cm space for watering purposes.
Now remove the rag from the pipe and water well by filling the pipe with water, and also watering the potting mix on the surface of the jar. Congratulations! You’ve just produced your first strawberry jar planting!
Which plants you put in a strawberry jar is up to you, but do remember all must be compatible. That’s why an all strawberry planting or an all succulent planting is particularly easy: the plants will all have the same needs. Most flowering annuals are fairly compatible, too, at least when it comes to their watering needs. You still have to remember that, while most annual flowers are sun plants, some, like begonias and coleus, prefer partial shade or even shade. Stick to small varieties: you can’t really grow giants like castor bean or sunflowers in little planting pockets!
Herb-filled strawberry jars are particularly popular these days, but can be a bit complicated. After all, not all herbs have the same needs. It won’t be easy, for example, to grow water-loving mints along with herbs that need good drainage, like sages and thymes. And fast-maturing annual herbs like dill and coriander (cilantro) really aren’t good choices for strawberry jars at all. The greatest range of herbs however, like sage, rosemary, basil, thyme, and parsley, are quite compatible: they all appreciate full sun and soil that isn’t overly moist or rich.
Alpine plants will need a specially gritty potting mix: try adding about 1 part sand and 1 part gravel to 8 parts of commercial potting mix. Since they’ll be outdoors all year, make sure the container chosen is frost resistant.
Water when the potting mix is dry to the touch (sink your finger into the mix down to the second digit to tell). Watering frequency varies enormously according to the type of pot (terra cotta dries out very quickly), the size of the pot, the type and the size of the plants, plus temperature and exposition: full sun plantings may need watering several times a week in hot weather.
At least once a week, water with a dilute solution of soluble fertilizer: the soil in containers is constantly being leached by rain and watering, so container plants need much more fertilizer than plants growing in the ground.
Finally certain plants may need a pinch or a prune or some deadheading now and then to stay in shape.
In most cases, you should empty out strawberry jars in late fall and overwinter them indoors. That’s because potting mixes expand as they freeze and can crack some materials, notably terra cotta and ceramic. If you intend to leave yours outdoors permanently, check with the supplier to make sure the model you choose is frost proof.
So, go ahead and grow your own strawberry jar next summer: you won’t regret it!