How to grow Heliotropium
There are hundreds of different species of this tender member of the borage family, originating mainly from warm places throughout the Americas. Just one, however, is widely cultivated throughout the rest of the world – the Peruvian native Heliotropium arborescens. Much loved as a traditional summer bedding plant, this species, along its numerous hybrids and cultivars, is popular for growing in containers, window boxes, and borders; prized for its beauty, long flowering period, and, above all, powerfully sweet scent. The many tiny flowers are held tightly in domed heads, their colour usually a deep violet, though white and pale shades are also available.
While technically a tender shrub, in our UK climate this species of heliotropium is typically grown as an annual. While it is possible to keep it going in a greenhouse, it tends to become scruffy after a growing season (two at the most). A better approach is to take cuttings in summer and start afresh each year(see propagation section below).
Heliotropium is also known by the common name of the cherry pie plant. It is not to be confused with winter heliotrope (Petasites fragrans), a spreading, winter-flowering plant in the daisy family. The two are unrelated and have little in common other than intensely scented flowers.
Zantedeschia is a genus of flowering plants from the family Araceae and is native to southern Africa. With a rich history dating back to the Ancient Romans, these deciduous or semi-evergreen perennials have been used as a symbol of celebration. Zantedeschia was Named after Professor Giovanni Zantedeschia, an Italian botanist.
There are two main forms of Zantedeschia: hardy and tender. Hardy forms of the plant can be grown outdoors, enjoy moist soil and full sun or partially shaded conditions - these are known as Arum lilies. Tender forms of Zantedeschia prefer being grown in containers or pots and should be brought inside over the winter - these are known as Calla lilies.
With tuberous flora in all colours from whites, yellows and oranges to deep reds and purples, Zantedeschias are not to be overlooked in any garden, as long as they have sufficient sunlight to grow in.
Ready to learn more about growing Zantedeschia? Read on for all there is to know...
Key Information
Soil pH
Position
Hardiness
Where & when to plant Heliotropium
Position - Full sun
Soil - Any fertile, moist, well-draining soil
Flowering Period - Summer
Hardiness - Tender, rated H1C (minimum temperature range 5-10°C)
Heliotropium hails from warmer climes than ours and can only go outside in the UK once risk of frost has passed. This varies from region to region, though tends to be mid to late May. If your plants arrive before it is safe to go outdoors, keep them in a bright, frost-free environment until the time is right. A greenhouse, conservatory, coldframe, or sunny porch or windowsill are all ideal. Just make sure you don’t let them dry out! Small plug plants are best potted up into 9 centimetre pots if they’re going to spend time in a ‘holding zone’ such as this.
An important thing to note with tender plants like heliotropium is the need to gradually harden them off, rather than suddenly move them outside. This slow toughening up reduces the chances of them going into ‘shock’, which can severely check growth.
The easiest way to do this is by using a cold frame opened in gradual increments over the course of a week or two. Keep the lid closed at night until the last couple of days of the hardening off period.
If you don’t have a cold frame, a bit of horticultural fleece combined with a spot of ‘musical pots’ works just as well. A week or so before you anticipate planting your heliotropium out, wrap the plants in a couple of layers of fleece and place outside during the day (moving back into a warm, protected environment at night). Do this for a few days then reduce the fleece to one layer. After a few more days like this, remove the fleece completely. If it’s warm enough you can leave outside at night too, though reapply the fleece for this. At the end of the hardening off period, leave outside completely uncovered for a couple of days and nights before planting out as below. Though tedious, your efforts will be rewarded with thriving, robust plants ready and raring to go when planted outside.
When it comes to choosing a spot, heliotropium is ideal for a summer container display or as a cheerful gap filler in borders. Try to plant it where its fragrance will be best appreciated, such as near a doorway, seating area, or well-used path.
How to plant Heliotropium
· For planting in the garden, dig the soil area removing any large stones and weeds and breaking up any lumps. If your soil is poor, now is your chance to mix in some organic matter such as manure or garden compost. Rake level and firm with your heels. Rake level again.
· Water plants well and allow to drain before planting.
· Dig a hole twice the width of the root-ball.
· Place the plant in the hole, ensuring the top of the root ball sits level with the surface of the soil. Too low and the plant may rot, too high and the roots can dry out.
· Backfill with soil and firm in gently.
· Soak well with water.
· Mulch around the base with well-rotted organic matter.
- For planting in a container, first choose an appropriately sized pot, window box or hanging basket, ensuring good drainage.
- If you are using a large or heavy pot, it can be a good idea to fill and plant it in situ to save yourself the trouble of moving once full.
- Use any good quality compost. If not already present (check the labelling on the bag) mix through some slow-release fertiliser granules.
- Start by partially filling the pot with compost; enough so that when placed on it the upper surface of the root ball is about 3 centimetres lower than the top of the pot.
- Fill around the plant with compost, firming down with your fingers then adding a little more so it is held tight.
- Pick up the container and lightly tap on the potting bench or ground a few times to help further settle the compost around the plant.
- Soak well with water.
- A mulch with horticultural grit will look attractive and help to prevent a ‘cap’ or crust forming on the top of the compost (something container plants can suffer due to the artificial nature of their watering).
What to plant with Heliotropium
For a generous and vibrant summer container display, team heliotropium with other long-flowering patio favourites such as begonia, diascia, nemesia, calibrachoa, fuchsia, and petunia.
How to care for Heliotropium
Pruning and Deadheading
Pinch the growing tip from heliotropium in early spring to encourage a bushier habit. While this will delay flowering initially, it will give you larger and more prolific blooms for the rest of the season.
Deadhead during the flowering period to encourage further blooming.
Once your heliotropium has been knocked back by the first frosts, simply remove the entire plant to the compost heap. Alternatively, move it into a greenhouse or conservatory as temperatures begin to drop in early autumn. Plants have been known to carry on flowering well into winter when protected from the frost in this way.
Watering
In the open ground, heliotropium should be given a good soaking on planting, then a handful of times over the following few weeks. Once established it should be largely self-sufficient, needing watering only in prolonged periods of hot, dry weather.
Container-grown heliotropium will need watering regularly. A good rule of thumb to avoid overdoing it is to water only once the top few centimetres of compost have dried out. Be aware, however, that in the height of summer this can happen in as little as 24 hours – particularly with small or very full containers. If you’re going to overwinter your heliotropium in a greenhouse or conservatory, reduce watering during the colder months to just enough to prevent the compost drying out completely.
Feeding
On healthy, fertile soil there should be no need to provide heliotropium with additional feed.
In a container, try to use a good quality compost with slow-release granules mixed in. This generally provides enough nutrients for six weeks, after which a monthly dose of balanced liquid feed is recommended throughout the growing season.
Cold Protection
Heliotropium is unlikely to survive a UK winter outdoors and is usually confined to the compost heap once hit by the first frosts.
If you are going to try and keep it going for a second year by overwintering in a greenhouse or conservatory, ensure the temperature remains above 7°C.
Pests and Diseases
Heliotropium tends to be trouble free.
How to propagate Heliotropium
Heliotropium can be propagated by taking semi-ripe cuttings in summer. This is a good way to ensure replacement plants for the following year:
· Look for current year’s growth which is firm and woody at the base while still flexible at the tip. You’re aiming for a cutting of 10 centimetres or less (any longer and they are more likely to dry out and fail). For best results, choose stems where the leaf nodes are close together rather than far apart.
· Using a sharp knife or secateurs, sever the cutting from the plant and put in a plastic bag straight away to keep it from drying out.
· Fill a pot (or several, if you have a lot of cuttings) with a perlite-heavy compost mix (at least 50% perlite).
· Trim the end of the cutting to just below a node (point at which leaves grow).
· Remove lowest leaves, leaving 2-4 on the cutting.
· If the remaining leaves are large, cut them in half with a sharp knife to reduce water lost through transpiration.
· Insert the cuttings into the compost and water lightly. Several cuttings can be put in the same container if there is enough space to do this without them touching.
· Place in a propagating unit with gentle bottom heat if you have one, or covered with a plastic bag on a windowsill if not (out of direct sunlight). Note that bottom heat will significantly increase your success rate.
· Keep the cuttings misted and occasionally watered until they root. You will know this has happened when roots emerge out of the bottom of the container.
· Gently remove rooted cuttings and pot them into individual pots. Grow on in a warm, protected environment such as a heated conservatory or greenhouse, or a windowsill until they are large enough to be used as above.
* Many plants carry Plant Breeders Rights and cannot be propagated for commercial purposes.
Common Heliotropium Questions
What does the name heliotropium mean?
It is derived from the Greek words ‘helios’ (the sun), and ‘trepein’ (to turn), as the flowers are said to follow the sun throughout the day.
Is heliotropium poisonous?
All parts are toxic to humans and dogs if ingested and contact with the foliage may irritate skin and eyes.
Does heliotropium benefit wildlife?
Yes. Its flowers are attractive to several pollinators, particularly butterflies.
Can heliotropium be grown indoors?
Heliotropium needs plenty of light, so tends to be suitable as a greenhouse or conservatory plant rather than houseplant. Even with enough light it tends to become scruffy after a growing season or two; take cuttings in summer to ensure replacements.
