Cacti and outdoor succulents: Planting, growing, and maintaining

Botany

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Cacti and fleshy plants naturally grow in particularly arid environments, and have had to evolve to cope with the blazing sun and long periods of drought. They are xerophytic plants (= adapted to drought). These harsh conditions have led them to take on very particular forms, giving them a silhouette quite different from plants growing in cooler, shaded environments.

However, it is important to distinguish between these plants: all cacti are succulent plants (as their tissues have thickened to store water), but not all succulent plants are cacti! Cacti constitute a distinct botanical family, the Cactaceae, while the broader term “succulent plant” (or “fleshy plant”) encompasses plants from various botanical families (Crassulaceae, Asparagaceae, etc.). These plants simply share the characteristic of having fleshy tissues (usually stems or leaves) that allow them to store water and mineral elements. The term “succulent” means that they store water and mineral elements in the form of juice. It is more accurate than “fleshy plants,” which implies that they store fat, which is incorrect.

Opuntia inermis: botanical illustration

To withstand drought, cacti and fleshy plants have also adapted their metabolism: it is of the CAM type (Crassulacean Acid Metabolism). This means that these plants open their stomata (small holes in the epidermis of the leaves) at night to carry out gas exchanges (oxygen, carbon dioxide, water…), and close them during the day, which limits water loss. If they opened their stomata during the day like other plants, all the water in their tissues would risk evaporating, and they would dry out very quickly!

Most hardy cacti and succulent plants are species that naturally grow in mountainous regions, at altitude. The Echinopsis subdenudata, for example, originates from the high mountains of Paraguay and Argentina. As for the Cylindropuntia imbricata, it is found in the wild in northern Mexico and the southwestern United States, between 1,200 and 2,300 metres in altitude. The Agave montana, on the other hand, originates from the mountains of northeastern Mexico, between 3,000 and 3,500 metres in altitude. Thus, these succulents and cacti are better adapted to low temperatures than other species that grow in the plains.

Cacti take on quite diverse forms: they can be rounded-globose, like the Echinopsis subdenudata, or form upright stems, as seen in candle cacti. The Cylindropuntia imbricata has a surprising silhouette for a cactus: it forms a true ramified bush! The Opuntia, on the other hand, form flattened stems (called cladodes, or pads), with segments that follow one another. Some opuntias are creeping.

By replacing their leaves with thorns, cacti have gone further than other succulents in adapting to water scarcity. Indeed, leaves are a site of gas exchange with the atmosphere, and thus lead to water loss. Thorns, in addition to protecting cacti from herbivores, can also shelter the plant from the sun (when the density of thorns is high) and capture dew drops. However, there are primitive cacti that still have leaves: the Pereskia.

Some hardy cacti that can be planted in the ground: Cylindropuntia imbricata (photo: Skarz), Opuntia engelmannii ‘Rastrera’, Echinocereus reichenbachii baileyi (photo: Peter A. Mansfeld)

Regarding other succulent plants, most of the time the leaves are still present, but they are fleshy: they have thickened to store water and mineral elements. Additionally, the epidermis is generally covered with a thick, sometimes waxy cuticle, which limits water loss.

Many succulent plants form rosettes with overlapping, fleshy leaves: this is the case, for example, with Agaves, Aloes, and Sempervivum! The Aloe polyphylla is distinguished by its very geometric shape, with leaves inserted in several successive spirals. We can also mention the sedums, which generally have a creeping habit and small, rounded, fleshy leaves. Sedums and Sempervivum are remarkable for the diversity they offer in terms of foliage colours, allowing for the creation of original and colourful flowerbeds.

Hardy succulents: Agave havardiana, Sempervivum arachnoideum ‘Rubrum’ and Aloe aristata

Cacti generally produce very colourful and bright flowers! The Opuntia phaeacantha Mojavensis, for example, bears very beautiful cup-shaped flowers, yellow tinged with reddish-orange. We also appreciate the pink flowers of the Cylindropuntia imbricata. The Echinopsis subdenudata, on the other hand, bears splendid large white flowers.

Among other succulent plants, Aloes offer beautiful colourful flowers, often yellow, orange, or red. We appreciate their warm hues and very exotic style! The Aloe striatula is valued for its very generous flowering, in spikes reminiscent of kniphofia flowers! As for agaves, their flowering is truly impressive: they deploy gigantic flower spikes, very tall. The rosette, however, dies after flowering, but generally, it has had time to produce other rosettes that will then take over.

After flowering, opuntias have the advantage of producing edible fruits: the best are the prickly pears of the Opuntia ficus-indica, but the fruits of most other species can also be consumed. However, care must be taken to remove the prickles from the epidermis before consumption.

The colourful flowering of Opuntia phaeacantha Mojavensis, Aloe aristata, and Echinocereus reichenbachii baileyi

The main varieties of cacti and succulents for the garden

The most popular varieties

Our favourite varieties

Other varieties to discover

Cylindropuntia imbricata

Cylindropuntia imbricata is an unusual cactus, with fine, elongated stems bearing irregular midribs and numerous thorns. It branches out and over time takes on a true shrub-like silhouette! It also produces beautiful purplish-pink flowers. It can withstand temperatures between –15 and –20 °C.

• Flowering time June, July
• Height at maturity 2,50 m

See the full description

Agave havardiana

This is a stunning agave, with grey-blue leaves. The leaves are numerous and arranged regularly, giving it a relatively rounded and harmonious silhouette. Very hardy, it can tolerate temperatures down to –20 °C.

• Flowering time August, September
• Height at maturity 50 cm

See the full description

Opuntia compressa Millevaches - Prickly Pear

This is a small variety of prickly pear with a prostrate and spreading habit, not exceeding 30 cm in height. In spring, it produces cup-shaped yellow flowers, followed by dark red edible fruits. It can withstand temperatures down to –15 °C, or even –20 °C.

• Flowering time June, July
• Height at maturity 30 cm

See the full description

Echinopsis subdenudata

Less hardy than other varieties, Echinopsis subdenudata can still tolerate temperatures between –5 and –10 °C in well-drained soil. It forms a rounded, globular stem marked with regularly punctate white areoles. It also offers a stunning pure white flowering, with large trumpet-shaped flowers.

• Flowering time June
• Height at maturity 20 cm

See the full description

Agave montana

Mountain agave is a robust and completely hardy plant, tolerating temperatures down to –20 °C. It forms rosettes of thick leaves edged with thorns. The leaves also end in a point at their tips.

• Flowering time August, September
• Height at maturity 1 m

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Aloe polyphylla

This remarkable aloe, native to Lesotho, features imbricate leaves in successive spirals, with perfect geometry. It is appreciated for its exceptional graphic quality! It can withstand temperatures between –8 and –10 °C in dry soil.

• Flowering time July, August
• Height at maturity 30 cm

See the full description

Opuntia engelmannii var. indheimeri - Prickly Pear

This cactus forms flattened stems (prickly pears) that are grey-green, dotted with thorns. It also produces very beautiful cup-shaped flowers, orange-red in colour, followed by edible fruits, similar to those of the prickly pear. At maturity, it can reach up to two metres in height. It can withstand –15 °C.

• Flowering time July to October
• Height at maturity 2 m

See the full description

Sempervivum arachnoideum

This is a lovely houseleek that forms small rosettes covered in white bristles, giving the impression of a spider's web. Each rosette does not exceed 3 cm in diameter. It also produces beautiful star-shaped pink flowers in summer. It is hardy down to –15 °C.

• Flowering time July, August
• Height at maturity 8 cm

See the full description

Aloe aristata

Aloe aristata is a dwarf aloe, not exceeding 30 cm in any direction. It is distinguished by its dark green foliage speckled with white, and it produces coral-pink flower spikes in summer. It can tolerate temperatures down to –10 °C.

• Flowering time July, August
• Height at maturity 30 cm

See the full description

Planting

Where to Plant?

Cacti and succulents require warmth and excellent light: it is therefore important to choose a well-sunny location, for example, by placing them against a south-facing wall. They should also benefit from well-draining, filtering soil. Avoid heavy, clayey soils where moisture tends to stagnate. If possible, place them in an elevated spot, such as on a mound, slope, or at the top of a hill, as the soil will dry out more quickly. You can also create a rock garden to accommodate them, which will also highlight them beautifully!

You can also place your cacti or succulents under an eave, as this will protect them from rain and reduce the risk of rot.

Choose a well-sunny location for your cacti and succulents, such as against a south-facing wall

When to Plant?

Plant your cacti and succulents in spring, as soon as there is no longer a risk of frost. This will allow them time to settle in before facing winter.

How to Plant?

1. Dig a planting hole about three times the size of the root ball.
2. Add a mixture of one-third potting soil, one-third garden soil, and one-third drainage materials (gravel, coarse sand…)
3. Remove your cactus or succulent from its pot and plant it, ensuring that the collar is not buried. You can use newspaper or thick gloves to avoid injury from the thorns.
4. Wait at least 15 days before starting to water. Otherwise, the roots that may have been damaged during planting could rot.
5. You can apply a mineral mulch (gravel, pumice, slate…)

For more tips and information, check out our guides How to Plant Cacti in the Garden?, How to Plant Succulents in the Ground in the Garden?, and How to Plant Succulent Plants in Pots?

Don’t hesitate to create an elevated rock garden to host your cacti and succulents

Entretien

Cacti and succulents planted in the ground generally do not need watering. However, you can carry out occasional waterings in the year of planting to help them settle in. Afterwards, they will easily manage without watering.

However, if you have placed your cacti in a sheltered spot from rain, such as under an eaves, remember to water them occasionally during the growing season, from spring to autumn. Preferably use rainwater.

For more information, you can consult our sheets How to Water a Cactus? and Watering Cacti: Mistakes to Avoid.

It is advisable to place a mineral mulch (gravel, pumice, slate…) around your cacti and succulents, a few centimetres thick. In addition to its aesthetic appeal, this limits the growth of weeds (and it is particularly tricky to weed and intervene around cacti due to their thorns… It is better to prevent weeds from growing than to have to regularly pull them out). Furthermore, mineral mulch has the advantage of storing heat during the day and releasing it at night, providing protection against the cold.

Although some cacti and succulents are relatively hardy, it is best to protect them in winter, especially from moisture. The drier a cactus is, the better it will withstand the cold. Therefore, you should reduce watering as winter approaches to encourage them to dehydrate and limit the risk of rot. Similarly, we recommend installing a removable roof over your cacti for winter (for example, using a sheet or plastic tarp, preferably transparent to allow light through).

You can also cover your cacti and succulents with fleece to protect them from the cold, but remember to remove it occasionally when temperatures are milder to allow for ventilation and prevent rot.

For more tips and information, discover our sheet “Preparing Your Succulents for Winter: Our Tips and Tricks” and “How to Protect Cacti in Winter?

Multiplication

We recommend propagation by cuttings for cacti, while clump division is more suitable for succulents (agaves, sempervivum, etc.).

Propagation by Cuttings

Propagation by cuttings has the advantage of being a simpler and quicker technique than sowing. It works very well, for example, with the pads of Opuntia. Propagation by cuttings is also a good solution for saving cacti that have been damaged, rotted, or affected by a fungal disease.

1. Cut the part of the cactus you wish to propagate, using a sharp, disinfected knife.
2. We recommend sprinkling charcoal powder on the wound to prevent the development of fungal diseases.
3. Then allow the cutting to dry by placing it in a cool, dry place, out of direct sunlight. This period can last from a week to several months, depending on the species you are propagating and the size of the cutting. You should see a callus forming on the cut surface.
4. As soon as the cutting has healed, plant it in a pot filled with well-draining substrate and place the pot in a bright location, but out of direct sunlight.

Clump Division

Some succulents, including agaves, aloes, and houseleeks, produce offsets over time next to the original rosette. It is quite possible to remove them to propagate the plant.

1. Gently remove the soil around the offset you wish to take.
2. Separate it from the original plant by detaching it at the base. Use a sharp, disinfected knife if necessary.
3. Allow it to dry for a few days.
4. You can then plant it in a pot or in the ground at another location, in well-draining substrate.
5. Wait at least two weeks before watering.

→ Discover our tutorial “Propagating Cacti and Succulents”

Association

Enjoy cacti and succulents to create a stunning dry and exotic garden! You can, for example, combine them with palms, cordylines, Phormium tenax, or euphorbias. Also discover the stunning Dasylirion wheeleri, which resembles yuccas but can withstand temperatures as low as -20 °C! For flowering, we recommend favouring warm shades (yellow, orange, red…) that will enhance the exotic atmosphere: you can plant alongside kniphofias, crocosmias, hedychiums, agastaches, Armeria maritima… The kniphofias, in particular, will pair beautifully with the yellow inflorescences of Aloe striatula! Also enjoy the graphic flowering of agapanthuses and eucomises.

For a garden with a very exotic style: Chamaerops humilis, Opuntia engelmannii var. linguiformis (photo Krzysztof Ziarnek, Kenraiz), Kniphofia ‘Fiery Fred’, Crocosmia and Aloe polyphylla (photo Stan Shebs)

For more inspiration on plants to include in this type of garden, discover our advice sheet: 10 hardy plants for an exotic dry garden

You can also create a stunning Mediterranean atmosphere by combining your cacti and succulents with lavenders, sages, helichrysums, phlomis, helianthemums or cistus. Plant these in a mineral-dominant garden or in a raised rockery. We recommend playing with shades by incorporating some plants with blue or silver foliage, such as Stachys lanata, Senecio cineraria, santolina or Eryngium. Also discover the Euphorbia myrsinites: a lovely small euphorbia with sprawling stems and blue leaves. Finally, you can integrate some grasses like Stipa tenuifolia or Festuca glauca into the bed, which will bring contrast and lightness alongside the succulent plants.

For a dry rockery, in a Mediterranean style, with some plants with silver foliage: Agave americana Variegata, Cistus purpureus, Euphorbia myrsinites, Echinocereus coccineus subsp. coccineus (photo Andrey Zharkikh) and Lychnis coronaria