The Dune Aloe is perfect for seaside plantings

Aloe thraskii Picture courtesy Kumbula NurseryAloe thraskii Picture courtesy Kumbula NurseryThe dune aloe is easy to cultivate under a wide variety of climatic conditions, provided it is planted in full sun and in well-drained soil. It is also a good choice for inland gardens with mild winters, and not overly damp summers. Read all about this beautiful and resilient aloe below.

The Dune, or Strand Aloe is also commonly called Strandaalwyn, Umhlaba, and Ikhala, and as its name implies, it is most useful for seaside plantings. This magnificent aloe has been given tree status in South Africa, and its national tree number is 30.7. Generally it grows about 2 meters tall with a single stem, but with maturity it can reach up to 4 meters with a width of up to two meters, producing 3 or 4 branched flowering stems with 15 to 25 erect, cylindrical flower heads. The large inflorescences of the dune aloe appear in June and July, and are a striking yellow with orange anthers and lovely green tinged petal tips, giving the flowers a bicoloured look.

In gardens and parks it makes a wonderful feature plant that is tall and robust, with enormous olive green leaves, whose margins are armed with reddish-brown teeth, and which are recurved back to the trunk, sometimes even touching the shaggy remains of old leaves cloaking the trunk. Aloe thraskii is closely related to Aloe excelsa and Aloe rupestris, and can be distinguished from them by its severely recurved leaves.

Click here to see Google images of Aloe thraskii

It is so amazing how plants have adapted to their environment, and the aloe is no exception. The beautiful rosette shape of the leaves around the stems forms a natural funnel that channels water down to the roots, where it is immediately and very efficiently absorbed by the dense and fibrous, superficial root system. The root system also continuously renews itself, and for every new leaf a corresponding root develops, but when that leaf dies the root still remains as an anchor.

The dune aloe has a limited distribution along the KwaZulu-Natal and Eastern Cape coast, where it occurs from Mtunzini to Port St Johns, and because it occurs nowhere else in the world it is referred to as being “endemic” to these regions. It is extensively cultivated in gardens and parks worldwide, where the climate is suitable for its growth, and is a sought-after collector’s item.  

In South Africa it occurs in dense coastal bush, on dunes from the beach margin to a few hundred metres inland, but no further than the top of the first sea-facing slope. It grows in large groups, and major habitats include: Maputaland Coastal Belt, Subtropical Dune Thicket, KwaZulu-Natal Coastal Belt Grassland, Pondoland-Ugu Sandstone Coastal Sourveld, and Subtropical Seashore Vegetation.

Sadly, in 2019 this species was assessed as Near Threatened in its natural habitat, largely due to habitat loss and degradation caused by coastal development in KwaZulu-Natal, where the transformation of the coast has caused many dune systems to become very fragile, and subsequently they are more easily damaged by severe storms. Additional threats include removal of plants for horticultural purposes. In spite of extensive habitat loss, recent observations indicate that Aloe thraskii is still common along the KwaZulu-Natal south coast, but populations are fragmented, and subpopulations tend to be small, usually consisting of less than 50 mature individuals. There are fewer records from the Eastern Cape coast south of the Umtamvuna River,  as this area is much less accessible than further north.

In South Africa, aloes, with only a very few exceptions, are protected plants and may not be collected from the veld without the necessary permit, and the permission of the landowner.

Aloe thraskii UCLA Botanical Garden Los Angeles Picture courtesy Vahe MartirosyanAloe thraskii UCLA Botanical Garden Los Angeles Picture courtesy Vahe MartirosyanIn the Garden:

As the roots are very tenacious, helping to stabilise the soil in seaside gardens, the dune aloe is wonderful to plant on a hillside or slope, along with other succulent sand dune specialists like the Natal Sourfig (Carpobrotus dimidiatus). It can serve the same purpose in inland gardens.

The dune aloe looks great with so many plants like cycads, most succulent plants, indigenous groundcovers and shrubs such as agapanthus, wild iris (Dietes), and plectranthus, wild dagga (Leonotis leonurus), Strelitzia reginae, and the winter flowering red hot poker (Kniphofia sp.)

This wonderful architectural plant will add accent and interest to your garden and will attract nectar and insect eating birds. Plant it as a single specimen, or in large groups for a magnificent effect. The dune aloe also grows beautifully in large containers.

Cultivation/Propagation:

The dune aloe is easy to cultivate under a wide variety of climatic conditions, provided it is planted in full sun and in well-drained soil. Although it originates in the mild, subtropical eastern seaboard of South Africa, because the dune aloe tolerates wetter conditions than most aloes, as long as the soil is free draining it will grow well in any garden near the sea, including the winter rainfall regions of the country.

The dune aloe is also a good choice for inland gardens with mild winters and not overly damp summers. It will tolerate only light frost, so if you wish to try growing this aloe in colder regions, it will need protection. Luckily it grows well in larger pots which can be placed in a warm and protected position. In colder regions keep the plants on the dry side during the coldest months.

If it is given adequate water during warm weather the dune aloe will grow very quickly, developing a "trunk" early in life, but if your soil does not drain freely be careful not to overwater. If you are planting on slopes, or in sandy or stony soil, compost or mature kraal manure can be added to improve aeration and drainage, and the plants can be fed every 3 months or so with an organic fertiliser. However, because the dune aloe thrives in poor soils it does not need much feeding and if over fertilised it will develop excess vegetation, which is easily attacked by fungal diseases.

This aloe grows well in larger pots with free draining soil which contains good amounts of compost, combined with generous quantities of washed river sand (available from garden centres). A specialist succulent potting mixture would be ideal. To test how well your potting soil drains, water the pot before planting, and if you have the right mix, the water won’t collect on the top of the soil before draining down. Potted specimens can be fed moderately using a fertiliser specifically formulated for cactus and succulents (high potash fertiliser with a dilute low nitrogen), diluted to ½ the strength recommended on the label. Be careful of overwatering specimens growing in very large pots, but those growing in smaller pots will require more frequent watering than those growing in the ground, so check your pots frequently and water as required.

Maintenance is minimal and basically involves the removal of old flower stalks. In nature the leaves hang onto the stems like a skirt but you can remove them if you wish.

Aloe thraskii Aloe thraskii Aloe thraskii does not produce suckers until it is mature, but can be propagated by seed sown in a well-drained medium in shallow trays. Sow and cover lightly with sand or the seed will blow away, and water before placing in a warm, bright spot until germination. Once the seeds begin to germinate, keep the soil moist but watch out for overwatering as the seedlings could rot. After several months, or when the seedlings are about 3 to 4 cm high, transplant them into small pots using a sandy loam medium and feed with an organic fertiliser at least every 3 months to ensure healthy growth.

Aloes, including the dune aloe are also easily propagated by planting the tops of old plants. However, as the dune aloe only produces a single stem until mature, this method is not recommended unless the plant is very old and you wish to propagate it. It is said that the plant can also be grown from a single leaf. No matter the method you use, place your cutting or leaf on a piece of newspaper in the shade for about two weeks. This allows the cut section where it has been wounded to dry out, and helps to prevent soil borne pathogens like fungi, bacteria, and nematodes from entering the plant. Once dry, simply push the cutting into some washed river sand (available from garden centres) and water, keeping the soil only slightly moist until roots develop. If you wish to speed up the rooting process, you can dip the cutting into a rooting hormone before planting. Treat young aloes regularly with a copper based fungicide.

Problems, Pests & Diseases:

Nearly all problems occur as a result of overwatering and poor ventilation, especially when weather conditions are dull and cool, or very humid. If the leaves take on a coppery sheen, this is usually a sign associated with stress.

Insects such as scale, aphids, and snout beetles sometimes attack aloes, and they occasionally fall prey to fungal diseases, such as rust, especially if they are growing close together. Use a systemic insecticide to stop sucking insects in their tracks, and a fungicide with a copper base can help to control diseases such as rust, which are a nuisance in humid climates. When spraying, ensure that the poison runs into the growth points between the leaves as well.

Warning:

Aloe thraskii is not listed as toxic.