12 drought-tolerant plants that can take the heat.

12 drought-tolerant plants that can take the heat

Aeonium arboreum ?Zwartkop’. This cultivar of the more common green-leafed species has dark reddish-purple leaves that sometimes look black. It grows up to 6 feet tall and wide and is easy to propagate from cuttings.

Agave guiengola. Not easy to find, but it’s worth seeking out. Its beautiful wide, blue-gray leaves form a rosette to about 3 feet across.

Agave parryi var. huachucensis. This small agave forms clusters of 1-foot rosettes that look like large blue artichokes. It’s a spectacular plant, despite the vicious spines on the leaves.

Aloe arborescens (Candelabra aloe). This South African plant quickly forms a 12-foot-tall, 6-foot-wide, shrubby mound with each branch sending up tall scarlet spikes of cylindrical 11/2-inch flowers in late spring. Some books present this aloe as a houseplant, however its excellent salt tolerance makes it perfect for dry outdoor coastal gardens.

Aloe brevifolia. A fairly small-scale aloe, this plant forms tight clumps of many 3- to 7-inch greyish green rosettes. It grows less than a foot tall and can be divided and replanted to form an attractive ground cover. In some areas of the country, it’s a fall bloomer, but Anderson says his blooms in the summer.

Aloe marlothii. This aloe has extremely large, thorny leaves to 3 feet long. When it blooms each summer, its candelabra of yellow or orange flowers is spectacular. This tree slowly grows up to 5 feet across and 12 feet high.

Aloe striata (Coral aloe). This aloe is very showy, fairly easy to find, and easy to grow. Its stemless rosettes of spineless gray-green leaves produce pendulous coral-red flowers on multi-branched spikes. It blooms in summer for more than a month.

Crassula perfoliata var minor (Propeller plant). Pale grey-green leaves are shaped like curved propeller blades standing on edge. Its brilliant red, fragrant flowers resemble small broccoli heads and appear in summer. Growing 3 feet tall, this plant is also great in pots.

Echinocactus grusonii (Golden barrel cactus). This slow-growing cylindrical cactus, also called mother-in-law’s cushion, eventually reaches 3 feet in diameter. Its distinctive golden spines almost glow when they’re backlit by the sun.

Euphorbia milii (Crown of thorns). This slow-growing shrubby euphorbia with ferocious-looking thorns amid bright green leaves comes from Madagascar. Very showy bracts that look like flowers appear year-round in red, pink, yellow, or white. It’s an excellent pot specimen.

Euphorbia rigida (Gopher plant). This plant has showy clusters of chartreuse bracts in late winter and early spring, so it makes an excellent companion to aloes with their bright orange and red blooms. Growing up to 2 feet tall and 2 feet across, it reseeds freely but is also easy to weed out.

Hunnemannia fumariifolia (Mexican tulip poppy). This 3-foot plant boasts brilliant, golden yellow flowers over finely divided blue-green leaves. It’s a short-lived perennial that reseeds freely when growing well.

horsetail

If you’re looking for a water plant that’s unique and unusual, and you don’t mind a bit of a challenge, then take a look at horsetail (Equisetum hyemale, also known as scouring rush). With its stiff, hollow, bamboo-like green stalks, E. hyemale adds an exotic note to any water or bog garden. This evergreen perennial does not flower, but has small, scalelike leaves tightly bound into grey sheath at intervals around the stalks. Horsetail is extremely invasive and difficult to eradicate once it’s established, but if you follow a few precautions you can enjoy its handsome, quirky good looks without ruining your reputation.

Common name: horsetail, scouring rush, rough horsetail

Botanical name: Equisetum hyemale

Plant type: Aquatic perennial
Zones: 3 to 11
Height: 2 to 4 feet
Family: Equisetaceae

Growing conditions

• Sun: Full sun to part shade
• Soil: Tolerates many soil types and up to 4 inches of standing water
• Moisture: Medium to wet

Care

• Mulch: None needed.
• Pruning: None needed.
• Fertiliser: None needed.

Propagation

• By division.

Pests and diseases

• No major insect or disease problems.

Garden notes

• Always grow horsetail in a container, whether in soil or water. If it’s in your water garden, it should be in a pot sunk into the water to contain the rhizomes.
• E. hyemale looks great in Japanese gardens, bog gardens, and water gardens, and is striking as a vertical accent in large patio containers.
• All parts of horsetail are poisonous.
• If you have a wet or boggy area that you want covered quickly, horsetail could be your plant. But be sure that the area is bounded by some type of barrier (like sidewalks or driveways) and is not adjacent to any waterway or natural area. Also be sure that you do want horsetail to inhabit that space permanently.

All in the family

• The genus Equisetum is found on every continent, except Antarctica.
• Equisetum is the only surviving genus of a class of primitive plants that evolved more than 350 million years ago. It reproduces by spores rather than seeds.
• The common name “scouring rush” comes from the fact that the stems have a high silica content and can be used to scrub and polish metal or wood. Equisetum is not a rush, however.

Horseradish

Gardeners and chefs looking for a unique addition to their herb gardens should consider horseradish (Armoracia rusticana). The spicy root of this European native is the part we grind up and use on roast beef sandwiches, but the aboveground part has appeal, too. Horseradish’s large, broad green leaves look almost tropical. Think rhubarb leaves but with an oval shape. The plant is extremely tough in the face of heat, cold, drought, and neglect. Horseradish will happily settle in any sunny corner of your garden, but beware: You’ll have a hard time evicting it if you ever change your mind. Each tiny piece of horseradish root that stays in the ground can sprout a whole new plant.

Common name: Horseradish

Botanical name: Armoracia rusticana
Plant type: Perennial
Zones: 3 to 10
Height: 2 to 3 feet
Family: Brassicaceae

Growing conditions

• Sun: Full sun
• Soil: Average
• Moisture: Medium

Care

• Mulch: Mulch to preserve moisture in the soil.
• Pruning: None needed
• Fertiliser: None needed

Propagation

• By division

Pests and diseases

• Vulnerable to downy mildew, powdery mildew, root rot, and leaf spots.

Garden notes

• Unless you’re planning to start a small farm, you don’t need more than one or two horseradish plants. Each fall or spring, dig up the entire root system. Harvest the biggest roots for kitchen use and replant a few of the small roots—these will become your next harvest.
• Horseradish isn’t a rampant coloniser, but it will spread over time. It is also incredibly persistent. New plants will sprout from tiny pieces of overlooked root. You’ll have less trouble if you dedicate one spot to this vigorous herb and don’t try to move it.
• Be sure to give horseradish plenty of room. This is not a small plant, and its big broad leaves will shade out smaller plants if they’re too close.
• The big leaves have a pleasant, faintly spicy scent.

All in the family

• Cabbage, broccoli, cauliflower, collards, and Brussel sprouts are also in the Brassicaceae family.
• Most of the commercial horseradish grown in the United States comes from southwestern Illinois. Collinsville, a town in this region, holds the International Horseradish Festival every year.

Horse chestnuts

Horse chestnuts are magnificent large trees with attractively divided foliage. This hand-shaped foliage often turns tones of yellow in autumn, though the autumn foliage is often not as attractive as it is in some other Aesculus species. In spring, horse chestnuts bloom with clusters of white flowers, often shaded pink. When pollinated, these flowers give way to large, shiny seeds held in prickly coverings. These seeds look something like large chestnuts, but are quite poisonous.

Plant facts

Common name: Horse chestnut
Botanical name: Aesculus hippocastanum
Zones: 3 to 8
Size: To 80 feet tall and 70 feet wide
From: Areas of Europe
Family: Hippocastanaceae(horsechestnut family)

Growing conditions

Sun: Full sun
Soil: Moist, but well-drained soil rich with organic matter is best. The trees tolerate a range of soil types from sand to a bit of clay. Avoid heavily compacted soils and heavy clays.
Moisture: Water during times of drought to keep the trees looking healthy. The leaves turn brown if not given a bit of additional moisture during times of drought.

Care

Mulch: A 2- to 3-inch-deep layer of mulch over the soil around the tree will help conserve moisture, reduce competition from weeds or turf grass, and protect the tree’s bark from damage from lawn mowers or string trimmers. Leave a 4-inch gap between the mulch and the tree’s trunk.
Pruning: Pruning is generally unnecessary. The best time for pruning, however, is early winter.
Fertiliser: In most soils, fertilising is unnecessary. Use a balanced fertiliser in spring if necessary.

Propagation

Seed: Gather seeds once they fall from the ground. Remove the spiny shells and sow the seeds immediately.
Cuttings: Take hardwood cuttings in early winter.

Pests

Anthracnose: If the leaves look scorched and spotted, the cause may be anthracnose. The spots may be grey, tan, or dark brown; dry or slimy. To deter the disease, prune off any infected branches, dipping your pruning tool in a bleach or alcohol solution between cuts. Prune some of the inner branches to keep good airflow in the tree’s centre.

Canker: Forms dark water-soaked cankers on the bark and branches of the tree. The cankers can spread, becoming larger. To deter the disease, prune off any infected branches, dipping your pruning tool in a bleach or alcohol solution between cuts.
Japanese Beetles: These beetles are darkly coloured and chew holes in plant leaves. Handpick the beetles from the plants and drop the insects in a bucket of soapy water. You might also try spraying with a pesticide made from neem, a tropical tree. Apply a bacterium to your soil called Milky Spore. This bacterium attacks the grubs from the beetles, but can take a couple of years to control the beetles.

Leaf spot: This disease appears summer or autumn in the form of yellowish or darker-coloured spots, often made of concentric rings. To deter this disease, prune some of the inner branches to keep good airflow in the tree’s centre.
Powdery mildew: Powdery mildew appears in mid- to late summer and looks like affected leaves have a greyish powdery covering on them. The leaves then drop off. To deter the disease, prune the plant to keep good air flow and avoid wetting the foliage in afternoons and evenings.

Rust: Usually looks like leaf spotting that’s followed by small masses of rusty-coloured powder on the leaves. Infected leaves die by the end of the season. To deter it, avoid getting the foliage wet; make sure there’s good air circulation around plants.
Scale: Scale insects crawl up plant stems, find a permanent home, and sort of plant themselves on the plant. They appear as small, raised spots and are easy to overlook. To deter scales, try encouraging beneficial insects; apply insecticidal soap or horticultural oil.
Notes

The beautiful fruits, that look similar to polished wood, are often used in crafts. These fruits are poisonous—keep them away from children or pets.

Selections

Aesculus hippocastanum ‘Aureovariegata’: Slow-growing cultivar with golden leaves. Colours better with some afternoon shade.
Aesculus hippocastanum ‘Baumannii’: This selection is smaller than the species-only growing about 50 feet tall, has showier flowers, and is sterile, so it doesn’t produce fruits.