Hollyhocks are old-fashioned plants often used in heirloom and cottage gardens. The plants grow from a clump of hairy, scallop-shaped light green leaves that are sometimes lobed. From this clump come spectacular spikes of single or double, hibiscus-like flowers. These flowers range in color from nearly black to white.
- Common name: Hollyhock
- Botanical name: Alcea spp.
- Zones: 3 to 9
- Size: To 8 feet tall
- From: Areas of Asia
- Family: Malvaceae (mallow family)
- Sun: Full sun to partial shade.
- Soil: Moist, but well-drained soil is best.
- Moisture: Water during times of drought. The leaves may become brown if the plant stays too dry.
- Mulch: Lay a 2- to 3-inch-deep layer of mulch over the soil to help conserve moisture and reduce weeds.
- Pruning: Cut the plants to the ground after they freeze in autumn or before growth in spring.
- Fertilizer: In most soils, fertilizer is unnecessary.
- Staking: To stake the tall plants, sink a tall stick or stake into the ground a short distance from the plant (so to not harm the root system). Tie the plant stem to the support. It is best to use a figure-eight pattern to tie the plant-with the stem in one loop and the stake in the other. This helps prevent against excessive rubbing, which can cause disease problems.
- Seed: Hollyhocks self-seed readily. Collect and transplant young seedlings or collect and start seeds in spring. Note: Self-sown and collected seeds rarely come true from named selections such as ‘Crème de Cassis'.
- Aphids: These small insects often appear in large numbers on new growth. Spray them off daily with a stream of water; they will not attack a plant after being knocked off. Use an insecticidal soap or neem-oil-based spray if infestations are severe.
- Fungal diseases: Deter them by pruning the plants to encourage good air flow, avoiding wetting the foliage, and mulching the soil around the plants.
- Leaf spot: In summer or autumn, the leaves become spotted yellowish or with darker colored spots. Each spot often has concentric rings around it, forming something of a bull's-eye pattern.
- Powdery mildew: This disease tends to appear in mid- to late summer and looks like someone dusted affected leaves with a grayish powdery covering. The leaves then drop off.
- Rust: Usually looks like leaf spotting that's followed by small masses of rusty-colored powder on the leaves. Infected leaves die by the end of the season.
- Japanese beetles: These beetles are darkly colored and chew holes in plant leaves. Hand-pick 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. Or, 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 achieve good control.
- Hollyhocks are short-lived perennials that may act as biennials in some gardens.
- Alcea ficifolia: This species has large lobed leaves and spikes of pink flowers. To 8 feet tall. Zones 3 to 9.
- Alcea ficifolia ‘Happy Lights Mix': This mixture has large single flowers in a range of colors. Plants resist rust diseases better than most other hollyhocks. To 8 feet tall. Zones 3 to 9.
- Alcea rosea ‘Chater's Double': Blooms in a mix of colors with double flowers (having twice the normal number of petals). Grows to 8 feet tall.
- Alcea rosea ‘Crème de Cassis': Single, semidouble, or double blooms are blackberry purple in color with a white edge. Grows to 6 feet tall.
- Alcea rosea ‘Nigra': Blooms are a dark purple-red that look nearly black. Grows to 6 feet tall.
- Alcea rosea ‘Peaches ‘n Dreams': Double blooms are in shades of peachy-pink. Grows to 6 feet tall.