Clematis 'Asao' 2 pruning group

Clematis ‘Asao’

Categories: pink clematis, 2 pruning group, large-flowered

Clematis variety ‘Asao’ was obtained in 1977 by Japanese breeder Kasushige Ozawa as a result of crossing the famous varieties ‘Ernest Markham’ and ‘Star of India’. In the early 80’s this clematis was introduced to Great Britain, from where it probably came to the USA.

Table of Contents


Group Early-flowering large-flowered clematis
Pruning Group 2 (light pruning)
Height 6.6…9.8 feet (2…3 meters)
Flowers Large, 4.7…7.9 inches (12…20 cm) in diameter, simple or semi-double
Flower Color Pink
Blooming In May-June and again in August-September
USDA Zones 4-9


Clematis ‘Asao’ forms shoots up to 3 meters long. It blooms twice: the first time on the shoots of the last year from May to June, the second time on the shoots of the current year from August to September.

Flowers are large, 12 to 20 cm across, simple or semi-marginal. Sepals are 5 (6-8), lanceolate or elliptic in shape with pointed tips. Coloration is pink, from deep pink at the edge to almost white in the middle. The stamens are yellow or greenish-yellow.


Clematis ‘Asao’ planting and care

Clematis ‘Asao’ is quite popular in the USA, UK and many European countries. This is due to its relatively high winter hardiness

‘Asao’ is a fairly typical variety of clematis from pruning group 2. In general, its care is similar to that of any other early flowering large-flowered clematis.

Clematis planting time

Clematis is best planted in late summer when the soil temperature drops to about 68 degrees Fahrenheit, or in the spring when the soil has warmed to that temperature. Many people believe that August planting is preferable because the clematis will then actively build up its root system and be better prepared for its first winter. However, some flower growers have the opposite opinion.

Unlucky time for planting – late spring and summer. This is the time when clematis is actively growing. When planting at this time, there is a risk of damaging the roots or the above-ground part of the plant: therefore, if you purchased ‘Asao’ in summer, it is recommended to either keep it in the pot until the end of August or carefully transfer it to the open ground with a clump of soil.

Selection of planting location

In northern states with cold winters, it is recommended to plant ‘Asao’ against south, east or west walls, in well-lit and wind-protected areas. In states where summers are very hot and winters are cold, choose a spot near a north wall to protect the clematis from midday rays that can damage its flowers and overheat the root system. In hot states such as Texas and Florida, the greatest danger to clematis is heat, not cold.

Soil for planting clematis should be loose, fertile and slightly alkaline, neutral or slightly acidic. In such soil clematis develop best Clematis feel bad in heavy loamy soils, where their roots do not get enough air and can be affected by soil fungi. A slightly alkaline environment makes it more difficult for pathogenic soil fungi that cause clematis wilt to develop: therefore, if wilt frequently affects clematis in your region, a slightly alkaline soil reaction should be maintained.

Preparing the planting hole

Preparing planting hole for clematis Asao

For the first 2-3 years, the clematis roots will develop mainly inside the planting hole, so it should be large enough and well prepared. It is recommended to dig a hole at least 1.5 feet in diameter and also about 1.5 feet deep. Use the soil that was excavated from the hole to fill it, mixing it with compost or humus in a one-to-one ratio. Also add one ounce each of superphosphate and potassium sulfate, which can be replaced with a fertilizer with higher phosphorus and potassium content.

If you plant clematis in spring or fall, carefully inspect the clod of soil and roots. Cut off any damaged or rotted roots and sprinkle the cuttings with charcoal or ash. It is also recommended to powder the entire root system with a mixture of sand and ash to provide additional protection against pathogenic fungi, at least for the first time. This will help to reduce the risk of wilt development.

If you have an adult clematis with a woody underside, it can be planted with the stem buried one or two pairs of buds. This will allow the plant to grow thicker and more lush. If the clematis is still young and the lower part of the stems are green, it should be planted as it was growing in the pot. When planting, the roots should be carefully spread out and directed downwards, then press the soil firmly against the roots and water abundantly.

Care of clematis ‘Asao’

How to water?

‘Asao’ prefers moderate moisture, but in general it is better for it to have a lack of moisture than an excess of it. It should only be watered when there is a prolonged drought. Watering is best done with warm water, infrequently but abundantly. An adult plant may need up to two gallons of water at a time, while a young plant will need half as much.


Mulching the soil helps protect the soil from overheating and prevents excessive evaporation of moisture. Mulch also enriches the soil with organic matter. Freshly cut grass, hay or straw can be used as mulch. It is important not to press the mulch too tightly against the stems.

Fertilizing clematis ‘Asao’

In the first year after planting, it is not necessary to feed ‘Asao’ clematis, but a small amount of nitrogen (about 5 grams of active ingredient) can be applied in spring to stimulate growth. In the second and subsequent years, fertilization is necessary as the clematis renews its above-ground part every year and this requires resources.

The scheme of feeding clematis ‘Asao’ is as follows:

  • In spring, at the beginning of growth, apply organic fertilizer to the rootstock. This can be compost or humus. They can be simply poured on the surface of the soil without embedding, given that the clematis has shallow roots. In addition, it is recommended to introduce into the soil in the form of a water solution of 10 grams of nitrogen, 5 grams of phosphorus and 5 grams of potassium by active substance.
  • The second feeding is carried out when the clematis has mass appearance of buds of the first wave. Introduce 5 grams of nitrogen, 5 grams of phosphorus and 5 grams of potassium, as well as a full complex of trace elements. This will ensure a more spectacular flowering.
  • The third feeding is about 3 weeks after the second and includes 5 grams of nitrogen, 5 grams of phosphorus, 5 grams of potassium plus macro- and micronutrients.
  • The fourth top dressing is carried out at the end of August. It is recommended to put into the soil in the form of a solution of 5 g of phosphorus and 5 g of potassium.

Pruning clematis ‘Asao’

Clematis ‘Asao’ belongs to pruning group 2. Its main flowering occurs on the shoots of the previous year. This means that they should be saved.

In the first year after planting, the stems of clematis should be cut back by two buds, leaving only two pairs of buds at the bottom. This is done to make the plant more bushy the following year. You will lose that year’s first wave of blooms, but you will form a thicker plant.

For the following years, the clematis is pruned in two stages. In summer, after the completion of the first wave of flowering, from the shoots of the previous year should be cut off the part with flowers, leaving only the vegetative part with leaves. Leave the current year’s shoots unchanged. In late fall, after flowering is completed on the current year’s shoots, cut off a part of the shoot, leaving the buds for the next year.

If you are planting in a region with cold winters, such as Michigan, Wisconsin or Minnesota, the clematis should be covered for the winter. In the fall, after ‘Asao’ has lost its leaves, lay the stems on the ground and press them down with staples. Cover the plant with a covering material so that air remains inside. Then cover the structure from above with waterproof material and make ventilation holes in the sides. Under these conditions clematis successfully winter even in regions with very cold winters, such as South Dakota – especially if snow falls in winter.

Clematis ‘Asao’ Reviews

  • South Dakota: ‘Asao’ was purchased a long time ago on eBay and turned out to be a true clematis matching the description. It has had to be carefully covered each year by erecting a full dry shelter over it, because the plant is not covered with snow until frost in all years. So far only once have the shoots of last year been lost. During the whole time the blooming was very beautiful, it is an ornamental and fast-growing clematis.
  • Colorado: ‘Asao’ was purchased from an acquaintance on recommendation. The clematis is currently 3 years old in its new location. It has produced a few flowers each year, but not as spectacular as the photos on the internet so far.
  • UK, near Lancashire: ‘Asao’ was bought from a local nursery about 10 years ago. It is only fed once a year, pruned back to about 100cm height. Blooms twice a year and is very beautiful.
  • Canada, near Ottawa: ‘Asao’ is one of the most valuable clematis in the collection. It is covered every year extremely carefully, and so far there has not been a year when the shoots of the previous year were lost. The flowering is weak because it apparently lacks heat.

If you too have grown clematis ‘Asao’, please leave your feedback in the comments to the article – it will be useful to other gardeners.

About the author

Fedor Fironov
Graduate of Plant Protection Faculty at GSAU. Main area of interest – clematis, peonies and perennials of Lamiaceae .

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