Herbaceous clematis

Introduction

Herbaceous clematis may be less well known than their climbing relations but make equally good garden plants, besides being easier to grow and prune. There are many scented forms, most are non-climbers, and all are fully winter-hardy. Herbaceous clematis are mostly true perennials (the stems die back to the ground at the end of the growing season and emerge from ground level, or below, each spring). A few have stiff stems that eventually form a woody sub-shrub base. All herbaceous clematis grow and bloom well when facing in any direction.

The numerous selections and hybrid forms of clematis integrifolia and clematis heracleifolia are probably the best to start with.

Clematis integrifolia occurs in many shades of purple, blue, red, pink and white, plus some interesting bicolours. Mature plants will vary in height from around 50cm to 1.5m, and are slow clump-formers. Their flowering period lasts from two to well over three months, starting in May. For best results, some form of support will be required unless grown through low or prostrate shrubs. Tie in young foliage to prevent wind damage. Some integrifolias are scented and these perform better when in the sun for at least part of the day.

Clematis heracleifolia occurs mostly in shades of white to pale blue, through to dark blue and purple. The size of a mature plant will usually be between 1 metre and 1.5m, but there are some pink and blue dwarf versions which will grow to less than 50cm. Like integrifolias, heracleifolias gradually form clumps. Heracleifolias bloom for nearly three months from June onwards

Planting

Herbaceous clematis are tolerant of many different types of soil and will perform equally well in acid and limey soils. All that is needed is a decent garden soil that is deep, well drained, yet moisture-retaining. Plant level with soil surface in a hole that is at least twice the depth and width of the pot the plant came in. The plant should be well soaked prior to planting and once firmed in the ground should be watered again and then weekly until it has had time to establish itself.

Pruning and aftercare

Pruning is simple and can be done at any time after the plant has become dormant in late autumn/early winter. Cut all stems off just above ground level if it is an integrifolia and at about 30cm if it is a stiff-stemmed heracleifolia. With mild winters, plants may not die right back, in which case they should be pruned in February instead.

Herbaceous clematis require very little aftercare, but because they start off each year from or below ground level they produce juicy green shoots for the slugs and snails, plus mice and some birds – a veritable feast early in the year. Most people have their own pet methods for controlling these pests.

Growing in containers

All herbaceous clematis are suitable for container growing, as specimen plants, or as companion plants to other suitable host shrubs. The container should be large and deep (46cm x 46cm), with thick walls if possible, and the compost should be free-draining. Plant the clematis at the same level as it is in the plant pot. Watering will be a high priority throughout the growing season, even more so if facing south.

Feeding

For plants in the ground, bone meal, or blood, fish and bone in autumn and spring is sufficient but container plants will usually require a liquid feed weekly during the growing season to replace lost fertiliser through leaching out by the amount of watering required.

Propagation

Both integrifolias and heracleifolias are simple to propagate by division in late winter and early spring. They can also be propagated from cuttings taken early in the growing season and from seed at any time of the year. Whilst division and cuttings will give you an identical plant, those raised from seed will produce plants likely to vary greatly from the original plant. Plants that are five years old benefit from being lifted and divided, with only a section of the original plant being put back in the ground.

Suggested plants

Integrifolia Indigo blue, slightly scented

Integrifolia Rosea Bright pink, scented

Heracleifolia Cassandra Gentian blue, scented

Heracleifolia Roundway Blue Bird Dark blue, scented

There is an enormous range of other herbaceous clematis to choose from as experience is gained. These include clematis recta, with a scented white flower on erect stems to about 1.5m; clematis fusca and ianthina, which are herbaceous climbers to over 2m, in a range of colours from pale pink through reds and purples to even jet black.