Growing Woodland Plants
Woodland plants require a moisture retentive, humus rich soil in the partial shade to succeed. Very few of us have such conditions in the garden but they are very easy to create. Excavate a hole about 30cms (12in) deep and at least 1 metre (3ft) across in an area that is in shade for at least part of the day. If your soil is heavy clay line the hole with horticultural textile such as the fabrics used to suppress weeds and fill with a mixture of some, or all, of the following: garden compost, well rotted manure, composted bark and peat substitute. Use sharp sand to bulk the mix out. Do not use mushroom compost which is alkaline. In a sandy soil follow the same procedure but line the hole with polythene sheet to retain moisture, but punch a few holes in the base with a garden fork. Each year top dress in early spring with whatever organic material is to hand. In exceptionally dry weather it may be necessary to water the area as these plants must never dry out.
Many Arisaema are hardy and can be grown outside in light shade. They do best planted 15cms (6in) deep in a woodland type soil – humus-rich, moisture retentive but well drained. If grown in containers, use a deep pot of at least 2 or 3 litres initially for young tubers. Larger tubers do best in 5 litre pots. The roots of Arisaemas grow from the top of the tuber so they need to be placed well down the container on a bed of perlite to aid drainage. A compost mix of John Innes loam, multipurpose compost and composted bark appear to suit most. Keep just moist until growth shows in late spring and then water well and liquid feed every two weeks. As frost can penetrate containers some growers lift the tubers in November and store them in a refrigerator until April.
Arums do well in a well-drained, gritty loam-based compost with about 25% organic matter. They require a sunny position but one that avoids early morning sun if possible. Plant about 10cms (4in) deep. Liquid feed every two weeks when in growth. Reduce watering when the leaves begin to die back in summer. Do not bake or over-dry the tubers. In late August resume watering. Repot annually.
For cultivation Corydalis divide into three groups:
• Western Woodlanders (ww) - These are the easiest to grow. All can be grown outdoors under normal garden conditions. Plant about 10cms (4in) deep. In pots use a loam-based compost with added grit. Keep shaded or plunged in summer when dormant.
• Bulb Belt (s) - These are accustomed to drier summers and therefore are most suited to a bulb frame covered from the rain in summer.
• Eastern Woodlanders (ew) - These enjoy similar conditions to their western counterparts but they prefer a more humus-rich compost (peat or leaf mould) high in nutrients. Do not dry off.
Most of the Crocus offered are spring flowering. Many will do well outside in a well-drained situation, but most are seen at their best in pots of John Innes loam with added grit in the alpine house or frame protected from rain.
Cypripedium hybrids are easy to cultivate. We grow them out in the garden with other woodland plants. In pots we use a mix of John Innes No 3, perlite or pumice, potting bark, and a coarse commercial peat based compost with pine duff. Cypripedium roots grow sideways rather than down. Spread roots horizontally and lightly cover.
Generally easy to grow, enjoying a humus rich soil in the garden. As with most bulbs avoid heavy wet clay.
More difficult to generalise. Fritillaria acmopetala, F. meleagris, F. messanensis, F. pallidiflora, F. pontica and F. pyrenaica are all good garden plants. Many others will thrive in well drained locations such as raised beds or among the roots of deciduous trees but it may be safest to grow them in pots in an alpine house, cold frame or bulb frame until such time as you have spares to experiment with.
Iris of the Section Iris: varied in size and conditions – generally full sun and well drained soil. Oncocyclus: do not mind the cold but do best with overhead protection from excessive rain. Grow in pots in a loam based compost with large amounts of grit or sharp sand for perfect drainage. Regelia: may succeed in a sunny, well drained spot outside - otherwise treat as Oncocyclus. Juno Iris, or more correctly Subgenus Scorpiris: generally bulbs for the alpine house or frame. I.cycloglossa, I. bucharica and I. graeberiana are easy garden plants together with most of the hybrids. Hermodaltyloides (Reticulata): although the common cultivars are easy garden plants the rarer species are probably best grown with some protection.
Most enjoy slightly acid, fertile soils with the bulbs shaded from strong sun. All do well in pots or containers and most thrive in woodland conditions.
Woodland plants that do well in the garden where the soil has been improved with generous amounts of organic matter. However, our experience of organic-based composts in pots is that while most other woodland plants do well, many Trillium divisions often go backwards – we now use mixes consisting of at least 75% John Innes No 3 loam.