The corydalis (Corydalis) are herbaceous plants that include both annual and perennial species. Their outlasting or storage organs are fibrous tubers or bulbous, fleshy rhizomes, from which the stems then grow. These can grow erect or creeping, as well as simple or branched. These plants reach heights of growth of up to 30 cm and widths of up to 60 cm. The most common species are Corydalis cava, Corydalis solida, Corydalis solida and Corydalis lutea. The imposing inflorescences consist of spurred individual flowers arranged in panicles or racemes. The bright white, yellow or blue flowers appear in the first days of spring in April and then bloom until October.
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Potted plants from the garden trade can be planted from March to early December, provided the soil is frost-free. However, the best season for planting is autumn. The soil should be properly prepared before planting.
When planting, it is advisable to provide the soil with compost and organic fertilizer, such as horn shavings, to provide it with additional nutrients. Then the tuber or bulb is planted about three times as deep as the diameter of the tuber, which is usually between 5 and 10 cm. The space requirement per plant is important and should be taken into account when planting. It is between 25 and 30 cm, which also applies to the planting distance to other plants. After planting, the whole thing is well watered.
location and soil
- Location requirements can vary from species to species.
- Some species prefer shady or semi-shady locations.
- Others, on the other hand, thrive better in sunny locations.
- In sunny locations it can happen that the lark spur stays a little lower.
- The soil should be as permeable, nutrient-rich, humic and calcareous as possible.
watering and fertilizing
The water requirement and the watering behavior depend on the respective location and the weather conditions. As a rule, however, it should be watered regularly, especially in summer. If the larkspur is already on a rather damp soil, it is advisable to water at larger intervals, as too much moisture can lead to root rot.
If the soil contains sufficient humus, additional fertilization is usually no longer necessary. Otherwise, as soon as the flowers start to wither, you can give a bulb flower fertilizer every 3-4 weeks.
- After flowering, this perennial goes into hibernation.
- Most Corydalis are usually hardy plants.
- Despite everything, they should be additionally protected from severe frosts.
- You can cover them with leaves, peat or straw, for example.
Propagation by seed
The larkspur belongs to the cold germs. Accordingly, the seeds must be subjected to cold treatment before sowing. To do this, they are placed in the refrigerator for about 10 days, for example, which removes the inhibition of germination and promotes germination. Then potting soil is mixed with about a third of coarse sand and placed in a suitable planter. In addition to potting soil, coconut fiber is also very suitable because both substrates are permeable and low in nutrients.
The seeds usually have different sizes. The larger ones are lightly covered with sand and the smaller ones spread over the substrate and just pressed on. Now the whole thing is moistened and kept evenly moist until germination. Then you cover the planter with cling film or glass and place it in a cool place until the seeds germinate. It is advisable to remove the film or glass from time to time and air it, this prevents mold from forming.
Direct sun should be avoided for the first six weeks after budding. The small seedlings can be isolated or pricked out about 5-8 weeks after they have sprouted. When planting out, you should be very careful not to damage the young roots. It is best to plant them in so-called tuffs, ie in smaller groups, so they usually develop more vigorously.
propagation by division
Some species of Corydalis can be propagated by division, others by seeds. Older plants often form daughter or brood tubers that can be used for division. The right time for vegetative propagation, ie division, is during hibernation.
Summer-flowering species can be divided in spring and spring-flowering in fall. The tubers or bulbs are carefully removed from the ground and the individual bulbs separated or divided and planted with the appropriate distance from each other and other plants. The bulbous, fleshy rhizomes can also be divided by separating them from each other and then replanting them individually.
diseases and pests
- Root rot – root rot in larkspur is usually the result of too much moisture or waterlogging. If both are avoided, this disease can be prevented very well. Otherwise, this plant is relatively resistant to diseases.
- Spider mites – A spider mite infestation can usually be recognized by small webs on the affected plant. Systemic agents against this pest are commercially available, which are absorbed by the plant either through the leaves or the roots. These agents can be used both preventively and to combat them.
- Snails – Traces of feeding or slime on the plant can indicate snails, because they also like the corydalis. Sometimes the snails themselves can also be seen during the day. For example, commercially available organic slug pellets can be used to combat them, which are simply distributed around the affected plants.
Most famous varieties
Hollow Corydalis ‘Corydalis cava’
The hollow corydalis growing from an underground, hollow, walnut-sized tuber reaches heights of growth between 15 and 30 cm. This deciduous species grows in clumps and covers the ground. This larkspur is a shade plant. Accordingly, it thrives very well in partially shaded and shady locations. The storage organ of this plant, the tuber, is surrounded by a cavity in which daughter tubers form, especially in older plants, which can then be used for propagation.
The red-violet, deep pink or, relatively rarely, white flowers of this perennial herbaceous plant are in a terminal raceme and appear in early spring from March to May. The three-lobed, finger-shaped leaves are blue-green to dull blue.
Of the native species of Corydalis, this species is the most widespread. It is very well suited for underplanting trees and shrubs, for mixed borders, but also for natural gardens. This plant does not look so good in a single position, group plantings with up to 50 bulbs or tubers are better. The planting distance should then be about 10-15 cm.
Corydalis corydalis ‘Corydalis solida’
In contrast to the corydalis corydalis, this early summer green corydalis grows from a solid, non-hollow tuber. It is also known under the names Fester-, Vollwurz- or Finger Larkspur. It thrives in sunny to shady locations, preferring lighter locations in spring and more shady locations in summer.
The flower colors vary between a pale lilac, a light blue and a crimson, bright red or white. This species also flowers from March to early May and grows to a height of between 20 and 30 cm. It can take several years until the first flower or until this variety flowers for the first time. After flowering, the plant usually withers.
The fingered larkspur is less common than, for example, the hollow larkspur. In Lower Saxony and Saxony it is on the ‘Red List of Endangered Species’, although it is not considered endangered in Germany.
Yellow corydalis ‘Corydalis lutea’
In contrast to many other species, the yellow corydalis with its filigree foliage grows in a highly branched manner, resulting in a bushy habit. It reaches growth heights between 15 and 30 cm. The flowering period extends from May to September, almost throughout the summer. Accordingly, the yellow larkspur is also one of the permanent bloomers.
The flowers are bright yellow, with the outer petals being partly lighter and the inner ones turning orange-yellow. In optimal locations, it can seed heavily. Locations in light penumbra are preferred. Locations that are too dark impair flowering.
When its leaves begin to become unsightly, pruning can be advantageous, always at the beginning of budding, from the beginning of February to March. The plant is cut back about hand high. The yellow corydalis is very suitable for sunny places in the rock garden. The soil should then have a high lime content.
Particularly beautiful varieties
Blue Corydalis ‘Corydalis elata’
This extraordinarily beautiful and robust variety impresses with its growth, but above all with its bright blue flowers, which appear from May to July. The steel-blue flowers stand high above the foliage and exude a subtle scent of bitter almonds. This aromatic plant grows to a height of between 30 and 40 cm and prefers partially shaded, not too dry locations.
Light Yellow Corydalis ‘Corydalis ochroleuca’
This beautiful variety produces whitish flowers with yellow tips from May to September. Over time, it forms bushy clumps. This larkspur reaches growth heights of 20-30 cm. About 8-10 plants should be planted per square meter, spaced about 35 cm apart. The location should be as semi-shady as possible, on fresh soil.
Fern Corydalis ‘Corydalis cheilanthifolia’
This evergreen corydalis, which grows to a height of 20-40 cm, is reminiscent of a fern with its filigree leaves, as the name suggests. It loves semi-shady to shady areas in the garden, where about 6 of this species are planted per square meter.
The foliage is initially fresh green and later becomes darker and darker. In winter it takes on a warm bronze tone. The evergreen rosettes reach a diameter of up to 40 cm. The bright yellow flowers stand high above the foliage from April to June.
Corydalis, no matter what kind, are beautiful plants that are suitable for different areas in the garden. They come into their own particularly well in combination with other perennials or as underplanting for woody plants. Larkspur makes no great demands on care. It propagates easily by self-seeding and, with proper care, is relatively resistant to disease.