The mammoth leaf (Gunnera manicata) is affectionately known in its native Brazil as the “parasol of the poor” (Sombrilla de pobre). No wonder, because the plant can grow up to three meters in height and develop leaves with a diameter of a whopping two meters. The exotic giant perennial forms small, fine flowers on long, bulb-like panicles in the summer months, which, however, are less impressive in relation to the spectacular leaves. The flowering period is between July and August. With the right care, the mammoth leaf also thrives here in Central Europe, provides shade in summer and impresses every garden visitor with its size. The plant is often referred to as giant rhubarb because of the similarity, although it is in no way related to rhubarb.
Table of Contents
sowing
Seeds of the mammoth leaf should not be stored for a long time, but should be sown as soon as possible after the harvest (around the end of August).
To do this, proceed as follows:
- Remove pulp from seeds
- Cover seeds lightly with soil in a small flowerpot
- Always keep the soil moist, because even a single dry phase can prevent germination!
- Simple potting soil is sufficient for germination, alternatively use pond soil
- Use a small greenhouse or a hood over the flower pot to protect the soil from drought
- Do not let the soil get too wet, as there is a risk of mold!
- As soon as drops collect on the glass walls, ventilate the greenhouse or hood to regulate the humidity
The flower pot can be at room temperature or in a cooler room around 15 degrees Celsius. For fresh seeds, the germination period should not be long. Dried seeds may have reduced germination capacity and take several weeks to germinate.
After germination and an initial strengthening of the plant, the mammoth leaf can stand in a flower pot on the balcony or terrace in summer. A mammoth leaf should overwinter in a pot in a cold room in the house. This can be dark because the plant dies above ground in autumn.
Sometimes cultivation by sowing is not successful. In principle, the propagation of the Gunnera manicata is recommended by dividing the mother plant.
plant
Perennial Gunnera manicata has thorny stems and large leaves that bear a resemblance to rhubarb. The plant is therefore often described as herbaceous. The leaves grow basal and cover the ground. In summer, bulb-like panicles grow that can reach a length of up to one meter. Flowers form on the panicles and later small, round, reddish fruits. These are only about 2.5 mm in size. The above-ground part of the plant dies off completely in autumn and sprout again in spring.
A place should be chosen for planting where the mammoth leaf has three to four meters of space to spread out. The plant can reach a massive height of up to 3 meters and a width of up to 4 meters in good conditions.
repot
Repotting is not necessary in a garden location. A potted plant should only be repotted if there is not enough space in the flower pot. The mammoth leaf should be able to grow undisturbed, so don’t repot it too often.
maintenance
The sequoia is generally considered to be low maintenance and requires little maintenance in the summer, provided the water supply and soil conditions are good. In any case, you should not let the soil dry out and water generously, as the plant is sensitive to drought. The flowers are normally hermaphrodite, occasionally unisexual, and pollinate themselves. You can help pollination by gently sliding your finger over the flowers. As a rule, small, reddish-colored fruits develop independently.
In the autumn months the leaves die off. The mammoth leaf should therefore be pruned towards autumn and prepared for wintering. Therefore, the mammoth leaf is regularly cared for more intensively once a year. Pruning in the fall and building up winter protection are the biggest points of care.
location
In order to ensure optimal growth, these points should be included in the choice of location:
- choose a semi-shady place
- Choose a humus-rich and moist location where the plant can grow undisturbed
- Mammoth leaf draws a lot of water to sprout the large leaves and flowers
- Garden sites on watercourses, ditch banks or near a pond are ideal
- As a solitary plant, there should be enough space available, as the perennial can become quite extensive and cover several square meters
- Calculate a distance of approx. 1.5 – 2 meters to the next plant
- Choose soil that is as deep as possible so that the roots can solidify well
watering and fertilizing
If the location is not naturally damp, it is essential to ensure sufficient watering, as the mammoth leaf needs a lot of water and is sensitive to drying out. Ideally, the Gunnera manicata is planted on the edge of a pond, ditch or watercourse so that watering is largely unnecessary.
The mammoth leaf requires a relatively large number of nutrients due to the size of the plant. That is why regular fertilizing is important. Especially in early spring and spring, as the leaves sprout in the spring and flowers are formed in the summer.
Mulch and any substrate that is nutritious and slightly acidic is suitable for fertilizing.
To cut
The mammoth leaf should be pruned every fall as it loses all of its leaves before winter anyway. It is also advisable to cut back the stems to strengthen the plant. To do this, cut back all stems to a length of approx. 30 cm.
- Stems can grow more than 10 cm thick
- Large and powerful cutting tool makes sense
hibernate
As an exotic perennial, the mammoth leaf is sensitive to cold temperatures. If the plant gets frost, the leaves become dark and limp. This is a sign that the leaves were supercooled. The plant itself will not usually suffer any damage from a frost. If the temperatures drop more or if they last longer, the entire perennial can freeze to death. It is advisable to start with the winter preparations in November at the latest.
Preparations:
- cut off leaves
- Shorten the petioles to a length of approx. 30 cm
- Thoroughly clean the ground around the mammoth leaf
- Remove damp leaves or other plant parts so that nothing can rot
- make sure there are no snails or other pests nesting around the plant
The following materials are suitable for protection against frost:
- trimmed mammoth leaves (not shredded, stems up)
- dry foliage
- brushwood
- fir branches
- The coconut mat
- Coconut skin
When layering the winter protection, make sure that enough air pockets can form. It is advisable to apply several materials in alternating layers. If you use the cut sequoia leaves, you should stack them with the stems up and overlapping like a roof shingle.
Also make sure that nothing can blow away. The winter protection should also keep out moisture as much as possible, otherwise there is a risk that rotting processes will start. A net or wire throw can be useful for this. Branches or boards can also be used for attachment.
In botanical gardens, a large wooden box is often put over the Gunnera manicata, which can be opened at the top. This has the advantage that the plant can be aired occasionally. This method can also be used in the home garden, but then you should install a wire basket so that the plant is not damaged by voles or house mice nesting in the warm box.
The following are important for dismantling the winter protection:
- do not remove too early, frost damages the plant
- it is recommended to start in May
- from March the plant can be aired
- Gradually remove winter protection
- Check for frost every day if possible and cover again if necessary
- When the temperatures are warmer, remove the antifreeze, otherwise the new leaves will rot and pests can settle in
- after the cold Sophie (May 15) there should hardly be any frost, so that it makes sense to uncover the mammoth leaf again
propagation
Propagation can take place by seeds in autumn (see sowing) or by division in spring. Propagation by division is recommended, as larger plants can be grown more quickly.
The best way to do this is to dig up and divide the plant after the winter protection has been removed and when it begins to sprout. Make sure that each shoot has at least one leaf base. In order to ensure better rooting, first pull the divided shoot up a little in a flower pot before planting it back in the garden soil. Potting soil or pond soil can be used, which must always be kept moist.
pests
The most common damage is caused by snails that are interested in the flower buds. Slug pellets or snail protection, which prevents the snails from running up, can help.
Other pests can be rodents that look for a hiding place in the winter shelter around the mammoth leaf and use this opportunity to tamper with the plant. In this case, too, a wire basket around the plant makes sense.
Otherwise, the mammoth leaf is not known to be susceptible to pests.
