Laburnum        

Family. Legumes.

Origin. Europe.

Description. Laburnum are small trees or large shrubs with smooth, gray or light green bark. Depending on the variety, they can have either erect, abundantly branched shoots or drooping branches.

The leaves are divided into three segments, on long petioles resembling clover, arranged alternately, segments 2–5 cm long, elliptical-lanceolate or obovate, matte green with gray-green pubescence below.

Bright yellow flowers are collected in drooping, dense, long brushes 10–40 cm long. Each flower reaches 2 cm in diameter. The flowering tree looks magnificent and resembles a waterfall with large, drooping inflorescences.

The seed pods resemble peas, ripen in the fall, turn brown and remain on the tree all winter.

Height. Laburnum grows up to 2.5 m. In nature, in a warm and favorable climate, trees up to 10 m high are found.

When grown in harsher conditions, the height does not exceed 3 m.

Plants develop quickly and can add up to 30 cm in height in just one season. At home, the height is regulated by pruning.

Planting and care

Growing in open ground

Planting in open ground is carried out with seeds, sowing them in mid-autumn or spring, after preliminary pre-sowing treatment. You can also plant young seedlings outside in spring and summer.

A well-lit place without strong gusts of wind is suitable for growing. Plants should not be planted in the shade - flowering will be less abundant or will not occur at all. Lands with shallow groundwater or flooded lowlands are also not suitable for the tree.

For planting, choose seedlings with swollen buds, whose leaves are about to start to bloom. It is not worth planting green bushes - they will tolerate planting worse and may even die. If you are late with the planting dates and the shoots already have leaves, then you will need to plant them in the garden in the fall, when the leaves fall. When planting in the fall, it is worth choosing a period of time during which the root system will have time to form before the onset of cold weather. The planting area is loosened, weeds are removed.

• Depending on the planting scheme, holes are prepared, the height and width of which should be twice as large as the root ball of the seedling. On average, the depth and height of the holes will be 45 - 55 cm.
• At the bottom of the planting holes, drainage is laid out from crushed stone, broken brick, and sprinkled with a small layer of river sand.
• A nutrient layer in the form of humus mixed with soil is placed on the drainage and laid out in a heap. For planting, prepare a mixture of garden soil with humus and sand. It would be a good idea to add crushed chalk or lime to the mixture - laburnum plants respond very well to calcium supplements. Soils that are too acidic need to be enriched with lime.
• The plants are removed from the shipping container and shaken off old soil.
• If necessary, cut off old and rotten roots with sharp pruning shears and sprinkle the wound surface with wood ash or crushed charcoal powder.
• The seedlings are placed on a hill and the roots are straightened, and then they begin to be sprinkled with prepared soil.
• During planting, if necessary, the bush is provided with support.
• After planting, the soil is compacted to remove air pockets and then thoroughly watered with plenty of warm water.
• The bases of the plants are mulched with mowed grass or straw to prevent water from evaporating in the soil surface. A layer of mulch will also inhibit the growth of weeds.

Further care will consist of timely weeding, watering and fertilizing. Flowers in the garden are fertilized only 2 times per season.

In the first spring feeding, nitrogen-rich fertilizers are applied - they allow the bush to form a dense head of greenery. In the autumn months, the laburnum will respond positively to fertilizers rich in potassium and phosphorus - they will strengthen the root system and prepare it for wintering.

It will be useful to loosen the tree trunk circle to a shallow depth, trying not to damage the superficial roots of the laburnum plant. 

The first winter will be a real test. In severe winters with little snow, the bush can freeze to the ground - the entire above-ground green part will suffer. Fortunately, the above-ground part quickly recovers - the bush releases fresh shoots from the roots and completely forms a new crown within a few seasons.

To protect against frost, plants are mulched in mid-autumn, covering the root system with a layer of soil and fallen leaves. Young seedlings are wrapped in several layers of non-woven material when the first frosts occur.

Before the onset of frost, the stems of the bushes are pulled together as much as possible and tied with ropes, and then covered. You can try to bend the shoots to the surface of the earth, but since they are quite brittle, this should be done with caution.

You can also build a small wooden frame over the plant.

Remove the cover as soon as the snow melts - first lift the non-woven material during the daytime, gradually increasing the ventilation time, and then leave the bushes open at night. Mature plants can withstand winter frosts without shelter.

In the spring, with the appearance of the first leaves, sanitary pruning is done, removing old, diseased and frozen stems of the plant over the winter.

When growing in the garden, it is worth trimming off flowering clusters and seed pods so that the laburnum plant does not spread on its own through self-sowing. 

Reproduction - laburnum from seeds 

Propagated by seeds sown in spring or autumn. Propagation by seeds is quite simple, and when grown in open ground, self-seeding can often be found under the plants.

When planted in open ground in autumn, the seeds undergo natural stratification. The sowing dates are maintained so that the first shoots do not have time to appear before winter.

Plants obtained from seeds first produce buds at the age of 3-6 years.

Samples obtained from seeds are resistant to the climatic conditions of the area where they were planted.

Seeds from your own collection can be used for sowing - for this, the pods are allowed to fully ripen on the plant and only when they begin to dry out and turn brown, the peas are extracted from them.

Since the seeds are large and have a hard outer shell that prevents germination, the planting material is subjected to preliminary preparation. Such preparation consists of destroying the outer protection of the seeds by heat treatment, chemical or mechanical methods.

Heat treatment can be either hot or cold. Before planting, seeds can be scalded with boiling water or subjected to cold stratification in the vegetable compartment of the refrigerator for 6-8 weeks.
If you have the necessary experience working with chemicals, you can soak the planting material for half an hour to an hour in sulfuric acid.
Good results are achieved by mechanical treatment - scarification - deliberate damage to the seed coat with a file or sandpaper.
Germination of fresh and properly treated seeds reaches 95 percent.

1. Sowing of seeds is carried out using a plastic box, on the bottom of which a small drainage layer in the form of fine expanded clay is laid.
2. The container is filled with soil consisting of a mixture of peat and river sand and the seeds are sown.
3. From above, the seeds are covered with a layer of soil 5 - 10 mm thick.
4. After planting, the soil is thoroughly moistened using a fine spray bottle.
5. Crops are covered with a transparent lid, plastic bag or glass to create a greenhouse effect and maintain high air humidity.
6. The seedlings are placed in a warm, well-lit place, but protected from direct sunlight.
7. Every day the cover is removed and the seedlings are ventilated, and when the first shoots appear, they are removed completely.

You can plant immediately in separate cups, placing 2 - 3 seeds - peas - in each cup. In this case, you can avoid picking and simply remove the weaker sprout as it grows.

The first fertilizing with a very weak solution of mineral fertilizer with a high nitrogen content is carried out 7-10 days after picking.

Air layering can be formed in spring or in the first half of summer.

1. A smaller container with soil is placed next to the main pot.
2. Small cuts are made on the branches at 1/4 or 1/5 depth or simply deep scratches are applied.
3. The side shoots of the plant are tilted into this container and pinned to the surface of the ground.
4. The shoots are sprinkled on top with a small layer of substrate, which is kept evenly moist until complete rooting. The upper section of the cutting should be above the ground surface.

After 4 weeks, you will be able to see young shoots appearing from under the ground - this will indicate the formation of roots in the leaf nodes underground.

The cuttings are separated from the mother bush next year - in spring or summer. The advantage of this method is that from one air layering you can get several young bushes at once, since the root system is formed in each buried leaf node.

Plants obtained by air layering bloom at the age of 3-4 years. 

Semi-lignified stem cuttings about 15 - 20 cm long root during the summer.

1. The cuttings are cut with sharp sterile pruning shears and the bases are dusted with growth hormones.
2. Up to half the leaves can be removed from cuttings to reduce moisture loss.
3. Rooting is carried out in a moist and loose substrate, in a warm place, under a cover of plastic film or transparent plastic. When covering with film, make sure that it does not come into direct contact with the surface of the leaves.

If all conditions are met, the first signs of new growth can be noticed within a month.

Growing at home, pruning

The shoots of young trees can be pruned to give the tree a beautiful compact shape.  When kept on site, the first pruning is carried out in early spring, removing frozen and weak shoots.

Formative pruning, if necessary, is carried out carefully - the laburnum tree reacts negatively to too many removed shoots. When pruning, it is worth removing young and weak branches; the shrub does not like pruning adult shoots.

Most often, plants branch on their own and form side shoots and do not need pruning. Pruning is carried out with a sharpened tool, and the cut branches should be immediately treated with garden varnish for speedy healing. 

During the summer months, the pot should be taken outside. The bush will respond gratefully to such placement if it is placed in the shade from direct sunlight and protected from strong wind and rain.

Fading inflorescences should be trimmed to maintain a beautiful and neat appearance, as well as to prevent the bushes from wasting their energy on forming seeds.

In autumn, leaves may fall - this is a normal process.

When it blooms 

May June. The flowering period takes 2 - 3 weeks.

Buds are formed abundantly - the emerging inflorescences almost completely hide the foliage. Flowering occurs simultaneously with the formation of foliage.

Soil 

Prefers organic-rich soil with good drainage. 

The soil can be composed of components such as garden soil, peat, humus, light turf or leaf soils. To improve drainage, a sufficient amount of coarse river sand is mixed into the substrate.

Since representatives of this genus are very fond of calcium, it would be advisable to mix crushed chalk into the soil.

The soil should not only have good drainage, but also allow the root system to breathe.

For loosening and additional nutrition, you can add a small amount of charcoal to the substrate.
The substrate for the flower should have a neutral or alkaline pH, it tolerates even soils with a low nutrient content.

Transplant 

Young specimens are replanted in the spring, as they grow and develop, annually.

1. To grow laburnum, take  roomy pots with large drainage holes.
2. A drainage layer in the form of expanded clay, broken brick or clay shards is placed at the bottom of the pots.
3. A layer of earth is poured onto the drainage layer.
4. Plants can be replanted or transferred to a new container using the transfer method, keeping the root ball as intact as possible.
5. After planting, the earth around the bush is lightly compacted, avoiding too much compaction of the earth.
6. The transplanted bushes are watered and placed in shade from sunlight for 7-10 days.

Transplanting large tub specimens causes difficulties, so every spring the top 5-7 cm layer of soil is replaced with fresh soil.

Plants grown in open ground are immediately planted in a permanent place, since adult bushes have too large a root system and do not like it to be damaged during transplantation. If it is necessary to move the flowers, they are replanted in the autumn months, when their foliage has fallen. 

Feeding

The laburnum grows quickly and needs a lot of nutrients during the growing season. Potted plants are kept in a confined space and cannot get enough minerals from the soil. 

During the growing season, the flower is fed with liquid mineral fertilizers 2 times a month.

Apply fertilizing to moist soil after abundant watering, since contact of a nutrient solution with the root system in dry soil can cause a chemical burn.

They begin to fertilize in the spring, when young twigs and leaves appear on the bushes. In the autumn months, the frequency of fertilizing and the content of nutrients in it is gradually reduced to nothing and in the winter months the flower is not fed.

Plants respond well to both mineral and organic fertilizers.

Humus and humus or cow and horse manure are added as organic matter. Manure must be well rotted - if fresh, it can cause burns to the roots. You can also use a weak solution of bird droppings for feeding.

In general, laburnum are more likely to tolerate a lack of nutrients than an excess of them.

Diseases and pests 

• If the content is too cool and humid, or if there is insufficient air humidity, the plants may show signs of fungal diseases, such as powdery mildew.
• Leaf spotting.
• Laburnum does not bloom when grown in partial shade or severe frost damage.

Among harmful insects, aphids and mealybugs may appear. 

Conditions - temperature

Normal room temperature is suitable for growing, during the winter dormancy period the temperature should be reduced to 10° C.

A cool dormancy period will allow it to rest and gain strength for abundant bud formation. In addition, low air temperature will delay the development of the bush, and in conditions of insufficient light, new shoots will become elongated and unsightly.

Laburnum is thermophilic and with sufficient watering and air humidity will endure the strongest summer heat.

When grown in open ground, the bush can tolerate short-term frosts down to -25 ° C.

The most resistant to freezing will be shoots that are fully matured and covered with dense bark; young branches can die in harsh winter conditions.

Lighting

In partial shade from direct sunlight.

Laburnum will feel good on western or eastern windows. When growing on the south side, the bush should be placed at the back of the room or protected from direct sun with a light curtain. On the northern windowsill, the flower will not have enough strength to bloom, and the shoots that appear will be too weak.

Shoots and leaves can bathe in the sun's rays only in the morning and evening hours; in spring and summer days they should be shaded.

In October - November the leaves will fall and lighting at this time will not play any role.

Spraying 

There are no special requirements, tolerates dry indoor air well.

Spraying can only be done to prevent the invasion of harmful insects. When spraying, make sure that water does not get on flowers and buds, and does not remain on the leaves during the day, when the plants are exposed to direct sunlight. Wet leaf blades can get burned, since drops act as a lens.

Spraying is carried out mainly in the first half of the day, with settled water at room temperature.

To increase humidity, you can place a room humidifier next to the bush or simply place several pots with plants in a cramped space.

Watering

Prefers uniform humidity in the warm season, does not tolerate stagnation of water at the roots.  Plants are more likely to tolerate a short drought than a flood.

Young bushes will need regular watering, but with age, the flowers become more tolerant of the frequency of watering and you can dry them out a little.

In spring and summer, water with plenty of water, completely soaking the lump of earth. For irrigation, use warm and well-settled water for 24 hours.

In the autumn months, the frequency of watering is gradually reduced and in winter they water minimally, trying simply to protect the soil from completely drying out. After watering, excess moisture that appears in the pan must be drained. 

Purpose

An ornamental shrub with abundant and long flowering, but even without flowers it looks very attractive. Among other things, the plant is an excellent honey plant; during the flowering period, the buds attract many bees and other beneficial insects to the site.

When grown outdoors, it can be used as a hedge.

Laburnum is quite widely used in urban landscaping, as it easily tolerates the street atmosphere polluted by exhaust gases.

With proper care, it can decorate a garden plot or the interior of a house for 20 years.

Both group plantings and single bushes look impressive. With the help of long shoots, you can form large flowering arches.

Note

All parts of the plant are poisonous and can be fatal if consumed. The highest concentration of toxins is found in the tree's seeds.

Symptoms of poisoning may include severe drowsiness, vomiting, seizures, and unevenly dilated pupils.

Use gloves when handling the plant and wash your hands thoroughly with soap and water after any contact. Keep it away from children and pets.

As it ages, it may bare the lower part of its stems, losing its leaves - replace such specimens with new seedlings obtained from seeds or cuttings.

Varieties:

Laburnum anagyroides

A very beautiful, spreading tree, native to Central and South-Eastern Europe. In its natural habitat it reaches a height of 7 m. During the flowering period, it covers you with abundant and large racemes, consisting of drooping racemes with white or yellow flowers and resembles wisteria. The leaves are green, compound, consist of three oblong-lanceolate leaflets, each of which reaches a length of 7 cm. The lower surface of the leaf blades may have a slight silvery pubescence. All parts of the plant are poisonous. 

Laburnum alpinum

A small deciduous tree or large shrub, reaching a height of 7 m. It has dark green compound leaves - they consist of 3 tablet segments. During the flowering period, in spring, it forms large drooping racemes consisting of yellow flowers. The brushes can reach a length of 30 cm. The seeds of the plants are poisonous.