Hibiscus in northern garden

Hibiscus, or rosemallow, is a large genus which includes more than 200 species of deciduous and evergreen shrubs and trees, as well as annual and perennial herbaceous plants. Almost all of them are native to tropical and subtropical regions throughout the world (including the popular houseplant – the Chinese hibiscus (Hibiscus rosa-sinensis)); hence only very few of the genus can be grown outside in temperate climate. The common garden hibiscus (Hibiscus syriacus) is the most widely grown hardy species.

Hardy does not always means really hardy… Garden hibiscus may succesfully grow here for many years if winters are not very cold, and die back to the ground in a heavy winter like we had this year. Anyway new shoots grow fast and start flowering in late summer. Young plants are more frost-sensitive. Hibiscus feel good during our cool summers, they can be container-grown, moving them inside for the winter. Heavy mulching helps roots to survive the winter.

The common garden hibiscus (Hybiscus syriacus) is native to China and Western Asia. This species of hibiscus is well-loved and widely grown in Europe. These are compact shrubs of variable height up to 2-4 m. Flowers, which are smaller than those of true chinese hibiscus, come in a variety of colours – ranging from white to lilac, often bicoloured, single or double.

Garden hibiscus are widely used as landscape shrubs or small tress. They thrive in sunny, well-lit and moist locations. During hot weather, they require copious watering and feeding in order to extend their flowering from mid-July up to the first frosts. They tolerate shady position, but the flower display will be less spectacular. However in sunny position they overflower very fast.

Propagation is from seed (species), or by green and semi-woody cuttings (cultivars). Seeds are sown in early spring after the cold germination treatment.

Common hibiscus are not particular about the soil (they do need a well-drained spot though), but they strongly prefer full or half full sun, growing spindly in shaded location. They dislike strong winds. They are drought-resistant, but produce exceptional quantities of flowers, when regularly watered and fertilised. During cold spring with recurrent frosts, the young shoots of hibiscus should be protected (but mostly they sprout quite late, after the spring frosts are passed).

Winter thaws can be lethal to rosemallows, if their roots remain waterlogged for some time, therefore a thick layer of draining material should be spread at the bottom of the planting hole when planting hibiscus is clay soils.

© Giedra Bartas, 2010

The great divide

Spring is the perfect time to divide and plant herbaceous perennials. After 2-5 years clumps of most perennials become overcrowded and their vigour deteriorates. As a result plants produce fewer flowers, and loose some of their ornamental value.

As a general rule, spring is the best time to divide and plant summer- and autumn-flowering plants (starting with mid-June), and ornamental grasses (miscanthus, reed grass, feather grass). This is best done at the time when new shoots appear, which makes it easier to see how the clump should be divided. Make sure you divide the plant before shoots become too tall – this way damage will be kept to a minimum.

Plants, which flower in early spring (up to early June), should be divided in autumn. There are exceptions, however. Primroses, as well as most of the flowering alpine plants (creeping phlox, aubrieta, basket-of-gold, several sedums) can be divided soon after the flowering is over. This does not harm these plants in any way. Daylilies can be divided at any time throughout the growing season; the best time for bearded irises is after flowering, while peonies are usually divided in autumn.

Here are some tell-tale signs that your herbaceous perennials need rejuvenating: clump becomes congested and contaminated by perennial weeds, which are impossible to remove. the plant produces fewer flowers each year, and goes dormant earlier in the season. the middle of the clump dies down, with new shoots growing on the perimetre.

Dig out the overcrowded clump, shake off as much of soil as possible and carefully divide into several portions, each with viable roots and strong shoots. Give away smaller portions to your gardening friends, or move into nursery bed (pots) for growing on. Discard dead parts of the plant and woody roots, carefully removing any perennial weeds. If you intend to plant the rejuvenated plant back into the same spot, replace some of the planting soil. Plant at the same depths as before, and water well.

Some plants are easily divided by hand, but a sharp knife will come useful while dividing others. Old clumps of miscanthus are notoriously difficult to divide. Clumps of deadnettle, lady`s mantle, lungwort, sea thrift, creeping jenny, coralbells, columbines, bugleweed, bleeding-heart, primula, creeping phlox, maiden pinks are easily divided by hand. But you will need a sharp knife to divide overgrown plants of yarrow, bellflower, rudbeckia, coneflower, bee balm, asters, hosta, goldenrod, catmint, astrantia, salvia, bugbane, some of the poppies, aconitum and perennials tickseed.

© Giedra Bartas, 2010

Get planting tulips in October

tulpeMost bulbs are planted in autumn to flower next spring.  Usually tulips are planted in early October, when soil temperature at the depth of 10-12 cm drops to +10C. If autumn is warm, tulips can be planted throughout October, even as late as early November. Experienced growers maintain that one can plant tulips even in midwinter, as long as the ground is not frozen over. Bear in mind that mulching with a 25cm layer of sawdust, peat or compost is absolutely necessary in such case. Bulbs root within three weeks – this is how long it should take before the ground completely freezes over. If planted too early, bulbs will break into growth too soon.

Prior to planting, pick over the tulip bulbs, discard the damaged, diseased or any bulbs, uncharacteristic to the particular cultivar, if it has not been done yet. Sort the bulbs by size, cultivar and colour. Never ever take the discarded bulbs to compost heap!

 Soak bulbs for 30-60 minutes in a 0.5% solution of permanganate of potash before planting. Once this has been done, plant them straight away into prepared beds. The bulbs soak up water fast, their bottoms swell and soon the roots break. Do not wait for this to happen, since the new roots are very fragile, and they will not sprout back, once broken.

Tulips can grow in flower beds for 3 or 4 year without transplanting. However, they should be lifted annually or every second year, if the bulbs are grown for selling of blooms or bulbs, or when the tulips are very rare and expensive. Offset bulbs grow much better, if moved to the nursery bed, than in an overcrowded flower bed. Annual replanting helps to avoid fungal diseases, since bulbs are picked over each year, and the diseased ones are discarded. Virus-ridden or oddly looking plants should be discarded as soon as detected, for a single sickly bulb can infect others.

 Most tulip growers plant bulbs in flower beds 1-1.2 metre wide for ease of cultivation. If the water table is high, tulips are best planted in raised beds (20-25 cm above soil level). If planted in mixed borders, tulips look best in groups. Single species planting of tulips is a spectacular feature, where several groups of tulips of varying heights and colours are combined to the most flattering effect.

 The general rule of thumb is to plant most bulbs at the depth of 3 bulbs, if planting on well-drained soil, and at the depth 2 bulbs, if planting on heavy soil, but never deeper than 20cm. The distance is measured from the bottom of the bulb to the soil surface. Large bulbs should be planted in rows with a 8-12cm spacing, and rows 20-25 cm apart. Small bulbs are planted in two-drill rows – the drills 5cm apart, with a 15cm spacing between the rows. The tiniest offsets are planted in nests of 8-10, since only 60% of them will survive until spring. If planted too densely, tulips will produce very few replacement bulbs. It is maintained, that 50 large bulbs planted to a square metre will produce the most replacement bulbs.

 Do not push tulip bulbs into the soil with your fingers; a far better way is to make a row, place bulbs in it and cover with soil. When pressed too hard, bulbs can be injured, and will become vulnerable to diseases. Special tools for bulb planting are readily available in garden centres, should you dislike the idea of planting in rows. Some growers recommend planting tulip and other bulbs on a bed of sand. A 3-5cm sand layer should be spread on the bottom of the planting hole or the row. Bulbs should be pressed lightly into the sand, then toped with more sand, and only then mounded with soil. Tulips grow healthier in the sand, and their bulbs are less prone to rotting, since any excessive moisture drains away freely from the sand. This is an especially useful method for cultivating rare and expensive tulips.

© Giedra Bartas, 2009

Baths of clay and paraphine for dahlias

One of the most spectacular of autumn flowers – dahlia – unfortunately is not hardy enough to overwinter outside. However, be in no rush to lift them – many late-season blooms will still be produced during warm autumn days; while minor frosts cause little damage to dahlias, if their tubers are mounded.

Start lifting dahlias, when autumn frosts become regular, or when a prolonged cold period is forecasted. Depending on the weather conditions, sometimes dahlias need to be dug up in mid-September, but last year and this year they will keep flowering until late October.

Using a garden fork, lift the dahlia clump from the ground and leave to dry in the sunshine, or bring them inside, into a dry and ventilated place, such as a greenhouse. Clean tubers carefully in 5-6 days, removing any damaged and diseased parts, and cut the stems down to 2-4 cm. Sprinkle cut surfaces with crushed wood coal, and keep the tubers warm (20-25C) for another week, to give the cuts some time to heal.

Novice dahlia growers may want to buy dahlia tubers in spring, rather than trying to store them through the winter. On the other hand, experience is the best of teachers.

There are several ways to keep dahlia tubers through the winter. Line a square box (80x50x60cm) with  paper, spread a 3cm layer of dry soil or peat and place a single layer of dry dahlia tubers. Tubers are best stored at temperatures of +1+7C and humidity of 80-100 %, covered by a layer of soil, sand, peat, perlite, vermiculite or sawdust.

Dahlia tubers can be stored in open boxes in a cellar (+3+6C, humidity of 70%). The cellar should be ventilated 3 times a week for 20-30 minutes, alternatively, an air fan should be installed. .

Gardeners know a lot of ways to store dahlia tubers throughout the winter, however, a number of plants still rot. The decay starts from the stalk stump, and later reaches the point where the tuber connects to the main stalk. The rotting tuber is not easy to detect, therefore the rot spreads rapidly until the whole plant is lost. The rot can be avoided – peal off the bark of the stump and carefully remove all of the soft tissues, then leave to dry for 2 or 3 hours.

Tubers rolled in clay paste usually survive winter well. After you dig the tubers, shake off the excess soil and dry them for several days, as described above. Clean them carefully and soak for 12 hours in a strong solution of permanganate of potash. Remove then, dry briefly and dip in slurry of clay and fungicide, made to a consistency of sour cream. Dry briefly until the coating sets. Store in a cool cellar. In spring knock on tuber lightly to crack the coating; there is no need to remove it completely.

Store the tubers layered with dry sawdust or peat in perforated plastic bags, if the cellar is warm, or if the tubers are kept at room temperatures.

If you intend to store tubers in warm and humid conditions, they are best coated in paraphine. Washed and dried tubers are dipped in the melted paraphine. After the coating sets on the tubers, the procedure should be repeated. Tubers with the paraphine coating should be stored layered with sawdust or peat in plastic bags. Knock on the tubers lightly to crack the paraphine coating prior to planting.

© Giedra Bartas, 2009

Summer beauties

Water lily rhizomes come in a multitude of sizes and forms (those of a finger, a pineapple, a tuber, etc.). Usually, divisions of water lilies are sold when they are 10-15 cms long, while their diameter varies by the cultivar (from that of a finger to that of a small ‘pineapple’). Rhizomes of miniature water lilies are tiny, only 4-6 cm long. Depending on a variety, a division can weigh from several grams to a few hundred grams.

The rhizomatous rootstock of water lily consists of one or several large, straight or branched rhizomes covered in numerous roots. The finger-shaped rhizomes sprout roots only on one side, so make sure you do not plant them upside down (in most cases, one can easily see where the roots were attached to the rhizome previously). The rhizome should be planted horizontally, at an angle of approximately 45 or 70 degrees, buried in the soil, with the crown just above the soil. When the growth tip does not show, the division should be planted cut side down.

The pineapple-shaped rhizomes should be planted vertically, since their roots grow all around the rhizome, but the plant will not be harmed much, if you plant it in the usual way.

Miniature, small and medium water lilies are best planted into aquatic baskets or pots, since they will have to be moved for overwintering either into the deeper end of the pond or into a basement, in case your pool is on a shallow side. However, if the pond does not have a natural lining of soil, and is lined by the plastic lining or concrete instead, large water lilies are best planted into baskets too. Same advise should be followed if you need to control the growth of water lilies, or if you intend to grow the plants less than 1 metre deep (even in natural ponds).

A common question is whether it is better to plant a water lily into an aquatic mesh basket or into a simple pot. The mesh baskets are a very good choice, if your pond is a natural one, with soil at the bottom, or if there is a considerable amount of mud above the plastic lining. The roots then fill the basket promptly, and carry on into the outside. The mud provides the plants with supplemental nourishment and ensures favourable growing conditions. Planting baskets with wide-meshed sides will need to be lined with some fine-mesh material, otherwise the soil will fall out before the roots have a chance to grow and bind it together.

If you choose to plant your water lilies in a pond lined with the plastic lining or concrete, you may  plant them in a simple plastic pot. An ordinary large pot will do the job well, as long as you choose a wide and a spacious one. You should also keep in mind, the rhizomes of pot-grown water lilies tend to smell of mud and are more prone to disease.

Hardy water lilies show them best in a soil like clay. if you plant to a basket, use heavy soil from your garden.  Be sure there is no unroted organic in the soil, cause it will rot or float to the top in your pond. The soil is best wet, you can do this by soaking the pot in the water until the soil is soft enough to push your fingers down into the soil.

Plant rhizome and cover soil with gravel just for to not let it float up. Be sure not to bury the rhizome to deep, try not to cover new growth coming with soil or gravel.

The life cycles of water lilies, just like all other plants, are largely depend by weather conditions. Our nursery is located in 5 zone, in the middle of Lithuania. Usually, ice on the lakes and ponds melts in April, although sometimes it may happen as early as the beginning of March. The planting season of water lilies starts in May. In a cold and cloudy spring, the water warms up very slowly, therefore water lilies are in no hurry to start new growth, so they float their leaves only in 8-10 weeks. Until that moment, new shoots linger underwater. If the spring comes early and the water warms up promptly, then new leaves of the plants will appear on the surface earlier.

In order to get the maximum amount of blooms water lilies need plenty of sun, usually 4-6 hours of direct sun is required.

© Giedra Bartas, 2009

Growing and propagating delphiniums

Seedlings start flowering same year after sowing, in their fourth month. The growth of delphiniums halts, when seeds ripen, so inflorescences are best removed after the flowering is over. Delphiniums may flower repeatedly in autumn, if the spent blooms have been removed. Bear in mind that this wears the plant down, as it does not have time to set new buds, which may result in less than spectacular flowering next year. Hence it is advisable to cut the autumn flower spikes at the very root, as soon as they appear.

Delphiniums are best planted in late August or early September to allow them sufficient time to establish themselves. Tall hybrid delphiniums are best planted at 50-60 cm intervals in a sunny location, which is shaded from midday sun by trees, fences or walls. Delphiniums prefer growing in the sun, but midday sun can scorch their flowers, and the flowering will be over soon.

A planting hole for a delphinium should be 50 cm deep, filled with a mixture of compost, peat and garden soil, with an addition of fertilisers, rich in potassium and phosphorus. Aim to achieve the same planting level as before. Water well newly planted delphiniums, and water again in 2 or 3 days, if the weather is dry.

Delphiniums need spring feed, when their shoots grow 10-15cm tall – apply complete mineral fertiliser or watered-down slurry of manure (a bucket of manure to 10 buckets of water; a bucket of slurry being sufficient for 5 plants). An additional feeding with potassium fertiliser is appropriate, when plants start producing their flower spikes.

Delphiniums respond well to mulching with peat or compost, which should be spread to a 2-3cm layer around the base. A vigorous plant produces a lot of flower spikes and soon becomes congested. Shoots can be thinned out, when they grow 20-30 cm tall. First, remove al the weak stems from the centre of the clump. If you can bear to be ruthless enough, and leave only 3 to 5 stems per plant, you will soon be rewarded with exceptionally large flowers on tall flower spikes. Besides, the removed shoots can be rooted to produce new plants.

The plant supports should be installed, when plants grow 40-50 cm tall. A plant needs 3 to 5 twigs, around 1.8m long. All stems need to be tied in, since they break easily in the wind. The stems can also be tied around with a wire, which is attached to a stake. The support will soon be mask by foliage, and stems will grow well-supported.

The weakest spot of the delphinium is where stems attach themselves to the crown: they break easily, so are best tied in two places, 40-50 cm and 100-120cm above the ground. If the flower spikes are especially tall and heavy, they should be tide in at three levels – at 40, 80 and 120 cm above the ground.

In a prolonged dry spell plants should be watered every week, 2-3 buckets of water per plant. A shallow frequent watering brings more harm than use. The caked-up soil should be tilled regularly. Delphiniums need most water, when they are setting flowers. At times flowers get aborted on the spike due to the heat, or they flower inconsistently along the spike. Sometimes plants produce deformed inflorescences, if they are short of potassium or phosphorus.

In autumn, when the leaves die back, the stems are cut down to 25-30 cm above the soil. In a very severe and snowless winter, young plants should be covered with straw, hay or conifer branches.

© Giedra Bartas, 2009

Catalpas dislike strong winds

The name of catalpa tree derives from the Indian language, meaning “elephant`s ears”. These are attractive, mostly deciduous (sometime evergreen) trees with broadly rounded crown. The leaves are heart-shaped and large with long petioles. The showy bell-shaped flowers up to 7 cm long, held in large terminal sprays, are white or cream, with lower lips splashed with purple blotches and spots. Long (up to 40cm) fruits, which resemble bean pods, open to release quantities of light winged seeds. The tree retains these curious seed pods well into winter, which only increases its ornamental value.

Southern catalpa (Catalpa bignonioides Walt.) grows to 15-20 m tall, with wide-spread branches and a rounded crown. The bark is light brown. Leaves of this species, resembling those of lilacs, if only larger and wider, are light green with downy undersides. Flowers are up to 5 cm long, white with purple blotches and two yellow strips, held in broad frothy panicles, which carry on flowering for about 20 days.

In spring catalpas start breaking into new growth in mid-May, stopping in August. Leaves drop after the first frosts, without giving any colourful autumn displays. It is a fast-growing tree, sometimes at a rate of half a metre in a growing season. However, sometimes all this growth dies down during a particularly cold winter. It is also susceptible to draught, so watering young plants during a prolonged dry spell is essential. Catalpas associate well with magnolias and oaks, however, they dislike being planted in exposed locations, where winds tear their leaves to shreds.

The cultivar `Aurea` is grown for its lime-green foliage, while yellow leaves of `Koehnei` are patterned with green veining and a dark spot in the middle of the leave. `Nana` is a very compact and rounded cultivar, and is often top-grafted on a tall stem, which makes it suitable for planting in knot gardens.

The leaves of Northern catalpa (Catalpa speciosa Warder et Engelm.) are narrower that those of southern catalpa, and break into growth later in the spring. Leaves are green, shiny and downy on the undersides. Fragrant, frilly flowers are up to 7 cm long are creamy white, with lower lip splashed in purple and decorated with two yellow strips. Flowers are held in 15-20 cm long panicles and carry on flowering for about 20 days. Long (up to 45 cm) seed pods mature by the end of the summer.

Northern catalpas grow fast in favorable conditions, putting on up to 1 m of new growth in a growing season. They are drought-tolerant, but young shoots are prone to freeze-damage in severe winters. Generally, they start flowering by the end of June, but this may happen any time sooner or later, depending on the weather. In a prolonged period of drought they need abundant watering and an occasional overall shower.

Catalpas are sun-loving trees, which dislike being planted in a waterlogged site or in locations, where the water table is high. Trees grow best when planted in moist, well-draining soil. Planting should be done in spring. Seeds fully ripen only in warm and long autumn without early frosts. Propagate catalpas by seeds, cuttings or layering.

The foliage of northern catalpa `Pulverulenta` is mottled white or cream.

The leaves of Chinese catalpa (Catalpa ovata) resemble those of the tulip tree. Its flowers, which appear in mid-July, are scarce. The tree sets seeds, but they do not fully ripen. Seeds pods are shorter than those of the catalpas of other species.

Plant catalpas in a sunny and sheltered location, since the luxurious leaves suffer if exposed to severe wind. When planting an alley of trees, space them at 4-5 m intervals. If you plant in a poor soil, dig a planting hole 0.8-1.2 m deep, fill it with mixture of well-rotted compost, loam, sand and peat (3:2:1:2), and add 5 to 8 kg of wood coal ashes. Catalpas dislike growing in acid soil, with pH 6.5-7.5 being optimum.

Water thoroughly, once a week, at a rate of 15-20 l of water per planted tree. When the tree breaks dormacy in spring, remove damaged or dead branches. If trees are planted in autumn, mulch around them thickly with peat, or alternatively, insulate them with some horticultural fleece and straw.

© Giedra Bartas, 2009

A seat fit for clematis

clematis_vagabond

Clematis do not need a lot of space. They associate well with other plants. Low-growing early-flowering perennials, such as creeping phloxes or rock cress, make perfect companion plants for clematis. They are already in flower, when clematis breaks into growth in spring. In summer they make a green carpeting ground cover around clematis, which helps to preserve moisture. Pergolas and trellises, planted with clematis, mask dying foliage of tulips and daffodils well, while looking unobtrusive during April and May, when these bulbs are in flower. Exuberant growth of clematis soon hides their unsightly dying leaves.

If you have a vast lawn, you should try pairing clematis with tall sturdy perennials, but vigorous deep-rooted plants are best avoided. Feeding roots of these plants and clematis will mingle to an extent, where transplanting will be impossible without damaging the roots.

A beautiful plant needs a beautiful backdrop, so do not plant clematis against a shabby and pealing wall. The clematis cultivars, flowering on previous year`s wood, are best planted on the south-, east- or west-facing walls. Clematis, which flower on current year`s growth, are best given southern exposure, so as to receive sufficient warmth and light. Plant clematis at least 30-60cm away from the wall, and 20 cm away from the wire fence. Clematis dislike excessive heat, which brick walls accumulate in summer. Capron or wire netting, metal or wooden trellises with 15 to 20 cm eye diameter – these all are feasible supports for clematis. The supports should be well-made and ornamental by themselves, since some clematis are slow-growing, and fill out only by late summer. Avoid using Capron or metal netting for clematis, which flowers on previous year`s growth, since it will be next to impossible to untangle its stems in autumn, in order to lay them down to be protected in winter.

In small or narrow gardens clematis can be used to divide various parts of the garden. They take much less space than trees or shrubs. An unsightly wire fence, surrounding the plot, can be disguised by growing a small-flowered species clematis over it. This arrangement would look best on a fence slightly more or less that 1.7 m (the eye level). The large-flowered clematis are best planted in open locations, grown over pergolas, benches or arbours.

Buds and flowers of clematis always turn towards the sun. A spectacular flowering carpet can be achieved by spreading a net some 15 to 20cm above the ground. Clematis can be planted to drape over an old watering well, a dry tree stump, or even an ordinary wooden stake. Young plants should be tied-in every 15 cm, and the foliage will hide the string in no time. Tree trunk can be wrapped in wire netting. A wooden log, 2-3 metres tall, can make a stunning feature when planted with 3-5 clematis of different colours. To enable clematis to climb freely, the stake should be wrapped in a mesh. The cultivars `Anastasia Anisimova` and `Sizaja Ptica` are non-clinging, so they need to be tied in.

Spectacular combinations can be created pairing blue hybrid `Jackmanii` with bicoloured `Nelly Moser`, dark purple `Gypsy Queen` with sky-blue `Ramona`, red `Ernest Marhham` with white `Joan d`Arc`. Combine clematis with similar pruning requirement for easier maintenance – come autumn, you will have a tough job untangling the stems, if one of the clematis needs to be cut down, while another one has to have its stems taken down for overwintering.

Spring is the best time to plant clematis. It should be planted with its crown deeper by 10-15 cm than it grew in the pot. These are low-maintenance plants, and can be grown anywhere, except in pure sand. But, when grown in poor soil, they will grow and flower poorly, and the individual flowers will be small. Dry sandy soils should be amended with manure, peat or compost, while heavy clay should be improved with a mixture of sharp sand and peat. Before planting, fill the hole with 2 buckets of the mixture, made of well-rotted manure, compost and garden soil, add 2-3 handfuls of chalk or bonemeal, and 200g of potassium-rich fertiliser. When planting on a damp spot, spread a 15 cm layer of crushed stone or clay crocs on the bottom of the hole to improve drainage.

Clematis prefer sunny locations, but they dislike when their roots bake in the sun. The soil around them should be mulched with peat, sawdust or planted with creeping early-flowering plants. The small-flowered compact marigolds make an excellent companion plant: not only they provide clematis with a cool rootrun, but they also prevent pests and diseases.

Fertilise clematis often, every 10 days, with a diluted liquid feed. Foliar feeding with a solution of complete mineral fertilizers has proved to be effective, and can be applied up to the moment when the flower buds appear. Feeding with nitrogen-based fertilizers should stop in August, but plants will still require fertilisers high in potassium. In late autumn apply 80-100 g of superphosphate and 2-3 cups of crushed wood coal to each clematis plant.

The stems of clematis, flowering on current year`s growth, should be cut down to 1-2 buds above the ground in late autumn or early spring. They do not need to be covered for the winter, and are susceptible to freeze only in the most severe winters.

Clematis, flowering on the previous year`s growth, should be shortened by a third. Dead and disease-ridden stems should be removed in summer. When stems of the clematis of this type are removed to the ground, they will only flower in late summer or autumn. Shortened stems should be laid on the ground. When earth freezes over, and average temperature drops to -5oC, clematis should be covered with conifer branches. Avoid covering plants too early, since this may cause plants to rot, or to burst into growth and die. If winter thaws are frequent, provide the clematis with a covering of ruberoid to prevent its roots from rotting.

Carpets of rock cress for rockeries

The Latin name for rock cress Arabis derives from the word Arabia. This is a plant for sandy, stony and infertile places, which thrives planted in rock gardens and stone walls. The genus consists of some 100 species, 4 of which are native to Lithuania. They are sand rock cress (Arabis arenosa), Arabis gerardii, tower rock cress (Arabis glabra) and hairy rock cress (Arabis hirsuta).

These are mostly prostrate plants with creeping and rooting stems. Their leaves are densely hairy; white, pink, lilac or cream flowers are up to 1.5cm wide. They are single or double, held in small and dense racemes. Some species, such as alpine and wall rock cress, have long been cultivated in the gardens; while others – A.procurrens, A.x arendsii, A.ferdinandii-coburgii  – are less common.

Alpine rock cress (Arabis alpina L.) is native to the Ural Mountains, the Far East, North Scandinavia and higher elevations of Western Europe and North America. This perennial plant grows to 35cm tall, and produces cushion-shaped mounds, which stay evergreen over the winter. The leaves in the basal rosette are ovoid, although the stem leaves are oblong and grey. Flowers are white or pink, up to 1cm, fragrant, and held in racemes. It flowers in April and May for 25-30 days. Seeds ripen in July.

`Schneehaube` alpine rock cress grows 10-25 cm tall, with white flowers up to 2cm wide, held in 15cm long racemes. It flowers in April for 25-30 days.

`Flore Plena` rock cress is very similar in appearance to the species, but flowers are twice the size, racemes are longer and resemble those of snowflakes (Leucojum). It flowers profusely from early May to mid-June.

`Rosea` rock cress grows to 20cm tall, with pink flowers up to 2cm wide. Racemes are up to 12cm long. It starts flowering in late April, and continues for 30-35 days.

Most rock cress grow best in full sun, some species tolerate light shade. In favourable conditions rock cress flower abundantly, and spread quickly to form loose mats of dense rosettes. They dislike standing water, heavy or very fertile soil, and half-rotted organic matter. When planting on heavy garden soil, replace part of it with a mixture of compost and sand (1:1 or 2:1), and lay some draining material at the bottom. These are perfect plants for rock gardens, stone walls, etc.

In an exposed location, especially on a hillside, rock cress are susceptible to winter injury in snowless winter, and need to be covered with conifer branches or leaves. If snow melts early in spring, but the earth is still frozen over, rock cress need to be sheltered from direct sunlight, just like conifers or rhododendrons would.

Species plants are propagated by seeds, while the double-flowered and variegated cultivars are usually propagated by division or softwood cuttings. Seeds are sown in spring or in late autumn, and seedling start flowering in the second year. The best time to divide plants is in late summer. About 20 new plants can be easily produced from 3 or 4 mature plants. These should be planted at the 30-35cm intervals. Softwood cuttings are best taken from mid-May to mid-June. Cut terminal shoots from new growth, about 6-8 cm long. Remove 2-3 bottom leaves and plant into nursery beds. The propagation beds should be shaded and thoroughly watered. Cuttings break roots within 2 to 3 weeks. Move plants to their permanent position in August.

Wall rock cress is more widely planted than the alpine one. Some authors ascribe them to separate species, while others describe them as a subspecies or a variety of the alpine rock cress. The main difference between alpine and wall rock cress is in the flowering time – the wall rock cress flowers later in the season.

© Giedra Bartas, 2009

Rhododendrons: planting and feeding

The best time to plant rhododendrons is either in spring, from early April to mid-May, as soon as soil warms up, or in autumn, from early September to early October, so that plants would still have time to root the ground freezes over. Rhododendrons can be planted any other time, if need be, except when in flower or when new shoots are growing fast, which is usually after, and sometimes during, the flowering period. Potted rhododendrons can be planted any time during growing season. Even mature rhododendron bushes tolerate replanting well. Their roots suffer hardly any damage, being compact and shallow-rooted, which is rather an exceptional quality, comparing to other plants. Before moving rhododendrons, water them well, which will make replanting easier, and the plants will not be subjected to the moisture shortage.

Having replanted the bushes, water them thoroughly. If the rhododendron has set many flower buds, it is best to remove some of them, so that the plant would not waste valuable nutrients on flowering before it gets established.

Large flowers of rhododendrons come in abundance, so a generous supply of nutrients is important to keep up their vigour. Both organic and mineral fertilisers can be used on young and adult plants alike. Ideally, a well-balanced fertilizer should contain main elements N:P:K in ratio of 3:1:2. Nitrogen (N) is essential in spring and early summer, when plants are growing fast. Phosphorus (P) is required for flowering and for the flower bud setting. Potash (K) is necessary throughout the growing season, since it aids absorption of other nutrients. Phosphorus and potassium also play a major role in reproduction of plants and seed setting. Due to these elements, shoots grow faster and harden off in due time to withstand the winter freeze.

The best organic fertilizer is well-rotted manure. In addition to feeding plants, it improves soil structure, making it crumbly and well-drained. Mulching plants will also help to replenish the soil with organic matter.

Mineral fertilisers are mostly synthetic. They provide rhododendrons with macro- and micro elements. Plants require considerable quantities of macro elements (nitrogen, phosphorus, potassium, magnesium) and only traces of micro elmements (boron, copper, iron, manganese, molybdenum and zinc), but the latter ones are very important. The well-balanced complete fertiliser containing all required micro elements is ideal for the purpose. Rhododendrons, [banner] grown on acid soil, absorb minerals much better. Larger quantities of micro elements could poison plants grown on alkaline soil. Acid fertilisers – nitrogen sulfate, superphosphate, potassium sulphate, magnesium sulphate – are preferable, and, of course, complete fertilisers balanced especially for rhododendrons, both in liquid and granular forms. Granular fertilisers generally are slow-release type, and are used once during the growing season. Liquid feeding can be applied regularly, every 10-14 days. Mineral fertilisers, containing chlorine, are best avoided, since they prevent absorption of the other nutrients. The vigor of the plants, the abundance of blooms, the color and the size of the leaves are the tell-tale signs whether the plants are getting sufficient nutrients. But bear in mind, that too much of fertilizers is just as bad as too little of them.

The best time to apply slow-release fertiliser is in early spring (March-April), while liquid feeding should stop in mid- to late July. If you continue to fertilise plants later than this, especially in damp and warm weather, rhododendrons will respond with a new flush of growth, which will not have sufficient time to harden off before onset of winter, and will suffer winter damage.

© Giedra Bartas, 2009