Flowering and Foliage Conservatory Plants

It is vital to choose plants that are suitable for growing in the temperature and light conditions of your greenhouse or conservatory. If you do not mix plants with very different requirements, for example, succulents, which need plenty of light, and ferns, which need shade and moisture, you will obtain far better results. It may, however, be possible to suit individual needs to some extent by putting plants which require shade under staging, for instance.

Buy plants only from reputable suppliers. Make sure they are healthy and correctly identified and labelled. There are specialist nurseries for some types of plants but many others can be grown successfully and cheaply from seed.


Never use garden soil for pot work nor, in most cases, the greenhouse ground soil. The use of unsterilized garden soil and crude fertilizers, such as animal manures, is inviting failure and disappointment; all manner of pests and diseases can be introduced.

There are a number of proprietary seed and potting composts available from which to choose. These are mostly peat based, are free from pests, disease and weed seed, and have an ideal fertilizer balance. The John Innes composts, which are loam based, are also a good buy provided they are made exactly to the original formulae set by the John Innes Horticultural Institute.

When a lot of compost is needed, it is cheaper to make up a peat and grit mix yourself and add a ready-mixed fertilizer concentrate, available with full instructions from garden shops. Such DIY composts can be made up with very little effort in a few minutes. The John Innes composts have more complicated ingredients, including special loam, and DIY preparation is, therefore, not often attempted.


Plastic pots are now widely used. They are lightweight, easy to store and clean, and retain moisture better than clay so the compost does not dry out so quickly. Clay pots, being porous, are a better choice when plants need to be plunged in a moisture-retaining material.

Pot sizes mentioned in the text are all average. When potting most decorative plants, use a pot just large enough to take the plant comfortably. As it grows, the plant needs to be potted-on. This means transferring it into successively larger pots as the roots fill the existing one. Tap the plant out of the container, if there’s a mass of tangled roots encircling the pot, the plant is ‘pot bound’ and should be put into a slightly larger container with fresh compost. This ensures that the roots always have a supply of ‘sweet’ compost with the right balance of nutrients. Exceptions to this treatment are plants known to be fast growers and vigorous. These, which include certain vegetable crops, can be given larger pots in the early stages. Obviously, after a time, plants cannot be potted-on any further. If they are perennial, they can simply be repotted. This means removing the plant from its pot, carefully reducing the size of the root ball, teasing away old roots and compost, and potting back into the same sized pot with fresh compost. You should do this just before the plant is expected to make new growth.

Another method for plants in final pots is to top dress. This means removing the upper layers of compost and replacing them with fresh. Alternatively, mix in some balanced fertilizer at the top of the pot. Nowadays, the excellent systemic and foliar feeds available make the feeding of established plants easier and top dressing less important than it used to be.

When potting, always leave a space between the surface of the compost and the top of the pot. This is the watering space. It assures water penetration and helps to assess the amount needed.



This entails sprinkling water over as much of the floor and staging as is convenient. Evaporation of the water then causes cooling and increases humidity which growing plants like. A moist atmosphere also means that they need less frequent watering. Damping down must not be done in winter. The air then should be kept on the dry side since too much humidity encourages moulds and mildews when conditions are cool.


Always use clean water. Rainwater collected from roofs and stored in dirty butts should never be used as it is likely to be contaminated. Most plants will be far healthier with tap water. In areas where this is ‘hard’, plants disliking lime can be watered with clean rainwater collected in bowls. However, it is doubtful if this is really necessary provided that such plants are grown in special lime-free ‘ericaceous’ composts, which are available from garden shops.

The best general rule for watering plants is to keep the roots constantly moist. It is vital to avoid absolute dryness or water-logging. Water must also be given according to a plant’s needs and not in standard doses. When plants are dormant, as in winter, little if any water is required. Wet conditions then will lead to rotting and possibly to cold damage. In summer, however, water may be needed frequently: vigorous plants may require watering several times a day.

In general, plants need more water when conditions are warm and bright than when they are cold and dull. The best time to water is in the morning. Erratic watering leads to wilting and bud, flower or leaf shedding. Overwatering is often indicated by a sickly appearance, poor growth and yellowish foliage.


The rules given for watering also apply to feeding. Feed according to a plant’s needs and vigour. When a suitable potting compost is used, feeding is not necessary until the plant is in the final pot. Feeding can be done with proprietary feeds which contain the nutrients in the correct, scientifically balanced proportions. These should be used according to the instructions on the label. Using DIY mixes, hit and miss fertilizers, or crude manures is most unwise. Overfeeding is harmful and you should never exceed the recommended doses. Frequent feeding with weak solutions gives the best results. Do not feed when the roots are dry. Foliar feeds, which are sprayed onto the leaves, can give a quick improvement. Some contain plant vitamins and hormones.


Make every effort to ensure that the temperature does not fall below the minimum required by your plants in winter. Thermostatic control of artificial heating usually makes management easy. In summer, conditions must not be allowed to become too hot. Damping down, shading with a white compound (such as Coolglass) and careful use of ventilators enables temperature adjustment. Excessive heat can prevent some plants from flowering. Erratic temperature changes lead to bud shedding and physiological problems.

Well as the more popular bedding plants, many of which make fine pot plants.

Some people think that starting from seed is a slow and difficult way to begin. This is not true, and if you follow the techniques given in success can be assured.


The cheapest way to acquire plants is to grow them from seed. Look through the catalogues from the leading seed firms and you will find an exciting and extensive range to choose from. There are always lots of seed novelties on offer as


The word ‘bulb’ is often used by the layman to include corms, tubers, rhizomes, and similar items which are known as ‘storage organs’ by the botanist. These storage organs all contain food, which ensures the plant gets a good start in life. When you buy them, look for high quality, since their performance depends on how well they have been produced.

Always purchase from a reputable firm. Do not accept anything soft and spongy or showing signs of rot or mildew. Small size is also best avoided, since it may indicate that die organ is not developed enough to produce flowers.


Always use a proper potting compost. Choose a pot of suitable size for the particular bulb. Small bulbs can be grouped, large bulbs need individual pots. Most bulbs grown for the greenhouse can be potted shallowly with their tips protruding well above the compost surface. This gives plenty of room for the roots in the pot. Decorative bowls are popular for growing bulbs in, but take care as these may become waterlogged if there are no drainage holes.


Plant storage organs fall into two categories: hardy and tender. The treatment of each is quite different. The hardy group includes the popular, well-loved spring-flowering favourites such as daffodil, hyacinth and crocus. These are indispensable for unheated or cold conditions. The tender group includes many of the greenhouse ‘exotics’, for example, gloxinia, begonia, and hippeastrum, which require warmer conditions.


(Hardy) The great majority of these should be potted from August to October. After potting they should be plunged in moist peat or grit, outdoors, to give about 150mm (6in) covering. The plunge must be kept moist but protected from rain to prevent waterlogging. On no account keep the containers in a warm place. Leave them in the plunge for about six to eight weeks. The bulbs should by then have made plenty of roots and can be brought into a cool greenhouse or conservatory and gradually introduced to full light. Too much warmth is harmful to this group and may cause weak, lanky growth and failure to flower.


(Tender) These are potted or started into growth in gentle warmth from early to late spring. Those storage organs without an obvious growing point, such as gloxinia and begonia, should be just covered with moist peat in a warm propagator. Inspect them daily and, as soon as you can see roots or shoots, pot into a suitable potting compost. Again they need only be potted at a shallow depth. Most of this group require a minimum temperature of about IOC (50 degrees F) and will grow faster if it is a few degrees higher. Keep the atmosphere moist and protect from direct sunlight.


Plants of the hardy group can be put outdoors in any convenient place. Continue to water and feed them until the foliage dies down naturally, this is important to their flowering in future years. The bulbs often multiply and may need separating and repotting in the future.

The tender group should also be watered and fed until the foliage shows signs of deterioration, and then allowed to become dry. When dry, tip out of the pots, free from compost, remove stem and leaf vegetation, and store dry in clean sand in a frost-free place over winter. Delicate or brittle storage organs, such as some rhizomes and tubers, can be left in their pots, which should be turned on their sides until next repotted.


This term is used to describe bulbs and other storage organs that have been especially temperature treated to induce early or out-of-season flowering. The suppliers’ instructions should be closely followed regarding cultivation and temperature. The temperature stated is sometimes initially rather high and may not be practical to attain in an ordinary greenhouse. The forcing can then be done in a warm room indoors. When approaching flowering, move the plants to the cooler conditions of a conservatory.


Many pot plants can be bought from florist shops and large stores. Garden centres are another source. Those plants described as ‘houseplants’ are often excellent for the greenhouse and conservatory, frequently growing more vigorously there than in the house itself, which rarely provides a good environment for flowering plants. Most of these plants have been grown by rooting cuttings. You can often increase your stock in the same way once you have established them.

AZALEA (Rhododendron).

There are two kinds, one hardy and die other tender. The easiest to grow and also the best for greenhouses or conservatories are the hardy evergreen named types, often sold by nurseries and garden centres. Those sold by florists around Christmas are Indian azaleas (Rhododendron simsii) which are especially forced. They will not flower again at the same time of year if kept and must be overwintered in a greenhouse. During summer, azaleas can be stood outdoors in a shady place, but watering must not be forgotten. When potting, use an acid, cricaceous compost and, if possible, water with dean rainwater.


Shrimp plant is the name given to B. guttata because of the strange colour and appearance of the bracts around the flowers. When buying for the greenhouse, it is wise to remove the flowers and bracts that have already formed. This encourages die plant to grow larger and become more decorative. Shade is often recommended, but good light, even some direct sunlight, produces superior colouring. A minimum winter temperature of about 7 C (45 degrees F) is needed.


It is not widely realized that these well-known evergreens make fine pot plants when young, and flower well. They make superb conservatory plants, especially where conditions tend to be chilly. With glass protection, blooming is early and the flowers are not ruined by weather as so often happens outdoors. Give an acid, cricaceous compost and water with clean rainwater if possible. Do not allow the pots to dry out at any time. This needs to be watched particularly if the plants are stood out for the summer.


C. isophylla is an old favourite for hanging baskets in conservatories. It forms an attractive cascade and becomes smothered with blue or white flowers from about July to Autumn. Sometimes leaf variegation occurs spontaneously. When this happens the shoot can be removed as a cutting and rooted. Cream and green variegated plants often have smaller flowers.


With a little care you can grow exquisite carnations just like those sold by florists. These are called perpetual flowering (PF for short) because they continue to produce blooms for cutting almost die whole year round. A minimum winter temperature of about 7-10 C (45-50 degrees F) is essential. Provided you have a greenhouse with plenty of light, they usually fit in well with other plants.

Buy named varieties of rooted cuttings from a specialist nursery in early spring. Not all are fragrant. For beginners the ‘Sim’ varieties are recommended. In recent years low-growing types have been introduced.

Grow the cuttings for a few weeks in small pots and then transfer to 180mm (7in) pots. Usually, young plants have already been ‘stopped’ by the nurseryman, if not, you should pinch out the tips. Also ‘stop’ the side shoots that form later, ‘stopping’ the fastest growing first. Do not ‘stop’ them all at once. This procedure is to encourage the growth of stems, all of which will bear one large bloom. The small buds that form from the stem or around the main bud (crown bud), must be removed carefully by bending them back. They usually snap off. This is to direct the plant’s energy into development of the crown bud.

Special carnation feeds are sold, but a tomato feed will also give good results. The stems need careful support with canes or special wire carnation supports. It is inadvisable to keep plants for more than three years. Calyx splitting, which causes petals to bulge in one place and spoils the bloom, is a common problem. Avoiding wide temperature fluctuations and erratic watering and feeding will help prevent it.


These make wonderful conservatory plants. Certain types are also grown for cutting and can follow a tomato crop. When choosing, consult a descriptive catalogue from a specialist nursery since there are so many types. The catalogue will also give guidance regarding ‘stopping’ which is particularly important for the large-flowered types.

The large-flowered forms are classified according to flower character, for example, ‘incurved’ when petals turn inwards, and ‘reflexed’ when they turn outwards. The plants are grown from rooted cuttings. These can be bought in spring and put outdoors in large pots for the summer. They must be carefully staked to prevent wind damage. They need regular watering and feeding and should be ‘stopped’ at the recommended time. To obtain high quality blooms, allow only a few stems with one bud on each to develop. The large-flowered varieties also need disbudding to ensure the development of one huge bloom on each stem. Transfer the plants to the greenhouse in autumn for the final training and blooming.

Much easier are the Charm types which can be grown from seed. The rooted cuttings or seedlings must be ‘stopped’ but they can then be allowed to develop naturally. They first form a neat compact bush, then spread out, later becoming smothered with small ‘daisy’ blooms forming cushions of colour.

Some other chrysanthemums are also easy to grow from seed, notably the F1and F2 hybrids. For example, ‘Autumn Glory’ and ‘Petit Point’ which are neat and compact. Korean hybrids are worth growing too.


Oranges, lemons, limes, grapefruits, and the like are often grown from ‘pips’. The results can be disappointing and it is far better to buy named plant varieties or species from a specialist nursery. Citrus mitis, which is often sold as a houseplant, is very popular. It has fragrant, white, waxy star-shaped flowers, followed by small oranges the size of a walnut, which remain decorative for most of the year. Pot on when necessary into an acid, ericaceous compost and use clean rainwater if your tap water is ‘hard’. It likes full sun and can be put outdoors in summer. A minimum winter temperature of 10 C (50 degrees F) is necessary.


This is an impressive conservatory plant with strap-shaped foliage and enormous umbels of large orange flowers in spring. It need only be kept just frost free, but is severely damaged or killed if temperatures fall below freezing. It should be grown in large pots or small tubs and should be left undisturbed until it is seriously root bound. Avoid direct sun and in winter put in an unheatcd room and water sparingly.

CYTISUS (brooms)

Two brooms are often sold as houseplants, genista (C. canariensis) and C. x racemosus. If given large pots they will grow to the height of a man. Restricting pot size and severe pruning can keep them more manageable. Genista has scented yellow flowers, spring to summer, and is ever-green. C. x racemosus has showy, yellow, scented flowers, winter to spring, and greyish-green foliage. Prune back after flowering and stand outdoors for the summer. Do not allow it to dry out at any time; give slight shade. Bring indoors in September and keep cool but frost free. Water liberally during flowering.

ERICA (bell heathers, or heaths)

From about Christmas time onwards, Erica gracilis, which has pink or white flowers and E. hyemalis, with pink tubular flowers, are sold by florists. These plants are usually forced for early bloom. After flowering, pot into an acid, ericaceous compost and stand outdoors during summer. Do not allow to dry out. Water with clean rainwater if necessary. Return to the greenhouse for winter. A minimum temperature about 7 C (45 degrees F) is needed.


Fuchsias are among the most popular of all pot plants. The flowers have a particular fascination and die plants lend themselves to training in various shapes. There are now innumerable varieties and before making a choice it is best to obtain descriptive catalogues from specialist nurseries. The most convenient way to acquire plants is to buy rooted cuttings in spring, which will flower well the first year.

Training is done by pinching out the tips of shoots. This technique, known as ‘stopping’, causes several new shoots to grow, all of which will carry flowers in due course. It is important to remember to cease ‘stopping’ about eight weeks before you want the flowers. Some fuchsias are marvellous displayed in hanging baskets.

To train a standard, select a strong-rooted cutting. Do not ‘stop’ the tip of the cutting, but allow it to grow normally. Do pinch out all side shoots that may form, but not leaves growing from the stem. When the stem has reached the desired height, pinch out the tip. This causes many shoots to form below- and these should be ‘stopped’ in turn, to produce a bushy ‘head’. Leaves can then be removed from the supporting stem. A stout cane will be needed for support.

Fuchsias can be overwintered as long as they are kept frost free, but standards need warmer conditions to prevent die back. Shade them in summer and water well. Give good light in winter and water sparingly.


This is a popular gift plant. After flowering cut off the heads and any straggly growth. Stand outdoors in a shady place with pots plunged. New shoots should form. Cut out the old stems (that produced flowers) just above the new ones. The new shoots should flower the following year. Water with clean rainwater if your tap water is ‘hard’. Return to the greenhouse in autumn, but do not allow the temperature to rise much above 10 C (50 degrees F) until February as this could inhibit flowering. The flowers will not have rich colour if the compost is alkaline. Use an acid, ericaceous compost for potting.

NERIUM (Oleander)

An ideal evergreen plant for the cool conservatory. Masses of flowers are produced from summer to autumn, in white, pink, and shades of carmine. The plants become untidy unless properly pruned. Shoots that form at the base of the flower trusses should be removed promptly, and in autumn, after flowering, the shoots of the previous year’s development should be reduced to about a finger’s length. This will encourage new growth from the base. Water well in summer and sparingly in winter. Keep frost free. Note that the sap is poisonous so handle with great care. It can be kept in 20cm (8in) pots for some years.


The great majority of orchids we cultivate are hybrids created by man. There are many that grow well alongside other plants in our green-houses and conservatories – it is not essential to have special conditions. Some people think that orchids are difficult and expensive. This is just not true; they can be cheaper and easier than some other plants we grow.

Orchids do need a special compost of fibrous texture, but this is easy enough to obtain from nurseries specializing in the plants. Such nurseries are also the best source for die orchids themselves. Try to visit nurseries and choose your plants when most orchids are in flower, from winter to spring. Some large stores now also sell fine plants. Since the average home greenhouse or conservatory has a cool winter minimum, it’s wise to select orchids accordingly. Undoubtedly top of the list should be the cymbidiums. These bear arching stems of typical orchid flowers with delightful colours and markings, and the blooms are amazingly long lasting. They do very well in a ‘mixed’ greenhouse. During summer they can be put in a bright position outside.

Many people find paphiopedilums fascinating because of their slipper shape and quaint markings. There are plain-leaved and mottled-leaved kinds; die former are usually better for cool conditions. Unlike most, these orchids do not have pseudobulbs, and they need more shade than cymbidiums. Cattleyas are very exotic and need a higher temperature, but they are compact, and perhaps just part of the greenhouse could be especially heated for them. You could also consider growing die beautiful odontoglossums, miltonia’s (pansy orchids), and some laelias and vandas.

Orchid growers will advise you on which plants are most suitable for the conditions you have. They will also probably have useful literature giving details of the best treatment for all the many, very varied orchid types available.


These rival fuchsias in popularity. There are a large number of named cultivars and when choosing you should consult a specialist catalogue.

The plant commonly called ‘geranium’ is, in fact, the zonal pelargonium. The named types now have considerable competition from the F1hybrids which are easily grown from seed. Most of die group have zoned leaf markings. There are many colours, as well as doubles, semi-doubles, types with variously shaped petals and miniatures. Also some with beautiful leaf colouring and variegation.

The regal group have exceptionally showy flowers but these are not borne over such a long period. They are best kept in a greenhouse and can reach a considerable size after a few years. They are very impressive when in flower.

The ivy-leaved group are long flowering and particularly suitable for hanging-baskets. Use three or four plants per basket.

All these can be bought as rooted cuttings. ‘Stopping’ is important to prevent lanky, untidy development. Overwinter in the same conditions as fuchsias and be sure to ventilate freely when possible. Most pelargoniums need plenty of light, and moderate ventilation. Do not ovcrwatcr.


An evergreen climber with waxy white tubular flowers having a powerful fragrance. Although it will often survive conditions little more than frost free, it really prefers moderate warmth and humidity. In good conditions it will climb up into the roof of a greenhouse. The stems should be trained on a support and cut back after flowering. Water well in summer and sparingly in winter. It likes a position of moderate light.

STRELITZIA REGINA (Bird- of-paradise flower)

This is one of the most spectacular of all pot plants, the famous bird-of-paradise flower. It has bold, evergreen spear-shaped leaves and large flowers in orange and blue like an exotic bird’s head. The flowers, produced twice a year in summer and at Christmas, are on tall stalks and last for several weeks. Although its appearance is exotic it is, in fact ideal for a frost-free conservatory and does not demand high temperatures, as is often stated. Give a position in good light, but shade from hot sun. Water well in summer and very sparingly in winter. A mature plant needs a 250mm (lOin) pot or larger, and should be left until seriously pot bound. Large plants that have ‘clumped’ can be divided by cutting through the roots in spring. The roots should be separated so that each piece has a ‘fan’ of leaves. A young plant may take up to two years before it flowers.


The correct botanical name for this is Tibouchina urvilleana, but it’s usually labelled T. semide-candra. It is a favourite conservatory perennial, bearing pansy-shaped violet-coloured flowers summer to autumn. Buy plants as rooted cuttings and pinch out the top and the tips of any laterals that form after potting. Pot in 180mm (7in) pots for flowering and give a cane for support. Water well in summer and sparingly in winter; cut back severely in late winter.

26. August 2013 by admin
Categories: Featured, Garden Management, Top Tips | Comments Off on Flowering and Foliage Conservatory Plants


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