Horticultural uses of the Protected Environment

Question 1

Describe use of protected environments for OVER-WINTERING of plants:

Answer 1

Glasshouses (heated or unheated) can be used for overwintering tender plants.

Polytunnels are also used for overwintering of half-hardy and sensitive plants.

Cold frames and cloches can be used for overwintering vulnerable plants.

Question 2

Describe use of protected environments for PRODUCTION of plants:

Answer 2

Production of bedding plants, e.g. Impatiens walleriana, sown in trays in early spring, in a greenhouse.

Greenhouses, polytunnels and cold frames are also used for crop production (cold frames for sowing seeds).

Question 3

Describe use of protected environments for DISPLAY of plants:

Answer 3

Specialist greenhouses, such as alpine houses are a good option for the display of alpine plants.
Alpine houses provide optimum ventilation whilst providing protection against the rain (which alpines need).

A conservatory can also provide an attractive place to display tender or tropical plants all year round.

Question 4

Describe the production of a salad crop plant (give example)

Answer 4

Solanum lycopersicum

Propagation and establishment:
Mid-Jan to early Feb in heated greenhouse;
Late Feb to mid-March in unheated greenhouse;
Sow at 18 degrees - modules or individual small pots - one seed per pot;
Seed compost with layer of vermiculite on top;
Transplant to 7.5-9cm pots when they have two TRUE leaves (handle by cotyledons and don’t let dry out);
Transfer to 23cm pots or grow bags when first truss flowers begin to open;
Keep growing medium moist and add slow-release fertiliser;
In polytunnel beds, place 40cm apart in double rows;
In pots, allow space between each pot for air circulation;
Keep well-watered.

Maintenance:

Cordon/vine - tie main stem to cane at intervals as they grown up, and pinch out lateral shoots at leaf axils regularly when they become 2.5cm long (redirects energy to developing trusses!);

Bush or hanging basket cultivars do not need tying in or lateral shoots pinching out.

Water regularly, avoiding long wet/dry periods;

Feed every 10-14 days with balanced liquid fertiliser, followed by high potassium fertiliser once first fruits start to set.

Remove the growing point of main stem two leaves above the top truss, once six trusses have set.

Encourage pollination by “tickling” with finger or using a soft brush on each flower.

Control of P&D and disorders:
- Sticky traps or Encarsia formosa (parasitic wasp) for Glasshouse Whitefly;
- Misting plants or predatory mites for Glasshouse Red Spider Mite;
- Ventilation, good hygiene, spacing, lower humidity for Tomato Leaf Mould and Grey Mould (Botrytis);
- Good hygiene and aphid control for Tomato Spotted Wilt Virus;
- Lack of calcium can cause Blossom End Rot - regular and careful watering needed;
- Split fruit caused by irregular watering (periods of wet and dry)

Question 5

Describe the production of a decorative pot plant (give an example)

Answer 5

Cyclamen persicum.

Propagation and establishment:

Raised from seed, planting in late summer - takes 18 months before flowering;
Soak seeds 12 hours before sowing to soften seed coat;
Sow in seed trays or modules and cover with layer of grit;
Keep somewhere dark, as light inhibits germination!
Once large enough to handle, plant into 7.5cm pots with loam-based compost;
Most are bought as mature plants in autumn and tubers re-potted when they go dormant the following summer;
They like a well-lit position but out of direct sunlight.

Maintenance:
Keep compost just moist and avoid wetting the crown;
Combat low RH by misting occasionally or standing in tray of moist gravel;
Feed every two weeks when in flower;
Hate hot and dry conditions - do best at 13-15 degrees C; and water from below;
After flowering allow plant to dry off and become dormant by laying plant on its side in a cool dark place.

Control of P&D and disorders:
Sciarid fly - sticky traps; predatory mite; cover compost with gravel or sand layer.
Vine weevil - monitor for signs of adults; use nematodes.
Red spider mite - raise humidity and mist regularly;
Grey mould - increase air circulation and water from beneath.
Yellowing leaves is a sign of overwatering! Never leave sitting in a tray of water.

Question 6

Describe the production of a cut flower (give example)

Answer 6

Chrysanthemum x morifolium.

Propagation and establishment:

Take basal softwood cuttings from new shoots;
5-10cm cuttings Feb - April - cut below a node and leave 5 leaves at tip of stem;
Can dip in rooting compound
Keep 10-15 deg in propagator
Once rooted, pot up into 7.5-9cm pots
April - transfer to 12cm pots
May - transfer to 20cm pots with cane/s to stake/support

Maintenance:
Early June, move plants outside onto a hardstanding;
When plant is 20cm high or more, the growing tip should be “stopped” or pinched out - stimulates early growth of flowering side-buds;
“Disbudding” is removal of all lateral buds and shoots to produce one “super bloom” per stem;
Insert garden cane and tie plant in as it grows;
Water regularly - keep soil moist;
End Sept - pots back to greenhouse and disbud if necessary;
Feed every week-and-a-half until buds swell and show colour;
When flowering is over, cut back stems to 12cm - lift roots carefully and shake off soil - trim off any leaves and straggly roots;
These “stools” should be closely packed in wooden boxes, surrounded by damp compost/firmed in;
Store boxes in frost-free cold frame or greenhouse - only water when new growth appears.

Control of P&D and disorders:

Chrysanthemum White Rust (fungus) - will weaken plant - remove any affected leaves - destroy plant if badly affected - Tebuconazole if fungicide really necessary.

Mildew and Grey Mould - keep good hygiene.

Aphids - squashing by hand, screening with insect mesh, companion planting (Garlic?), remove badly infested leaves, parasitoid wasp as bio control.

Chrysanthemum eelworm (nematode pest) - destroy plants and don’t use same soil for Chrysanthemums in the future.

Question 7

Describe the production of a bedding plant (give an example)

Answer 7

Impatiens walleriana.

Propagation and establishment:

Sow in seed trays in greenhouse in early spring;
Scatter evenly over surface of prepared seed compost, and water with fine rose;
Cover tray with clear glass/perspex sheet, or propagator. Keep warm (18) and remove cover once germinating;
Thin as necessary and prick out when large enough to handle, into individual cells, cotyledons just above surface of soil;
Harden off in cold frame before planting out in late May/early June after risk of frost;
25cm apart - water thoroughly.
Suitable for shade, part-shade or full sun, and also do well as container plants in moisture-retentive, free-draining compost.

Maintenance:
Pinch back new growth every few weeks to increase flowering buds (“stopping”);
Keep soil moist, but never soggy;
Deadhead to encourage further flowering.

Control of P&D and disorders:

Impatiens Downy Mildew - serious fungal disease - destroy plant by burning! Avoid using the same soil for Impatiens for at least one year.

Grey Mould - remove affected material; ensure good airflow between plants; don’t overcrowd; don’t overwater or water from above; good hygiene.

Damping off - affects seedlings. Don’t overcrowd or overwater. Good hygiene and ventilation.

Whitefly - sticky traps or Encarsia formosa.

Aphids - squash by hand, encourage predators.

Question 8

Describe the production of a bulb for forcing (give an example)

Answer 8

Narcissus ‘Tête-à-Tête’ -

Propagation and establishment:

“Forcing the bulbs” -
Plant bulbs early autumn in bulb fibre compost.
Arrange bulbs close together but not touching - growing tips showing just above the compost;
Place bowl in cool (4-5 deg), dark place for 8-12 weeks (e.g. cool sunless wall covered in bark, or covered with clingfilm in corner of shed/garage/fridge;
Check moist but not over-wet;
Shoots 3-5cm high and roots developed, place in cool (10 deg) place in indirect sunlight - leaves will turn green along with stems;
Then move bowl to display position close to a window in warmer surroundings (15-20).

Maintenance:
Keep out of draughts and away from direct heat sources;
Humid atmosphere preferred - moist tray of grit;
Don’t water erratically (buds may fail to open);
If leaves develop faster than flower buds, move to a cooler place and cover to keep dark - but no longer than a day or two!
Deadhead after flowering but keep watered and fed and let foliage die back;
Then remove bulbs, remove dead foliage and store in cool, dry place;
The bulbs will not provide another indoor display so plant in garden in the autumn;

Control of P&D and disorders:

Daffodil basal rot (fungus) - can affect bulbs in storage or in the ground. Look out for signs and remove/destroy any affected. No treatment for this fungus, though there are resistant cultivars (N. tazetta);

Sciarid fly, whitefly, red spider mite - look for signs and treat accordingly;

Daffodil blindness - not enough resources due to overcrowding, dry soil, lack of nutrients, foliage being removed too early.