Greenhouses | Polydome

Electricity in your Greenhouse

As the days get shorter and colder, you might think about bringing an electrical power supply to your tunnel or glasshouse. Electricity can power lights, heaters, soil warming cables, propagators and climate controllers, letting you grow a wider range of plants over a longer season. But it’s not just a matter of running an extension cable out from your house; domestic cables and fittings are neither shockproof nor waterproof enough for safety in greenhouses. Electricity and water are a lethal combination. If you only need working lights you could use wireless battery or solar-powered lights with high-efficiency LED bulbs. If you already have a low-voltage garden lighting circuit nearby you could take a short spur off it, provided it can handle the extra load.

If you need mains power, you must get a registered electrical contractor to do the specialised wiring work. At the least, the supply from the house should be through Steel Wire Armoured (SWA) cable buried at least 50-60 centimetres underground with warning tape above it. It should pass through a Residual Current Device (RCD), which monitors the flow of current out from the distribution board and back and trips instantly if they are not the same (i.e. current shorting elsewhere). All sockets, plugs and fittings should be of heavy-duty industrial type with a much higher Index of Protection (IP) rating than domestic ones. They are not cheap, but neither is human life!

Pelargonium Cuttings

Pelargoniums (geraniums) are easy to grow from cuttings whenever the plants are growing, but easiest in late summer. Fill a pot with seed compost and moisten it by standing it in water for a while. Then let the surplus water drain away. Choose your healthiest, most vigorous pelargonium plants for cuttings. Non-flowering stems are best because flowers give off hormones that inhibit root growth, but if you have to use flowering stems remove any flowers and flower-buds. Stout stems grown in good light are better than spindly stems grown in poor light; a few weeks on greenhouse staging can produce good stems.

Cut the chosen stems below the third node (joint) from the top. Cut off all but the top leaves, insert them into the pot leaving one node and the top leaves showing and firm them in gently to ensure good contact between the cutting and the compost. Place the pot in a warm bright spot out of direct sun. Don’t cover it as dampness can rot the cuttings. For the same reason, water it only from below by standing the pot in water for a while and letting it drain as before. Remove any cuttings that start to rot. Plant out the rooted cuttings when new leaves appear on them: let them recover where they were until growth starts again before placing them in full sun.

Junior Orangery Greenhouse on display

The newest addition to our display area in Birr is this lovely Junior Orangery Glasshouse from Janssens. Using ‘box section’ aluminium profiles and 4mm toughened glass this greenhouse is good and strong. The protruding Porch makes for a lovely and unusual feature in the garden. It comes in black only – or as Henry Ford said about the Model T car – every colour you want so long as it is black. The Junior Orangery measures 3.14m x 3.96m giving room for a the essential table and chairs to relax in along with some plants to talk to and enjoy 🙂 The price for this impressive Greenhouse is only 3,515 euro as a DIY kit, we do offer a construction service the price for which varies with location – please enquire for a price if you are not DIY inclined. We need a flat and level base (or flat and level lawn) to be in situ before we arrive to build it. You are welcome to come and see this and other models at our display area in Birr.

Dahlias – our resident horticulturalist Peter Whyte gives some tips

Every year somebody predicts a hard, cold winter. If they are right this year, the roots of plants such as Dahlias will be killed when the soil freezes. To keep them safe you should lift the root tubers and store them indoors until spring. As soon as their stems are blackened by frost, dig up the plants carefully, avoiding root damage. Gently shake off the loose soil, and cut the stems back to about 15 centimetres. If you have different varieties label them with their names and colours right away – you may well forget which one was which before spring. Stand them on wire mesh or similar in the greenhouse for a few days to dry off fully. Then place them upright on a layer of dry peat or soil in containers, filling more in around them to cover the tubers. Keep them dry and cool but frost-free under staging until spring, and then divide and plant them out a fortnight or so before the last likely frost date for your area. If you want to take cuttings, start them growing in the greenhouse in February and use the new shoots as cuttings when about 75mm high.

Paperwhite narcissi

Paperwhite narcissus is a type of white scented daffodil which can be forced to flower for Christmas. A greenhouse makes it easier to grow better blooms. You need to buy specially prepared bulbs, and compost them afterwards because they rarely flower normally again. Store the bulbs in a cool, dry, dark, airy place until 4-6 weeks before you want them to bloom. Place them on a 5-centimetre (2”) layer of damp (not wet) bulb fibre or potting compost or even pebbles in a container such as a shallow bulb-pan. For small containers an odd-numbered group of (for example) three or five bulbs looks better than an even-numbered group. They should be close together but not touching each other or the sides of the container, with their pointy ends upwards and leaning in towards the middle of the container. Add a little more compost or pebbles to firm in between the bulbs but leave their tips exposed.

Place the container in a cool spot away from direct sunlight. Check them every couple of days to make sure they don’t dry out completely, but never add enough water to reach the bottoms of the bulbs or they will rot. As soon as the green shoots appear, move the containers to your greenhouse and give them as much light as possible. The more light and the less heat they get the less leggy and floppy the stems will be. Keep the greenhouse cool by ventilation but frost-free at nights, and make sure the plants don’t dry out. Turn them often to keep growth regular and upright. Bring them into the house when the buds are well formed, and the flowers will open in a few days.

Peter Whyte

Polytunnels

4.5m Tunnel with raised beds A recent construction we did in Dublin was a 4.5m x 8m Polytunnel. This Polytunnel had ‘side purlins’ fitted which are an optional extra providing extra strength particularly against wind. The customer also ordered a large number of raised beds which we also supply. This Polyunnel also has the optional attractive finish of having the ends of the tunnel without pleating and folding the polythene. This feature is made possible by having an aluminium rail fitted over the end hoop so that a separate cover can be fitted to the gable end (and fixed into the rail over the end hoop as is the polythene on the roof).

We are pleased to configure our Tunnels to suit each customer from a wide range of options.

Beautiful Antique Greenhouse

We just built this lovely Janssens Helios ‘Antique’ Greenhouse from Janssens for a happy customer in Blackrock, Dublin. The customer uses it as a space to sit in and enjoy his garden in – he even has installed an electric kettle to make cups of tea and coffee. The budget for this stylish and very strong Greenhouse is just under 11,000 euro on walls prepared by others.

Recording Thermometers Horticulturalist Peter Whyte gives some expert advice

Greenhouse users (both Polytunnel and Glasshouse) need to know what the temperature was when they weren’t around to check it. Did it get too hot yesterday afternoon, stressing the plants and stopping the lettuce seeds from germinating? Did it get too cold last night, and should I have closed the vents a bit more? Did I overheat the greenhouse last night? A maximum and minimum recording thermometer will answer those questions. Both digital and traditional analogue types are available. Analogue types are generally cheaper and simpler to use, and need no power source. Instead of a single tube and bulb with mercury or coloured alcohol, they have a U-shaped tube with a bulb at each end and a column of mercury in the middle. A temperature change pushes the mercury down one arm and up the other. The mercury pushes a floating pin along each tube as it moves and leaves it behind when it moves back, showing how far it went since you last reset it. The thermometer is reset by tipping it up on end or pulling the pins back with a small magnet. Digital models are reset by pushing buttons as per the user’s manual. For best results place the thermometer or its digital sensor at the level of the plants and shade it from direct sun, which overheats it and gives a false high reading.

Holiday Tips

Holiday tips

Whether it’s Bali or Ballybunion, everyone wants to go away for a break. So what happens to your tunnel or your glasshouse while you’re gone?

Automatic watering is ideal. Be sure to set the controls well in advance so you’re sure it’s working well and regularly, and delivering enough water. Ventilation is easier; you can leave the vents wide open in mid-summer without fear of night frost but automatic vent openers are less liable to storm damage. They need no electricity and are easy to fit. Wedge doors nearly closed or screen them with wire mesh to keep out pets and wildlife.

Bribe a neighbour to keep an eye on it with free produce or a promise of looking after theirs later. Automatic watering and ventilators are good but nothing beats the human touch: unexpected problems can crop up (pun deliberate) and the comings and goings of neighbours deter thieves.

Move out pots to a sheltered, shady spot where they can get rain or be watered if needed. Remove more bottom leaves from your tomato plants than usual: the leaves on the top 70cm of the plants contribute most to their growth. This reduces their need for water and lets more fresh air around the plants, which helps control fungus diseases.

Remove flowers and developing fruit from plants to reduce the amount of unwanted and over-mature fruit growing while you’re away. It also further reduces the plants’ need for water.

Tidy up and clear out any weeds; also dead and dying leaves, dropped fruit and other plant remains that could host diseases. Bon voyage!

Written by horticulturalist Peter Whyte

Garden Festival at Hillsborough Castle

Looking forward to the Airtricity Garden Festival at Hillsborough Castle next weekend (17th, 18th and 19th of May). We will have a Janssens Victorian SL Greenhouse up and Jonathan Pyle (a Director of Polydome) will be there to meet and greet visitors to our stand. Monty Don (pictured) will be appearing on Friday 17th. Hillsborough Castle is a beautiful location for the festival which has been running for some years and is one of the main events in the Gardening Calendar in Ireland. Further information on the Garden Festival can be obtained at the organisers website: http://www.gardenshowireland.com/