Peter Whyte’s Blog for October – battening down the hatches in case of storms

Storms can do a lot of damage to polytunnels and glasshouses.  Wind-pressure increases with about the square of its speed, so doubling windspeed quadruples its force.  But there’s plenty you can do to prevent it.

Buy the strongest-framed structure you can afford.  Secure it well into the ground, following the supplier’s instructions for your conditions.  Be careful where you place it; solid walls or buildings nearby can increase windspeed and cause damaging turbulence.

Check the cladding.  Polythene should be secure at the sides and around doors and vents, and any holes or tears cleaned with isopropanol, dried and taped inside and out with clear cold shock resistant repair tape.  Secure loose glasshouse panes and replace cracked or broken ones and missing or displaced glazing clips (you did keep those spare clips, didn’t you?).  If glazing clips slide hold them in place with silicone mastic.  Tighten loose bolts.

Store away any empty pots, buckets and bins that a storm could pick up and hurl through the greenhouse.  Close and secure all doors and windows when a storm is brewing.

If you do have storm damage, stay away until the wind abates to avoid injury.  Check all cladding, doors and vents again, and do repairs as soon as possible before the next storm.  A damaged greenhouse is more prone to further damage, as any opening lets in the wind to burst it like a balloon.  Keep glasshouse assembly instructions for reference if they have the pane sizes, and consider keeping pre-cut spare panes in store if replacement glass is hard to get quickly.

Shelter (hedges, plastic webbing etc.) should be partly permeable to filter and slow down the wind, not block it and cause damaging eddies.  If shading is a problem, shelter works nearly as well behind a greenhouse as in front.

Taking cutings, Peter Whyte gives some tips

Heat Mat with PlantsAugust is the latest month for taking semi-ripe cuttings.  Fuchsias, Pelargoniums, evergreens, perennial climbers and most deciduous shrubs can still be propagated now, if you use the warmth of a glasshouse or tunnel to boost their growth.

Choose non-flowering shoots or cut the flowers off.  Cut off slips 7-15 cm long by cutting just below a node (the thickening on a stem where a leaf or side shoot grows outwards).  Clematis does better when cut between two nodes.  Alternatively, tear off a side shoot of the right length with a piece of the main stem still attached like a foot, and cut off the ‘toe’ leaving the heel.  Remove any leaves that would end up buried below the surface.  Take plenty of cuttings: some won’t grow and the tighter they are crowded together the better they root.

Fill a container with a mix of two parts peat or leaf mould to one of sand, and water it well.  Dip the bases of the cuttings in hormone rooting powder if you want, and lower them into holes dibbled around the edge with a pencil or similar.  Firm the compost in well to ensure good contact with the cuttings.

The cuttings will lose water through their leaves and wither unless kept in the shade.  Place them under solid staging, or rig up a shade above them.  Use tinfoil or white plastic instead of black plastic, and keep it up from the plants to prevent heat build-up.

Lay clear plastic over the cuttings to keep in humidity.  Hold it off the plants with hoops of wire or similar.  Pelargoniums and plants with grey, silver, silky or hairy leaves resent humidity and are best left uncovered.  Check the cuttings regularly and remove any dead bits.  They are ready to pot on when they start growing.


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 thaVENTOMATIC UNIT COPYt could host diseases.  Bon voyage!Polytunnel ventilation for blog


Written by horticulturalist Peter Whyte

Growing tips for Tomatoes

TomatoEveryone with a polytunnel or glasshouse is tempted to grow tomatoes – and why not? They taste so much better when picked just before eating.  Here are a few tips for the best crops.

Choose well-flavoured varieties like Shirley or Alicante.  Some traditional varieties like Moneymaker are insipid.  If you are buying plants, look for healthy ones about 20cm tall.  Yellow leaves indicate poor feeding or cultivation and bluish or purplish leaves indicate chilling: such plants will take time to recover and crop later.  Drawn, leggy plants will be the same.

If planting in the soil try to have the plants in slight hollows rather than on top of mounds, so water will soak in rather than run away.  Water them in well, and let the ground surface dry off between waterings.  Vine tomatoes need support: if using canes put them in before the plants to avoid root damage.  Strings are better than canes for plants in grow-bags.  Cherry tomatoes are wide and bushy plants, so give them plenty of room to spread.  

Feed the plants with high-potash feed as per the instructions, starting when the first fruits appear.  Tie in the growing vines to canes or wind the support strings around them regularly, as stems are hard to train when they thicken up.  Hook very long trusses up on themselves or higher leaf-stems to keep them up from mud and slugs.

Break out sideways any side-shoots growing from the angles between leaf-stems and the main stem.  Snap off upwards any dying bottom leaves to let light and air around the fruit.  Bush tomatoes need no training.  Pick a tomato by thumbing down on the knuckle just above it while twisting the fruit upwards.  The green oil on tomato plants is irritant; wash your hands with soap and water afterwards.

Peter Whyte  B Agr Sc (Hort), Nat Dip Sc (Apic), Dip Tr & Ed, MI Hort

Polydome’s first day at the Hillsborough Garden Festival

The Hillsborough Garden Festival is starting today. Here is our Greenhouse which is a Janssens Victorian SL. The site was challenging with a 40cm slope across it but despite it being a first time for Director Jonathan Pyle it was completed thanks to a tree surgeon who provided some logs to level it and neighbourly help from fellow exhibitors when an extra pair of hands was needed.

UTV’s Radio Station U105.8 have taken up residence inside our Greenhouse and will be live on air at 12 noon until 3pm and they will be interviewing Monty Don among others.

photo - Copy


This magnificent Rhododendron is the largest in Europe.

Rhododendron at Hillsborough Garden Festival


These Yew Trees have been painstakingly trained and trimmed into barrel shapes.

Yews Trees in Hillsborough Gardens

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.monty-don3  Further information on the Garden Festival can be obtained at the organisers website:


Polydome Googled by Google

Internet giant Google ordered a Greenhouse from us recently.  One member of staff suggested she would like to grow carrotts so they acted and called us.  We visited the site and as it was very exposed to the wind recommended a Janssens Junior Victorian Greenhouse which they ordered and it was promptly delivered.  We suggested they put it up themselves as a team building excersize and as there are good instructions, a dvd as well as our free telephone support the experience should be a pleasant one.


Elegant and strong Greenhouse

Elegant and strong Greenhouse

Flying start to the season

A customer visited us last week by plane!  Birr Airfield is next door to us so we got a call to ask if we would meet him and bring him over which we did.  He brought his mother (for her first flight) and no doubt they had a great view of our display of Greenhouses and Polytunnels from above.   Of course nothing beats seeing them up close and getting a feel for size and quality, but it reminds me of the ad for the car where you find any excuse to go for a drive.  Great stuff.

Customer leaving from Birr Airfield

‘Cool’ ventilation tips from Peter Whyte

Bayliss XLNever mind how cold it is in your garden; the sun is getting higher every day and even short clear spells will allow it to build up a lot of heat in your glasshouse or polytunnel. You might think this is a good thing, but not always so. Lettuce seed won’t germinate if it’s too warm, and temperatures above about 35°C (95°F) will destroy the red pigment in ripening tomatoes so they never colour up properly. Overheated plants need more water to keep cool. As well as that, high temperatures put plants under stress and promote diseases such as grey mould and pests such as red spider mites. You can’t stand there 24/7, thermometer in hand, to open and close doors and vents with each change in temperature. Ordinary mortals adjust the ventilation once in the morning for the expected daytime temperatures and once in the evening for the night, and that’s near enough most of the time. The weather forecast can help you decide how much ventilation to give in the morning. A recording thermometer can show you how you did today, helping you to fine-tune your settings for tomorrow. End doors alone give enough ventilation for most polytunnels up to about 20 metres long. Side windows, roll-up vents and louvre vents are good but not cheap. Glasshouse vents can be fitted with gas-filled struts that automatically push them further open when they get warmer, without needing electricity. The best ventilation comes from a through flow of air, so open both ends of a polytunnel or more than one window in a glasshouse. Open many vents a little bit instead of opening two vents wide to reduce draughts. Be cool!

Peter Whyte (Lanscape and Garden Consultant) B Agr Sc (Hort), Nat Dip Sc (Apic), Dip Tr & Ed, MI Hort

Ready, steady, SOW

GT-DP-H 02Traditionally, people sowed vegetable seeds in their gardens on Saint Patrick’s Day.  That was because they were off work and free to do it rather than weather and soil conditions being suitable.  But, right enough, the soil is often dry enough to dig and warm enough for seed germination about then.

If you have a glasshouse or polytunnel you don’t have to wait for all that.  You can sow  crop seeds earlier under cover and have plants to put out instead of seeds, gaining several weeks of extra growth.   Sow leafy crops like cabbages and lettuce in modules for planting out later, and also a few seeds in the border soil inside to mature early.  If you have lots of room, keep one courgette plant growing inside until the outdoor-planted ones start fruiting.  You can then chop it out and use the space for something else, but it will have been cropping for weeks by then.

Tap-rooted plants such as carrots can’t be transplanted and don’t take kindly to modules, but you can still sow some inside for early crops.  Freshly-dug baby carrots, washed instead of peeled, and eaten raw are fit for a king.

Seedlings are easiest to raise in a heated propagator.  If using it inside the house carry the seedlings  out to a glasshouse or tunnel in the propagator with the cover closed to protect them from cold winds as the temperature shock would be too much for them.

The sun is getting stronger, so be prepared to open vents or doors on sunny days.  But make sure to close them at night!  Throw a sheet of bubble-wrap or fleece over plants on frosty nights.