May – Raindrops Keep Falling on my Head!

Our frequent rainfall keeps Ireland green and beautiful. However, since you’ve put up a tunnel and blocked it out, now it is up to you to keep your plants hydrated!

Water, along with oxygen, sunlight and soil, is a basic need of all plants, even though their requirements can vary considerably. From one type of plant to another, from tiny seedling to full-grown, from pots to open soil, and from overcast days to sunny ones this job can keep you on your toes!

How Often?

There is no correct answer to this, but you want to keep your plants somewhere between waterlogged and parched! If the soil feels dry below the top inch or two, it is probably time to water. If plants start to droop or lower leaves begin to yellow they are too dry. When you see moulds and mildews appearing on the soil surface, it is likely too damp.  Intuition for this develops quickly enough.

Morning vs. Evening

This is a point of debate. Most everyone agrees that in the heat of the day is not the best time to water. However, if a plant is wilting or is a tiny seedling drying out, it is always better to water than let the plant suffer damage or death. The advantage of evening watering, particularly in very warm weather, is that the moisture can be retained overnight and will evaporate the next day once the heat soars again. The advantage of morning watering is that if you have a hearty nocturnal slug and snail population you can discourage them from slithering along on moist soil munching all of your plants overnight by keeping things at their driest then.

Manual vs. Automatic

This is another point of debate and probably something in between is ideal. Automated systems can be put on a timer and adjusted throughout the season. This is ideal to cut down on time and effort, but it is always wise to monitor the situation and not fully depend on automation. Manually watering allows you to reach every plant and give more or less in specific situations, but it does require a dedication of more of your time. Polydome does supply irrigation equipment, including simple battery-powered automatic timers.

Overhead vs. Underneath

Overhead watering, including overhead irrigation lines and the use of a hose, does have the advantage of washing down leaves like the rain. However, some plants work better with underneath watering, from watering a tray under a pot to using capillary mats or low-level drip lines. Reason for this vary, but this often suits plants that are prone to mildews or blight from remaining damp or leaves that scorch from being watered in the sunlight. In a protected structure where there can be less natural wind and ventilation, this is often an ideal solution. An example of this is using low-level drip lines for tomato plants to avoid blight or feeding potted cyclamen from a capillary mat to keep their leaves healthy.

In the winter, having a roof that keeps excess rain out is a great advantage to many plants. However, the surrounding areas outside the tunnel moisten the areas near the edge, so this is something to bear in mind.

So, the next time it rains, enjoy the raindrops! They are little droplets supporting life!

April- The Winds of Change

April can be quite a roller-coaster of weather events. Night-time frosts and heavy hail showers intertwined with beautifully warm sunny days keep the daily greetings interesting. However, these ever-changing conditions can be a challenge to manage in a greenhouse setting at a time when so many seedlings are just getting established. So, this month we will discuss ways to counter some of these extreme swings.

Ventilation to let in fresh air is essential in any greenhouse. Plants require a steady supply of CO2 as they turn it into oxygen, so they can’t exist long-term in a closed off environment. Ventilation can also be used to adjust the temperature and humidity.

Temperature requirements vary between plants, but as a rule of thumb night-time temperatures between 12 and 19C and day-time temperatures between 21 and 26C are considered optimal for growth. Once temperatures go beyond 29C plants can suffer distress. A simple thermometer can be useful in monitoring this.

Ways to increase night-time temperature include closing vents overnight (preferably before sundown) to retain the daytime heat. Covering sensitive plants with frost-protection fleece or bubble-wrap can further help retain heat and protect from overnight frost.

Ways to lower temperature during particularly warm or sunny days include opening all doors and vents, the use of fans or shade netting and watering the path or other solid areas. These processes can be automated by temperature-sensors or timers.

Too much humidity sets conditions for moulds and diseases, which can be lowered by simply allowing a better flow of air via ventilation.

Inadequate humidity is usually only an issue in Ireland during a heat wave but can still lead to plant distress. Adding moisture by watering is the obvious antidote. Since day-time watering can lead to sun-scorch, watering is best done either in the morning or in the evening. But in intense heat, watering the ground or solid surfaces during the day can be useful to both slightly lower the temperature and increase humidity.

Ventilation in polytunnels can be achieved by opening end doors and netting can be used to keep out birds and animals if necessary. This is adequate for certain shapes, especially very small tunnels. For longer areas, netting along the side(s) is more effective. Roll-up sides allow even better climate control by covering and exposing the netting as needed.

Fortunately, plants are resilient enough to withstand natural fluctuations in conditions. So, with a little bit of extra care, they can really thrive in the enhanced environment provided by your greenhouse. And so can you!

March- Propagation time!

It’s March and high time to start some seeds! Here are a few tips for success.

1)Unless you are sowing directly into the soil, having a bench that is the correct height is a must. This saves your back and also allows you better precision when sowing tiny seeds that are difficult to see.

2) Next, follow the instructions on the packet. Not all seeds are sown in the same way.

3) There are several factors involved in triggering a seed to germinate. These include light, temperature and moisture. At this time of year, the temperature is too low for certain seeds, so using a heating mat or heating cables in sand can speed up germination, resulting in a stronger plant.

4) It is a good idea to label everything clearly as you go along. This can avoid confusion later on when the little darlings start to emerge and you don’t know who is who! It is also a good idea to record when and what you sow in a notebook or diary for future reference.

5) A seed is a tiny miracle that contains everything it needs for life. However, once the outer coat has been broken down, the emerging seedling is very vulnerable until it has formed sufficient root to acquire moisture and nutrition for itself. At this stage it is vital that it isn’t allowed to dry out. Here are some ways to ease your seedlings through this delicate stage:

*Pre-water the growing medium well.

*Partially cover seed trays with polythene or glass (allowing some air flow) to retain moisture.

*Gentler forms of watering such as using a watering can with a rose, overhead irrigation, drip lines or capillary matting are preferable to using a garden hose on young plants. (Of course, the more vigorous plants like peas and beans will withstand much more than a delicate cactus seedling.) 

6) Did you know that keeping your young plants up on shelving isn’t just for convenience? It also serves to protect them from pesky mollusks. Yes, slugs and snails. They love damp, dark corners to hide in during the day, saving their energy to come out and graze all night. So, keep your root babies as far away from them as you can!

Best of luck to everyone who is setting out to sow seeds for the first time or the 50th time!

February- Is it Spring yet?

As the days start to get longer, a new season is here and signs of life are starting to appear all around us. The sight of snowdrops and daffodils remind us that the years march on regardless of what else is happening in the world around us.

On beautiful days when the sun gives that early spring glow we can feel that the year has turned and are tempted to sow something. The reality is, though, that we can still have plenty of wintery weather ahead of us at this stage and it is too early to start anything without protection.

This is the time of year where a polytunnel really shines. As the sun comes out, there is a bit more heat and gentle growth in your greenhouse. With a heated seed bed, you can begin to start your tomatoes, peppers, lobelia, lettuce, onion or pea plants. If you are into bedding plants, you can start lobelia, salvia or sweet pea. Electric heaters or frost protection fleece will help protect your young seedlings from the elements even further.

It is also at this time of year that having a well-built polytunnel really pays off. There is nothing as discouraging as seeing all your young plants destroyed due to a damaged structure after a windy night.

Polydome polytunnels are built to last and withstand the unpredictable Irish weather to give you peace of mind.

So enjoy the season and being one step ahead of the elements!

This photo of a beautifully laid out tunnel interior was sent to us by Rosie Green from Dingle. Thank you, Rosie!

January- A Time to Plan

January is a quiet time for tunnel growing and an ideal opportunity to sit back to relax and reflect. However, it can quickly become the most exciting time of the year as you begin to plot and plan for the coming year. When we make plans, we are filled with hope and excitement. We all know the best of plans can go a bit awry at times, but looking forward to a new season is always exciting!

First, I would look at what it is you wish to reap from your polytunnel or garden. Would you love lots of beautiful flowers? Your favourite salad items? Hearty winter veg for storing? Make a list of what you would like, and then check to see what growing conditions they require. The beauty of a polytunnel is that the growing season, yield, and produce quality are greatly increased. They can be increased even further using extras such as a heated bed for seedlings, frost protective fleece, or internal cloches.

Then it is time to look for seed or planting material. You may be able to source them locally, but there is also an astonishing variety of seed available online. You could wow your friends and neighbours with unusually coloured varieties of tomatoes, French beans, courgettes or even strawberries that you would not find in your local supermarket. There is nothing like salad leaves, spinach or sugar snap peas that have just been freshly harvested from your own efforts.

Don’t forget to look at the final size of what you are going to grow, including the height. Taller plants can be supported best in the centre of your tunnel unless you have straight sides. Also, some plant combinations make better companions than others. For instance, tomatoes work well with garlic (to repel aphids) or basil (to improve flavour) but won’t thrive as well next to cabbage or kale and shouldn’t be placed near potatoes as they are both susceptible to blight.

So, it’s time to get out your pen and paper, plot out your beds and start dreaming! Then make your dreams a reality. Life is an adventure and so is polytunnel gardening!

Strawberries

Early strawberries are one of the great pleasures of having a tunnel or glasshouse. Whether from pots or border soil, they taste like a promise of summer and so much fresher than shop-bought ones. Tidy up the plants, removing any dead leaves and bits. Check potted plants for vine weevils. Cut off any runners to divert the plant’s energy from growth into filling fruit. Keep the plants watered and give them as much light as possible, giving them some liquid feed as per the instructions on the packaging. Ventilate on sunny days to keep the temperature cooler and less stressful for the plants, and reduce the danger of fungus diseases. The flowers are more frost-sensitive than the leaves, so protect them from frost with fleece or cloches on cold nights. You will need to hand-pollinate the flowers as fewer insects visit plants under cover. Brush the flowers gently with a soft brush or cotton wool to transfer pollen from one flower to another. You need to repeat this on a number of days to ensure that each flower is fully fertilised and will form a complete strawberry. Continue feeding and watering, and watch out for pests such as aphids and slugs. Remove and destroy any mouldy fruit or leaves to prevent disease spreading. Pick and enjoy the fruit as soon as they are ready, but if slugs are a problem pick them a bit sooner and let them finish ripening in the kitchen.

Onions from seed

Most people plant onions as sets; semi-mature bulbs which will hopefully grow bigger and be harvested before they go to seed. But you can also raise onions from seed sown in your greenhouse instead of from sets planted later. This is especially useful on cold, wet soils or in cold, wet springs, as onions cannot tolerate those conditions. Seed-raised plants are cheaper than sets, you have more varieties to choose from, and the plants are less likely to bolt or be pulled out of the ground by birds. On the downside, seedling onions need a longer growing season so February is definitely the last month for sowing, and the longer growing season means more time for pests and diseases to attack them.

Sow the black, angular seeds thinly in a seed-tray, or in modules at up to five seeds each. Keep them at about 10-15°C. The seedlings come up in loops, and you should prick them out from seed-trays into pots before they pull their tips out of the compost and straighten up. If multiple seedlings come up in modules, either leave them to push each other apart later as they grow, or single them with a fine-pointed scissors to give the one remaining plant room to grow a bigger onion. Keep the compost neither bone-dry nor saturated. Grow on the plants in bright, cool conditions until they have two or three leaves, harden them off well and plant them out at about 15cm apart each way. Wider spacing gives you bigger bulbs, and tighter spacing gives smaller ones.

You can also plant sets in pots and give them a head-start under cover, planting them out only when conditions improve.

Plant garlic now

Garlic has many health benefits, and growing our own is easy when you know how. Homegrown garlic has only the chemicals you apply, and you can eat the leaves and flower-stems when they are young. Planting garlic in a tunnel or glasshouse now can give you bigger and earlier bulbs than outdoor crops, but even starting a crop in modules or pots under cover and planting it out later gives some benefit.  It stops the birds pulling them up too.

The ideal soil for garlic is light, well drained, moderately fertile and neutral or alkaline. Wet sticky clay can rot the bulbs and very rich soil encourages leafy growth at the expense of the bulbs.  A good supply of potash helps, so dig in some wood ashes before planting.  Garlic needs a long, cool growing season and a cold spell to stimulate maturity, so autumn planting is ideal.  However, you need to choose your material carefully.

Do not plant shop-bought garlic and expect a decent crop; you may be lucky but it is sold for eating rather than planting and may be treated to inhibit growth, or carry plant diseases that will persist in your soil for many years. Get disease-free sets of varieties suitable for autumn planting from a garden shop or centre.  Gently split them into cloves, and plant the bigger ones 2-5cm deep into the soil 15cm apart, in rows about 30cm apart, with the pointy end up and the flat base down.  Plant the small cloves close together to produce leaves like chives.  Water the crop lightly and let it dry out between waterings to prevent rotting.  Dig up the bulbs gently when harvesting, and avoid pulling them.  They bruise easily and then will not keep.  Dry and store them in a cool, airy place.

Mizuna – tips on growing from horticulturalist Peter Whyte

Mizuna is one of the oriental greens that Europeans should grow and eat more. It’s best grown rather than bought because it needs to be eaten right after harvesting for maximum flavour and nutrient value, though it will keep for a couple of days in the fridge.  Like lettuce, you can sow seed little and often all year round in a glasshouse or tunnel.  September sowings will produce deeply cut leaves up to April or May: single leaves can be cut off after about three weeks and whole heads after six to eight weeks.

Mizuna likes moist rich soil, so dig in plenty of compost or other organic matter before sowing. Sow the seed about a centimetre (half an inch) deep in drills about 30cm (12 inches) apart.  Protect the seedlings from slugs.  Keep it well watered and ventilate on sunny days – it is prone to bolting in hot dry conditions.  If it does bolt remove the flowering stems right away to keep it leafy and sow another batch to replace it.  Don’t worry if it wilts after a frosty night: it is hardy and usually recovers.  It is a member of the cabbage / brassica / crucifer family so don’t sow it in the same ground as any of its relatives for at least three years to prevent disease build-up

Mizuna has a milder flavour than either mibuna or rocket, and is good in mixed salads. Like spinach it can be steamed, boiled or stir-fried but it shrinks a lot, so harvest plenty.  ‘Kyoto’ is a good variety to try.

Growing Basil

Basil is easy to buy from the shops, but you can grow a wider range of types yourself at lower cost to you and the environment. The type sold in non-returnable pots is usually sweet basil suitable for salads and pesto, but there are also cinnamon and lemon basil, varieties with purple leaves that look great in green salads and spicy or liquorice-flavoured Thai varieties that combine well with Asian food.

Basil is a fast-growing, tender annual that needs lots of light, heat and water. Being very sensitive to cold, it is an ideal candidate for tunnels and glasshouses, especially in our unpredictable summers.  It improves the flavour of tomatoes when served with them, and some say that it also does so when grown with them.  It grows best in well-drained acid or neutral soil.  Sow a succession of crops, but just a couple of plants each time is enough for regular use unless you want extra for pesto.  Either sow them in cell-trays or in situ in the greenhouse soil, thinning them to single plants as soon as they are big enough to see.  Use a scissors to avoid root disturbance.  Thin or place the plants to about 30 centimetres apart.  Harvest leaves as soon as the plants are about 20 cm tall, by cutting off shoot tips.  Leave on the lower leaves until you discard the plant; they will produce the food to grow new shoots from the lower side-buds.  Even if you need no basil, cut off the tips to prevent flowering (which makes the leaves bitter) and encourage fresh sprouts to grow.  Surplus leaves can be either frozen for later use or composted, and the flower-buds are edible too.

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