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!
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!
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!
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!
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.
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.
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 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.
Pollination occurs naturally outdoors, where wind and insects carry pollen from one flower to another to fertilise them and set fruit. Tunnels and glasshouses shelter plants from wind, and fewer insects go inside so natural pollination is sometimes not enough to set a full crop of fruit. Incomplete pollination of a flower can produce a fruit that only develops and grows on one side while the other side remains hard and misshapen. This can be a problem with strawberries. Peaches, nectarines, grapes, melons and aubergines among others can yield better with help.
Hand-pollination is the answer. When the first flowers are just fully open and conditions are dry, brush over the flowers gently with a very soft brush or a little cotton wool. In the past gardeners used rabbits’ tails, but animal welfare was not a consideration then. Paintbrushes are a bit too stiff for pollination, but the likes of a camera lens brush is perfect. Never use one on a lens afterwards, because it picks up oils from pollen that would smear the lens. Pollen grains have spines for gripping onto hairs such as on bees’ bodies, and they brush off onto the sticky stigmata of other flowers – job done. It is best to repeat for a few days running to ensure good pollination and catch the later flowers. Tomatoes are easy to pollinate by vibration; tap on the flower trusses or the supporting canes or wires, or water them from above with a coarse spray of water.
Cold frames are four-sided boxes with transparent covers sloping towards the sun. You can buy readymade ones or easily make your own with new or recycled materials. They are out of fashion nowadays because more people have tunnels or glasshouses, but still very useful.
You can use cold frames to hold plants for which there is no room in your greenhouse just now. They are good for hardening off vegetable plants or half-hardy annuals raised in the greenhouse before planting them out in the garden. You can sow seeds earlier than possible outdoors if greenhouse space is not yet available, or quarantine new plants, or keep plants that need warmer or cooler conditions than you have in the greenhouse. Cold frames are good for rooting cuttings, or warming up water or potting compost before use. If you need an extra degree or two of frost protection for plants inside the greenhouse, you can put a lightweight cold frame over them for the night.
Cold frames are best placed near your greenhouse for convenience, and facing as near south as possible. Their south walls should be low enough to let in the sun. To ventilate, prop open the downwind side of the top cover. If you raise its upwind side, a gust could flip it off, and if you slide it the gap may be on the wrong side letting in chilling draughts. It is harder to control their temperature due to their small volume, so you must anticipate the day’s weather and ventilate accordingly, closing the cover at night. If you expect hard frost, lay a quilt of weighted bubble-wrap or sacks stuffed with leaves over the cover for extra insulation. Water plants in the mornings to let the leaves and soil surface dry off before night.