Roses remain one of the most beloved flowers in gardens around the world, known for their beauty, scent, and variety. Whether you're looking at them in a grand garden or simply enjoying them on your kitchen table, roses bring joy to many gardeners.
This guide covers everything you need to know about picking, planting, and looking after roses so they grow well and produce gorgeous blooms year after year.
A solid base is the backbone of any greenhouse. You might think skipping this step saves time, but trust me—I've seen plenty of greenhouses fail because of poor foundations. A dodgy base causes more headaches than you'd believe.
What happens with a bad base? Glass cracks. Doors jam. The structure twists. Water pools where it shouldn't. And fixing these problems costs way more than doing it right first time.
Don't be fooled by their name. These aphids come in green, black, yellow, and even pink variations, all equally destructive. They target the most vulnerable parts of your plants: tender new growth, developing flower buds, and nutrient-rich stems. Their feeding strategy involves piercing plant tissue and extracting sap, essentially bleeding your plants dry while injecting toxins that deform growth.
Roses remain one of the most beloved flowers in gardens around the world, known for their beauty, scent, and variety. Whether you're looking at them in a grand garden or simply enjoying them on your kitchen table, roses bring joy to many gardeners. This guide covers everything you need to know about picking, planting, and looking after roses so they grow well and produce gorgeous blooms year after year.
Placing your greenhouse in the right spot makes all the difference between thriving plants and disappointing results. As a greenhouse specialist who's spent 15 years helping UK gardeners optimise their growing spaces, I've seen first-hand how position affects everything from temperature regulation to plant health.
Let me share what actually works in our unique British climate. The greenhouse position might seem like a minor detail, but it's one of those things that can make or break your growing success. I made this mistake myself when I first started - my poorly positioned greenhouse meant I was fighting an uphill battle with inadequate light and temperature fluctuations.
April is the month when gardening truly kicks into high gear. The soil is warming, days are getting longer, and plants are bursting with new growth. As an experienced gardener of 15 years, I can tell you April is one of the busiest and most rewarding months in the garden calendar.
This month marks the transition from spring preparation to active growing season. You'll be sowing seeds, caring for emerging plants, and setting the foundation for summer success. The work you do now will determine how your garden performs throughout the year.
I still remember my first attempt at growing shallots outdoors in the UK. It was a wet spring, and half my sets rotted before they even sprouted. That's when I decided to try my greenhouse instead—and what a difference it made! Growing shallots in a greenhouse is honestly a game-changer if you love cooking with these tasty little bulbs.
Growing your own ginger (Zingiber officinale) might seem like a challenge in the UK climate, but with a greenhouse, it's surprisingly straightforward. This aromatic root vegetable brings a punchy, warming flavour to cooking and has numerous health benefits. While ginger is native to tropical Southeast Asia, UK gardeners can successfully grow this versatile plant with the right setup.
Have you ever wondered why March feels so odd for gardening jobs? In this month, the garden seems to wake slowly and yet there is much to do. Do you find it peculiar how early tasks set the tone for the coming season? Many ask, “Why is planning so important in March?” and the answer lies in the quiet preparation that helps every plant thrive later on.
Before sowing your first seed, optimise your greenhouse environment. Position seed trays on the south-facing side where they'll receive maximum natural light. Install shelving to maximise vertical space—a standard 8x6 greenhouse can house 12+ seed trays when properly configured.
Insulate against temperature fluctuations by using bubble wrap on greenhouse walls during February–April sowings. This simple step maintains 3–5°C warmer night-time temperatures, crucial for heat-loving seedlings like tomatoes and peppers.
Peonies are known for their lush, vibrant blooms and can add a touch of elegance to any garden. Do they remind you of grand old gardens? I reckon they do, and they are easy to care for if you follow some simple rules. What are these rules? We shall explore them in this guide.
Have you ever wondered what makes peonies different from other flowers? Their long lifespan and distinct blossoms might surprise you. Could they be the perfect addition to your garden? Yes, indeed they can, if you prepare your ground and choose the right variety. Do not worry if you are new to gardening; this guide is meant to be simple and clear.
Orchids are pretty and delicate plants that can brighten up any space. Growing them in a greenhouse makes it easier to keep the air warm and moist. In this article, we explain how to care for orchids inside your greenhouse using clear, simple language. I have spent many years caring for these plants, and I will share tips that have helped me and many others.
Keeping your greenhouse glass clean is important for both your plants and your enjoyment of the space. When the glass is free from dirt, dust, and smudges, more sunlight comes inside, which helps your plants grow stronger and healthier. A bright greenhouse also makes the space look more inviting and cheerful.
Imagine having an extra room in your garden—a space separate from your house but just as welcoming. In 2025, garden rooms are practical spaces that offer extra room for work, relaxation, or play.
Want extra living space without major construction? A garden room gives you exactly that - a standalone structure that works as a home office, studio, or guest space. Here's what makes these buildings different from basic sheds and what you need to know about planning, materials, and costs.
February brings the first hints of spring to UK gardens, with early bulbs pushing through and daylight hours steadily increasing. These essential gardening jobs will set your garden up for success in 2025.
Tired of cats ruining your garden? It's frustrating when you spend ages on your flower beds only to have them dug up, or worse - used as a toilet. But there's good news! You can sort this out using bits and bobs from your kitchen cupboards, without hurting our furry neighbours.
Your potting shed is about to become your best friend this January. As winter settles in, getting ready for the growing season ahead means focusing on practical tasks that set you up for success.
Let's start with removing any tired plants and clearing space. Take out anything that's finished growing, pop healthy materials in your compost bin, and give your shed a proper sweep. A clean growing space makes all the difference - you'll thank yourself later when spring arrives.
Growing potatoes offers a rewarding experience for any gardener. A well-planned potato patch not only yields fresh produce but also creates opportunities for garden decoration. While your potatoes grow, consider adding beautiful stone garden ornaments to create visual interest throughout your growing space.
A greenhouse is an asset to any garden. Greenhouses extend the growing season, protect plants when they are their most fragile, and open up a wider range of options for the gardener. The best plants to grow in your greenhouse in the winter will depend on where you live, how big your greenhouse is, and your gardening goals.
Lavender is a lovely plant known for its calming scent, pretty purple flowers, and many uses. If you want to grow a beautiful lavender field or just add some charm to your garden, this guide will help you grow and look after lavender plants.
The best time to plant lavender is in spring, usually between March and May. This gives the plants enough time to grow strong roots before winter. You can also plant lavender in early autumn, but make sure to do it at least six weeks before the first frost so the roots can grow properly.
If you own property in Britain, Japanese knotweed might be the most expensive plant you'll ever encounter. This aggressive invader costs UK homeowners millions each year in damage repairs, and I've seen it tear through gardens, foundations, and driveways like paper. Whether you're a first-time gardener or a seasoned property owner, spotting knotweed early and knowing how to handle it properly could save you from costly repairs and legal headaches. Let me walk you through what every property owner needs to know about identifying and managing this troublesome plant - before it manages you.
Whether you're growing vegetables in a greenhouse all year round or tending to an outdoor plot, your soil's characteristics will determine your growing success. In my own garden, I've transformed challenging soil into productive growing space by following practical, tested methods. Let me share what I've learned about making any soil type work for your garden.
Growing melons in your greenhouse offers a taste of summer sweetness, even in our British climate. These tender fruits need warmth and care, making a greenhouse the perfect growing space. With the right setup from our best selection of wooden greenhouses in the UK, you'll soon be picking your own home-grown melons.
There is something deeply magical about unpacking dahlia tubers in early spring. Each wrinkled, earthen-colored crown whispers promises of summer's most spectacular blooms. As I unwrap each newspaper bundle in my frost-free garage, memories of last season's garden dance through my mind – the towering Cafe au Lait that produced armfuls of dinner-plate blooms, the vibrant Happy Single First Love that became a haven for every bee in the neighbourhood.
Your garden tells a unique story - one of seasons passing, of dreams taking root, of nature and human design intertwining. Adding a summer house to this living canvas isn't just about placing a structure; it's about creating a space where indoor comfort meets garden magic, where every window frames a view of your carefully tended landscape.
In my greenhouse, where morning light filters through dewdrops on glass panes, lettuce leaves unfurl like nature's own watercolour painting. From delicate butterheads to robust romaines, each variety tells its own story of transformation from seed to harvest. As California's Salinas Valley grapples with challenges like INSV and Pythium wilt, many of us are rediscovering the profound joy and security of growing our own leafy greens.
Growing greenhouse peppers gets easier with practice. Watch your plants closely, give them consistent care, and enjoy fresh peppers throughout the growing season. Each year brings new learning opportunities and better harvests.
Welcome to our comprehensive seed sowing guide for UK gardeners! As an avid gardener, I know how crucial it is to have a reliable monthly planting schedule. This guide will walk you through the best times to sow vegetable seeds, flower seeds, and more, helping you make the most of your garden all year round.
Winter can be a challenging time for gardeners, but with the right preparation, your plants can not only survive but thrive until spring. This guide will walk you through the steps to make sure your garden is ready to face the cold months ahead, ensuring your hard work flourishes even in the harshest weather.
Growing herbs in a greenhouse is a fantastic way to enjoy fresh flavours all year round. Whether you're a seasoned gardener or just starting out, this guide will help you make the most of your greenhouse for herb cultivation. I've been growing herbs in my greenhouse for years, and I'm excited to share my tips and tricks with you. Let's dig in and explore the wonderful world of greenhouse herbs together!
Growing garlic in a greenhouse is a rewarding experience that can yield a bountiful harvest of this flavourful and versatile vegetable. Whether you're a seasoned gardener or just starting out, greenhouse garlic cultivation offers numerous advantages over traditional outdoor growing methods. In this guide, we'll explore the ins and outs of indoor garlic growing, from choosing the right varieties to harvesting and storing your crop.
Growing grapes in a greenhouse is a rewarding experience that can yield delicious fruit even in cooler climates. The controlled environment of a greenhouse provides ideal conditions for grape cultivation, allowing for better temperature management, protection from pests, and extended growing seasons. Whether you're a seasoned gardener or a curious beginner, this guide will walk you through the process of cultivating grapes under glass.
Heating a greenhouse without electricity might seem like a tricky task, but it's actually quite doable with a bit of know-how. Whether you're looking to save on energy costs or simply don't have access to power in your greenhouse, there are several clever methods you can use to keep your plants cosy. Let's explore some practical ways to maintain warmth in your greenhouse without relying on electrical heating.
This free guide to using raised beds in a greenhouse will help you make the most of your growing space. Raised beds in greenhouses offer a brilliant way to create ideal conditions for your plants, boosting growth and yield. In a large greenhouse, you can combine shelving along the sides with one or two raised beds in the centre, ensuring you leave enough room to move about comfortably. Let's dig into the details of this gardening method that's taking root across the UK.
Growing strawberries in a greenhouse is a delightful way to enjoy fresh, juicy berries throughout the year. Whether you're a seasoned gardener or just starting out, this guide will walk you through the process of cultivating strawberries under glass. Let's explore how to grow strawberries in a greenhouse and savour the sweet rewards of your labour.
Growing mushrooms in a greenhouse can be a rewarding experience, offering a controlled environment for these fascinating fungi. Whether you're a seasoned gardener or a curious beginner, this guide will walk you through the process of cultivating your own mushrooms in a greenhouse setting.
Growing tomatoes in an unheated greenhouse can be a rewarding experience, extending your growing season and providing a bountiful harvest. But timing is crucial. Let's dig into when and how to plant tomatoes for the best results.
Greenhouses are remarkable structures that enable gardeners to cultivate plants throughout the year, regardless of outdoor conditions. These ingenious garden buildings function by harnessing the sun's energy to create a warm, nurturing environment for plants to flourish. Let's delve into the fascinating world of greenhouses and explore how they operate to provide ideal growing conditions for a wide variety of plants.
As the seasons change and the weather turns colder, many UK gardeners find themselves longing for the lush, productive days of summer. But what if I told you that you could continue growing vegetables in a greenhouse all year round, right here in the UK? It's not just a gardener's dream – it's entirely possible with the right knowledge, equipment, and a bit of passion. In this comprehensive guide, we'll explore how to transform your greenhouse into a year-round vegetable paradise, providing you with fresh, homegrown produce even in the depths of winter.
Autumn is here, and you might be wondering, "What are the best gardening jobs for autumn in the UK?" As the leaves start to turn and temperatures begin to drop, it's the perfect time to give your garden a bit of extra love before winter sets in. Whether you’re a seasoned gardener or just starting, this guide will walk you through the essential gardening tasks for autumn.
So, you've got a greenhouse, and you’re wondering, “What on earth do I grow first?” You’re in good company. Many of us start with grand dreams of year-round gardening but are unsure what plants to begin with. If you're looking for easy-to-grow crops, some fast-growing plants, and a step-by-step approach to greenhouse gardening, this is the guide for you.
April is the peak of spring. It is an important time for attending to a number of basic gardening chores ahead of summer. The what-to-do list for April must be flooded with preparation and planting tasks. To enjoy your garden to the fullest this coming season, you must be prepared to do certain garden tasks in April.
The month of March heralds the beginning of spring. It is the month when your garden comes alive with the emergence of colourful spring bulbs.
The winter cold spell is almost broken and as the worst of the weather is now over there is plenty to do in your garden in March. In this post we look at some of the key jobs you have to do on your garden in March as you prepare for the spring planting season.
The month of February is a major turning point in your gardening activities. February is still cold but the good news is that spring is starting to show its early signs.
Wherever you look, you'll notice bulbs reluctantly emerging from the ground and of course, the days are finally getting longer. Mother Nature will also shower you with the blessings of a few blossoms here and there.
If asked why they don’t grow fruits in their gardens, a majority of people would claim that they don’t have enough room in their gardens or that flowers look prettier, or even that the birds will eat all the fruits before harvest. If you are one of the people with such excuses, you are indeed wrong because growing fruit at home is easier than you think. It all depends on the type of fruit you want to grow in your garden.
Recent World Health Organization reports state that COVID-19 is here to stay and will soon become an endemic that we should all learn to live with. So, what impact will the endemic have on our dining culture? Mandatory temperature checks at the restaurant entrance, large gaps between tables, and being served by robotic masked waiters?
From the 430 BC Athens plague to the Middle Ages’ Black Death and the Spanish Flu in the modern era, pandemics have always shaped the way people live whether in cities or in farming communities. The current COVID 19 is no exception to the rule. Presently, the coronavirus pandemic is affecting the entire global community in every imaginable way possible, from economy and healthcare to food supply.
Urban gardening could be one of the greatest answers to peace, prosperity, and well-being. Next to water, food is one of the most essential tangible things in life. Food fuels the ability to work, to think, to invent, to play, even to love.
Greenhouses help us produce more food for a longer time - we know this already! But what if we went the extra step and took our greenhouse to the next level? Greenhouses alone can extend the growing season by months - without any extra heating.
Whether you’re interested in just extending the growing season in your local climate or want to shift towards growing indoors all year round makes no difference, learning – and mastering – the secrets of the greenhouse will change the way you look at gardening from here on out!
Have you ever wondered if you can grow food on your apartment balcony? The answer is yes! If you have a balcony, you have the space to grow plants and vegetables. Balconies are a great place for a mini garden. It can be just a few favourite plants or a wide variety. Many plants and vegetables will grow quite well in a small area. Don't let lack of space be the reason you don't have fresh vegetables this year!
Many people have fond memories of their grandparents. Let's face it, they are the best when you’re a little kid. Most grandparents are full of amazing stories about their lives and they create fun memories. Here are some fun ideas for family gardening that we have learned from grandparents.
With the new year, comes new years resolutions and one of your resolutions may be sorting out your garden. This article will help you get the most out of your garden with 12 industry secret tips to get your plants popping.
A greenhouse can be used for growing all types of plants, even when the weather normally wouldn’t allow them to thrive. For your greenhouse to really work though, humidity is a crucial factor.
Even though the cooler weather is here and winter is approaching, you aren’t done in your garden yet. Like most gardeners, you have probably spent quite a bit of time in the spring preparing your garden.
Rain is a bit elusive in July, but regardless of that, there is still plenty to do in the garden.
In this guide, we share some July gardening tips so you can still keep your garden in tip-top condition.
With the winter months upon us you may feel a familiar emptiness creeping in. There will soon be a season of no gardening until that glorious spring season returns.
It’s beautiful to see there are still people who wish to grow their own vegetables. The urban era is gaining fast, and most people think that the easiest way to live healthy is to order your vegetables online or shop at your closest grocery store.
Gardening is a wonderful pastime. Those of us who relish the scent of the soil, the hum of the bees, and the slow satisfaction of watching our works grow to (literal) fruition, know this well. However, gardening is traditionally considered an older person’s hobby. Visit any garden centre, and the target audience becomes evident.
Cucumbers are one of the most popular vegetables in the UK and are packed full of micronutrients and goodness. A staple in everything from sandwiches to salads, cucumbers are one of the most versatile summer vegetables you can grow.
One of the things gardeners find most appealing about annual plants is their diversity and variety. Annuals allow creative growers to put together eye-popping combinations of colours that will last a whole season. From bright eye-catching flowers such as Mexican sunflowers and zinnias to the pastel hues of lavatera, annual plants give you a great palette to choose from!
Greenhouses come in many different shapes, sizes and styles, making it easy to find one that suits your tastes and wallet best. There are all sorts of designs from classic to contemporary styles. The best rule of thumb for buying a greenhouse is definitely with what you can afford; buy the best and biggest that you can. As always, quality shouldn’t be overlooked.
Don’t be discouraged by the cost of building your own greenhouse, as greenhouse gardening is really the newest innovative way to garden. You need to weigh up the gains from greenhouse gardening against the cost you will incur from building it.
After reading this article, it will become obvious that the benefits of greenhouse gardening far outweigh the costs.
Many herbs take well to growing in a sunny kitchen window, although some will bolt, as in send up a flower stalk and try to set seeds, much earlier at room temperature. Constantly harvesting indoor-grown herbs can keep them in a constant state of renewal.
A greenhouse is a perfect place to get herbs started for the season, and also to grow more tender or tropical selections like basil, bay leaf, marjoram, and lemongrass.
Knowing how to regulate the temperature and keep it from rising to levels that could potentially kill your plants is essential if you’re to have a consistent, healthy crop and while in Britain moderating winter temperatures is more difficult, maintaining productive temperatures during the summer can be just as important.
Although the question of whether pots grow bags or border growing is best in the greenhouse seems simple, the answer isn't clear-cut. It depends on what you are growing and your circumstances.
Growing your own produce in a greenhouse is an incredibly fulfilling and enjoyable pass time, but as with any hobby that requires a degree of skill and knowledge, the learning curve can be quite steep. Even when growing the hardiest of plant species, there is a large number of variables that can affect growth rates and the success of a yield.
There’s no better way to re-use your garden and kitchen waste than to transform it into nutrient packed growing material that you can use for plants. Making your own compost is easy, cost-effective and fun and this guide will give you everything you need to start composting.
As well as the natural immunity boost you get from being outdoors in the sun, getting your hands dirty in the soil also gives your immune system a significant boost. Mycobacterium Vaccae is a strain of bacteria that is found in almost all garden dirt. Mycobacterium Vaccae is known as a “friendly bacteria” as it has been shown to reduce allergic reactions, asthma and a number of skin problems and diseases.
If you like growing flowering plants for decorative use as well as edible crops in your greenhouse, the petunia is an excellent choice to plant at this time of year. Unlike some other plants you can grow from March, petunia plants do not need an additional heat source in early spring, and will grow comfortably in the shelter of your greenhouse.
One of the things that can cause the most weakness in a greenhouse is when it is not properly level. This can leave the panels and glass slightly loose and less protected than they should be – something that becomes far more of a problem when it is windy or wet. Choose a good greenhouse with the best build quality you can afford, and make sure you erect it so it is straight, level and stable.
Those who are new to greenhouse gardening often think that glasshouses are best suited to growing flowers, herbs, and perhaps cool season crops like leafy green vegetables. The common belief among novices is that “picky” summer vegetables like tomatoes and peppers can be started in a greenhouse in late winter or early spring, but must be moved outdoors once the weather warms up.
Most garden pests die off over winter because it is cold and they can’t survive in freezing temperatures, but in the relatively comfortable environment of a greenhouse, any remaining pests will thrive. Slugs, aphids, red spider mite and mealy bugs all like to hibernate in hidden places inside a greenhouse. If you don’t eradicate them before spring, your newly sown seedlings will provide a tasty banquet for them to feast on. A deep clean will help you locate any sneaky slugs and other pests before they cause havoc when you start sowing seeds.
We're all tempted to grow the extremes, the biggest or most flavourful and with chilli peppers, the hottest. But do think it through, there's little point in putting a lot of effort into growing a pepper that is so hot you can't actually use it. A milder variety means you can add flavour as well as heat to a dish where even one of the super-hot chillies can be too hot to taste and just makes the dish hot.
Greenhouses provide a warm, safe environment for gardeners to grow their precious plants and tender seedlings, but they are not always very environmentally friendly. But don’t worry because there are lots of ways you can make your greenhouse greener.
At one time ring culture was a popular greenhouse growing method for tomatoes, cucumbers, peppers and melons. The idea was that water was supplied to the plants through a trench filled with aggregate and the plants were fed via the compost held in bottomless pots placed onto the aggregate.
At the end of the season the plants and the small amount of compost would be recycled into the garden and the aggregate removed and cleaned. This was less work than digging out and replacing border soil each year but still fairly time consuming.
It's pretty obvious that the larger the greenhouse, the higher the cost of heating it but it is possible to curtain off a section of the house in the winter with bubble-wrap and reduce the volume that has to be heated.
Unless your garden is exceptionally small, or it’s a no-man’s land you rarely visit, there’s probably a good reason to have a garden shed somewhere on your property. You might use the shed to store a lawnmower or gardening tools, to grow or pot plants away from the elements, to house recreational items like footballs, bikes, or sleds, as a playhouse for the children, or even as a calm spot where you can escape from the family for a few minutes. You may only want a small structure with one room and a single door for access, or you may find that something fancier with windows, a shingled roof and even electrical power better meets your needs.
There are many complexities of greenhouse gardening that confuse people today. However, many of the rules and regulations that cause the most confusion are ones you can simply forget about. To have a really well cultivated greenhouse you simply need to use some real soil, add plenty of light and air, water when necessary and nourish the plants.
Greenhouse gardening is the best way to undertake winter gardening because it allows you to enjoy your hobby when it's freezing cold outside. Of course, if you want to see success here, there are some things you will need to do. Keep reading to find out more.
The first thing to decide is how much of your greenhouse you want to keep warm and so need to insulate. Usually a greenhouse starts to fill when the weather is warming in spring and in the cold of winter it's probably just overwintering some tender perennials and getting an early start on some seedlings so not needing all the available space.
Things will grow very slowly if at all in December and January. Not so much because of the temperature but because the length of the day is at its shortest around the winter solstice (21st December). They will be gathering their energies ready to leap ahead come February when the days noticeably lengthen so long as the greenhouse is at least frost free.
Grey mould, properly called botrytis, is caused by the common fungus Botrytis cinerea, and presents as a furry grey mould. As the season comes to an end and the nights grow cooler, the atmosphere in the greenhouse becomes more humid which encourages fungal growths like botrytis but it can be a problem at any time of the year.
“How can I get an allotment?” is one of the most frequently asked questions I receive. The first thing to do is to find out where your local allotments are. Often sites aren't obvious from the road, being set behind houses and accessible from a nondescript lane. Many sites prefer to remain, if not hidden, then not obvious as this helps avoid problems from vandals and thieves.
Autumn is the time to restore and repair your lawn after a summer as a games field for the children. Start by scarifying – raking out any moss and dead grass which builds up into a thatch restricting the grass growth.
Spiking the lawn will improve drainage ready for the winter rain. Just insert a fork about 15 cm into the ground, rock it back and forth to open the hole and then repeat about 30 cm ahead. For bowling green standards, use a special hollow tined fork that removes a plug of soil.
To maximise the growing season, start tomato seedlings off indoors on a south facing window sill in February. Because the day length is still short and the light weak, the seedlings can be drawn and leggy. To help avoid this put a piece of cardboard covered with aluminium foil behind the seed tray to reflect light back onto the seedlings.
Usually though, those buying their first greenhouse won't realise how immensely useful they are until they have gone through a season. My first greenhouse was a 6x8, six feet wide and eight long.
That first summer I found myself trying to cram in 5 varieties of tomato, 3 types chilli peppers, 3 types of sweet pepper, cucumbers, aubergines and hanging baskets being brought on for the summer.
Greenhouses serve to both extend the growing season and to provide better growing conditions during the season, enabling us grow tender crops such as tomatoes and aubergines even in a bad summer.
In a good summer though the greenhouse can become a very hostile climate to grow in. It's surprising how quickly the temperature can soar to levels that kill our plants as surely as if they were put in the oven. That same sunlight that powers photosynthesis and growth can turn to scorching, killing the leaves.
To be honest, cleaning the greenhouse on a cold winter's day is not the most pleasant of tasks but it has to be done. Over the year the glass gets dirty and possibly has algae growing on it which will reduce the light that gets through by as much as 10%.
The other reason to thoroughly clean the house is to kill off the pests and problems that are overwintering inside, sheltered from the elements.