Greenhouses are great at any time of year but I do like them in winter when the weather gets cold. Not only do they provide valuable shelter for tender plants but also weary gardeners.
I’ve been out in all weathers this week planting bulbs, a worthwhile but deeply boring task. The secret to getting through it is regular stretches and little visits to the greenhouse to see some of the little delights therein.
In the greenhouse
Here’s a view inside the greenhouse, where tender plants such as bananas and brugmansia are assembled to save them from the effects of a chilly Chilterns winter. This main section is unheated but stays above freezing even when the outside temperature is well below zero.
Specials in an Alpine Sand Box
Specialist alpine houses generally have very good ventilation as cold air flow is preferable to stagnant humid air. Although the ventilation is good, my greenhouse is not designed as an alpine house but I wanted a few little ones in there over the winte to visit and delight in.
I decided to use this old wooden wine box as a sand plunge and place it near the vents of the greenhouse. I try to open the vents on most days of the year to reduce damp humidity in the greenhouse. The benefits of the sand plunge are to provide moisture to the plants through the terracotta pots and to reduce fluctuations in temperature at the roots.
This little box makes me so happy every time I go to the greenhouse as it’s filled with what I like to call my “specials”, pretty little plants that might not need to be outside but which may flourish for longer, or earlier next spring, because they are under glass.
Androsace sarmentosa 
The flowers on this look at first like a primula but this is actually an Androsace, a group containing a wide variety of lovely alpine plants.
This one is described as being easy to grow in a trough or stony scree bed but I couldn’t resist having it in the sand box inside as I am completely in love with it.
Up close the centres of each mauve flower start greeny white before darkening to amber and then red – just like little traffic lights.
The label on this plant originates from Namche in Nepal. I looked this up and the town of Namche is at 3,440 metres up in the Himalayas. My chiltern garden is only at 152 metres above sea level but I hope it’ll be happy regardless.
Chrysanthemum ‘Avignon Pink’
These plants are now in their second year. Bought inexpensively as rooted cuttings from Sarah Raven in the spring of 2018, I now have a large number of sprays of pale pink flowers. 
These were flowering in pots in the greenhouse last winter, moved out from late spring and then back inside in late august. They only just started flowering a couple of weeks ago and may just keep the party going until Christmas.
Tender salvia
This was a gift from one of my garden society friends and I don’t know the variety. It a real draw to the greenhouse and the photos here really don’t do it justice. The tufty mauve flowers really do glow – especially in dull light.
Not only is the flower heart-stoppingly beautiful but its shape is also delightful. The woody stems are sparse but dainty.
This salvia is not frost hardy so has been brought into the greenhouse where it doesn’t need heat, just winter protection.
Waiting for spring
Outside the greenhouse, lined up in my cold frames, with the lids wide open are most of the alpines I grew from seed from the Alpine Garden Society Seed Exchange. Most alpines are perfectly happy in the cold but they don’t usually like winter wet. Using the cold frames, I can provide them with some airflow but they are protected from rain drumming down. They’ll be planted in my rockery next spring.
Last week I swelled the queue of alpines waiting in the cold frames to be planted in the rockery come spring. I attended a talk from Aberconwy Nurseries and they were selling some dainty alpines. The plant with starry pink flowers on the left is a lovely saxifrage, the darker mauve one is a type of oregano and the tufty pink one on the right is a miniature allium.
This seasonal diary is part of a weekly link-up of garden bloggers from around the world, called Six on Saturday. For more information and links to other blogs crammed with gardening activity, check the blog of host The Propagator.
I’m envious to have a frost-free space in the greenhouse like yours …(-5°C outside is the limit to have frost inside without heaters, so I avoid) ) My tender plants would be nice though..
Very beautiful Androsace , I didn’t know it.
I’m not sure my greenhouse would stay frost free below -5 either but those temps are fairly infrequent where I live in the UK. I have a little zone that I do heat but space there is limited.
Having read Jim’s SoS and now yours, I’m feeling a bit of greenhouse envy! Those chrysanthemums are lovely.
I was rather envious reading Jim’s post too!
The info on ventilation was useful. I’d seen the sand plunges before &’d wondered about using it for overwintering, but didn’t know all the ins & outs of how it worked – just thought it was insulation, not considering the moisture aspect of it all. Love both the Avignon Pink & the traffic light androsace. Beautiful colours, especially this time of year.
Hi Lora, yes I hadn’t really thought about the moisture issue of sand plunges until I started mixing with some alpine sorts and they filled me in. As long as the sand is kept moist the plants seem to get all the water they need. I also have an outdoor sand plunge made from an old cold frame. I’ll feature it soon as I have some special snowdrops in pots there.
The alpine sand box looks so beautiful with the little miniature plants. I’ve never grown alpines before but I may not be able to resist the temptation if they look that good.
Alpines – the new rock n roll!
I like that crysanth, is it not hardy outside?
I’m not convinced it is hardy unless a mild winter. Also it’s so late flowering I think the greenhouse helps to force it to flower a bit sooner. As it’s in the greenhouse anyway I just cut it back after flowering and leave it there.