Many great gardens have an iconic greenhouse as a centerpiece and the Royal Horticultural Society’s garden at Wisley is no exception. The Society is celebrating its Bicentenary with the creation of a stunning new Glasshouse which will be opened in mid-June 2007 (see www.rhs.org.uk for details) and I was fortunate enough to be one of the first to be allowed inside. It will house a massive collection of warm temperate and tropical plants from around the world, including hundreds of Orchids and other plants, many of them extremely rare in cultivation. Ventilation, lighting, the screens for shading and all the other essentials for plant growth will all be computer controlled and to ensure longevity, like every top quality greenhouse, the structure has been powder coated. It will be worth visiting not only for the plant displays but for the interpretation boards which will be offering gardening advice so you can grow similar plants in your own greenhouse.
Staff have been busy taking cuttings and sowing seeds to provide plants – at this time of year, seed sowing is at the top of everyone’s list. Greenhouse crops that should be sown now include cucumbers, tomatoes plus ‘Sweet Peppers’ and ‘Aubergines’ that need a long growing season. ‘Sweet Pepper’ germination can be temperamental so keep the compost constantly warm at 18-20C to ensure success. Always buy fresh seed sowing compost at the beginning of each season, turning the bag ‘end over end’ to ensure that it is well mixed then keep it in the greenhouse rather than a cold shed so it warms up before use. Alternatively, fill and water several seed trays and put them in to propagator for twenty four hours to warm the compost before sowing. In March take note of the growing conditions before sowing seeds out doors, germination is poor in cold, waterlogged soil, it is much better to wait until the soil is warm, even if it is later than the recommended sowing time, then germination will be much more successful. Warm the soil by covering it with clear or black polythene; clear polythene has the advantage that weed seeds germinate and can be hoed off before sowing, so they don’t compete with your germinating crops. It is also worth covering the ground with horticultural fleece afterwards as this protects the seedlings from pests and diseases and chilling winds.
Indoor display constructionLate summer and autumn clematis should be cut back to within 30cm of the ground to a pair of strong buds, then fed with slow release general fertiliser and mulched with a good layer of well rotted compost. While you have the secateurs to hand, prune the ‘Winter Jasmine’ too, cutting out any dead, diseased or dying wood and the shoots that have flowered to within 2” of the main framework of older wood then turn your attention to ‘Dogwoods’ cutting them back to within 2-3” of the base then feed with general fertiliser to encourage colourful young growth for next autumn’s display.