What to do now: greenhouse

Reproduced from February 07 issue of Gardeners' World magazine. This month's issue on sale now Subscribe now by direct debit and save 25 per cent.

Divide primroses...dahlia tubers...seed tips...





4 steps to...dividing Cape primroses
After two or three years, I find the flowering performance of my Cape primroses (streptocarpus) starts to decline. You can propagate new ones from leaf cuttings or divide older plants to make new ones. Follow my step-by-step guide to divide yours and pot on into larger containers as plants develop next summer
1. Gently remove the plant from its pot and clean it up by pulling off old, dry flower stems and leaves.. 2. Use a sharp knife to cut large plants into two or more pieces, each with leaves and a section of roots. 3. Plant each section into its own small pot using a multi-purpose potting compost and water in well.
4. Dividing older plants helps rejuvenate them. Feed them weekly and keep in a warm, bright spot.
Tips for seed-sowing success

  • Good hygiene is essential when sowing seeds. Either wash old pots and trays thoroughly or use new ones.
  • Sow into fresh seed compost and don't use old bags of multi-purpose. .
  • Water compost with a solution of copper fungicide, such as Bio Cheshunt Compound, to prevent dampingoff disease. .
  • Water seedlings with tap water - not rainwater from a butt, which could carry disease. .
  • Pay attention to the temperature. Seeds need warmth to germinate, so invest in an electric propagator
    • .
Be dazzled by dahlias
Buy dahlia tubers now to plant in pots and trays. Ready-potted plants will be available later in the spring, but tubers are usually cheaper. Make sure they are firm, and not soft or showing any signs of rot. Pre-packed ones hanging in warm shops often dry out and are unlikely to grow. Plant the tubers at once and keep them in a warm propagator or greenhouse. And remember, dahlias are frosttender and cannot be planted outside until later in May.

Pick of the pots
At last there is an environmentally friendly alternative to plastic pots. Garden centre plant stockist KinderGarden Plants is now growing the majority of its young plants in rice-husk net pots. The biodegradable pots are made from a by-product of commercial rice production. More than 400 garden centres sell the KinderGarden range, so thousands fewer plastic pots will be discarded each year. After potting on the plants, the pots can be thrown on the compost heap, along with the remains of the bedding plants, and will decompose within about 12 months.

Brush up on fruit blossom
Bring potted peach and nectarine trees under cover now. The warmer conditions will encourage blooms to open earlier than those of outdoor trees. Keeping them under glass will also deter peach leaf curl, a fungus disease spread by rain splash. Blooms must be cross-pollinated but, as few bees and flying insects are active at this time of year, you'll need to do the job yourself. Dab the blooms with a soft, bushy brush to transfer pollen from flower to flower.

Adam says: strawberries fruit earlier under glass
It's time to bring potted strawberries into the greenhouse or dig up established plants from the garden and pot them up. Warm conditions under cover will encourage earlier growth, flowering and fruiting. Watch out for greenfly and vine weevil, both of which can attack plants.

Check list

  • Use a greenhouse heater at night to maintain frost-free conditions for tender plants.
  • Plant begonias, gloxinias, gloriosas, cannas, eucomis, agapanthus and other summer bulbs.
  • Put pots of spring bulbs in the greenhouse to develop.
  • Sow begonias, verbenas, lobelias, ageratums, pansies, violas, antirrhinums and other summer bedding.
  • Crops to sow in heated propagators include celery, tomatoes, aubergines, onions and peppers.

Keep tabs on greenhouse temperatures
Peering out into the darkness on winter evenings, it's hard to tell how low the temperature in the greenhouse has dropped. Is it freezing? Is the heater working? To monitor conditions, I've invested in a digital thermometer with a remote sensor that measures and transmits the temperature from up to 30m away. With the sensor in the greenhouse and main unit in the house, I can see the temperature at a glance. The unit also records the maximum and minimum temperatures, making it a useful gadget to use all year round.

Tip: clean your glazing
Wash glazing inside and out to remove grime and mould, and to let in more light. Do this now, before you start sowing seeds, because all plants appreciate higher light levels during the early months of the year.