Episode 22: Plant Hardiness Classifications and Gardening Jobs & Plants of Interest for January
Understanding plant hardiness classifications, our plant of the month; Chimonathus praecox, plants of interest for this month; Cyclamen coum and Erica carnea 'Myretoun Ruby' and jobs to do in the garden for January.
In this month’s edition of the podcast we look at plant hardiness classifications, seasonal gardening jobs to do in the garden during the month of January, and a selection of plants that look good in the garden at this time of year.
Understanding Plant Hardiness Scales - 01' 19"
We discuss plant hardiness classification systems, in particular the new RHS system, but also the US and European systems and how they can help you to choose the right plants for your geographical position.
RHS Hardiness Classifications - Minimum Survivable Temperatures
- H1a (>15°C) Heated greenhouse, tropical
- H1b (15 to 10°C) Heated greenhouse, subtropical
- H1c (10 to 5°C) Heated greenhouse, warm temperate
- H2 (5 to 1°C) Tender, cool or frost-free greenhouse
- H3 (1 to -5°C) Half hardy, unheated greenhouse/mild winter
- H4 (-5 to -10°C) Hardy, average winter
- H5 (-10 to -15°C) Hardy, cold winter
- H6 (-15 to -20°C) Hardy, very cold winter
- H7 (<-20°C) Very hardy
For more details see RHS Plant Hardiness Ratings.
Plant of the Month - 12' 40"
Our plant of the month for January is Chimonathus praecox – Wintersweet or Japanese allspice.
- Fully hardy, deciduous shrub, native to China
- Introduced into the UK in 1766
- Chimonanthus means "winter-flowering"
- RHS H4 – Hardy through most of the UK (-5 to -10°C)
- Likes full sun, so good trained against a south facing wall in a sheltered position
- Height up to 4m, spread 3m
- Growth Rate: Fast
- Soil: Moist but well-drained
- Flowers: From December to February with small bowl-shaped yellow flowers, strongly fragrant, tinged purplish-red inside and borne on bare branches in winter. May take a few years to get established before it starts to flower.
- Maintenance: Minimal pruning required, best in late spring. Remove dead, diseased or crossing branches. Mulch with compost.
- Good for flower arranging
- ‘Luteus’ cultivar has the RHS Award of Garden Merit
Jobs in the Garden - 14' 58"
- Plant Bare Root Trees and Shrubs
- Most planting done this month is of bare root plants that are often cheaper than container grown specimens, but only available during the autumn and winter. If the weather is suitable, the soil not too wet or frozen, then planting can still be carried out this month.
- Dig a hole wide enough and deep enough to accommodate the spread of the roots. Fork well-rotted garden compost or horse manure into the base of the hole and then position the plant in the hole. Next bang in a tree stake if necessary and tie it to the tree. Then backfill the hole with the soil you dug out, again with some added manure or compost, heeling in as you go so that the soil does not sink in subsequent days.
- Finally if you think rabbits or other pests might be a problem, put a tree guard around the trunk of the tree and remember to water well next spring and summer.
- Feed the Birds
- Many people feed garden birds all year around although, perhaps they should be encouraged to feed on the plentiful supply of insects, seeds etc. during the spring and summer months, which help to keep the pests down in the garden. It’s at this time of year however that they really need us to help get them through the winter. If you can, try to supply a good range of foods for the different species that visit your garden and make sure there is a regular supply of unfrozen fresh water.
- If heavy snow falls, shake it off the branches of trees and shrubs to prevent them snapping under the weight
- Check existing tree stakes and ties; make sure they are not too tight and digging into the bark of the tree. Remove any stakes that are no longer needed
- Get lawnmower serviced and blade sharpened
- Look through seed catalogues and decide what you would like to grow from seed when spring arrives
- Continue Fruit tree pruning
- Wisteria pruning – twice a year; summer and winter. Read our article on How to Prune a Wisteria.
In the Vegetable Garden - 22' 03"
- Sow inside: Peppers and Cauliflower
- Plant out: Rhubarb
- Harvest: Leeks, Kale and Cabbage
Plants of Note - 22' 41"
Two plants that we felt were worthy of note for this month are:
- Fully hardy deciduous, tuberous herbaceous perennial
- RHS H5 -10 to -15°C; Hardy in most places throughout the UK, even in severe winters
- Growth Rate: Average, 2-5 years to maturity
- 10cm tall, 10cm spread
- Partial shade
- Soil: Moderately fertile, moist but well-drained, humus-rich soil
- Flowers: Small (2cm wide) pink or white flowers with up-swept petals, January to March
- Foliage: Rounded silvery green marbled leaves
- Ideal around the base of deciduous trees or with ferns in shady areas
- RHS Award of Garden Merit
- Maintenance: In spring apply a mulch of leaf-mould when the leaves die back
- Pests: Vine weevil can attack pot grown specimens, but they’re generally disease free
- Fully hardy evergreen shrub
- RHS H7 less than -20°C Hardy in the severest European continental climates
- RHS Award of Garden Merit
- RHS Perfect for Pollinators Award
- Growth Rate: Average , 5-10 years to maturity
- 25cm tall, 45cm spread; low and spreading in habit
- Full sun but can tolerate partial shade
- Soil: Preferably well-drained acidic soil, but they can tolerate mildly alkaline soil
- Flowers: Masses of small, bell-shaped, tubular, deep rose-pink flowers from January to May
- Foliage: Dark-green needle-like leaves
- Maintenance: Generally pest free. After flowering, trim with shears to remove the spent flowers and encourage further bushy growth
Podcast produced by Richard Farrar.