March is officially the first month of spring, although I know gardeners of a Celtic persuasion count the festival of Imbolc, or February 1st, St. Brigid’s Day, as the true start of new growth and renewal. Certainly there were some early spring bulbs, and late winter flowering shrubs in February but March sees an exponential increase in the amount of visible blooms. With any luck there will also be an increase in the number of days when it feels warm enough to be outside in the garden, finishing off all those tasks which need to be completed before the end of the month.
The kind of things that need to be done without delay are all those operations that rely on plants still being largely dormant and not yet into active growth. Finish mulching and cutting back tasks in beds and borders. Lift and divide herbaceous perennials, as you go along, and generally chuck some ‘fish, blood and bone’ fertiliser about. Gently forking the soil between plants is very pleasing and finishes the bed nicely.
Remember to relieve compaction, in areas where you have trodden, by deep forking to remove your footprints and aerate the soil. I count ‘deep forking’ as the kind where you plunge the fork fully into the ground and then lean back on it. This lifts up the soil and encourages the air, which was squeezed out due to compaction by your feet, to re-enter the soil structure. Good air exchange in soil is necessary for healthy root growth which is why compacted, or waterlogged, soils tend to inhibit plant growth and can actually kill plants.
Shrubs grown for their winter stems should be ‘stooled’ (cut down to the base) to force them to produce new stems this growing season because it is the new growth which has the most vivid winter colour. The usual candidates for this sort of treatment are the various coloured stem Cornus (dogwood) and Salix (willow) varieties. Young specimens should not be treated quite so brutally as they need to be a few years old before they have the resilience to bounce back from being cut to the ground. A generous feed, with a general purpose fertiliser, is recommended both for the newly stooled plants and those that are still establishing.
It’s getting a bit late to plant bare-rooted plants but you should get away with it if you are fastidious with your watering and take extra care to plant them well, mulching generously. Most woody and shrubby plants can be planted bare-root, during winter dormancy, and it is practically de rigeur for roses which can be ordered from specialist rose growers and dispatched via the post. On the subject of roses, pruning should be completed this month, before applying fertiliser and a good dollop of well rotted manure at the base of each plant.
Last month I ventured that you might like to try sowing some hardy perennials indoors, or in the greenhouse, but March is the first month when you could try some outdoor sowing. Hardy annuals are one of the cheapest and easiest ways of adding summer colour and they can be sown as soon as the weather starts to warm up. As long as your flower beds are relatively weed-free then sowing the seeds in situ couldn’t be easier. If you are worried that you’ll not recognise your chosen hardy annuals from annual weeds then sowing in rows, just inches apart, means that they will be obvious once they start to grow. These sowing lines completely disappear once the annuals fill out and fill the space. If conditions take a turn for the worst, or there is a danger of birds and other wildlife disturbing the seed-bed, then covering it with horticultural fleece protects the seedlings until they fully established.
If the weather is warm enough for hardy annuals to germinate then, as sure as eggs is eggs, annual weeds will be germinating too. Removing annual and perennial weeds now, while they are still small, will save a lot of time during the rest of the year. Hand weeding is particularly effective while they are still small, and easily dislodged, but hoeing will only work when it is performed during dry weather and the disturbed weed seedlings die before they get a chance to grow new roots.
If you are growing your own tender annuals, the sort that are generally available later as ‘bedding plants’, you will need somewhere heated and light. In a cold greenhouse the extra heat may be supplied with a heated propagator. If you have sufficient space, and a nicely centrally heated home, then a warm windowsill may do and it’s much easier to keep an eye on germination when the seed trays are where you’ll see them everyday.
Some experimentation is required as a sunny windowsill may end up ‘cooking’ your seedlings while a north facing spot may never get warm enough for ‘exotic’ seeds which require a steady 65-75ºF to germinate. There is a danger that the seedlings will become etiolated (stretched) as they strain towards the light coming in from just one direction. Turning the pots on a regular basis helps or, if you are handy with such things, rigging up some sort of light reflecting screen, on the unlit side, should prevent the emerging plants from leaning towards the light. All the hassle and uncertainty, of raising tender plants, can be avoided if you are willing to pay a little more in order to obtain similar varieties as small plants via mail-order or from garden centres when they become available.
All this talk of tender plants is a little premature when the reality of March is that it’s still more likely than not that there will be overnight frosts. Also, there will be a majority of days when the average temperature remains below seven to eight degrees centigrade, the temperature required for most lawn grass to grow, so, despite the prevalence of spring flowering bulbs, the garden is still only just beginning to wake up.
