We sort of persuade ourselves that March sees the end of winter and that spring is on the way, but it can be very cold this month so keep an eye on the weather forecast and try to be patient. The other good news is that clocks also go forward this month, so longer daylight hours help plants to really get under way.
1. Weeds need your attention now
Weeds will be growing even more strongly than your plants during these weeks, so keep on top of them before they can get a hold. Digging them up with a hand fork is the best idea, as you can get all the roots out. Reserve hoeing for dry weather, as weeds can re-root if the soil is moist.
2. Pot up dahlia tubers
Bring them into growth in a light, frost-free place and they’ll get off to a great start, ready for planting outdoors after the danger of frost has passed in late spring. You can also use some of the shoots to make cuttings later on.
3. Mulching is the number one job
The most effective way of improving the soil in established borders is to mulch the surface with a three cm-layer of organic matter, such as garden compost. It will also help to suppress weeds and trap moisture in the soil. If your heap doesn’t produce enough compost to mulch the whole garden, it’s worth contacting your local council to see if it’s possible to buy the compost that’s made from the green-waste collections. Mushroom compost (though not for acid-loving plants, as it contains chalk) and composted bark make good alternatives and can be bought online.
Before you start, make sure you have thoroughly weeded the bed and that you have sufficient mulching material – this could be leaf mould, compost, well-rotted manure or bark chippings. Always leave a gap around the stem of plants.
4. Get some potatoes planted
While most varieties of potato are planted in April, earlies, such as ‘Rocket’, you can get some ‘earlies’ in the soil during March. Plant them about 40cm apart in rows 45cm apart in the ground. Bury the potato just below the compost surface. As shoots grow, cover with more compost until the pot is full. Cover the young plants with garden fleece if frosts are forecast. Make sure you water the pot regularly, so the compost is moist but not wet. By late June or early July, your potatoes should be ready to harvest. Check they’re ready by putting your hand into the pot and gently feeling for the tubers. If they feel big enough, tip out the contents of the pot, otherwise leave them to continue growing.
5. A final chance to get summer bulbs planted
Summer bulbs, such as alliums, agapanthus and cannas, should be planted in spring, when the soil is just beginning to warm up. Pot individual bulbs into containers of multi-purpose compost, making sure that each pot is at least half as wide as the pot. Water sparingly until the bulbs start to shoot into growth, then water each time the compost is dry. Earmark a final planting site for your bulbs that is free-draining and south-facing. If soil drainage is poor, the bulbs can rot and lack of sun can mean lack of flowers.
Mix grit into each planting hole if the soil is heavy. Spreading a mulch of good garden compost or well-rotted manure over the soil a month before planting will help improve thin, poor soils, boosting fertility and improving drainage.
6. Flower seeds to sow in March
Hardy annuals can be sown in trays indoors or under glass now but unless you live somewhere mild it’s a bit early for half hardies.
There’s nothing more depressing than seeds that fail and these should deliver: honeywort Cerinthe major ‘Purpurascens’, cornflowers, borage (great for bees and decorating drinks) and viper’s bugloss (also great for bees and for butterflies).
If seed trays have been stored somewhere outdoors or weren’t washed when you put them away, give them a good wash and brush up with hot soapy water and don’t think you’ll save money by using old compost or earth – you’ll regret it when seeds shrivel and die.
Use large trays, fill with seed compost to near the top and water with a can with a fine rose or stand in a sink until the tray’s absorbed moisture. Don’t use water from the butt as this can lead to disease and try to use lukewarm rather than freezing cold water.
Sprinkle over seeds as sparingly as you can manage and use a sieve to sprinkle a light layer of dry compost. Sit somewhere light and neither too hot nor too cold. You want an even temperature around 18°C or 64°F. Some people like to cover the tray with glass or a clear polythene. You should see results in a week or two.
Once the seeds germinate remove any covers or you’ll get condensation and rot. Whilst you are waiting watch that the compost doesn’t dry out but don’t overwater either.
It’s your last chance to plant out summer flowering-bulbs like lilies, as well as any forced bulbs you might have had indoors over winter, such as daffodils and hyacinths, if you haven’t already.
7. First feed for roses
If you haven’t already done so give roses their first feed of the year. Use a tailored rose feed as they need the correct mix of nutrients. And don’t think you’ll be doing them a favour by over feeding. You’ll end up with too much sappy soft growth that makes them less able to withstand pests. Feed again in April/May and, if you want, they can have a final feed in July but no later or that soft wood will make them vulnerable to winter cold.
8. Sow your first tomatoes
It may seem a bit early, but March is really the time to sow tomatoes for growing indoors. Wait until mid-month and then sow the tomatoes you’re planning to grow indoors, pricking out the seedlings into individual pots later. Plants for growing outdoors are best sown in April or they’ll be ready before it’s warm enough to plant them outdoors.
9. …and don’t forget your houseplants
When you see growth starting again it’s time to check your houseplants. Some may just need a tidy up, clearing away dead leaves and debris and a bit of a prune to get it back into shape. If roots are appearing through the base it’s a sign, they need repotting. If you can’t see the roots, but it’s a while since they were repotted, try to loosen the plug of earth out of the pot and see if the roots are circling as if desperate to get out. If so it’s time to repot.
Ideally, water plants a few days before repotting. Use washed pots, one size larger than the existing pot, and fresh clean potting compost – whichever is correct for the plant. Some plants like a lighter mix so mix up the soil for each plant using a combination of potting compost, sand and perlite as necessary.
You can add water retaining gel granules if you like and some plants benefit from a topping of grit.
If the plant’s just not going to come out of the pot you can try to eke out a little more time by top dressing. To do this carefully scrape off an inch or so from the top of the old soil, avoiding damaging the roots, and replace with fresh new potting compost. Water pots well and drain. Avoid putting newly repotted plants in direct sunlight but let them recover slowly.
After a week or so they should be nicely settled in.
10. Divide those perennials
This is the key moment for dividing clumps of perennials because it’s possible to break off the outer, vigorous pieces and replant them straight back into the soil with a dusting of blood, fish and bone. Only select clumps with sparse middles, or ones with perennial weeds, or clumps that need reducing in size. Lift them with a fork and most will pull part into hand-sized pieces (others may need chopping with a spade).
11. What seeds can you plant this month
Hardy crops can be planted out in March, although those in the very north of the country should wait until the end of the month or even early April, depending on the weather. Hardy vegetables include broad beans, peas, spinach, garlic, onions, radish, Swiss chard and beetroot. Sow in short rows at weekly intervals to ensure a steady crop over summer and autumn.
12. Plant a clematis
March is a good time to plant a summer-flowering clematis. These climbers race away now and those that flower after Midsummer’s Day (21st June) produce lots of smaller flowers from top to toe. Classic varieties include ‘Étoile Violette’, ‘Polish Spirit’, and ‘Betty Corning’. Pruning’s easy, just cut them back to the lowest buds and they won’t suffer from wilt.
13. March is still a busy pruning month
March is one of the busiest months for pruning with a wide range of shrubs and other plants requiring their annual prune.
Timing is of course everything when it comes to pruning.
By now it is too late to prune apples, pears and late flowering clematis. But climbing roses, hybrid teas and floribundas need a March pruning and the sooner the better, so they don’t waste their energy growing leaves which are about to be lopped off. Borderline perennials such as pestemons and phygelius can also be pruned.
Tender evergreen shrubs such as variegated griselinia are best pruned now. The new growth triggered by the pruning should not be damaged by hard frosts. Evergreen edging and topiary can be finished now to create a smooth finish.
BUT DON’T PRUNE…
The sap pressure tends to be very high in March so if you prune them they will bleed profusely – something which will either damage them or possibly kill them.
Unlike climbing roses these bloom on stems produced the previous year so prune and then re-train then straight after flowering.
Delay pruning the more tender forms such as French lavender and hyssop until May. This ensures that the subsequent re growth won’t be badly damaged by frosts.
Unlike the more popular B.davidii, these varieties bloom on last years’ wood so prune them after flowering in the summer.