Sage Advice

Spring cleaning

Callum Halstead

Every year, at some point in March I find myself questioning how, once again, I have managed to drift through more than two months of the year without having made any significant progress on any early season jobs. None of the wreckage of winter has been removed, no seeds ordered, none of my more tender plants provided with any form of adequate frost protection... and so on. Part of the reason has been the lack of evening light, but really it’s getting past the point in the year when I can still use that excuse. I could have been much more proactive than I have been, but the good news is that it’s not too late to get to work on most of these jobs and, while the frost damaged plants will probably bear the scars of my neglect for a good few months, they’ll get over it.

I’m more in the mood for gardening now. I like to get out into the garden earlier in the year to see the Snowdrops (Galanthus spp.) and other heralds of spring emerging from their long rest, but this doesn’t usually translate into much in the way of action. Now, however, I am ready to get going. Ready to fill gaps in the borders, to change a few plant combinations that didn’t work last year or that I’ve grown tired of, and— like many keen gardeners — ready to buy more new plants than I have room for.

When shopping, it’s easy to be seduced by the eye-catching plants placed conveniently close to the tills alongside the chocolate and paracetamol. Each of these items can, in its own way, doubtless help you to feel much better; but, where plants are concerned, you have to be wary about whether what you are buying is actually suitable for planting out before the weather has properly warmed up. Frost damaged and dead plants are in no way a gateway to happiness. Rather disappointingly, many retailers— including some garden centres —abuse our natural desire for a bit of greenery at this time of year, using it as an opportunity to sell plants that they know are unlikely to survive outside the cosy temperature-controlled glasshouses that they have been grown in. I’m sure that this is one of the main reasons why so many people believe that they are bad plant parents; they wrongly blame themselves for their glossy new plant’s swift decline, when in actual fact they were sold something that never stood a chance of surviving in the first place. Until the shops cease with this ridiculous and quite disingenuous sales tactic, what is needed is a little bit of education.

Enter the smartphone. What we are mainly concerned with at this time of year is ‘hardiness’— that is, how well-equipped a plant is to deal with cold and, more importantly, frost. Your first port of call should be the plant label, which will often give you a good idea of just how hardy the plant is. However, the quality of the information on plant labels can vary depending on where you are buying your plants, so for those who remain unsure of how tough the plants in their shopping trolley are, I would recommend quickly searching the plant’s name on the Royal Horticultural Society (RHS)’s website. The RHS has a pretty extensive online encyclopaedia of popular garden plants, so there’s a good chance that the plant that you’re searching for will appear. Once you have found your plant, scroll down to the section entitled ‘Position’ and hit the down arrow. Here you will see the word ‘Hardiness’, under which there will be a short code that starts with the letter ‘H’. The higher the number that follows the H, the colder the temperature the plant in question can handle without the need for additional protection.

If the plant is anything from ‘H4’ to ‘H7’, it’ll be pretty tough and should be fine outside in the cold throughout most of the British Isles. ‘H3’ is borderline, so if a cold snap is forecast, perhaps bring it indoors until the threat of frost has passed. ‘H2’ plants, often referred to as ‘half-hardy’, won’t take a frost at all; they need to wait until warmer weather can be guaranteed before being planted outside. That leaves the tender ‘H1’ plants, which are further divided into categories, decreasing in hardiness from C, through B, to A, to clarify exactly how much they detest the cold. (My sister, for example, is most certainly H1B, preferring a subtropical climate.) There are plenty of ‘H1’s that could make brilliant temporary additions to your garden, but there are many that should essentially be considered to be either house or warm greenhouse plants, as they will likely protest at being placed outside on anything other than a warm summer’s day.

Using this information alongside what you already know about your local weather patterns and climate, you should now be able to plan your purchases to avoid losing any of the more tender plants as soon as you put them in the ground. While many tender and half-hardy plants can be used to great effect in gardens, it is vitally important that they are planted at the right time of year in order to ensure their survival. Depending on where in the country you are, a little bit of patience may be necessary. Unless you live in the southwest of England, where the weather gods might just be on your side, late frosts are likely to feature in your local weather forecasts throughout March and much of April— possibly extending into the first few weeks of May, depending on how far inland, north or up a hill you live. If you live in Braemar, for example, you may wish to hold off until June.

For those who can’t wait and are eager for something new to plant now, allow me to suggest Dog’s-Tooth Violets (Erythronium spp.). Erythroniums are some of the most refined and graceful spring bulbs that you can plant, and yet they remain considerably less well known than the ever popular Crocuses (C. spp.), Daffodils (Narcissus spp.) and Tulips (Tulipa spp.). They are often sold as bulbs in summer, but you can also find them potted at this time of year, ready to be planted out in a good, deep, humus-rich soil in light shade. I find that they work extremely well as filler plants, positioned between other perennials that don’t get going until later on in the season. Choose neighbours that won’t swamp them entirely, keep them watered during dry spells, and your Erythroniums should be very happy. Some excellent varieties to look out for include the diminutive Erythronium dens-canis ‘Snowflake’, with its heavily spotted leaves and jazzy blue pollen, the tall and stately E. californicum ‘White Beauty’ (pictured), or, for a bit more punch, E. ‘Sundisc’, which holds its golden-yellow flowers high over its heavily mottled and almost reptilian looking foliage. All are fine garden plants and reliable H5s.

I appreciate that not everyone will be as keen on braving the outdoors just yet, so let us now turn our attention indoors. Those of you who have already caught the houseplant bug will shortly find that your own private jungle is beginning to wake up from its winter slumber, ready for a new season of growth. In anticipation of this, March is a good time to carry out a bit of spring cleaning and some repotting, to ensure that your plants are in top condition and continue to thrive. If it’s time to re-pot, then don’t be tempted to increase the pot size too dramatically. Using a pot that is too large— ‘over-potting’, as it is known —will leave your plant swimming in a sea of compost that is too vast for the plant’s root system to adequately colonise. As a result, the compost will sit wetter for longer after watering, which can lead to root rot and a general decline in the plant’s health. This is something that is important to keep in mind when potting outdoor plants, as well as house plants. If your plant has been sitting in its pot for a few years, then the chances are that the compost it has been growing in will have degraded over time. If this is the case, then I would recommend trying to loosen and dispose of some of this older compost before re-potting, replenishing what you have removed with fresh potting mix. Refreshing the growing medium in this way provides the maximum level of benefit to the plant by promoting better root health and providing fresh nutrients, while having the added bonus of reducing the populations of soil-borne pests such as fungus gnats, which may have overwintered in the old compost.

You can now turn your attention to sprucing up the top growth of the plant, cleaning leaves and removing anything that has died back over the winter. Rather than spending hours wiping down each individual leaf with a damp cloth, I save time by piling all of my houseplants (with the exception of Cacti and other succulents) into my shower tray before spraying them all down on low to medium power with cool water. Allow the pots to drain fully before returning them to their shelves and windowsills, so that they’re not sitting with too much water in their drip trays for the next few weeks. If you have reduced your watering schedule through the winter then it won’t be long now before you can start to increase this again. Assuming that the trip to the shower was their first drink for a few weeks, watering once a fortnight for the time being should be adequate— and, if you want to give things an early season boost, consider giving your plants their first feed of the season with an appropriate plant food when they are next due to be watered.

On the subject of Cacti and succulents, which generally should have been kept pretty dry and in as bright a location as possible through the winter, you can now give them a little dribble of water to whet their appetite at the very start of their growing season. This small amount will be sufficient to keep them going for another month without causing them to grow into weird and deformed shapes, which can occur if you overwater through the colder, darker months. With that, your gardening spring clean is complete.

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E. californicum ‘White Beauty’, copyright Callum Halstead