Give your plant pots a spa day ✨ – gardening tips for March

We 3Growbags have had such a lovely time this week giving talks to two marvellous groups of folk on the South coast!  Actually, we could talk about gardening till the cows come home.  

But there is so much to DO now spring has properly sprung! So let’s get out there making plant supports, re-potting specimen plants, and finishing the big cut-back…….

Plants in pots

Do you grow some treasured plants – perennials, grasses, shrubs, climbers….etc. in large pots rather than in the ground?  You may have chosen to grow them this way for all sorts of reasons: they need a particular soil, perhaps, or you want them in a special spot? Or maybe they are tender and you need the pots’ manoeuvrability (what a word!) in order to protect them through the winter?  I grow some things in pots so they can be handily moved to an out-of-the-way place once their moment of glory is over – much trickier to do with the plants growing in the borders!

For whatever reason they are pot-grown, spring is a smashing time to give them some love. Now is the time to check whether they have become pot-bound – so full of roots that it is not able to take up the water and nutrients that would enable it to thrive.  Look underneath – are roots coming out of the drainage hole?  Carefully take it out of the pot – the container knife we have in our shop is one of our very bestsellers and perfect for this job.  

Are there dry fibrous roots everywhere in the exact shape of the pot you have just removed?  The poor thing needs at the very least, the roots gently teased-out or trimmed, soaked in water, and re-potted in a slightly larger pot and fresh moist compost.  

If your plant is VERY congested with thready little roots, you might dare to be bolder…I once watched Neil Lucas of Knoll Gardens slicing the whole bottom half of the roots of a pot-bound ornamental grass crosswise, then putting the remaining plant and roots back into the same pot on top of fresh compost in the pot.  Many very pot-bound plants can cope with this tough treatment – the usual advice is not to take more than a third of the root ball off. 

If you’ve taken off quite a bit of the root ball, do consider trimming the top growth of your plant a bit to balance the water needs of the plant while it’s re-establishing, and thus reduce the stress of the move.

One more thing, don’t try the strong-arm treatment on something like a Bougainvillea, Clematis, or rather exotic things like Gardenias, or Grevilleas  – handle the roots of these beauties really gently or they will repay your attention by turning up their toes.

Your support network

I know I say it most years but do put your plant supports in early – now, in fact.  I know the whole ‘construction-site’ look is not appealing when they first go in, but everything is starting to shoot all over the place – even in Caroline’s garden in the Scottish Highlands – and those cat’s-cradles, canes etc., nets etc, will soon be obscured.  But they will still doing their important job like a sturdily-manufactured foundation garment.

The fancier plant-supports are SUCH a price these days.  What about buying some mild steel builders’ bars and making some supports yourself? You need the thickness to be enough to support heavy plants while also being flexible enough to bend – 6mm (1/4) is about right.  And if you get 3m lengths, you’ll have enough of the bar to anchor the ends firmly into the ground but still have a good length to bend round in a loop to support your plants. We’ve used ours for many years, and I know that our plant columnist Louise (and Monty Don!) has done the same.

Gardening shorts

• We 3Growbags are pretty excited about the new coir composts that are coming on to the market. We’ve all now done a few experiments using them alongside conventional peat-free composts and had very encouraging results. Yes, it’s true that coir has to be imported, but because it can be packed and sent without water and then reconstituted by the end-buyer (us!), the transportation costs compare very favourably with the usual bales and bags seen everywhere. Do give them a go! 

• If you’d like to make a copy of an expensive shrub in your garden, spring is a good time to try layering a stem which is growing low to the ground.  Use a knife or secateurs to clear the leaves from the stem and make a shallow cut below a bud on the newest wood. Mix some potting compost into the soil below the cut, then pin the stem down using a long hooked wire. Water the area then put a brick over the pinned-down bit of stem so that it stays stable.

Leave it there for the summer and in the autumn, you should see that the stem has developed roots at the cut, and can be separated from the parent plant, dug up and moved to where you want it to grow. Try it with Cotinus (smoke bush), Daphne, magnolias, rhododendrons, camellias, Forsythia, Hydrangea….Just have a go, nothing to lose, a lot to gain and the satisfaction is immense!

• Make sure you finish cutting back and clearing the old stems of your perennials very soon, or you run the risk of damaging all the new shoots that are pushing through.

• Sow some lettuce seeds into a tray of modules filled with compost, but don’t sow into all of the cells. Sow seed into the second half of the tray two weeks later, to stagger your harvest a bit. Cover the seeds with a little compost or vermiculite, then sit the cells in a tray of tepid water until the compost is moist. Let them germinate on a windowsill or in a propagator. Like beetroot, lettuce seedlings don’t enjoy root disturbance, so don’t re-pot or plant them outside until they have formed a properly strong rootball.

• I was very pleased to be spreading my homemade compost as mulch on to my flowerbeds yesterday. The very wet winter will have washed a lot of the nutrients out of my chalky free-draining soil, and a nutritious covering of compost should give all the plants a good boost as well as keeping the weeds at bay. I moved the contents of the other two bays ‘on-one’ as it were, and off we go again!

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Bred in Ireland, here is a beautiful, strong growing , hardy primula with a breeding name that belies its name. Discover more about Louise’s Great Plant this Month here:

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Get that plant out!

Plant completely jammed in its existing pot? You need this tool.

It slides around the inside of a pot allowing you to release a plant without disturbing its main root ball. Brilliant!

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A while back, Laura took Caroline on a little stroll down her pretty spring border full of woodland edge beauties:

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Five best plants for a woodland border

Woodland plants – those that thrive in the humus-rich, damp areas betwixt wooded areas and open space, have a very distinct charm. Here we recommend five that are five-star plants in our view

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