Hardening off and supporting – gardening tips for April

We 3Growbags were in Bristol last weekend designing a new garden for Caroline’s daughter.

It gave me ALL SORTS of ideas for this week’s tips column: plant supports, hardening off tender plants and how to grow rosemary amongst other things…

Hardening off

Have you got a load of trays of tender veg and flower seedlings or plug-plants filling up all the windowsills or greenhouse benches?  It is such as appealing thought that they might already be big and tough enough to cope with the great outdoors, but I’d like to counsel you to be very cautious about this.

There is a world of difference between that cosy windowsill and the chilly beds and borders.  You might be living in a part of the country that has already experienced its final frost of the winter, but that doesn’t mean that your pampered darlings can go straight out into the cold soil and be happy – the shock of the change will set them back and may even be enough to kill them. You may be the kind of person that enjoys going straight from a warm sauna to an icy plunge pool but your little plants won’t like it AT ALL. 

So do this ‘hardening off’ process gradually.  I know it’s a bit of a nuisance, but it’s much better to take the trays and modules and let them sit out the day in a sheltered part of your garden before bringing them in again at night.  That way they are gradually acclimatising to the colder, breezier outdoor conditions. A cold frame or open-sided mini-greenhouse is a handy piece of kit for this process: open the top or side during the day, close it in the evening.  Don’t forget!

Keep up this ‘out for the day, in for the night’ routine for 2-3 weeks, and your plantlets should then be ready to start camping out all night. If you live in a cold part of the UK where late frosts are more usual, I would still keep these tender plants in their containers for a couple of weeks more, so that they could still be brought indoors if a really cold night was forecast – or be prepared to tuck horticultural fleece around them.

Join the supporters’ club

It’s a rookie mistake to realise too late that you should have put in supports for your summer flowers which are flopping all over the place by July.  Hark at me!  I’ve been gardening for well over 40 years and I still find that I’ve missed a few tall perennials which end up lolling about like holidaymakers at the beach bar (brightly-coloured but sideways….)

By putting the supports (canes and string, custom-made jobs, brushwood sticks, using builders’ bars, netting…there are lots of choices) up BEFORE the stems are flopping, you avoid that ‘hung up round the neck’ look and you stand a much greater chance of making the supports invisible before the main summer season starts.

It’s probably pretty obvious but if you don’t tie in stems tightly but allow them to move a little in the wind without being blown flat, then they have the chance to develop stronger roots and sturdier stems.  This follows the same principle as the advice to secure a newly-planted tree to a supporting post quite low-down on the trunk and at an angle with the top of the stake facing into the prevailing wind. It’s a technique that also avoids banging a post straight through the tree’s root ball, which is helpful.

Sweetpea wigwams can be awkward to manage when the plants are small and Laura has a natty trick for this – before planting she pushes some well-branched brushwood sticks into the ground, and then arranges the wigwam of poles over the top of these tied together. The young sweet peas can ramble and scramble about through the twigs lower down before emerging triumphantly at the top.  They even looked quite elegant and architectural before the plants were even in the ground!

Gardening shorts

• What a fabulous spring it’s been for primroses!  Just as the flowers start to fade is the time to divide up the big clumps and increase the coverage of these delightful spring beauties – just dig up the clump and pull it apart with your hands into little groups of leaves and roots; then re-plant them quickly before they dry out. Water well.

• I might have already bored you to tears with how I managed to root some rosemary cuttings in water recently – see the link below for a video of the process if you’re interested.  A bush of rosemary does have the propensity to look very old and gnarly when it’s actually still quite young (I know a few people like that…🤣). But we put one in my niece’s garden which might solve the problem a little:  it’s a standard growing on one stem with a good bushy ‘head’.  So it seems to me that if one is diligent about keeping the top well-pruned and bushy, and the trunk clear, it might be possible to avoid that lanky, untidy habit that rosemaries so often adopt.  I’m going to try it with a couple of my cuttings – I’ll report back.

• I’m sorry if this sounds very cliché-d but aren’t new shoots a joy in April! Luscious red baby leaves on the roses, fat peony buds with their ruff of sepals, unfurling fern fronds….and all before any blooms appear. I’m crazy about Pieris shoots (just look at this week’s feature pic!) – I think they are even prettier than the white flowers that follow them. If you’re buying new shrubs and plants for your garden, don’t neglect this attribute. It can turn a good garden plant into a very special one by making it a multi-season gem.

• At one of our recent talks, Laura and I learned from a member of the audience how to make a garlic spray to deter molluscs, which we are happy to pass on. It was basically a bulb of garlic, broken up into cloves, peeled and whizzed in a processor. The mixture is then steeped in a pint of water overnight (some people use boiling water) then strained through a fine sieve or muslin. dilute 2 tablespoons of this concentrate with 5 litres of water and spray it on vulnerable plants once a week or more often if the weather is wet. I don’t think I’d use this on very young plants though for fear of causing damage.

• During the pandemic of 2020/21 we published a very popular set of articles about growing veg if you are something of a novice at it (as so many were during that terrible time). We thought this might be something that lots more people might be interested in, so we are re-launching it this spring, starting with potatoes, and continuing for the next few weeks.  Please click on this link GrowYourOwn to find it.  And if you’d prefer to have the series in a more succinct form, we turned the articles into a little book which is in our shop.

Are you after a tough and elegant plant for a dry, shady spot? Louise has the perfect one for you right here:

Here is the link to my adventure in rooting cuttings in water.

Tulip heaven at Arundel Castle

Arundel Castle Garden’s Tulip Festival runs throughout April! Laura found it spectacular, comparing it to a mix of Chelsea Flower Show and Harry Potter. Read about her and Elaine’s visit there.

We’ve had a most enjoyable connection with Henchman ladders over the last few years (you may often see Laura or me at the top of their ladders in the gardening press!) and they have got a competition running at the moment for any budding snippers and trimmers! Find out more about their Topiary Awards, and enter to show off your creative streak!

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