SEVERE frosts took their toll on several shrubby perennials growing outdoors during the winter just past.
And it was quite correct to allow those affected enough time to show signs of life rather than dig them up at the first sign of damage. However, if there has been no indication of life by now, it really is time to accept the loss and consider a replacement.
Locally, several mature Cordyline australis, Laurus nobilis (bay) and Lavatera Barnsley were victims, and their only hope of salvation lay in the appearance of green shoots from above the union in the case of grafted specimens, ground level in others.
When life signs do appear, all it takes by way of encouragement is the pruning out of all dead wood.
Sadly, most affected shrubs have not responded positively so well done those gardeners with the foresight to propagate replacements as insurance against frost damage.
Erysimum Bowles Mauve (perennial wallflower) and Lavatera Barnsley are always on our perennials at risk list and it was no surprise that minus 10 Celsius proved too much for them. Luckily there were several replacement plants standing by, the result of October cuttings growing under cover.
The lesson is clear – start the back-up strategy now by rooting softwood cuttings and continue propagating in stages until autumn.
Nothing special by way of heat is required to propagate the majority of our favourite shrubs. All they demand is a gritty rooting medium, a moist environment and shade from direct sunlight. Sharp sand mixed with recycled potting compost is ideal. If there is a cold frame available fine, but a box-like structure can be easily made, and moisture retained via a polythene, plastic or glass top.
I am continually being asked whether it is necessary to use hormone rooting powder on cuttings, and the answer is – no. It does help speed up the callusing which precedes root formation but frankly, I’m just happy to let nature take its course and save money in the process.
The best rooting material for June is young finger-length shoots of non-flowering growth, which are also the most vigorous. Collect them by holding the stem they occupy with one hand and giving them a sharp downward tug with the other. Remove all leaves save the topmost cluster of four, and ensure that there is a heel or leaf joint at the base. Best time to act is early in the morning when they’re fully charged with moisture and before the sun has a chance to dehydrate them. Even then I immerse everything in a bowl of water for an hour or so to get them fully turgid. Planting floppy cuttings is a mistake.
A quick mental trip around this garden brings candidates such as weigella, escallonia, viburnum, osmanthus, box and euonymus to mind. But there are many more possibilities. Winter heathers such as King George, Springwood Pink and White, also darleyensis, are dripping with young shoots. The good thing about these is that they can be crowded into a tray, pan or pot and rooted en masse. Add several alpines and herbs to the list and there really is an embarrassment of stem cuttings waiting to be picked and rooted at this time of year.
It’s a similar story under glass where the potential to raise new plants exists at every turn. The variegated Plectranthus coleoides has been a popular indoor, perennial foliage plant for years. With a combined upright and trailing habit it is also ideal for summer work in baskets, tubs or boxes. No sooner have you removed a growing tip for propagation than two more shoots replace it. This leads to oodles of clones for coffee morning stalls and the donor plant becomes much bushier in the process. Encouraging roots could not be easier. Just like fuchsia and verbena cuttings, they will take in a tumbler of water placed on the kitchen windowsill.
Even the side shoots that we are continually removing from developing tomato plants can be put to good use. We make a hole with a pencil or piece of cane in the greenhouse border, slot them in up to their necks and they root to order. When growth begins dig them up with a trowel and pot them up to secure a late run of fruits.
If the latest weather forecast for June is anything to go by, farmers and gardeners are going to face difficult growing conditions. Already there are signs of drought in the mixed border with achillea, astrantia and pulmonaria flagging at the peak of their growth cycle. They do regain composure some hours after we`ve offered a can of water but such setbacks gradually undermine the stability of a plant. If the hot, dry conditions prevail, we shall have to remain vigilant in certain areas.
Any shrubs, ornamental trees or fruit trees and bushes, planted during autumn or spring, will not have had time to establish vigorous root systems and are therefore at risk. If they were pot-bound at the time of planting and the roots were not teased gently apart to stimulate growth, there will be trouble ahead.
Top and bush fruits need lots of water to reach maturity. This is why we are continually bolstering the organic content of soil in which they grow with the annual mulch. It tops up the humus content, aids water retention, deflects the summer sun and suppresses weeds. Vegetables are just as demanding of water, as are lawns. Such hot, dry conditions as are forecast certainly stimulate conversation but take us way outside our comfort zone. Best plan is to keep in daily contact with your plants and prepare for action.