‘Cull some for the sake of the others’: Why we need to give space to plants

Adrian Higgins explains why thinning is one of the hardest things for novice gardeners to confront, despite being essential for their gardens’ success

Fast-growing greens, such as lettuce and rocket, need thinning repeatedly from seedling stage to maturity for optimum results (Washington Post)

Walking along the canal the other day, I noticed a single branched redbud tree stretching horizontally over the water. It was more of a twig than a tree, now in its purple-pink flower, and would form the perfect fishing perch for a kingfisher or heron. But the redbud isn’t lending a helping hand to anyone. It has spent its entire life stretching away from the woodland behind and into the light of the open water. For a plant, light is food and light is life.

Spring is the time for leaf unfurling, and this weeks-long process in itself is part of the joy of the season. Who can resist the slow-motion appearance of fern fronds, as their fiddleheads rise and uncoil? For plants stuck in a crowd of other plants, however, the race for light is anything but decorous; in fact, it is cutthroat. Some plants have evolved to live on a lesser diet of photons and inhabit shadier areas other plants cannot abide. Vines do the opposite: they stand on the shoulders of others.

In nature, the redbud likes to inhabit the edges of forests, where it finds the balance of sun and shade just to its liking.

My canal redbud was in less-than-optimum circumstances. The tree’s seed had found a crevice from which to sprout, and now, in maturity, it was nothing more than a meagre branch, clinging to rock at one end and lapping up the sunbeams at the other.

For the gardeners, observing this dance between plants and light levels is more than just nature appreciation; it’s an essential aspect of the whole enterprise of cultivating and appreciating plants.

A young, sunny garden can become an increasingly darker one after just five years, and because you are so close to it, you don’t see the fundamental shift. But there are signs. The daffodils stop blooming, perennials grow weak and shrubs become scrawny. Time to do some trimming and adjust the underlying plant palette.

Plants in a crowd compete for more than light; they are also jostling for space, nutrients and moisture. If they are overcrowded, they will be inherently weaker but also stretch more, and the result is something lofty but feeble.

This is why, when you are growing vegetables and annuals, you have to cull some for the sake of the others. This thinning is one of the hardest things for novice gardeners to confront, but it is essential for success.

As soon as the true leaves have appeared above the embryonic ones, it’s time to start pulling to leave seedlings with the space they need to get to the next stage. If this threatens to dislodge the keepers, you can use scissors.

Take lettuce, which grows to maturity over a period of eight weeks or so. You might need three thinnings, the first to give an inch between plants, the second 3in, the third 4-6in. The later thinnings will provide greens for sandwiches or salads.

It keeps a host of creatures safe and sated, and it delights us with the haw flowers of May through to the sloe berries of November

One reason to sow seeds too thickly is to anticipate a poor germination rate. Another is to get the sowing over with – many seeds are small and fiddly. Here’s a tip: don’t sow seeds in torrential rain; they stick to your cold, raw fingers and won’t let go.

Another thing I’ve learned the hard way: get comfortable – on your knees, perhaps – and do your seed spacing when you sow, even if this focus on separation becomes tedious. This will save so much effort later at thinning time. After germination, if you have gaps in your seed rows, you will soon know and can resow those voids.

There’s another reason to be careful with your seeds. The pandemic has burdened seed companies and led to shortages of some varieties, reminders that seeds are precious and thrift is a virtue. Who wants to waste seeds, especially now? Fold up a half-used packet and place it in a cool, dry environment. The seeds will be good for future harvests.

Giving plants their space produces optimum results but is not always necessary or desirable. Nature abhors a vacuum, as they say, evidenced by all the wild animals now flocking to empty towns around the world. I’d stay home a long time to see a herd of bison on the National Mall.

Advocates of naturalistic gardens, including me, point out that meadows are dense with wild plants that occupy two or three different layers. In natural grasslands, there is no double-shredded hardwood mulch, but a group of low, creeping plants that have evolved to fill the void.

English hedgerows, which frame farm fields and line country roads, are made by humans but copy new-growth woodland in all its primal race to survive. They can last for centuries with the occasional chop to stop them turning into trees. I saw a newly planted one a few years ago and was astonished at how close the shrubs and trees are set to one another – maybe just 8in apart, in double rows just 20in wide. A typical mix might include the hawthorn, blackthorn, wild roses, hazel and bloodtwig dogwood.

The resulting throng seems doomed to throttle itself, but the hedgerow comes together beautifully as a practical screen and a celebration of sustainable horticulture. It keeps a host of creatures safe and sated, and it delights us with the haw flowers of May through to the sloe berries of November.

It might be fun to play with such woody plant groupings and communities in your back yard – we typically don’t plant densely enough – but in the vegetable garden, your plants will need elbow room.

Gardening tip

Turf grass should not be left too long between mowings to avoid removing too much of the leaf and causing stress. During the spring growth spurt, you may need to cut the lawn every five days instead of once a week. Avoid mowing when the grass is wet.

© Washington Post