Emma Townshend: Magnolias can block out the sun - thank goodness for smaller varieties

Magnolias in full bloom at The Royal Botanical Gardens in Kew earlier this month (Getty Images)

My friend Kat and I are standing outside Helen's house, looking at her magnolia. It's Magnolia stellata, its elegant long stems covered with white buds, reaching out to the path and the party wall. "It's lovely, but it makes me feel sad," I say to Kat, because Helen planted the magnolia in memory of her brother, who died in terrible circumstances.

Often the magnolias of the world flower in strict order, with this one, stellata, mostly first, studded with white stars; followed by the taller M. soulangeana, a pinkier-flowered tree that will be instantly familiar to anyone who's ever driven longingly through upper-middle-class neighbourhoods in spring.

This year, they all seem out at once, in some sort of not-completely-unknown response to the way spring has sprung. It means that Helen's magnolia is accompanied by plenty of other blossomings, around the nearby streets.

There's little to complain about, viewing this display on a sunny March morning. In fact, the only problem with magnolias in small town gardens is that they grow large and full in shape, blocking out light, especially in front gardens planted close to the house. This is particularly true of varieties such as soulangeana (often the only one on sale at garden centres). And unlike most trees, they don't respond well to a chop. Their shape goes lopsided, and they lose the lovely spreading habit they have when left unhindered.

Luckily in recent years, breeders, especially New Zealand magnolia superstar Mark Jury, have developed smaller varieties. These often combine the neat shape of stellata, and its pretty starlike flowers, with the deep pinks and roses of the bigger magnolias. These days, for small gardens there's Magnolia "Satisfaction" (£39.99, crocus.co.uk – should grow to 3m tall tops), which has a wonderfully Japanese print feel, with stylish two-tone flowers, paler pink inside and deeper blush outside.

Of other promising varieties, my favourite is Fairy Magnolia Blush (£34.99 standard, £14.99 small, crocus.co.uk). Flowering on evergreen stems, it has the look of a pale camellia, with simple pink flowers against leaf green. There is also a pure-white version, Fairy Magnolia White (£24.99, crocus.co.uk), which looks far more like M. stellata in flower.

How you plant your magnolia will be important. Dig a much bigger and deeper hole than the rootball would suggest, and backfill with compost. Ease the roots out, especially if they are "pot-bound", tangled and overgrown, because magnolias often sit in nurseries for a while before they are purchased, and they need some incentive to form a relationship with their new planting position.

Then make sure you mulch for top-quality flowering. Their roots will be predominantly close to the surface and they love a winter treat of farm-quality manure. One proviso: many magnolias are grafted, and covering up the graft, at the base of the trunk, is a no-no. If you do mulch, make sure the soil surface is level.

They do grow quickly, and one year's fresh new branches will be the next's troublesome limbs. As a result, it's worth thinking early on about the shape you want your tree to take.

If you prefer the idea of a shortish, bushy specimen, lop out the top growing tip and encourage sideways growth; whereas in my garden, it's all about going upwards, so the flowering tips are visible from the kitchen sink: I've cut off all the lower branches as they have appeared to make a smooth, tall trunk.

Relatively free of pests and diseases, they are a good choice for a memorial plant, I think. So if it makes me feel sad – well, that's what I'm meant to feel, isn't it? And Kat replies, "Yeah, but when I see it flower, every year I do think of him, and that makes me smile." And I nod.