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The root plate of a quince sits shallow, in the top eighteen inches (45 cm), which is exactly the layer that dries first. That makes it the thirstiest of the common garden fruit trees and the one that punishes neglect fastest. The visible symptoms of drought are leaves that curl upward along the midrib, an early leaf drop in late summer and fruit that stops at half size and stays hard and green.
The critical window runs from the end of flowering until the fruit stops swelling, which is most of the summer. In that period an established tree wants the equivalent of one inch (25 mm) of water a week, from rain or from you. Deliver it as one long soak, ten to fifteen gallons (40-55 L) for a mature tree, poured slowly over the whole root spread rather than at the trunk. Frequent light watering trains roots upward and makes the problem worse.
Mulch is worth more than extra watering. Two to three inches (5-8 cm) of compost, bark or leaf mold spread out to the edge of the branches, renewed each spring, holds the moisture the shallow roots need and keeps grass off. Leave a clear collar four inches (10 cm) around the trunk so the bark stays dry.
| Stage | Water need | Sign you got it wrong |
|---|---|---|
| Bud break to flowering | Low; spring soil is usually wet enough | Rarely an issue |
| Set to midsummer | 1 in (25 mm) per week, rain included | Fruitlets yellow and drop by the handful |
| Midsummer to color change | 1 in (25 mm) per week, no gaps | Small hard fruit, leaves curling up at the edges |
| Color change to picking | Ease off; steady is better than heavy | Split skins after a downpour on dry ground |
| After leaf fall | None needed | Waterlogging over winter rots shallow roots |
Feed lightly or not at all
Quince fruits on the tips of shoots grown the previous year, but only on shoots of moderate length. A tree pushed with nitrogen makes long soft whips two to three feet (60-90 cm) long that do not set fruit buds, and that same soft growth is the tissue that leaf blight and fireblight enter through. Overfeeding is the commonest self-inflicted problem on a garden quince.
On reasonable soil with an annual mulch, an established tree needs nothing else. On thin or sandy ground, a light dressing of a balanced general fertilizer in early spring at around two ounces per square yard (70 g per square meter) over the root area, watered in, is enough for the year. Do not feed after midsummer; late nitrogen produces growth that has not hardened before the first frosts and dies back over winter.
Judge the tree by its extension growth rather than by a schedule. Shoots of eight to eighteen inches (20-45 cm) in a season on a mature tree are exactly right. Consistently under six inches (15 cm) means it is short of water, light or root room. Consistently over two feet (60 cm) means it is being fed too well and you should stop.
Thinning fruit, and letting it fall
Quince sets more fruit than it can finish and sheds the excess itself in early summer, usually within a few weeks of flowering. This drop looks alarming the first time, particularly on a young tree, and it is normal. Do not water or feed in response to it.
After that drop, thin by hand to one fruit per cluster and a hand's width between fruits along the shoot. Fewer fruits means bigger fruits, better color and, more importantly, less weight hanging on brittle wood. A branch loaded to the tip on a shallow-rooted tree will tear out in an autumn gale with the crop still on it.
Do the thinning while the fruit is walnut-sized and still hairy. Twist each unwanted fruit off with your fingers rather than pulling, because pulling strips the whole spur. Take off anything already marked, scabbed or lopsided at the same time, since damaged fruit will never store.
Support, ground and the seasonal round
Because the tree is shallow-rooted and the fruit is heavy, wind is the structural risk. Keep the stake for three years, then check for rocking each spring by pushing the trunk and watching whether a gap opens in the soil at the base. A gap means the root plate is moving and the tree needs restaking or a lower, more compact head.
Keep grass and weeds off the root zone permanently. Turf growing to the trunk competes for exactly the shallow water the tree depends on, and long grass keeps the bark damp. A mulched circle out to the branch tips is ideal; a three-foot (1 m) circle is the practical minimum.
Rake up and remove fallen leaves in autumn rather than leaving them under the tree. Quince leaf blight overwinters in that litter and reinfects the new leaves from below in spring, and clearing it is the single most effective thing you can do about the disease without spraying.
- Late winter Prune lightly while dormant, spread the annual mulch, and clear any leaf litter you missed in autumn. Check ties and stakes before the spring winds.
- Spring, at flowering Note the date the first flower opens. Do not spray anything while bees are working the tree. Feed only if the soil is thin, and only once.
- Early summer Expect and ignore the natural fruit drop. Once it has finished, thin to one fruit per cluster and start the weekly deep soak if rain is short.
- Midsummer Keep watering. Remove any blighted leaves and any shoot that has wilted and blackened at the tip. Stop feeding entirely.
- Autumn Pick as the fruit turns gold and the scent carries. Rake and remove all fallen leaves and any mummified fruit left hanging.
Keep one page a year for each tree: flowering date, date of the natural drop, how many fruit you thinned to, the picking date and the weight taken. Four years of that will show you whether your tree crops biennially, which many quinces do, and let you thin harder in the heavy year to even it out.