May in Chester County is the month the garden shows you everything it’s capable of. The peonies are coming in, the alliums are standing up over the borders, the Viburnum plicatum is doing exactly what a well-placed Viburnum should do. It’s genuinely beautiful right now. It’s also the month most people lose track of what needs doing, because the beauty makes it easy to just stand there.
There’s a hard deadline on spring-blooming shrubs that most people miss. Forsythia, lilac, weigela, Deutzia — these shrubs set next year’s flower buds on the wood they grow this summer. If you prune them now, within a few weeks of bloom finishing, they have the whole season to push new growth and set those buds. Wait until fall or next spring and you’re cutting off what you’ve been waiting all year to see. The window is short, maybe three weeks after flowering ends, and then it’s gone.
Peonies are worth a specific conversation in May. If you have a mature clump that reliably fails to bloom, depth is the likely answer. The eyes need to sit no more than an inch to an inch and a half below the soil surface. Planted deeper than that, they will grow, look healthy, and produce no flowers. It’s a frustrating problem because everything looks fine. This is also the week to get wire supports in place before the stems are fully extended. Heavy blooms after a good rain have a way of going all the way to the ground, and there’s nothing to be done about it once it’s happened.
The frost question is not quite over in early May. Chester County’s average last frost sits around May 10th, but I’ve watched late cold come through into the third week before. Tender annuals and tropicals are fine on a covered porch or in a cold frame. Putting them in the ground before Mother’s Day weekend is a gamble that loses more often than people admit. Memorial Day is the date I hold to for anything going into an exposed bed.
Mulching, if it hasn’t been done yet, should happen in the next few weeks. The goal is to get two to three inches of shredded hardwood down after the soil has warmed but before the heat of June sets in. It holds moisture through summer, moderates soil temperature and suppresses the weeds that are just starting to establish. Keep it pulled away from the crown of perennials and the base of any trunk. Volcano mulching — piled up against the bark — causes slow damage that shows up years later when there isn’t an obvious cause to point to.
One thing I see every May that costs people the following spring: cutting back bulb foliage before it has finished dying on its own. Daffodil leaves, tulip foliage, the strappy green of alliums after they bloom — it looks untidy, and the temptation to tidy it is real. But those leaves are doing the work of storing energy for next year’s flowers. Cut them before they’ve gone fully yellow and you’re borrowing against next May. Fold them over if you need to. Plant annuals around them to draw the eye. But let them finish.
The garden is at its best right now. Get out into it.
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