28 Strawberries a Plant from Cambridge Favourite in Quadgrow Self Watering Planters

Cambridge Favourite is a mid-season strawberry bred at the National Institute of Agricultural Botany in the 1950s. Its reputation comes from dependable cropping and garden tolerance, with size taking a secondary place. Pair the plant with a Quadgrow, a self-watering planter that holds four pots above a reservoir and draws water upward through felt matting, and the roots avoid the drought checks that stop berries from swelling in an open bed.

That is the plain explanation for a 28-fruit count from one runner. A plant that dries between waterings sheds or shrivels developing berries. A plant held at even moisture carries more of its set fruit through to ripeness, even when the runner itself would look ordinary in a nursery tray.

The standard Quadgrow reservoir holds around 15 litres, enough to take four plants through several warm days before it needs attention. During peak fruiting, a mature Cambridge Favourite uses more water than many gardeners expect. The float valve deserves the regular glance; if it sticks, the mat dries and the plants begin to sulk within 48 hours.

The wick and the shallow root zone

Strawberry roots sit high in the compost, mostly in the top 15 centimetres. In an ordinary pot, that band can swing from soaked to dry during a single hot afternoon. Every swing puts pressure on the trusses that are trying to fill fruit.

Capillary matting changes the pattern. The mat draws from the reservoir as the compost needs water, so the roots meet similar conditions at 7am and 3pm. The plant is spared the cycle of flood, heat, pause, and recovery that is common in a hand-watered container.

Fruit number in strawberries is set partly at flowering and partly while the berries swell. Water stress during swelling is the usual loss point. Some fruit that has set successfully simply stops advancing and dries on the truss, leaving a plant that flowered well with a smaller harvest than it seemed to promise.

The compost has to help the wick do its job. A peat-free multipurpose mix with around 20 percent John Innes No. 2 gives ballast and a slower nutrient background. Pure multipurpose can slump and compact over a season, which weakens the contact between the capillary matting and the root zone.

The loam fraction matters most after the first rush of growth. It keeps structure in the pot into a second year, when a collapsed compost column can sit above the mat with less reliable capillary contact.

Feeding through the reservoir

Once flowering starts, strawberries in this system respond well to a high-potassium liquid feed added straight to the reservoir. Tomato feed such as Tomorite works because the nutrient ratio is close enough for fruiting plants, and the shared reservoir spreads the dose evenly across all four pots.

Use roughly half the strength suggested on the bottle at every second refill. The closed reservoir does not flush salts in the same way as an open bed receiving rain and overhead watering, so heavy feeding can leave more behind than the plant uses.

Salt buildup is the real hazard. Through a long dry spell, water leaves the system through evaporation and wicking while dissolved feed concentrates. By August, a white crust can appear on the compost surface. Emptying the reservoir and refilling it with plain water once a month resets the system. When conductivity creeps too high, browning leaf margins usually show before fruit quality makes the problem obvious.

Blossom end rot follows interrupted flow

Tomatoes and peppers grown alongside strawberries in the same Quadgrow can show blossom end rot, the sunken leathery patch at the base of the fruit. Gardeners often treat it as a calcium shortage in the soil, although the block is usually transport. Calcium moves through the plant with water, reaching the fruit end only while the plant is transpiring and drinking steadily.

A self-watering planter often prevents the interruption because moisture stays even. The problem can still appear if the reservoir runs empty during a heatwave. The plant shuts its stomata to survive, water flow to the growing tip stalls, and the fruit set during that pause shows rot two weeks later, after the hot spell has passed.

The practical remedy is a full reservoir before a forecast run of 28-degree days. Foliar calcium products and extra soil calcium leave the transport failure unchanged when the compost already holds enough.

Runners to keep and runners to cut

Cambridge Favourite sends out vigorous runners from midsummer. Pin the first two from each plant into 9cm pots of John Innes No. 1 for next year, then cut the later runners so the parent keeps more of its energy in fruiting.

Peas, mesh, and the same protected bench

After the strawberries finish, the Quadgrow pots can carry an autumn sowing of a hardy round pea such as Meteor or Douce Provence. Sown then, they can crop weeks ahead of a spring sowing. In winter the self-watering base matters less because evaporation is low, although the raised position still helps by keeping crowns away from cold wet ground where mice and slugs work.

The stronger protection comes from a bionet cloche. This fine-mesh tunnel sits over the sowing, holds a couple of degrees of warmth, and still lets rain and air pass. Environmesh and similar 1.35mm meshes also stop pigeons stripping the shoots, the commonest way an autumn pea sowing disappears overnight.

Solid polythene gives a poorer winter cover for this job because trapped damp can rot stems at soil level. Mesh suits overwintering peas more cleanly. In a mild coastal garden, peas sown in October under a bionet can be podding by late May, a fortnight ahead of an unprotected March sowing catching up.

Carrots in a raised bed use the same attention to pest behaviour. A carrot fly cannot climb, so a 60cm vertical Environmesh wall around the crop keeps the low-flying females from reaching the foliage to lay eggs. The barrier fails when there is a gap at the base, or when the cover is lifted for weeding on a still warm evening while flies are active.

Citrus beside the strawberries

A lemon or calamondin overwintering in the same glasshouse as the Quadgrow needs a separate watering regime. Citrus hates the constant wet that strawberries enjoy. Repot it into a specific citrus compost, or into John Innes No. 3 opened up with around 25 percent horticultural grit, and keep it out of peat-heavy multipurpose compost that holds water around the roots and encourages root rot.

Move the plant up one pot size only, such as a 20cm pot to a 22cm pot. Citrus roots resent sitting in unused wet compost. Repot in spring as growth restarts, teasing out the outer roots and trimming any that circle the old rootball.

After repotting, water once and let the surface dry before the next drink. A citrus stood in a self-watering tray would be dead by summer, which shows how specific the Quadgrow method is to thirsty continuous croppers. Strawberries and tomatoes suit the wick-and-reservoir pattern; Mediterranean woody plants evolved with a drying phase between drinks.

A drip system such as the Hozelock Automatic Watering Kit, run from a tap timer, fits citrus better than any shared reservoir. Set it to a short burst every third day, then adjust the drippers so the grit-heavy compost receives a measured dose. The same timer can feed a separate line to top up the Quadgrow reservoir, which is the neat trick when the two crops share a bench while asking for different watering rhythms.

That leaves the second season as the awkward test: the compost has slumped, the matting has partly clogged with root, and Cambridge Favourite is a year older, with vigour fading after its first full cropping year. Can the same plant keep that count once the wick is older and the compost has sunk?